With the recent Maligiaq traffic I followed the links to the QCC web site (re Maligiaq and the boat he will race) and was very interested in the articles by John Winters on the site about his kayak designs. http://www.qualitycomposites.com/speakboat.htm The list comparing overall length vs water line length of many popular sea kayaks at: http://www.qualitycomposites.com/howlong.htm makes interesting reading. The general gist of the argument is that any part of the boat which overhangs the water line length at bow and stern is a waste of materials, adds weight etc, and does nothing for the boats handling or speed. John puts forward: "Some traditional designs have as much as two feet of skinny boat hanging out over the ocean. It looks pretty but it doesn't do much" John has designed some whizzy boats, and I'm aware that he also knows a fair bit more than I do about the design of traditional kayaks, but I would challenge that the pointy bows of 'traditional' designs are functional as well as aesthetically pleasing. It is very rare that I find myself paddling my sea kayak in anything approaching flat water, and thus it is also very rare for the bow of my boat to be just "hanging out over the ocean looking pretty". Paddling in any sort of sea the whole of the bow is frequently immersed, infact paddling in whitecaps or a steep oncoming sea so is pretty much the whole boat. How relevant are the wave making characteristics of the hull in flat water when the whole boat is being bumped around by waves orders of magnitude larger? Has anyone thought about analysing the shape of the deck, often frequently awash ? Which has more windage a low flat deck with balanced raised bows and stern with buyancy far forward, or a high angled deck with square bow and stern ? Which is dryer ? Which is faster in sea conditions ? I would also argue that flat water speed of a boat is a very poor measure of miles you can paddle a day at sea, and optimising a boat for wave making resistance doesn't necessarily make a good sea kayak. I demo'd a P&H spitzbergen at a symposium in May (an example of a boat designed to be 'fast' with a high waterline to overall length ratio). IMHO its a terrible boat and the last thing I'd want in any sort of sea conditions. I was discussing my thoughts on this boat with a friend recently who had had an aspirant BCU SSI turn up for his assessment in one. For the assessment they were out in somewhat challenging condition's and the result was the aspirant Senior Sea Instructor (aspirant but to be on the assessment never the less an experienced paddler - I'm not too hot on BCU stuff, but I believe you call SSI's level 4 coach in the states?) couldn't come close to keeping up in the conditions with his 'racing' boat. The assessors having a ball surfng along in supposedly much slower boats were apparently mightily amused. I'm aware that design of the bow profile isn't the only feature of this boat, but my point is that in real conditions design measures like the water line length and computer predicted drag do not equate with miles you can cover at sea. In open water conditions the ability to surf following seas (you can therefore also ditch your rudders <grin>) keep the paddler reasonably dry, and balance and cope with wind are key factors which the traditional pointy bow with low decks achieves. They have the added benefit that the shape will ride up over objects in their path - apparently important for the traditional hunter landing and launching from ice floes, but more importantly for the paddler today essential for a number of rescues. Maybe of minor concern but there is also a useful safety bonus of raised bows in collisions. I watched a potentially nasty coming together between a knordkapp and a sirrius last week in surf. Experienced Paddler in the sirrius was confronted by an inexperienced surfer in a knordkapp surfing very rapidly offline towards him. He capsized his sirrius, and you can bet he was glad the knorddapps bows were the shape they were as it rode up and over his hull. He rolled up with no damage to either boat or persons - due in great part to the bow shape of the knordkapp. For *** FLAT *** water use, I think that John's arguments about waterline length make a lot of sense. The QCC boats look not dissimilar in bow and stern shape to an old flat water touring boat I have sitting in my yard, which at 15 or so feet long with a water line length of 15 or so feet, is indeed noticeably quicker on flat water than my sea kayak, with an overall length a couple of feet longer. But I wouldn't want to paddle it in any sort of sea state. Cheers Colin Calder 57º19'N 2º10'W *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Colin wrote; (SNIP) >John has designed some whizzy boats, and I'm aware that he also knows a fair bit >more than I do about the design of traditional kayaks, but I would challenge that >the pointy bows of 'traditional' designs are functional as well as aesthetically >pleasing. It is very rare that I find myself paddling my sea kayak in anything >approaching flat water, and thus it is also very rare for the bow of my boat to be >just "hanging out over the ocean looking pretty". Paddling in any sort of sea the >whole of the bow is frequently immersed, infact paddling in whitecaps or a steep >oncoming sea so is pretty much the whole boat. First let me say that I cannot give a full course in naval architecture on this list so of necessity I must condense what would normally take chapters to explain. Also, I have never said that long overhanging bows do not have a functional purpose on traditional boats that may have lacked adequate reserve buoyancy in the hull through higher topside heights, deck crown, or greater flare. Many people make the mistake of assuming that their boat or the boats they know represent the characteristics of all boats. Just because one boat buries its bow one should not assume all boats bury their bows. Likewise, just because some boats use long overhanging ends to provide reserve buoyancy one should not assume that no other way of providing reserve buoyancy exists. One can easily design boats with short overhangs that do not bury their bows. Our friends in the US NAVY and various other design bodies have studied heavy weather performance and have determined what bow shapes work best. It is no surprise that Naval ships that must, of neccessity, stay at sea regardless of conditions do not have log overhanging bows ala traditional sea kayaks. Being practical peple they design to do the job not to please some aesthetic standard or historical precedent. Even I shape my bows with an aesthetic influence for no matter how much I would like it otherwise, buyers place high value on how a boat looks. I will only go so far. I am very much aware that waves impact on performance and design my boats around that environment. Years of ocean racing and paddling in open water have had their influence on me as well as other designers of short ended boats. Indeed, my boats have a fine reputation for their heavy weather performance (If you can believe the people who paddle them). All theories must come with a test that can prove the theory wrong. In this case, the theory that short ends lack seaworthiness is easily disproved by looking at well designed ships, short ended sea kayaks, short ended canoes and, yes, short ended power boats. > How relevant are the wave making >characteristics of the hull in flat water when the whole boat is being bumped >around by waves orders of magnitude larger? Naval architects have puzzled over this. They puzzled so much that they built wave tanks in which to determine the effects of waves and even measured performance of full size ships. What did they discover? They discovered that fast boats in smooth water tended to be fast boats in rough water. Obviously they qualified that by insisting that adequate volume be built into the topsides and that the topsides get appropriately shaped. J. Gerritsma in his highly regarded studies of sailboat resistance determined that the three major factors for resisatnce in waves were the significant wave heigh, the wave period, and the pitch gyradius. Surprise! Not one word about the length of the overhanging bow. A lot about gyradius, however, which suffers with a long over hanging bow and stern. Gerritsma's paper was deliverd at the 11th Chesapeake Sailing Yacht Symposium sponsored by the friendly people at the Society of Naval Architects and Marine Engineers for those who want to get the paper and read it for themselves. > Has anyone thought about analysing the >shape of the deck, often frequently awash ? Absolutely. However, some design boats to keep the decks dry in all but extraordinary conditions. If a boat spends a lot of time with its deck awash you might want to ask the question, Why? And, then consider if there is no other way to design a boat. >Which has more windage a low flat deck with balanced raised bows and stern with >buyancy far forward, or a high angled deck with square bow and stern ? This is an easy one. The short ends with the more streamlined rounded deck. Lots of wind tunnel tests to support this. You might rephrase the question thusly. Which has more windage the unstreamlined flat deck with its attendant turbulence when exposed to the wind and its high unstreamlined ends waving about in the wind or the short ended streamlined deck configuration that minimizes turbulence? >Which is >dryer ? Which is faster in sea conditions ? Once again an easy one. The good old US Navy has guidelines for dry decks (more important on a ship at sea with sailors walking about than on a kayak with the paddler tucked into his cockpit). I will not use space here repeating readily available research but can recommend the whole list of papers by N.K. Bales on seakeeping and seakeeping standards. Fortunately for us the laws of physics remain fairly constant and we can apply what we learn from ships to sea kayaks (always assuming one applies the laws strictly and without twisting them around to suit preconceptions) >I would also argue that flat water speed of a boat is a very poor measure of miles >you can paddle a day at sea, and optimising a boat for wave making resistance >doesn't necessarily make a good sea kayak. You can argue it but you can't prove it :) One does not optimize only for flatwater speed or even wave making resistance. Speed forms one part of the equation. I doubt if Matt Broze or Steve Killing (and certainly not myself) design for flatwater only and yet I am sure all of us try to obtain the lowest resistance possible given the boat's objectives. It helps to have some familiarity with the design process. I recommend Steven Hollisters ppaer on the "Design Spiral" as good reading for those of you who do not design boats and want to get a good idea of what teh designer goes trhough to put a smile of your face. You can find his paper on the New Wave web site (link on my resources page). > I demo'd a P&H spitzbergen at a >symposium in May (an example of a boat designed to be 'fast' with a high waterline >to overall length ratio). (SNIP) One should not asume that a poorly designed boat or one not designed for open water use provides and example of all short ended boats anymore that one should assume that a really poor example of a traditionally shaped boat is an example of all traditionally shaped boats. If the readers on Paddle wise will refrain from telling me their horror stories about poorly designed short ended boats I will refrain from telling my horror stories about long ended boats. >They have the added benefit that the shape will ride up over objects in their >path - apparently important for the traditional hunter landing and launching from >ice floes, but more importantly for the paddler today essential for a number of >rescues. Maybe of minor concern but there is also a useful safety bonus of raised >bows in collisions. I watched a potentially nasty coming together between a >knordkapp and a sirrius last week in surf. Experienced Paddler in the sirrius was >confronted by an inexperienced surfer in a knordkapp surfing very rapidly offline >towards him. He capsized his sirrius, and you can bet he was glad the knorddapps >bows were the shape they were as it rode up and over his hull. He rolled up with >no damage to either boat or persons - due in great part to the bow shape of the >knordkapp. Well I can't argue that. If I were designing my boats for collisions I would certainly give them more sloping bows and maybe even knife sharp tips so that I would win the fight after the collision. I, and a lot of other designers, design for paddling not colliding. But if surfing bumper cars turns you on, by all means buy a Nordkapp. Of course, my boats would ride up over a capsized Sirius too, so I fail to see the point. I guess I have no sympathy for paddlers who cannot understand the simple rules of surfing and it is no wonder that so many surfers like my nephew (a pretty good competitive surfer in his younger days) consider kayakers a menace on the waves. , >For *** FLAT *** water use, I think that John's arguments about waterline length >make a lot of sense. The QCC boats look not dissimilar in bow and stern shape to >an old flat water touring boat I have sitting in my yard, which at 15 or so feet >long with a water line length of 15 or so feet, is indeed noticeably quicker on >flat water than my sea kayak, with an overall length a couple of feet longer. But >I wouldn't want to paddle it in any sort of sea state. Well, maybe had it been designed by a more competent designer it could have done both or maybe it was designed by a competent designer who, if asked to make the boat suitable for open water would have done so and still kept his short ends. In any case, the long overhanging bows increase the moment of inertia and add weight in the least desireable place. I respect Colin's opinions. I have a few that I cherish myself. In this case, however, we have a wealth of information derived from many studies into the performance of boats in rough water spanning many years. With this at our hands we can temper our opinions with more objective information. I will submit that my statements on the QCC web site have support from a number of highly respected sources which I have listed in this message and in my web site on my "resources" page. Rather than get into an interminable argument over "my opinion" versus "your opinion" I suggest that interested parties read the literature first and then debate it with the naval architect or scientist who wrote it. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt Broze http://www.marinerkayaks.com -----Original Message----- From: 735769 <735769_at_ican.net> To: paddlewise <paddlewise_at_lists.intelenet.net> Date: Friday, July 23, 1999 10:42 AM Subject: Re: [Paddlewise] QCC boats and water line length ........ John Winters wrote: >Many people make the mistake of assuming that their boat or the boats they >know represent the characteristics of all boats. Just because one boat >buries its bow one should not assume all boats bury their bows. Likewise, >just because some boats use long overhanging ends to provide reserve >buoyancy one should not assume that no other way of providing reserve >buoyancy exists. One can easily design boats with short overhangs that do >not bury their bows. Our friends in the US NAVY and various other design >bodies have studied heavy weather performance and have determined what bow >shapes work best. It is no surprise that Naval ships that must, of >neccessity, stay at sea regardless of conditions do not have log overhanging >bows ala traditional sea kayaks. Being practical peple they design to do the >job not to please some aesthetic standard or historical precedent. I agree with most of this but I think you are reaching by bringing in naval ships. Being practical the navy isn't going to add a whole lot of cost to the ship by creating expensive overhang (even though it might well make the ship drier during a hurricaine) especially if an adequate hull for most rough conditions can be built much more cheaply using some rake and a lot of flare above the bow. This may create more spray in huge seas than the finer longer bow would but in a ship spray is far preferable to green water washing over the bow. I think John is stretching here by using the shape of Navy ships to make a point about kayaks. First kayaks often operate in far rougher relative wave conditions than Naval ships ever see, steep 16 to 20 foot long wind waves are common to kayaking but the equivalent seas to a 500 foot long naval ship probably do not exist in our oceans, and therefore the Navy does not need to design for them. Looking at the QCC kayak pictures on their website the bows I see bear very little resemblence to that of a Navy ship either so I don't see how that comparison is valid to the kayaks that were under discussion. Navy ships have far more rake and flare. <Snip> > All theories >must come with a test that can prove the theory wrong. In this case, the >theory that short ends lack seaworthiness is easily disproved by looking at >well designed ships, short ended sea kayaks, short ended canoes and, yes, >short ended power boats. As a group I have never thought of open canoes as seaworthy (well maybe a short rockered whitewater "open" canoe packed full of flotation). As I said above ships operate in a different environment than kayaks relative to wave sizes and steepnesses, although I'll agree naval ships offer the closest comparisons to long narrow kayaks that exist in the ship world. After designing our first Mariner (18'-5"x 20.5") I was surprised that most of the relationships between the dimensions were almost identical to those of a naval destroyer. There are many ways to skin a cat so I am sure kayaks without rake can be made to not pearl their bows. The only question I'd have is what else did you have to give up to do it? Fuller bow sections below the waterline are likely to mean more harsh pounding in waves and more of the "kayak on a spit" effect as two waves lift the narrow ends and suspend the middle in the trough between them. The proof is really in the paddling and all this theoretical talk pales next to a test paddle of many different kayaks in rough conditions. I have paddled dozens and dozens of single kayaks in rough conditions and as a general rule: longer kayaks, finer ended kayaks, lower bowed (and over all lower) kayaks, those with less overhang, those with less flare forward, those with lower or flater foredecks, and those decks that sloped inward down too close to the waterline in the foot and knee area (even though high and v-ed--the waves glance up off the slope into the cockpit), were more likely to have green water over the cockpit. Those with less rocker and rake in the bow also tended to get their generally more vertically sided bows trapped underwater in following seas and then broached more readily around the pinned bow. That said sometimes kayaks surprise me and do not perform as I have predicted based on my past experience. I always love it when that happens because that's when I get to learn something new. I know someone on this list has one of John's kayaks out here in Seattle because I have seen it. If you are reading this post lets go paddling on a rougher day (or through the Montlake Cut on a busy summer Sunday) so I can see for myself if John's design is an exception to my experience with bows with little or no rake. > <SNIP> >Gerritsma in his highly regarded studies of sailboat resistance determined >that the three major factors for resisatnce in waves were the significant >wave heigh, the wave period, and the pitch gyradius. Surprise! Not one word >about the length of the overhanging bow. A lot about gyradius, however, >which suffers with a long over hanging bow and stern. GYRADIUS? If you insist on using words I can't find in a nautical, scientific or Webster's dictionary please define them for us. Is pitch gyradius related to the moment of inertia as I'm imagining? I think you might be reaching here as well. I'm having trouble even picturing a displacement sailboat without a lot of overhang at the bow (and sailboats have a much different shape from a kayak, so I question the relevence). I don't know but I'll bet Gerritsma advocated keeping the ends of the sailboat light to reduce the "pitch gyradius" and didn't mention overhang at the ends at all because that wasn't something he experimented with. <SNIP> >Fortunately for >us the laws of physics remain fairly constant and we can apply what we learn >from ships to sea kayaks (always assuming one applies the laws strictly and >without twisting them around to suit preconceptions). Big waves do not get as steep as small waves so kayaks operate in rougher conditions than ships, same physics, different scale. Salt water waves (where most Navy vessels operate) do not get as steep as fresh water waves (where a lot of sea kayaks operate). Deep water waves (where ships operate) are not as steep as waves steepened by shallow water (surf) where sea kayaks sometime operate. I'm the first to admit that much can be learned from the study of "Ships in Rough Water". (In fact the book by that name--by Kent--was very influential in the design of our first kayak.) However, the situations are not totally analagous. <SNIP> >One should not asume that a poorly designed boat or one not designed for >open water use provides and example of all short ended boats anymore that >one should assume that a really poor example of a traditionally shaped boat >is an example of all traditionally shaped boats. If the readers on Paddle >wise will refrain from telling me their horror stories about poorly designed >short ended boats I will refrain from telling my horror stories about long >ended boats. Yes, it always gauls me too when I hear sweeping generalizations made from one or two examples. However, I have paddled over 500 single sea kayaks. While most of the paddles were for 1/2 hour or less in relatively mild conditions I have tried a lot of kayaks in rough sea conditions and many more times I have used the steep waves in boat wakes (and often their reflections in a narrow vertically sided channel) and steep fresh water wind waves bouncing off the floating bridge during storms to simulate rough wave conditions. I have done this partly because I find paddling in rough conditions great fun but I use an untried kayak when I can for the purpose of trying to find out what features of a kayak create which results. So if you think my opinions are all wet, I guess I'd have to agree. ;-) Colin wrote: >>They have the added benefit that the shape will ride up over objects in >their >>path - apparently important for the traditional hunter landing and >launching from >>ice floes, but more importantly for the paddler today essential for a >number of >>rescues. Maybe of minor concern but there is also a useful safety bonus of >raised >>bows in collisions. I watched a potentially nasty coming together between a >>knordkapp and a sirrius last week in surf. Experienced Paddler in the >sirrius was >>confronted by an inexperienced surfer in a knordkapp surfing very rapidly >offline >>towards him. He capsized his sirrius, and you can bet he was glad the >knorddapps >>bows were the shape they were as it rode up and over his hull. He rolled up >with >>no damage to either boat or persons - due in great part to the bow shape of >the >>knordkapp. John responded: >Well I can't argue that. If I were designing my boats for collisions I would >certainly give them more sloping bows and maybe even knife sharp tips so >that I would win the fight after the collision. I, and a lot of other >designers, design for paddling not colliding. But if surfing bumper cars >turns you on, by all means buy a Nordkapp. I think you are both missing the point here although both are right in what you said. We do design for collisions but not just with other kayaks. I often purposely collide with the shoreline at full speed. I skid right up on it (if the beach is sand or rounded rocks and the barnacles aren't too thick). That way I can step out on dry land with dry feet. Most kayaks I have seen with little rake at the bow tend to stick into the beach and stop dead within a few feet. Often the designers of boats like this tell the public the proper way to land on a beach is at a shallow angle. The absurdity of this approach is very apparent on the TASK (now TAPS) beginners paddling video where the "proper" landing technique is being demonstrated. The paddler is having a devil of a time getting out of his kayak what with the four to six inch high waves slapping against the side of his boat. When he does step out the little waves knock the boat into his legs. Imagine bigger waves and breaking ones on steeper beaches. One pitch black Baja evening I was paddling back to our campsite from a nice dinner in a little cantina. Out of the darkness loomed a large spit blocking our way. It was made up of large volcanic boulders so fine grained they tinkled like glass. Imagine a bank of channelized river rip-rap made from sharp edged obsidian. I turned to parallel the bank to go around it. The phosphoresence there was incredible in the pitch black night. it was so bright it hurt my dark adapted eyes. I became immersed in being able to see how the water flowed and swirled around my paddle blade. I watched the phosphoresent flow around the blade as I increased my speed because it could reveal a lot about how a paddle works that is usually hidden from view. Upon reaching top speed I heard and awful bang, crash and clatter as my highly raked bow lept skyward over the rip-rap (that had curved around in front of me in the blackness so I hit it head-on) and it came to a stop about three feet higher than the water with me teetering in the air while trying to reach way down to the water and brace to keep my balance and not tumble over. I slid (bang, bang, splash) backwards down into the water, luckily still dry and upright. Had I not had a raked bow I might have broken off the footpedals or had they been strong enough maybe broken my ankles. Maybe I would have punched in the bow or knocked a hole in it. This kayak is still our demo after13 years of regular use and the scratches from the sharp edged volcanic boulders (still clearly visible) were the only damage sustained. Unlikely you readers will be as stupid as me but I'd rather glance up over the unseen deadhead, below surface rock hidden by the suns reflection, or the underwater log in the waterway (all of which I have hit while moving at a good clip) than come to a sudden bone grinding halt. Once my brother glanced off my (quickly) overturned hull in big surf too and I was glad there was rocker and rake in his hull so no damage was done. I'll admit that for most paddlers this is an extremely rare. I know your may be thinking these are all fun little stories but certainly not everyday occurances for you or most other sea kayakers. You are right, so I will get to my real point (the one I think has been missed). Without enough rake and rocker a SEA kayak will push kelp or seaweed in front of it until it is forced to a stop rather than be able to slide easily over its slippery surface. On the West Coast the sea can be choked with kelp for miles. Even when it isn't, paddling in the kelp that does exists is often the most effective way to avoid BOOMERS. Breakers will tear kelp loose from the bottom so if you are in the kelp you know that not too many waves have been breaking there (not impossible just unlikely). We are so cognizant of this benifit of rake most of our kayaks are also raked at the stern so they can back up over kelp as well as slide over it forward. In steep waves too low or too fine a bow can bury itself under a mass of kelp and be very difficult to extract, especially from the stern if a rudder also makes pushing it off with the paddle difficult. <snip> >In any case, the long overhanging bows increase the moment of inertia and >add weight in the least desireable place. In a loaded sea kayak (which is the time it is most likely to put its bow under) this increase in inertia would be insignificant. Even in an empty sea kayak it would be quite small. Your argument is also assuming the same waterline length. I would argue with the primacy of waterline length here because, as the QCC website so rightly points out, more waterline length increases wetted surface and other things being equal that increases drag. A long waterline is essential to a racing kayak being operated at top speed but that extra waterline length is often a detriment to a sea kayak where it likely increases cruising resistence but more importantly often decreases controlability and responsiveness. > >I respect Colin's opinions. I have a few that I cherish myself. In this >case, however, we have a wealth of information derived from many studies >into the performance of boats in rough water spanning many years. With this >at our hands we can temper our opinions with more objective information. All the studies in the world don't mean much to me compared with test paddles of real kayaks in real conditions. My advice to kayak buyers is to paddle as many kayaks as you can and then take your favorites out into wind and waves and compare them head to head. You will know what is right for you without having to listen to all the confusing arguments for and against this feature or that and what study of ships or sailboats proved what. If at all possible don't buy a kayak without trying it out, preferably in some wind and waves! Matt Broze http://www.marinerkayaks.com *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt wrote; (Large SNIP) Matt, when you have read the papers you can tell me if I have interpreted them incorrectly. The Navy has never had much concern for costs where performance of ships at sea is concerned. How do I know? From my years building Navy ships and sailing with a senior officer from the Bureau of Ships. Perhaps Matt has better background than that. I would like to hear why they would place cost above performance when Matt is paying the bills via his taxes. :) >As a group I have never thought of open canoes as seaworthy (well maybe a >short rockered whitewater "open" canoe packed full of flotation). I guess you had to have been there to appreciate the seaworthiness of open canoes. or even open boats in general. Like Viking ships, the open boat that Bligh sailed, or the Umiaks, etc. Some some experience with them helps. . >As I said >above ships operate in a different environment than kayaks relative to wave >sizes and steepnesses, although I'll agree naval ships offer the closest >comparisons to long narrow kayaks that exist in the ship world. After >designing our first Mariner (18'-5"x 20.5") I was surprised that most of the >relationships between the dimensions were almost identical to those of a >naval destroyer. Ain't that neat? >I know someone on this list has one of John's kayaks out here in Seattle >because I have seen it. If you are reading this post lets go paddling on a >rougher day (or through the Montlake Cut on a busy summer Sunday) so I can >see for myself if John's design is an exception to my experience with bows >with little or no rake. Boy, I can apperciate how unbaised that will be. :) >GYRADIUS? If you insist on using words I can't find in a nautical, >scientific or Webster's dictionary please define them for us. Is pitch >gyradius related to the moment of inertia as I'm imagining? I think you >might be reaching here as well. I'm having trouble even picturing a >displacement sailboat without a lot of overhang at the bow (and sailboats >have a much different shape from a kayak, so I question the relevence). I >don't know but I'll bet Gerritsma advocated keeping the ends of the sailboat >light to reduce the "pitch gyradius" and didn't mention overhang at the ends >at all because that wasn't something he experimented with. Sorry for using a word you don't find familiar. I don't now wat you have read so you have the advantage of me here. I suggest you read the paper and discuss this with Gerritsma. > >Big waves do not get as steep as small waves so kayaks operate in rougher >conditions than ships, same physics, different scale. Salt water waves >(where most Navy vessels operate) do not get as steep as fresh water waves >(where a lot of sea kayaks operate). Deep water waves (where ships operate) >are not as steep as waves steepened by shallow water (surf) where sea kayaks >sometime operate. I'm the first to admit that much can be learned from the >study of "Ships in Rough Water". (In fact the book by that name--by >Kent--was very influential in the design of our first kayak.) However, the >situations are not totally analagous. Yes, they are. The Navy and Coast Guard also operate in fresh water. >So if you think my opinions are all wet, I guess I'd have to agree. ;-) I failed to keep track of the boats I have paddled or sailed. >I think you are both missing the point here although both are right in what >you said. We do design for collisions but not just with other kayaks. I >often purposely collide with the shoreline at full speed. I skid right up on >it (if the beach is sand or rounded rocks and the barnacles aren't too >thick). Gee I do that too with my boats. Maybe I am just a lucky guy sinvce my boatrs are designed all wrong. . > ><snip> >>In any case, the long overhanging bows increase the moment of inertia and >>add weight in the least desireable place. > >In a loaded sea kayak (which is the time it is most likely to put its bow >under) this increase in inertia would be insignificant. Do you have teh proff of this? Even in an empty sea >kayak it would be quite small. Your argument is also assuming the same >waterline length. I would argue with the primacy of waterline length here >because, as the QCC website so rightly points out, more waterline length >increases wetted surface and other things being equal that increases drag. >A long waterline is essential to a racing kayak being operated at top speed >but that extra waterline length is often a detriment to a sea kayak where it >likely increases cruising resistence but more importantly often decreases >controlability and responsiveness. Called design optimization >> >>I respect Colin's opinions. I have a few that I cherish myself. In this >>case, however, we have a wealth of information derived from many studies >>into the performance of boats in rough water spanning many years. With this >>at our hands we can temper our opinions with more objective information. > >All the studies in the world don't mean much to me compared with test >paddles of real kayaks in real conditions. My advice to kayak buyers is to >paddle as many kayaks as you can and then take your favorites out into wind >and waves and compare them head to head. You will know what is right for you >without having to listen to all the confusing arguments for and against this >feature or that and what study of ships or sailboats proved what. >If at all possible don't buy a kayak without trying it out, preferably in >some wind and waves! > >Matt Broze >http://www.marinerkayaks.com > > > >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.paddlewise.net/ >*************************************************************************** > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Hi- Thank you guys for this discussion. What a great list this is! In between your last 2 letters I got one with a wonderful quote in its sig (don't know why it called Paddlewise to mind ;-)): "Scientists are treacherous allies on committees, for they are apt to change their minds in response to arguments." - C.M. Bowra, 1898-1971 I too would like to have the definition of "pitch gyradius". e Elaine Harmon - eilidh_at_dc.seflin.org - eharmon_at_cs.miami.edu *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt wrote; (SNIP) >Being practical the navy isn't going to add a whole lot of cost to the ship >by creating expensive overhang (even though it might well make the ship >drier during a hurricaine) especially if an adequate hull for most rough >conditions can be built much more cheaply using some rake and a lot of flare >above the bow. This may create more spray in huge seas than the finer longer >bow would but in a ship spray is far preferable to green water washing over >the bow. (Large SNIP) Matt's experience with the Navy differs from mine and certainly differs from the Navy design standards. My experience working on their ships suggests that the Navy has more concern over performance and safety than cost. Rather remarkably they prefer not to have their sailors washed overboard. I sailed with a senior officer from the Bureau of Ships for a few years and he confirmed this. Of what importance is cost when you are spending Matt's tax money to build the ship. :-) Matt says Navy ships do not encounter the kinds of conditions that sea kayaks encounter. I guess the Victory at Sea series was doctored and my time aboard ships a foggy haze of imagination (not to mention my ocean racing in large yachts). Perhaps Matt is thinking only of the largest ships of the Navy and Coast Guard. In any case you will find a particularly fascinating picture - possibly a fabrication - of a Coast Guard lifeboat (short ended to keep cost down) running the breakers at Yaquina Bay Oregon in Skenes Elements of Yacht Design. My brother served in the Coast Guard and he has some interesting tales of "little" waves and "big" ships. Maybe he was smoking too much wacky tobaccy and imagined it all. I particularly disagree with Matt's comments about open boats. Matt makes much of paddling experience and having paddled open canoes extensively on the Great Lakes and having paddled around the northern tip of Labrador in open canoes I would suggest that I have some experience with their seaworthiness. One could also learn a bit about seaworthiness from open Viking ships, Umiaks, dories, and even Captain Bligh's open boat. HMMM. All short ended (relative to sea kayaks) too. Regarding the remainder of Matt's post, my suggestion that one read the papers I mentioned in my post will save a lot of time. If one disagrees strongly, one can skirt the middleman and argue with the author(s). I have passed along what I have learned from my studies, my instructors, my reading, my experience paddling and working in yacht design offices. Unfortunately I failed to keep count of the kayaks I have paddled so if the reader considers spending a little time in a lot of kayaks valuable then I recommend you embrace Matt's opinions. Finally, I apologise for the term "gyradius". Many people use "radius of gyration". Matt has the advantage of me here as he knows what words he and others know. I use them as I was taught. One can find the term used in such books as Introduction to Naval Architecture, The Symmetry of Sailing, Seaworthiness, the Forgotten Factor, Principles of Yacht Design, and maybe some others. I also use English spellings such as "colour" for the American "color". I hope this does not cause any problems for those who have no familiarity with English as written by the English. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Pease ignore this post as it was sent mistakenly before I edited it. I often write quickly and then edit later in an effort to make teh post more clear. -----Original Message----- From: 735769 <735769_at_ican.net> To: paddlewise_at_lists.intelenet.net <paddlewise_at_lists.intelenet.net> Date: Saturday, July 24, 1999 8:24 AM Subject: Re: [Paddlewise] QCC boats and water line length ........ >Matt wrote; > >(Large SNIP) > >Matt, when you have read the papers you can tell me if I have interpreted >them incorrectly. > > >The Navy has never had much concern for costs where performance of ships at >sea is concerned. How do I know? From my years building Navy ships and >sailing with a senior officer from the Bureau of Ships. Perhaps Matt has >better background than that. I would like to hear why they would place cost >above performance when Matt is paying the bills via his taxes. :) > > > >>As a group I have never thought of open canoes as seaworthy (well maybe a >>short rockered whitewater "open" canoe packed full of flotation). > > >I guess you had to have been there to appreciate the seaworthiness of open >canoes. or even open boats in general. Like Viking ships, the open boat that >Bligh sailed, or the Umiaks, etc. Some some experience with them helps. > >. > >>As I said >>above ships operate in a different environment than kayaks relative to wave >>sizes and steepnesses, although I'll agree naval ships offer the closest >>comparisons to long narrow kayaks that exist in the ship world. After >>designing our first Mariner (18'-5"x 20.5") I was surprised that most of >the >>relationships between the dimensions were almost identical to those of a >>naval destroyer. > >Ain't that neat? > > >>I know someone on this list has one of John's kayaks out here in Seattle >>because I have seen it. If you are reading this post lets go paddling on a >>rougher day (or through the Montlake Cut on a busy summer Sunday) so I can >>see for myself if John's design is an exception to my experience with bows >>with little or no rake. > >Boy, I can apperciate how unbaised that will be. :) > > > >>GYRADIUS? If you insist on using words I can't find in a nautical, >>scientific or Webster's dictionary please define them for us. Is pitch >>gyradius related to the moment of inertia as I'm imagining? I think you >>might be reaching here as well. I'm having trouble even picturing a >>displacement sailboat without a lot of overhang at the bow (and sailboats >>have a much different shape from a kayak, so I question the relevence). I >>don't know but I'll bet Gerritsma advocated keeping the ends of the >sailboat >>light to reduce the "pitch gyradius" and didn't mention overhang at the >ends >>at all because that wasn't something he experimented with. > >Sorry for using a word you don't find familiar. I don't now wat you have >read so you have the advantage of me here. I suggest you read the paper and >discuss this with Gerritsma. > > >> >>Big waves do not get as steep as small waves so kayaks operate in rougher >>conditions than ships, same physics, different scale. Salt water waves >>(where most Navy vessels operate) do not get as steep as fresh water waves >>(where a lot of sea kayaks operate). Deep water waves (where ships operate) >>are not as steep as waves steepened by shallow water (surf) where sea >kayaks >>sometime operate. I'm the first to admit that much can be learned from the >>study of "Ships in Rough Water". (In fact the book by that name--by >>Kent--was very influential in the design of our first kayak.) However, the >>situations are not totally analagous. > >Yes, they are. The Navy and Coast Guard also operate in fresh water. > >>So if you think my opinions are all wet, I guess I'd have to agree. ;-) > >I failed to keep track of the boats I have paddled or sailed. > > >>I think you are both missing the point here although both are right in what >>you said. We do design for collisions but not just with other kayaks. I >>often purposely collide with the shoreline at full speed. I skid right up >on >>it (if the beach is sand or rounded rocks and the barnacles aren't too >>thick). > >Gee I do that too with my boats. Maybe I am just a lucky guy sinvce my >boatrs are designed all wrong. >. > > >> >><snip> >>>In any case, the long overhanging bows increase the moment of inertia and >>>add weight in the least desireable place. >> >>In a loaded sea kayak (which is the time it is most likely to put its bow >>under) this increase in inertia would be insignificant. > > >Do you have teh proff of this? Even in an empty sea >>kayak it would be quite small. Your argument is also assuming the same >>waterline length. I would argue with the primacy of waterline length here >>because, as the QCC website so rightly points out, more waterline length >>increases wetted surface and other things being equal that increases drag. >>A long waterline is essential to a racing kayak being operated at top speed >>but that extra waterline length is often a detriment to a sea kayak where >it >>likely increases cruising resistence but more importantly often decreases >>controlability and responsiveness. > >Called design optimization >>> >>>I respect Colin's opinions. I have a few that I cherish myself. In this >>>case, however, we have a wealth of information derived from many studies >>>into the performance of boats in rough water spanning many years. With >this >>>at our hands we can temper our opinions with more objective information. >> >>All the studies in the world don't mean much to me compared with test >>paddles of real kayaks in real conditions. My advice to kayak buyers is to >>paddle as many kayaks as you can and then take your favorites out into wind >>and waves and compare them head to head. You will know what is right for >you >>without having to listen to all the confusing arguments for and against >this >>feature or that and what study of ships or sailboats proved what. >>If at all possible don't buy a kayak without trying it out, preferably in >>some wind and waves! >> >>Matt Broze >>http://www.marinerkayaks.com >> >> >> >>************************************************************************** * >>PaddleWise Paddling Mailing List >>Submissions: paddlewise_at_lists.intelenet.net >>Subscriptions: paddlewise-request_at_lists.intelenet.net >>Website: http://www.paddlewise.net/ >>************************************************************************** * >> > >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.paddlewise.net/ >*************************************************************************** > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt Broze http://www.marinerkayaks.com -----Original Message----- From: 735769 <735769_at_ican.net> To: paddlewise_at_lists.intelenet.net <paddlewise_at_lists.intelenet.net> Date: Saturday, July 24, 1999 6:59 AM Subject: Re: [Paddlewise] QCC boats and water line length ........ >Matt wrote; >(SNIP) > > >>Being practical the navy isn't going to add a whole lot of cost to the ship >>by creating expensive overhang (even though it might well make the ship >>drier during a hurricaine) especially if an adequate hull for most rough >>conditions can be built much more cheaply using some rake and a lot of >flare >>above the bow. This may create more spray in huge seas than the finer >longer >>bow would but in a ship spray is far preferable to green water washing over >>the bow. > >(Large SNIP) > >Matt's experience with the Navy differs from mine and certainly differs from >the Navy design standards. My experience working on their ships suggests >that the Navy has more concern over performance and safety than cost. Rather >remarkably they prefer not to have their sailors washed overboard. >I sailed >with a senior officer from the Bureau of Ships for a few years and he >confirmed this. One of the very reasons I suggested they would probably trade more spray for less green water on deck. Washing away the superstructure is another. I'll agree that compared to a business the navy is far more performance oriented than dollar oriented, but cost is always a consideration although not as important as the lives of the crew and the safety of the ship. If the goals can be achieved with less cost then that is likely the way it will be done. If a benifit is minor and costly and only applicable in rare circumstances then a lot of money will not be spent that could be used to better effect elsewhere. > >Of what importance is cost when you are spending Matt's tax money to build >the ship. :-) My pockets are only so deep so cost eventually will rear its ugly head. > >Matt says Navy ships do not encounter the kinds of conditions that sea >kayaks encounter. I guess the Victory at Sea series was doctored and my time >aboard ships a foggy haze of imagination (not to mention my ocean racing in >large yachts). Perhaps Matt is thinking only of the largest ships of the >Navy and Coast Guard. In any case you will find a particularly fascinating >picture - possibly a fabrication - of a Coast Guard lifeboat (short ended to >keep cost down) running the breakers at Yaquina Bay Oregon in Skenes >Elements of Yacht Design. My brother served in the Coast Guard and he has >some interesting tales of "little" waves and "big" ships. Maybe he was >smoking too much wacky tobaccy and imagined it all. Yes, I was considering the navy ships that would be relevent to this discussion. Those with roughly the same dimension and performance relationships as kayaks. These would be displacement hulled ships, not planing PT boats or stubby little surf lifeboats (although the picture I have of one (plate 39 in the 1980 edition of "Waves and Beaches" by Bascom shows substantial rocker and rake--I est. 60 degrees-- and lots of flare). My point was that a kayak operates quite often in wave conditions that if they were to be scaled up to the size of a similar shaped ship would quickly destroy it. The reason that ships have not all been destroyed by conditions like this already is because these conditions are extremely rare to non-existant. My understanding (I believe this came from "Ships in Rough Water" by Kent) is that the most difficult waves for a long vessel are those with roughly the same wavelength as the vessel is long. Wind waves in deep water topple into whitecaps when their height is about 1/7th their wavelength. This means that they cannot get steeper than this except under special circumstances such as clapotis. For instance, a 14 foot long kayak will be operating in its most trying condition with waves that are about 2 feet high and 14 feet long. It doesn't take much time to create seas like this with any wind of 20 knots or more. Eventually the wind will create waves that pass through a stage where they reach this steepness (2 foot whitcaps--- and here the angle of the wave crest will be about 120 degrees). Now lets up the scale about 50 times. A 700 foot ship would be operating in 100 foot high waves that are about 700 feet between crests to get the equivalent roughness of seas relative to its size. According to Bascom (page 51) a 50 knot wind blowing steadily over 1420 miles of fetch for 69 hours will create a sea where the average wave is 48 feet tall. Most of the wave energy will be in waves of about 1400 feet long. These waves will be less than 1/2 as tall and twice as long, or only 1/4 AS STEEP, as the 2 foot high whitecapping waves are on a 14 foot kayak. Furthermore even waves this big are only going to happen under the most freakish of conditions. 1420 miles is a long way to have to blow a 50 knot wind over for 69 hours to get seas as rough 1/4 as rough as a kayak regularily operates in. I don't know what it would take to have the average wave reach 100 feet with an average wavelength of 700 feet but I don't think I will live to see it. The fact that the far milder waves which were chosen to exite us about "Victory at Sea" or were big enough to impress the relatives with only demonstrates their rarity. Waves of the same relative size and steepness as create problems for a kayak would quickly destroy the far more delicate ships that suffer with the change in scale because mass increases by the cube but strength only increases by the square. My point is that a bow shape perfectly adequate for a ship may be very wet when scaled down to kayak size. > >I particularly disagree with Matt's comments about open boats. I believe I said open canoes not open boats. >Matt makes >much of paddling experience and having paddled open canoes extensively on >the Great Lakes and having paddled around the northern tip of Labrador in >open canoes I would suggest that I have some experience with their >seaworthiness. One could also learn a bit about seaworthiness from open >Viking ships, Umiaks, dories, and even Captain Bligh's open boat. HMMM. All >short ended (relative to sea kayaks) too. Although I fail to see why John has expanded the discussion to these other open boats, I believe that in general umiaks and dories are more seaworthy than open canoes too. This is partly because they are shorter and have higher freeboard and more flare and yes more rake to the bows and sterns. However if forced to chose a craft that I had to paddle or row for a few hours in any direction you want to chose in a 35 knot wind the kayak would be my first choice hands down and the canoe would be my last (even if I sat in the bottom to lower the center of gravity and used a kayak paddle so I could quickly brace on either side). The problem with any boat that doesn't have a lid on it is that the profile has to be high enough to avoid swamping by waves. Unfortunately this extra freeboard adds to the windage so the wind can blow it around a lot more. > >Regarding the remainder of Matt's post, my suggestion that one read the >papers I mentioned in my post will save a lot of time. If one disagrees >strongly, one can skirt the middleman and argue with the author(s). I have >passed along what I have learned from my studies, my instructors, my >reading, my experience paddling and working in yacht design offices. >Unfortunately I failed to keep count of the kayaks I have paddled so if the >reader considers spending a little time in a lot of kayaks valuable then I >recommend you embrace Matt's opinions. Because I keep track of the handling and performance of most of the kayaks I test on a spreadsheet in order to remind myself of the kayaks characteristics later, it is a simple matter to count the number of dates in the "month/year tested field to know how many I have tried. Pretty compulsive I know, but we all have our hobbies and one of mine is collecting experiences in a wide variety of watercraft. On the Fourth of July I even got to pedal a wavebike. >Finally, I apologise for the term "gyradius". Many people use "radius of >gyration". Matt has the advantage of me here as he knows what words he and >others know. I use them as I was taught. One can find the term used in such >books as Introduction to Naval Architecture, The Symmetry of Sailing, >Seaworthiness, the Forgotten Factor, Principles of Yacht Design, and maybe >some others. I also use English spellings such as "colour" for the American >"color". I hope this does not cause any problems for those who have no >familiarity with English as written by the English. I still am not sure what "Pitch Gyradius" is. While I read "Seaworthiness,..." a few years ago and much earlier read the relevent parts (and some not so relavent parts) of "Introduction..." and Skene's "Principles..." they were borrowed from a friend or the library so I don't have them handy like you apparently do. Since you are the one who used the word to make your point I fail to see why you haven't made it easy for the rest of us and simply defined the term rather than sending us off to the library to look for it? Wouldn't it have been just as easy for you to type the definition as to list the sources where we might find it? Also, since you think we should read the studies you suggest, at least if we question any of your conclusions, I for one would appreciate learning more about how to find those sources. I assume when you said reading the papers you mentioned will save a lot of time you were refering to your time not ours. I realize I am lazy and should have to muddle around in the library finding this information for myself like you probably had to, but I'm not even sure the information is relevent and just writing (and rewriting when Windows ate it) this post may mean I may not make my deadline for the next accident report in Sea Kayaker. How about doing us curious but lazy folks a favor and either tell us more details about the research you think is relevent or direct us on how to find the source in an efficient way. Sorry about the rant but you can be very frustrating to somebody trying to understand what you are saying and I'll bet I am not alone in feeling this way. I hope to get to test paddle your kayaks one day and I hope they make me reformulate my opinions. When I'm surprised by a kayak is the time I get the chance to learn something new. You needn't worry about me reviewing yours or any other kayak or giving my admittedly subjective opinions about any specific kayak to this group as a whole. Were I not a competitor I might feel freer about doing so, but I will restrain myself and leave the published subjective opinions about kayaks to the subjective reviewers at Sea Kayaker magazine whose axes to grind are probably real but far less obvious than mine. Matt Broze http://www.marinerkayaks.com *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt wrote; (SNIP) >I'll agree that compared to a business the navy is far more performance >oriented than dollar oriented, >but cost is always a consideration although not as important as the lives of >the crew and the safety of the ship. If the goals can be achieved with less >cost then that is likely the way it will be done. If a benifit is minor and >costly and only applicable in rare circumstances then a lot of money will >not be spent that could be used to better effect elsewhere. Absolutely. If you can achieve dry decks in storm conditions with short ends then why shouldn't you? As for rare and minor, well, maybe more time at sea in ships or yachts will affect your opinion or what constitutes rare and minor. > >Yes, I was considering the navy ships that would be relevent to this >discussion. >Those with roughly the same dimension and performance >relationships as kayaks. These would be displacement hulled ships, not >planing PT boats or stubby little surf lifeboats (although the picture I >have of one (plate 39 in the 1980 edition of "Waves and Beaches" by Bascom >shows substantial rocker and rake--I est. 60 degrees-- and lots of flare). Absolutely. By the way, what do you consider a lot of rake and a lot of flare? Might be helpful to define "a lot" . (SNIP about wave sizes applicable to ships longer than breaking storm waves) >I believe I said open canoes not open boats. I particularly disagree with what you said about open canoes too (see below). (SNIP) . > >Although I fail to see why John has expanded the discussion to these other >open boats, I believe that in general umiaks and dories are more seaworthy >than open canoes too. I don't see how this expands the discussion. Are not canoes open boats? If not, why not? A study of the boats will reveal that many canoes have similar lines and proportions to many Umiaks, dories,and Viking ships. >This is partly because they are shorter and have >higher freeboard and more flare and yes more rake to the bows and sterns. >However if forced to chose a craft that I had to paddle or row for a few >hours in any direction you want to chose in a 35 knot wind the kayak would >be my first choice hands down and the canoe would be my last (even if I sat >in the bottom to lower the center of gravity and used a kayak paddle so I >could quickly brace on either side). The problem with any boat that doesn't >have a lid on it is that the profile has to be high enough to avoid swamping >by waves. Unfortunately this extra freeboard adds to the windage so the wind >can blow it around a lot more. Yes, open boats do have drawbacks (as do kayaks). However, having cruised open water succesfully in canoes and learned to deal with those drawbacks (just as paddlers learn to deal with the drawbacks of kayaks ) I guess can't appreciate your problems with canoes. (SNIP) >I still am not sure what "Pitch Gyradius" is. >"Seaworthiness,..." a few years ago and much earlier read the relevent parts >(and some not so relavent parts) of "Introduction..." and Skene's >"Principles..." they were borrowed from a friend or the library so I don't >have them handy like you apparently do. Since you are the one who used the >word to make your point I fail to see why you haven't made it easy for the >rest of us and simply defined the term rather than sending us off to the >library to look for it? I thought I did define it by commenting that some people call it the radius of gyration, a term I thought (hoped) you would find familiar. Pitch, or pitching in the context of this discussion, is the angular component of the oscillatory motion of a hull about a transverse axis. The radius of gyration is the square root of the ratio of the mass moment of inertia (referred to body axes) to the mass of the boat. Hope that helps. If not maybe some one with better teaching skills than I can take a try. >Also, since >you think we should read the studies you suggest, at least if we question >any of your conclusions, I for one would appreciate learning more about how >to find those sources. Glad to help with this. Many libraries, universities, professional organizations etc. can supply copies or will search for them. Often on the Internet or by telphone so you can do it from the comfort of your own home. I can't tell you which will work best in the US as I live in Canada and rely upon CISTI, the Canada Institute for Scientific and Technical Information. I think Americans can use it too. I don't recall their web address (I bet a search engine will turn it up without a lot of effort) as I prefer to do it by telephone which is 613-993-9251. You will need an account number and should get their booklet on document searches. Maybe one of you Americans will tell me the best service in the US. Of course, you can also use SNAME for those papers published by them. I think I provided their address in my web page on resources (As I mentioned in my post). Bet they have a web address too but I have never used it. I don't think anyone has to read the papers to question my conclusions. It just helps in the discussion if they do. (see below) >I assume when you said reading the papers you >mentioned will save a lot of time you were refering to your time not ours. All of our time. I have such poor teaching skills. Not only that but, for example, Gerritsma's paper is 13 pages of math. I can't do it justice here. Maybe you can. More importantly, you might read it and come to quite different conclusions from me or might see flaws in the paper(s) that you will want to bring to the attention of the author(s). >realize I am lazy and should have to muddle around in the library finding >this information for myself like you probably had to, but I'm not even sure >the information is relevent and just writing (and rewriting when Windows ate >it) this post may mean I may not make my deadline for the next accident >report in Sea Kayaker. If you don't feel it is relevent then don't look for it. But don't you think you can better judge its relevence after you have read it? >Sorry about the rant but you can be very frustrating to somebody trying to >understand what you are saying and I'll bet I am not alone in feeling this >way. Don't rant, just ask politely. Matt (and readers), my experience, measurements, and testing of boats with long traditionally styled ends suggests that most of the length is wasted weight and length that acts detrimentally to performance. I support these conclusions with what I have read and learned from other boat designers and naval architects. I don't mind changing my mind but I like something more than opinion to change it. I don't think the Internet serves well for in depth debate on complex topics. No one can write fully on much of anything here. For that reason I refer interested readers to sources of more detailed information from whence they can draw their own conclusions. I try to make my point as clearly as I can and as simply as I can and I hope everyone recognises that I and others could say more. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
At 3:45 PM +0100 7/23/99, Colin Calder wrote: >With the recent Maligiaq traffic I followed the links to the QCC web site (re >Maligiaq and the boat he will race) and was very interested in the articles by >John Winters on the site about his kayak designs. > >http://www.qualitycomposites.com/speakboat.htm > >The list comparing overall length vs water line length of many popular sea >kayaks >at: > >http://www.qualitycomposites.com/howlong.htm > >makes interesting reading. > >The general gist of the argument is that any part of the boat which >overhangs the >water line length at bow and stern is a waste of materials, adds weight >etc, and >does nothing for the boats handling or speed. John puts forward: > > "Some traditional designs have as much as two feet of skinny boat >hanging out >over the ocean. It looks pretty but it doesn't do much" John is probably overstating the case when he says: "It looks pretty but it doesn't do much". Simple through-the-water efficiency is not the end all of kayak design. For many kayaks it is probably the last thing the designer looks at after maneuverability, and other handling properties at sea. The goal, generally, is to make as efficient a boat as possible given the other design constraints. This equation is probably reversed for racing kayaks, but most of us are not that interested in racing. We don't know the design constraints of the traditional designers, so we don't know what those overhangs were for. Therefore, we can't really comment about whether they did anything or not. There are generally several ways of solving boat design problems. Long overhangs and plumb-bows with flare, both solve the same problem of keeping the bow above the water in waves. With careful designing it is probably possible to create the exact same lifting response using either solution. However, each solution will have consequences on other aspects of the boat handling characteristics. For example, Navy designers must consider where they will mount the sonar system, or whether the ship will need to be able to get through the Panama Canal. These considerations can not help but impact overall efficiency and sea-handling characteristics. It is an oversimplification to say that the bow of a destroyer is shaped a particular way because that is the _best_ shape for going fast through waves, period. You may be able to say that it is the best shape for going fast through waves for a boat that will fit in a lock and have a sonar system slung under the bow and other considerations I don't know about. For any plumb-bow shape you can imagine, you can always design a higher volume bow with better ability to rise over waves by pulling out the top of the stem to give it more overhang. Making this modification will have consequences on how the boat surfs, how much storage room it has, how fiberglass lies into the mold, and strength running into an obstacle. What the best design is depends wholely on what you are trying to accomplish. I am under the impression that John likes keeping the overall length of his boats short (a good idea for a variety of reasons) and he wants them efficient (always a worthy goal). Combined with other design considerations he chooses a relatively plumb bow. His cat is skinned. Early British sea kayaks were essentially knock-offs of Inuit designs. They buggered with these designs slightly to acheive slightly different properties, but essentially they let someone else skin the cat. Nobody (accept maybe the good Professor) really knows what the Inuits liked about their cats so their method of skinning is not neccesarily the best for us today. For example the early British boats have long overhangs with very little volume in the ends. Looking straight down on some boats, the sheerline is concave on some boats. The leaves very little volume in the overhang for helping the bow over waves. With some of these designs, the first 6" to 12" could be sawed off without affecting the volume much. I don't know what this extra length is good for, but the Inuits probably had a good reason for it. That does not mean it has any usefulness now. Many newer British designs have much fuller overhangs. The designers of these new boats decided more volume in the ends better served their needs. It is possible that British boats will evolve a more plumb bow, but once you are used to the performance characteristics of one style of boat, chances are you will like those characteristics and not want to deviate much in your design choices. Nick Nick Schade Guillemot Kayaks 10 Ash Swamp Rd Glastonbury, CT 06033 (860) 659-8847 Schade_at_guillemot-kayaks.com http://www.guillemot-kayaks.com/ >>>>"It's not just Art, It's a Craft!"<<<< *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Nick wrote: snip > Early British sea kayaks were essentially knock-offs of Inuit designs. snip > It is possible that British boats will evolve a more plumb bow, snip Not so sure about your definition of early. Rob Roy canoes, PBK's, etc spring to mind. 'Early' British sea kayaks were beamy boats, with high decks and plumb bows, and were used to make some impressive sea trips. It wasn't really until the 70's/80's that sea paddlers started to 'knock-off' (I prefer admire ;-) Inuit designs, and the current commercial Inuit derived crop of boats appeared. There are/were however a number of designs (skua, sea tiger for example) that a lot of folk still paddle today that essentially are shorter, wider, high decked, plumb bowed boats. Maybe so called 'British' boats may 'revolve' back to a more plumb bow ;-) Cheers Colin Calder 57º19'N 2º10'W *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Nick wrote; (SNIP) >We don't know the design constraints of the traditional designers, so we >don't know what those overhangs were for. Therefore, we can't really >comment about whether they did anything or not. My comment was not directed at traditional boats. In fact, I have explained elsewhere why some Greenland boats probably needed the long overhangs due to their lack of reserve buoyancy and generally flattish bottoms. Don't know if they adopted their ends because of this or the boats got flat and low because they had long ends first. Interestingly the longish ends seem confined to the Eastern Arctic. (SNIP) >For example, Navy designers must consider where they will mount the sonar >system, or whether the ship will need to be able to get through the Panama >Canal. These considerations can not help but impact overall efficiency and >sea-handling characteristics. It is an oversimplification to say that the >bow of a destroyer is shaped a particular way because that is the _best_ >shape for going fast through waves, period. You may be able to say that it >is the best shape for going fast through waves for a boat that will fit in >a lock and have a sonar system slung under the bow and other considerations >I don't know about. The sonar thing is interesting because some modern boats have more overhang simply so the anchor will clear the sonar dome. If we expand the range of observation to include a wide range of boats and ships we find that short ends with flare predominate. We don't even have to restrict it to modern boats. Viking long boats provide but one good example of short ended boats highly regarded for their ability at sea. My contention has focussed on the net result of the end shape. Building excessively long ends into a boat with little volume (as in the examples Nick provdies later in his post) fit my statement that they look pretty (depends upon one's aesthetic values) but do not do much. I would contend that the very long overhangs of some (not all Greenland boats) stand out because they do differ from most types of boats. Had the Brits used the Aleut boats as a model this discussion might never have taken place and we might be arguing the relative merits of bifid bows. (SNIP) > >Early British sea kayaks were essentially knock-offs of Inuit designs. They >buggered with these designs slightly to acheive slightly different >properties, but essentially they let someone else skin the cat. Nobody >(accept maybe the good Professor) really knows what the Inuits liked about >their cats so their method of skinning is not neccesarily the best for us >today. (SNIP) Quite true to my mind. It seems some may get the idea that I advocate only one specific rake. Not so as a look at the full range of my designs will reveal. I try to suit every hull characteristic to the design purpose. Having designed flatwater canoes, whitewater canoes, racing canoes, power boats, sailboats, sea kayaks for inland use, sea kayaks for offshore use, kayaks for racing, rowing shells, ocean rowing shells, and, yes, one submarine that probably is better having never been built and I have found each had different requirements and, consequently differing end shapes. None have required long low volume overhangs. My comment concerned excessive overhang that serves no useful purpose other than slavish bowing to an arbitrary aesthetic (see Nick's comment on some boats). I have also criticised the rule mandated plumb bows of marathon racing canoes that do not allow seaworthy shapes. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
John wrote; >My comment was not directed at traditional boats. In fact, I have explained >elsewhere why some Greenland boats probably needed the long overhangs due to >their lack of reserve buoyancy and generally flattish bottoms. Don't know if >they adopted their ends because of this or the boats got flat and low >because they had long ends first. Interestingly the longish ends seem >confined to the Eastern Arctic. > Greenlander H.C. Petersen has some interesting comments and anecdotes about overhangs on page 45 of "Skinboats of Greenland". According to Petersen the shape of the stem and stern was "considered especially important in areas where the sea is often covered with a sheet of thin ice". Petersen goes on to relay a story in which one kayaker lived and another died due to the shape of their bows when the kayakers were forced to face into a rapidly advancing sheet of pack ice that could not be outrun. One kayak rose over the ice without damage and the other was forced under, severing the skin, with fatal results. Petersen notes "there are stories of ice cutting through the kayaker as well as the kayak." I find it interesting that Petersen goes on to state that long overhangs were not favored by seal catchers who hunted with harpoons since the long ends slapped the water in choppy conditions and frightened the seals. I looked through the text but could find no mention of the overhangs covering early sonar devices on either the East or West Greenland kayaks. I'm sure that the good doctor would have the scoop.... Greg Stamer Orlando, Florida *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt Broze http://www.marinerkayaks.com -----Original Message----- From: 735769 <735769_at_ican.net> To: paddlewise_at_lists.intelenet.net <paddlewise_at_lists.intelenet.net> Date: Sunday, July 25, 1999 7:23 AM Subject: Re: [Paddlewise] QCC boats and water line length ........ <BIG SNIP> Jophn said: >I don't see how this expands the discussion. Are not canoes open boats? If >not, why not? A study of the boats will reveal that many canoes have similar >lines and proportions to many Umiaks, dories,and Viking ships. Open Canadian canoes are a relatively specific type of craft without a lot of flare and rake as opposed to an umiak or dorie (and I want to exlude the Hiada Canoes from this Canadian canoe group too as they also have a large amounts of rake and a high bow. I find them extremely seaworthy craft. Even the forepiece that I had once assumed to be decorative is hugely functional. I saw some old film footage of a Hiada Canoe full of native paddlers coming straight in through the surf. The bow tilted down until the normally high raked "figurehead" rested on the green water surface in front of the breaker. As the craft surfed the breaker the water divided like Moses was standing on the bow. The water cleanly peeled up and out to each side of the "canoe" falling back to the waters surface just outside the hull which remained dry inside. I was impressed! I objected to bringing the raked and flared open boats into a discussion that was specifically discussing the dryness of a near vertical bow rake. If the examples had been of craft that had similar shape as well as were "open" (say a 327 or 432 canoe) I wouldn't have so much objection. I think the seaworthiness you are claiming for dories and umiaks is because of the high raked and flared ends in spite of them being open boats. In other word you are trying to claim craft to make your point that are actually examples that help make my point about rake and flare rather than yours about the advantages of a vertical rake. <SNIP> I wrote: >>This is partly because they are shorter and have >>The problem with any boat that doesn't >>have a lid on it is that the profile has to be high enough to avoid >swamping >>by waves. Unfortunately this extra freeboard adds to the windage so the >wind >>can blow it around a lot more. John responded: >Yes, open boats do have drawbacks (as do kayaks). However, having cruised >open water succesfully in canoes and learned to deal with those drawbacks >(just as paddlers learn to deal with the drawbacks of kayaks ) I guess can't >appreciate your problems with canoes. Just what drawbacks of kayaks are you alluding to? Please be specific. > >(SNIP) > I wrote: >>I still am not sure what "Pitch Gyradius" is. > John responded >I thought I did define it by commenting that some people call it the radius >of gyration, a term I thought (hoped) you would find familiar. Pitch, or >pitching in the context of this discussion, is the angular component of the >oscillatory motion of a hull about a transverse axis. The radius of gyration >is the square root of the ratio of the mass moment of inertia (referred to >body axes) to the mass of the boat. Hope that helps. If not maybe some one >with better teaching skills than I can take a try. "Radius of gyration" gave me a pretty good idea of what you meant but without an actual definition (I could understand) I couldn't be sure. Is the definition you offered above (which I have trouble understanding--anyone else care to try explaining it to me) the same as the one I found at http://www.unb.ca/web/physics/1040/torque.htm ? (The radius of gyration is the distance k from the axis of rotation at which a single point mass equal to the object's mass M would be put to have the same moment of inertia I as the object.) I think I understand that one so i hope the result is the same. <sNIP> >All of our time. I have such poor teaching skills. Not only that but, for >example, Gerritsma's paper is 13 pages of math. I can't do it justice here. >Maybe you can. More importantly, you might read it and come to quite >different conclusions from me or might see flaws in the paper(s) that you >will want to bring to the attention of the author(s). John you leave one with so little information to go on about what Gerritsma did that now I don't even know if he did an actual experiment or a strickly mathematical one. If I knew a little bit about what he did and why I would be far more likely to accept his conclusions and have a much better idea if your interpretation of them was relevant to the discussion and made sense. You wrote: "Gerritsma in his highly regarded studies of sailboat resistance determined that the three major factors for resisatnce in waves were the significant wave heigh, the wave period, and the pitch gyradius. Surprise! Not one word about the length of the overhanging bow. A lot about gyradius, however, which suffers with a long over hanging bow and stern." My bet is that the reason he said nothing about overhang is that that was never a variable in his "studies". I may find this out yet as Natalie has offered to help find the study. > > > > >>realize I am lazy and should have to muddle around in the library finding >>this information for myself like you probably had to, but I'm not even sure >>the information is relevent and just writing (and rewriting when Windows >ate >>it) this post may mean I may not make my deadline for the next accident >>report in Sea Kayaker. > >If you don't feel it is relevent then don't look for it. But don't you think >you can better judge its relevence after you have read it? Of course, but you wouldnt have had to tell me much about the study for me to have some idea if it was relevant to overhang. For instance had you said: "The study towed six sailboats with varying degrees of overhang but the same pitch gyradius in a towtank at three different wavelengths. It was found that the less overhang the sailboat had the less resistance it had in each of the tests." Would that be relevant? Most likely, but sailboats are not kayaks so if the differences were quite small I might be less likely to accept them as relevant than if the differences were great. If I needed or wanted more details I could search for the study. When you do direct us to the source I for one would appreciate something like (hopefully) a web address or some way where it can be found in an efficient manner. Thanks for all your help and your understanding of my frustration here. Matt Broze http://www.marinerkayaks.com > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Gregg wrote; (SNIP) > >I find it interesting that Petersen goes on to state that long overhangs >were not favored by seal catchers who hunted with harpoons since the long >ends slapped the water in choppy conditions and frightened the seals. I found this interetsing too. When I did my studies of the boats I found some that, with their long low angle bows, would have a "V'd" shape at the waterline as the flattish parts of the bottom lay well aft. Others had the flat portions almost at the waterline. I expected to find more uniformity in the boats based upon Eugene Arima's comment that he felt the Inuit were extraordinarily conservative people. One has to wonder if the variations resulted from the "by eye" method of building or from creative juices flowing. > >I looked through the text but could find no mention of the overhangs >covering early sonar devices on either the East or West Greenland kayaks. >I'm sure that the good doctor would have the scoop.... Talked to the Prof. yesterday and he plans to come over this evening and dictate a post. If I can keep him sober he may have something for tommorrow. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt wrote; >Open Canadian canoes are a relatively specific type of craft without a lot >of flare and rake as opposed to an umiak or dorie (and I want to exlude the >Hiada Canoes from this Canadian canoe group too as they also have a large >amounts of rake and a high bow. I find them extremely seaworthy craft. (SNIP) I guess one needs more experience with Canadian canoes to appreciate the range of shapes etc. > >John responded: >>Yes, open boats do have drawbacks (as do kayaks). However, having cruised >>open water succesfully in canoes and learned to deal with those drawbacks >>(just as paddlers learn to deal with the drawbacks of kayaks ) I guess >can't >>appreciate your problems with canoes. > >Just what drawbacks of kayaks are you alluding to? Please be specific. Difficult to load for one (relative to canoes). Not suitable for transporting family from one camp to another. Don't portage well. Just a few. > >"Radius of gyration" gave me a pretty good idea of what you meant but >without an actual definition (I could understand) I couldn't be sure. Is the >definition you offered above (which I have trouble understanding--anyone >else care to try explaining it to me) Best I can do. Maybe someone with better teaching skills can try. > >John you leave one with so little information to go on about what Gerritsma >did that now I don't even know if he did an actual experiment or a strickly >mathematical one. Based on tank tests at the Delft Tank. My brother wrote an article about about the effect of weight in the ends of a boat for Sea Kayaker that you might find useful. Don't recall the issue but maybe Chris Cunningham does. > >When you do direct us to the source I for one would appreciate something >like (hopefully) a web address or some way where it can be found in an >efficient manner. I would have appreciated it too. Don't know if the paper exists on the web. Not sure I even knew what the web was when I looked for it. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
At 8:45 AM -0400 7/29/99, 735769 wrote: >>When you do direct us to the source I for one would appreciate something >>like (hopefully) a web address or some way where it can be found in an >>efficient manner. > >I would have appreciated it too. Don't know if the paper exists on the web. >Not sure I even knew what the web was when I looked for it. > 735769 (aka John), Do you have a copy yourself? Would you be willing to make copies available to people who asked you nicely? Nick Nick Schade Guillemot Kayaks 10 Ash Swamp Rd Glastonbury, CT 06033 (860) 659-8847 Schade_at_guillemot-kayaks.com http://www.guillemot-kayaks.com/ >>>>"It's not just Art, It's a Craft!"<<<< *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
In a message dated 7/29/99 9:30:57 AM Eastern Daylight Time, 735769_at_ican.net writes: << Talked to the Prof. yesterday and he plans to come over this evening and dictate a post. If I can keep him sober he may have something for tommorrow. >> Oh, please, don't keep him sober. I'm sure he will be a lot more eloquent with a bottle of bubbly under his belt! Sandy Kramer Miami, FL *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
On Thu, 29 Jul 1999 Sandykayak_at_aol.com wrote: > In a message dated 7/29/99 9:30:57 AM Eastern Daylight Time, 735769_at_ican.net > writes: > > << Talked to the Prof. yesterday and he plans to come over this evening and > dictate a post. If I can keep him sober he may have something for tommorrow. > >> > > Oh, please, don't keep him sober. I'm sure he will be a lot more eloquent > with a bottle of bubbly under his belt! Hmmm. If he'd visit ME, he'd be entertained with a wee dram or more of Talisker, the great nectar of Skye. How's that for bribery? Slainte! e Elaine Harmon - eilidh_at_dc.seflin.org - eharmon_at_cs.miami.edu *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt Broze http://www.marinerkayaks.com >Matt wrote; > > >>Open Canadian canoes are a relatively specific type of craft without a lot >>of flare and rake as opposed to an umiak or dorie (and I want to exlude the >>Hiada Canoes from this Canadian canoe group too as they also have a large >>amounts of rake and a high bow. I find them extremely seaworthy craft. > >(SNIP) > > >I guess one needs more experience with Canadian canoes to appreciate the >range of shapes etc. I figure they are the same shape as Viking ships, so handle the same. What more do I need to know? ;-) You are making my point. Experience with a wide range of the type craft being designed is far more important to a designer than great expertise in a related design field. The absolute worst article on kayak design I ever read was written by a sailboat designer. "Basics of Bow Design, Kayak Drag and Skin Friction” by Tom Goddard in a mid 1996 issue was so hilarious and off base that I though maybe it was a hoax article foisted on the unsuspecting editors of Paddler Magazine. I wrote: >>Just what drawbacks of kayaks are you alluding to? Please be specific. John responded: >Difficult to load for one (relative to canoes). Not suitable for >transporting family from one camp to another. Don't portage well. Just a >few. An Eddyline Grand San Juan kayak should handle a family of four just fine, camp to camp. How big a family can fit in a solo canoe? I'd like to compare singles with solos (or at least doubles with tandems, seems more fair. By just a few do you mean that is all or only just a few of many? If the later, please continue as I haven't even heard about the on the water drawbacks of kayaks yet. about all I've been able to come up with is easier the step in and out of when wading the riffles on a shallow stream. > <SNIP> John wrote: >My brother wrote an article about about the effect of weight in the ends of >a boat for Sea Kayaker that you might find useful. Don't recall the issue >but maybe Chris Cunningham does. Yes if I recall correctly it was "Slug Feet Squared" or something similar. (Yup, Fall 1991 issue 30. V8,#2 p35 according to the Sea Kayaker index for those who would like to read it. I really like the looks of the kayak in the drawings too;-) It seemed (and still seems) to me to be a minor point in kayak design but it did point out the much bigger benefits of loading the heavier items close to the middle and lighter ones in the ends when kayak camping. But based on the information in the article shouldn't the paddlers in an open canoe sit close together in the middle rather than out near the ends. That would decrease its gyradius (or Equivalent Arm--EA) by many orders of magnitude not just the small increase more bow rake in the ends would cause (if waterline length is the chosen constant). I bow to you as my best source of expertise in open canoe design John. Please explain to me why open canoe paddlers sit so far away from each other--do they learn to hate each other so much that they choose to suffer the serious effects of their extremely increased moment of inertia to stay out of range of a canoe paddle swung in malice? (I can see all sorts of reasons why closed tandem slalom canoeists shoved their cockpits right together roughly twenty years ago. Passing through narrow slalom gates sideways, not having to wait until the second paddler 10+ feet away cleared the gate to turn, the new art of gate sneaking, yaw gyradius, pitch gyradius. Just a few.-) *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt wrote; >I figure they are the same shape as Viking ships, so handle the same. >What >more do I need to know? ;-) ROTFL >You are making my point. Ain't I nice. >The absolute worst article on kayak design I ever read >was written by a sailboat designer. "Basics of Bow Design, Kayak Drag >and >Skin Friction” by Tom Goddard in a mid 1996 issue was so hilarious and >off >base that I though maybe it was a hoax article foisted on the unsuspecting >editors of Paddler Magazine. Good reason never to listen to anyone who designs boats. :-) >By >just a few do you mean that is all or only just a few of many? No just a few. Kayaks are nearly perfect. (SNIP) >But based on the information in the article shouldn't the paddlers in an >open canoe sit close together in the middle rather than out near the ends. >That would decrease its gyradius (or Equivalent Arm--EA) by many orders >of >magnitude not just the small increase more bow rake in the ends would >cause >(if waterline length is the chosen constant). Absolutely. The amazing thing is that, with a properly designed short ended bow they still manage to work quite well out there in the ocean. >Please explain to me why open canoe >paddlers sit so far away from each other-- Everyone needs a little space. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
> >735769 (aka John), > Do you have a copy yourself? Would you be willing to make copies available >to people who asked you nicely? Unfortunately, No I don't. I had a borrowed copy that I returned after I read it. I can get a copy though. It may take a few weeks since I am away on vacation beginning tommorrow. Cheers, John Winters Redwing Designs Web site address, http://home.ican.net/~735769 *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
>(SNIP) >>But based on the information in the article shouldn't the paddlers in an >>open canoe sit close together in the middle rather than out near the ends. >>That would decrease its gyradius (or Equivalent Arm--EA) by many orders >of >>magnitude not just the small increase more bow rake in the ends would >>cause (if waterline length is the chosen constant). >Absolutely. The amazing thing is that, with a properly designed short ended >bow they still manage to work quite well out there in the ocean. Especially whitewater boats. This so-called "Gemini" position is preferred in such boats which are also rockered. One other advantage is that you can communicate with each other in a very noisy environment. Here in the NJ Pine Barrens where lifting over logs is a way of life, the Gemini position often means that you can slide over many that a "classical" tandem seating would have to get out and drag over. > >>Please explain to me why open canoe >>paddlers sit so far away from each other-- > They're not called "divorce boats" for nothing! You wanna be far enough away not to be within your partner's paddleswing radius! *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
> Matt Broze wrote: > snip < > ... but it did point out the much bigger benefits of loading the > heavier items close to the middle and lighter ones in the ends > when kayak camping. But based on the information in the article > shouldn't the paddlers in an open canoe sit close together in the > middle rather than out near the ends. That would decrease its > gyradius (or Equivalent Arm--EA) by many orders of magnitude > not just the small increase more bow rake in the ends would > cause (if waterline length is the chosen constant). I bow to you > as my best source of expertise in open canoe design John. > Please explain to me why open canoe paddlers sit so far away > from each other--do they learn to hate each other so much that > they choose to suffer the serious effects of their extremely > increased moment of inertia to stay out of range of a canoe > paddle swung in malice? Designs of different craft spring from the use of the craft during the evolution of the design, as I'm sure you know. The comment about seal hunters not wanting bow overhang in their kayaks slapping the water in waves is one illustration of the application affecting the design. Without pretending to be an expert of canoe design (or John), I offer the following as possible reasons: a) The open canoe at one point of its historical development was not a recreational craft, but a freighter. Rivers were the only 'roads' around, and transport of goods was what the canoe was designed for. The paddlers sat nearer the ends to provide more cargo space amidships. Today's trippers still need the cargo capacity. b) With paddlers near the ends of the boat, there is much more control in crossing current differentials, which is the trickiest part of river paddling, as one has to contend with different forces pushing different parts of the boat (open water paddlers have tide rips and breaking surf to offer the same challenges). Making an eddy turn with a loaded tandem open canoe (or any longer boat, loaded or not) requires that the boat stall out on the eddy line, with the bow in the eddy and the stern still in the current. Tandem canoeists near the ends of the boats have more leverage to put - or hold - the end of the boat where they want it. > (I can see all sorts of reasons why closed tandem slalom canoeists > shoved their cockpits right together roughly twenty years ago. Passing > through narrow slalom gates sideways, not having to wait until the second > paddler 10+ feet away cleared the gate to turn, the new art of gate > sneaking, yaw gyradius, pitch gyradius. Just a few.-) > Slalom boats are also application specific designs. One additional constraint here are minimum length requirements that most racing boats (of any type) must meet. Makes me wonder what slalom boats would look like if there were no restrictions imposed on the design? I'd venure a guess that they'd be much shorter. Play Hard, Erik Sprenne *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
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