I've put together a discussion on stability and would like to get a critique. Check http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let me know what you think. Nick -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
At 10:34 AM 2/15/01 -0500, Nick Schade wrote: >I've put together a discussion on stability and would like to get a >critique. Check >http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let me >know what you think. >Nick That was great Nick. I've always thought that your chapter on stability in your book was one of the clearest descriptions I had read. This article goes into much more detail but it's still (mostly) understandable. One minor correction: it "Weebles will Wobble" (you spelled it woble). There was something in the conclusion section that sparked some thoughts I've had on the whole notion of stability and why a beginner looking for a new boat will often place stability as their #1 criteria while a more experience boater will look at other criteria. I think it is safe to say that the #1 fear for someone getting into a kayak for the first time is tipping over and getting trapped inside. As a result, those wide large cockpit boats known as "recreational kayaks" are sold as "beginners" kayaks. Once someone has been in a kayak for a very short time, has intentionally done a wet exit, and especially after they've unintentionally capsized and done a wet exit, they've realize that tipping over really isn't a big deal. I've used the analogy of a beginning snow skier before to equate how a boat with high initial stablity will be judged differently depend on the boaters skill. When I first started skiing 30 years ago, one of the differences between ski boots for a beginner and boots for an advanced skier was their stiffness. A beginning skier is just learning how much pressure is necessary to edge the skis in order to turn. The softer beginners boots tolerate a little too much pressure as it dampens the effect so that it's not immediately transmitted to the edge of the ski. If the same amount of pressure were exerted while wearing stiff boots, it would be immediately translated to edging the ski, and they'd quickly find themselves on their butt. The stiffer boots are just not as forgiving of mistakes. As a skier become more experience they gain much better muscle control and are capable of very subtly angling their knees just the right amount to carve nice round turns. Their fine muscle movements are immediately transmitted to the edging of the skis when wearing stiff boots but they're able to control it. I think the same thing happens in a kayak. A beginner is just learning how far they can lean over and will tend to lean too far every so often. A boat with a lot of stability will be more forgiving of those mistakes. However, a boat with a lot of stability will not be sensitive to the subtle weight shifts and cock of the hip that the experience paddler is capable of. Last summer I had the opportunity to paddle a Guillemot that a local paddler built. I've paddled a couple of your (Nick's) boats at LL Bean and felt that they had just about the right amount of stability for my experience level. However, this boat I paddled only had a 1/2" foam pad for a seat and I felt like I was seating deep in the boat. My center of gravity felt much lower than in other boats I'd been in. When I tried to do a few low brace turns with the boat on edge, I cocked my hips, pressing my opposite knee up, trying to edge the boat and not much happened. I edged more and more and it didn't feel like the boat was going to heal over. I really had to lean over the side to get the boat over to where it felt like it was approaching it's final stability point. Because the seat was so low I was expending a lot of energy to get the boat on edge. If I wanted to quickly go from one side to the other it would have required a significant amount of pressure from one side to the other. As it was outfitted, it felt like it had way too much initial stability. Because I've finely tuned my paddling muscles I can make more subtle movements that I couldn't do when I first started. Now I like a boat that is sensitive to those movements and responds. A boat with too much stability doesn't do that. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Wow, Thanks. I'm hoping to find some time to go over that all again. It's quite a brain-full. If I find any places that a bit more clarification could help the explanation, I'll let you know offlist. Thanks again for that technical discussion. It's nice to get past the subjective descriptions now and then and understand what's really happening. Jeff -----Original Message----- From: Nick Schade [mailto:schade_at_guillemot-kayaks.com] Sent: Thursday, February 15, 2001 7:34 AM To: paddlewise_at_paddlewise.net Subject: [Paddlewise] Stability Discussion I've put together a discussion on stability and would like to get a critique. Check http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let me know what you think. Nick -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
John Said: I think it is safe to say that the #1 fear for someone getting into a kayak for the first time is tipping over and getting trapped inside. As a result, those wide large cockpit boats known as "recreational kayaks" are sold as "beginners" kayaks. Once someone has been in a kayak for a very short time, has intentionally done a wet exit, and especially after they've unintentionally capsized and done a wet exit, they've realize that tipping over really isn't a big deal. Jeff Responds: Actually John, I think this statement might be oversold by the experts. My wife and I -- both of whom are newbie paddlers -- both sat in rec boats. Neither of us had any value judgements surrounding the type of boat we bought. We were in it for the fun more than whether some other hypothetical paddler would approve of our boat choice. Even so, both of us felt that we much preferred the more nimble feel of boats like the looksha sport over the more stable feel of boats like the Carolina. I have an extremely well developed sense of balance and it wouldn't really occur to me to fear either tipping or wet-exiting. Carol, on the other hand, is much more towards the median on these things. Both of us, however, ended up at the same conclusion. Also of interest is that both of us felt comfortable in boats where there was a fairly definite "edge". Boats that didn't clearly define for us how far was too far felt uncomfortable and vaguely scarey. In other words, we both like a boat that leaned easily, but stopped that lean at a certain point with some assertiveness. I always hear the more seasoned paddlers make the assertion that newbies look for high initial stability. Not only for my wife and myself, but also the other newbies we have talked to, all of us felt that the hard edge on the near the top of the stability curve mattered more than initial stability. The only thing I can think of is that these people all did some fairly good research with a knowledgeable dealer before forming their opinions. I suppose that I could see that if someone just went out and bought a boat without talking to anyone about it or having any real knowledge of the fact that there are such things as primary and secondary stability much less the "edge" on the secondary stability, then they might feel more comfortable in a boat with high primary stability. On another note, although I'm sure that they exist, I have never talked to a single newbie paddler who feared being able to exit their boat. Most of us feared being dumped into 50 degree water *shiver* (bought my boat in December). Most of us wondered how the heck you get back in again. But nobody so far has feared not being able to exit before drowning. Jeff Doing my part to reconnect you old salts with a real newbie *chuckle* *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Nick: Your site is really terrific: well-designed, and beautifully written. Not only that -- your kayaks take my breath away. Be still my heart! I have a Romany sitting in Wales right now, but in the future I would love one of yours too (and a Feathercraft Khatsalano as well, for that matter). You know, I have an uncle who is very much into woodworking; maybe he could make one and ship it to me! Keep up the good work! Josh ============================================================================== Dr. Joshua Teitelbaum Tel: [972] 3-640-6448 Moshe Dayan Center for Middle Eastern and Fax: [972] 3-641-5802 African Studies E-mail:teitelba_at_ccsg.tau.ac.il Tel Aviv University Ramat Aviv, Tel Aviv 69978 Israel ============================================================================== *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Actually, paddling with a commercial outfitter, I've met a lot of newbies who are afraid of not being able to exit their boats. Not only that, people who stop to talk when we're out with the kayaks on top of the car frequently mention that as a fear - though these are mostly folks who aren't even newbies - they're just scared to even get in "one of those things." First we have to convincae the newbies that they won't get stuck in their boats - that, in fact, with the nylon sprayskirts most of them are using, they aren't even likely to be able to stay in their boats if they want to if the boats tip over. Then we have to convince them that they will be able to get back into the boat, with help at first, and hopefull, alone after awhile. Joan > On another note, although I'm sure that they exist, I have never > talked to a > single newbie paddler who feared being able to exit their boat. > Most of us > feared being dumped into 50 degree water *shiver* (bought my boat in > December). Most of us wondered how the heck you get back in again. > But > nobody so far has feared not being able to exit before drowning. > > Jeff > Doing my part to reconnect you old salts with a real newbie > *chuckle* > *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
At 10:13 PM 2/15/01 -0500, volinjo_at_juno.com wrote: >Actually, paddling with a commercial outfitter, I've met a lot of newbies >who are afraid of not being able to exit their boats. Not only that, >people who stop to talk when we're out with the kayaks on top of the car >frequently mention that as a fear - though these are mostly folks who >aren't even newbies - they're just scared to even get in "one of those >things." > >First we have to convincae the newbies that they won't get stuck in their >boats - that, in fact, with the nylon sprayskirts most of them are using, >they aren't even likely to be able to stay in their boats if they want to >if the boats tip over. Then we have to convince them that they will be >able to get back into the boat, with help at first, and hopefull, alone >after awhile. My experience helping a friend run lessons and rentals out of his shop mimics Joans (wave), although I'd have to say that certainly not every new paddler is afraid of capsizing and getting stuck. In the introductory classes I help teach, after some basic forward paddling, reverse paddling and sweep strokes without their skirts attached, the next thing we do is wet exits. Usually, I demonstrate one first and tell them that I'm going to take my time getting out. I'll tip over, slap the hull a few times, wiggle my fingers, wave to everyone, and then do my wet exit, reinforcing the idea that being upside down in a kayak is really nothing to worry about. Most people come up with a smile on their face the first time they do an intentional wet exit. The first one gives them some confidence in the fact that they won't get trapped. The first time they unintentionally capsize and wet exit gives them even more confidence. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Nick: It's the first time I've understood the curves. Very clear exposition. Thanks. Dennis St. Paul Nick Schade wrote: > > I've put together a discussion on stability and would like to get a > critique. Check > http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let > me know what you think. > Nick *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
I agree with much of what you have written. Some points that I would emphasize perhaps even more than you have #1: The seat height is SO critical to the appearance of the stability curves that it is easy to game the system. For many people there is a tradeoff between seat height and comfort. Many stiff old types such as myself, find higher seats more comfortable because we are not very limber. If a manufacturer makes a kayak with a very low seat then his stability curves will look MUCH better. His seat may be so low that everyone who actually uses that kayak adds some padding to the seat. Another manufacturer may offer essentially the same boat with a comfortable seat that does not require building up the seat. His boat will look a lot less stable. I have always thought that SK should do the curves from the bottom of the boat and just add an explanation about the status of the seat. As it is, IMO, those curves are just an elaborate way to tell you how wide the boat is and how high the seat is. #2: You give a definition of initial stability and dance around giving a definition of secondary stability. (curve under area to the max height point). If you accept these definitions, it is VERY hard to find a boat that has "poor" initial stability but "good" secondary stability. Except for some extreme cases (sponsons above the waterline) NO kayak will fall into this category. And yet, many people seem to like the idea of having a kayak with these characteristics and it is very common in the reviews to read reviewers talking about "poor" initial but excellent secondary stability. The great thing about there being no mathematical definition of secondary stability is that these claims can be made without fear of contradiction. #3: Knowing three numbers (waterline width, width of seam line, and height of the seat) you can very closely "predict" the stability curves. I venture to guess that there is no commercial boat with a waterline width of 22 inches that has more initial stability than a commercial boat with a waterline width of 23 inches assuming that the seat height is the same. #4: By your definitions there is no magic out there. People seem to want to believe that some clever underwater design can make a skinny boat more stable. Using your definitions, I think not. At least, the influence will be minor. But see the below. #5: You make a good point about how the flare influences your definition of secondary stability and it does. However, the initial slope (initial stability) also has a great influence. Therefore in the "real" world, where there is not all that much difference in flare between the common kayaks, secondary stability can be pretty accurately estimated by only looking at seat height and waterline width and not even bother with seam width. I have long thought that I should just go through all the old Sea Kayaker magazines and plot your definitions of initial and secondary stability against only TWO variables (seat height and waterline width) and see if there were any real "outlyers". I suspect there are very few. #6: I have a little trouble believing that the paddler particularly perceives just starting down the slope after the maximal height has been reached. Throughout this region, even after you have slipped "down" away you are getting a good righting force. I am not sure that you are particularly concerned or appreciate that that force is a little less than it was a few degrees ago. The above addresses refinements of what you have written. ------------- Having said all the above, I think that there is an important issue that your do not address. You have neglected something. This is that the paddler changes his position in the boat by bending at the waist. Therefore the CG moves and moves rapidly. This has nothing to do with bracing etc. Beginners often do it TOO much. They almost "vibrate" back and forth as they feel the boat tipping under them. If you get a chance to make a corrective lean, you will feel comfortable. Imagine the two copies of the same kayak. One has a daggerboard that hangs down three feet. Imagine that the daggerboard is very thin from side to side so it has no real influence on the stability curves. (Actually what influence it has will be to make the boat less stable using the traditional stability curves) That boat with the daggerboard will be perceived as being much more stable than the other boat. It resists, by dynamic forces on the water, rapid tipping. As the kayak starts to tip, the paddler starts leaning the other way to compensate. He will hardly even know he is doing it. That kayaker can take pictures etc from his boat without worry. The daggerboard acts like a built in "brace". With a big enough daggerboard, a beginner would feel comfortable in an 18" wide boat. Now, of course, kayaks do not have daggerboards though I suspect even a skeg could be perceived. But they do have different underwater shapes. A completely rounded shape does not push any water around if that kayak is rapidly tipped. A square shape, however, does. A square cross-section resists rapid tilting and thus gives the paddler a chance to react with leaning the body (or if more experienced) with setting up a paddle brace. I believe that this factor is very important in the perception of how stable a given kayak is. This is NOT captured in the stability curves. IMO, chined boats feel more stable than a rounded hull with exactly the same stability curve. This is certainly true in calm water. How it plays out in rough water is more complicated because those shape can give waves and currents something grab. As a kid, I used to paddle logs around. Round logs 20" wide were tricky. Flat planks 18" wide were no problem. (I had a low CG in those days) These were simple shapes. You could spin that round log in the water around its long axis with no problem. There would barely be a ripple. The plank would splash and kick up a huge wave system if you tried to spin it the same way. If these logs are virtually submerged, they don't really have ANY stability by the traditional curves and yet the rider can easily tell the difference between the two. Robert Livingston rlivingston_at_mac.com livingston_at_post.harvard.edu ----- Original Message ----- From: "Nick Schade" <schade_at_guillemot-kayaks.com> To: <paddlewise_at_paddlewise.net> Sent: Thursday, February 15, 2001 7:34 AM Subject: [Paddlewise] Stability Discussion > I've put together a discussion on stability and would like to get a > critique. Check > http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let > me know what you think. > Nick > > -- > Nick Schade > Guillemot Kayaks > 824 Thompson St > Glastonbury, CT 06033 > (860) 659-8847 > *************************************************************************** > PaddleWise Paddling Mailing List - Any opinions or suggestions expressed > here are solely those of the writer(s). You must assume the entire > responsibility for reliance upon them. All postings copyright the author. > Submissions: PaddleWise_at_PaddleWise.net > Subscriptions: PaddleWise-request_at_PaddleWise.net > Website: http://www.paddlewise.net/ > *************************************************************************** > *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Nick Schade <schade_at_guillemot-kayaks.com> wrote: >>>>>I've put together a discussion on stability and would like to get a critique. Check http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let me know what you think.<<<<< Typo in this line:extra words in brackets >>>side will cause the center of buoyancy to move toward [that towards] the side you are tipping. If the boat is shaped to be stable, the CB will move out to the side faster than the CG.<<< Much later the word "how" is missing before "much": >>>>>Raising or lowering the CG will effect the stability in a predictable manner. The exact change in stability can actually be calculated based on much the CG is changed, but<<<< Word "be" is missing below before "sure" >>>>You can never sure of the personal preferences of someone describing a boat. A salesman <<<<<, Nick wrote: >>>>>>>The peak of the curve is where the stability starts to diminish. Having this point either be higher or at a greater angle of heel will make the boat feel like it has more secondary stability. By looking at the area under the curve until the peak of the curve (the dark blue area) you can get one value for the secondary stabilty.<<<<<<< Note: last "stability" misspelled. (and said similar things elsewhere in the article) While the above may be a possible definition for "secondary stability" (if we could all agree on one) it wouldn't make me happy. For one thing it is trying to combine two different things into one number, height and angle of lean at the maximum height (area under the curve). Greater height to the stability curve usually means a greater angle of the slope getting up to that height. If a kayak is too hard to lean then the paddler must lean further out to the side (using his weight hanging by his knee to overcome that righting force) and that puts one into a very vulnerable position hanging out over the water, if his knee slips he's going to get wet. So for me just increasing the height of the curve (beyond some necessary minimum) has little or nothing to do with my perceived feeling of "secondary stability" (when leaning a kayak up to as much as I want to lean it to use the change in the underwater shape to help control it--without hanging out over the water). The angle at which maximum stability occurs works somewhat better for me but it too has its drawbacks. If that angle is too far out to one side, I can't bend enough to get near it and it is therefore wasted on me. Or the slope is made too shallow too soon for me to feel much righting moment to give me a feeling of security. Maybe a ratio of the slope of the curve coming off zero (initial stability) to the slope of the curve at some angle (some reasonably easy for the average paddler to bend too angle like 20 or 25 degrees) might work better to meet what I "feel". I'm just speculating here. Personally, I think the slope of the curve determines what one perceives, not the area under it up to that point. Maybe a ratio between the slope of the curve and the angle of lean would work. I'll have to think more about that. An expert kayaker defines "secondary stability " by the feeling of security he has while leaned a good bit. Because he bends at the waist the actual righting moment (height) isn't critical to that feel, but the angle of the slope is (as you explained very well in your discussion of it). So I guess what I'm saying is I'd be very hesitant to define "secondary stability" without some discussion included about what expert paddlers feel. I'd then try to figure out what are the parameters that influence that feel and see if we can't come up with a way to calculate it from the stability curve graph. Great article, by the way, accurate and understandable. I'm going to ask Chris Cunningham to look at it on your website, maybe Sea Kayaker would like to publish it (or an abridged version). I hope all the back and forth we did about secondary stability on Paddlewise had something to do with your inspiration to write it. P.S. Could you also redo the graph keeping the overall widths (maybe by using wider widths) of the shapes the same so they all have some positive stability? Matt Broze http://www.marinerkayaks.com *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Matt, Thanks for your comments. The discussion we had here motivated me to have another go at an article I'd been working on for a while. The discussions here have helped me create a more fully realized understanding of some of the concepts which were kicking around loosely in my brain. Reading other's explanations here on Paddlewise (and wave~length before) and having the opportunity to try putting words to my thoughts has been invaluable for my own understanding. One of the concepts which is still rattling a little loosely is secondary stability. As such I tried to put that moniker on something I do think is important. The area under the curve to the maximum point is a good indication of how much energy the boat can absorb before it gets scary. If some was to paddle by and punch you in the shoulder, this is how hard he would have to hit you to push you over the hump. I agree that this is not exactly the same thing as what a skilled paddler feels as "secondary" but I still think it plays a part. The reason I didn't include a curve-slope derived definition into "secondary" is I don't have any fully realized thoughts on how to do it. So, my definition was a bit of a cop out. I will need to spend more time playing with the first derivative (slope of the curve). To plot out the first derivative from point data, just divide the vertical difference between two adjacent points by the horizontal difference. Plotting this out for a variety of boats should help show if there are any patterns which might be useful. Maybe you will have more influence with Chris C. than I did. :-) Thanks, Nick >At 11:35 PM -0800 2/15/01, Matt Broze wrote: >While the above may be a possible definition for "secondary stability" (if >we could all agree on one) it wouldn't make me happy. For one thing it is >trying to combine two different things into one number, height and angle of >lean at the maximum height (area under the curve). Greater height to the >stability curve usually means a greater angle of the slope getting up to >that height. If a kayak is too hard to lean then the paddler must lean >further out to the side (using his weight hanging by his knee to overcome >that righting force) and that puts one into a very vulnerable position >hanging out over the water, if his knee slips he's going to get wet. So for >me just increasing the height of the curve (beyond some necessary minimum) >has little or nothing to do with my perceived feeling of "secondary >stability" (when leaning a kayak up to as much as I want to lean it to use >the change in the underwater shape to help control it--without hanging out >over the water). The angle at which maximum stability occurs works somewhat >better for me but it too has its drawbacks. If that angle is too far out to >one side, I can't bend enough to get near it and it is therefore wasted on >me. Or the slope is made too shallow too soon for me to feel much righting >moment to give me a feeling of security. Maybe a ratio of the slope of the >curve coming off zero (initial stability) to the slope of the curve at some >angle (some reasonably easy for the average paddler to bend too angle like >20 or 25 degrees) might work better to meet what I "feel". I'm just >speculating here. Personally, I think the slope of the curve determines what >one perceives, not the area under it up to that point. Maybe a ratio between >the slope of the curve and the angle of lean would work. I'll have to think >more about that. >An expert kayaker defines "secondary stability " by the feeling of security >he has while leaned a good bit. Because he bends at the waist the actual >righting moment (height) isn't critical to that feel, but the angle of the >slope is (as you explained very well in your discussion of it). So I guess >what I'm saying is I'd be very hesitant to define "secondary stability" >without some discussion included about what expert paddlers feel. I'd then >try to figure out what are the parameters that influence that feel and see >if we can't come up with a way to calculate it from the stability curve >graph. > >Great article, by the way, accurate and understandable. I'm going to ask >Chris Cunningham to look at it on your website, maybe Sea Kayaker would like >to publish it (or an abridged version). I hope all the back and forth we did >about secondary stability on Paddlewise had something to do with your >inspiration to write it. > >P.S. Could you also redo the graph keeping the overall widths (maybe by >using wider widths) of the shapes the same so they all have some positive >stability? > >Matt Broze >http://www.marinerkayaks.com > -- Nick Schade Guillemot Kayaks 824 Thompson St Glastonbury, CT 06033 (860) 659-8847 *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Very excellent page. I really like the yardstick animated GIF. I think that brings the stability concept out very clear. I appreciate and like the work that went into the stability curve comparisons. I would really like to see one more graph that takes the 5 shapes you compare and give the widths for the same stability curve (really just getting the line to cross back at zero at the same point for all 5 shapes. I would use the rectangle as the baseline and then do the rest as rectangle-x or rectangle+x in order to compute the comparative results. It would be nice to see how much wider a V would have to be to get the same stability (till capsize) as a round bottom. Being very picky, it would also be nice if the animated rolling hull, rolled a bit slower. It is hard to watch the graph, watch the hull and read the arrows. The height curve is very revealing. Now I am especially going for the lowest seat I can. Great job. Marvin ----- Original Message ----- From: "Nick Schade" <schade_at_guillemot-kayaks.com> To: <paddlewise_at_paddlewise.net> Sent: Thursday, February 15, 2001 9:34 AM Subject: [Paddlewise] Stability Discussion > I've put together a discussion on stability and would like to get a > critique. Check > http://www.guillemot-kayaks.com/Design/StabilityArticle.html and let > me know what you think. > Nick > > -- > Nick Schade > Guillemot Kayaks > 824 Thompson St > Glastonbury, CT 06033 > (860) 659-8847 > *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
skylakeboatworks wrote: > // Now I am especially going for the lowest seat I can. // Next time out, I plan on removing the seat all together - Sit directly on the bottom of the boat - I am not experienced too much - What say you on this proposal ?? Wayne Smith *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
On Fri, 16 Feb 2001, Wayne Smith wrote: > Next time out, I plan on removing the seat all together - Sit directly on the > bottom of the boat - I am not experienced too much - What say you on this > proposal ?? That depends on the shape of the hull relative to the shape of your butt. I have a skin boat that I sometimes sit very low in. The padding needs to be properly done to be comfortable. With the wrong padding it's like sitting in the crook of a tree. It's okay for few minutes but it gets real old after a while. Without any padding I can only paddle about 10 minutes. With V shaped hulls I need some padding to raise my seat so that the hull isn't narrower than my hips where I'm sitting. An inch of seat height can make a tremendous difference in how stable the boat is. kirk *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Wayne Smith wrote: > Next time out, I plan on removing the seat all together - Sit directly on the > bottom of the boat - I am not experienced too much - What say you on this > proposal ?? That's where my tush is on my hardshells -- with minicell foam padding to flesh out the remainder of the "seat." Been paddling that way for over five years. Caveat: a quarter-inch-thick layer of neoprene or similar down there is a good idea, to minimize conduction of heat away from yourself. My 3 mm wetsuit is not enough, sometimes, so I occ. supplement with a Thermarest seat cushion, partially inflated, when the water temp drops below 42 F or so. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Marvin <skylakeboatworks_at_yahoo.com> wrote: <SNIP> I appreciate and like the work that went into the stability curve comparisons. I would really like to see one more graph that takes the 5 shapes you compare and give the widths for the same stability curve (really just getting the line to cross back at zero at the same point for all 5 shapes. I would use the rectangle as the baseline and then do the rest as rectangle-x or rectangle+x in order to compute the comparative results. It would be nice to see how much wider a V would have to be to get the same stability (till capsize) as a round bottom.<<<<<<SNIP> Back about 20 years ago when Cam and I had just started designing kayaks, We met Robert Livingston (same one now posting here on stability) who was also designing sea kayaks. We became friends and surf kayaking buddies. Robert wanted to find out about stability (probably because his first design didn't have any to speak of). He programmed his computer to calculate the relative stability of various midship section shapes and placed the paddler's center of gravity the lowest a seat that could fit an average butt could go down into that particular shape. If I recall correctly Robert had done about 50 curves of various shapes and widths (and I have the printouts still on file but unfortunately the program apparently went out along with an old computer several generations ago). Why I'm bringing this up is because I think those who want to know which shapes of equal width will have the most stability (or how much wider a shape has to be to have the same stability) are barking up the wrong tree. What I was looking for most in analyzing Robert's graphs back then was not how to get the most stability from the narrowest kayak or even the narrowest waterline (although I paid attention to that as well). What was more important to me was which shape gives the most stability for the least amount of wetted area. So what I'd like to see are some stability curves that hold wetted surface as the constant for the differing shapes. Those with considerable flare should do well by this measure (as well as doing well on the equal waterline width measure). Lots of flare will also satisfy the expert who wants an easy to lean kayak but also a secure feeling once leaned (what most define subjectively as "good secondary stability"). By his third design Robert took flare to the extreme (rather than just concentrating on minimizing wetted surface--as with his first design) and came up with a very successful little kayak that had a lot of influence on the design of our Coaster model. Also I wouldn't worry about the angle of final capsize, I'd look at which shape produces a curve with the steepest rate of increase in the 20 to 30 degree range (with an empty kayak). Matt Broze http://www.marinerkayaks.com *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Good points. I would second that request. My intention was to get a bit of and idea of the difference based on same width, just to see how much of a difference there really is. Just to have a better idea when everyone's adds claim their design "....is amazingly stable." Just how much *more* stable can it be? A table of the theoretical maximums for a given shape/same width would reveal just how much/little there is to the claim. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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