Chesapeake Light Craft's shop notes discusses adding graphite to the epoxy used to finish the bottom of the boat. The Notes indicate it creates a tough scratch resistant, low friction surface. My knowledge of fluid dynamics tells me a low friction surface has minimal effect on boat performance, but does it make the finish more scratch resistant? Anyone have any experience with adding graphite to the epoxy finish? ,,, (o o) ==================oOO--(_)--OOo========================== Bob Washburn whiterabbit_at_iw.edwpub.com or rwashbu_at_siue.edu The only difference between a rut and a grave is the depth. ========================================================= *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Cheap, easy to do, works good (less friction on rocks and sand), lasts a long time. Do your filling with microballoons and a coat of clear epoxy, sand with 220 and apply 2 coats of epoxy/graphite mixed per the Gudgeon Brothers instructions that come with the graphite powder. As I remember, use the high end of the suggested range of graphite proportions. Roger Bob Washburn wrote: > Chesapeake Light Craft's shop notes discusses adding graphite to the epoxy > used to finish the bottom of the boat. The Notes indicate it creates a > tough scratch resistant, low friction surface. My knowledge of fluid > dynamics tells me a low friction surface has minimal effect on boat > performance, but does it make the finish more scratch resistant? Anyone > have any experience with adding graphite to the epoxy finish? > ,,, > (o o) > ==================oOO--(_)--OOo========================== > Bob Washburn > whiterabbit_at_iw.edwpub.com or rwashbu_at_siue.edu > The only difference between a rut and a grave is the depth. > ========================================================= > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Kia Ora, I do not know about graphite for bottoms.But one kayak manufacturer here,mixes carburundum powder (they make grinestones out of the stuff)with the epoxy. I have just had my boat redone.and it stops a lot of wear when dragging a glass boat over sand or hittting a rock. I have heard that instead of carburundum powder they used alluminium oxide powder which seems to be very hard,that mixed in with the epoxy saves a lot of wear. I was told by a boat builder that they used that stuff on the bottom of power racing boats.These boats use Water jet engines and travel in very shallow water at high speeds,with the expected results ,a lot of wear on the bottom were they hit the riverbed. I was not aware that graphite was that hard and scratch resistant? Eddie. Bob Washburn wrote: > > Chesapeake Light Craft's shop notes discusses adding graphite to the epoxy > used to finish the bottom of the boat. The Notes indicate it creates a > tough scratch resistant, low friction surface. My knowledge of fluid > dynamics tells me a low friction surface has minimal effect on boat > performance, but does it make the finish more scratch resistant? Anyone > have any experience with adding graphite to the epoxy finish? > ,,, > (o o) > ==================oOO--(_)--OOo========================== > Bob Washburn > whiterabbit_at_iw.edwpub.com or rwashbu_at_siue.edu > The only difference between a rut and a grave is the depth. > ========================================================= > *************************************************************************** > PaddleWise Paddling Mailing List > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.gasp-seakayak.net/paddlewise/ > *************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Bob wrote; >Chesapeake Light Craft's shop notes discusses adding graphite to the epoxy >used to finish the bottom of the boat. The Notes indicate it creates a >tough scratch resistant, low friction surface. My knowledge of fluid >dynamics tells me a low friction surface has minimal effect on boat >performance, but does it make the finish more scratch resistant? Anyone >have any experience with adding graphite to the epoxy finish? I have placed a discussion on fluid friction on my web site http://home.ican.net/~735769/shape.htm ) so won't take up space here repeating it. As for carbon filled resin being more abrasion resistant I have seen no test reports to support that. My experience suggests that the resin hardness contributes more to abrasion resistance unless one uses a really hard filler like metal powder etc. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
John Winters wrote: >As for carbon filled resin being more abrasion resistant I have seen no >test reports to support that. My experience suggests that the resin >hardness contributes more to abrasion resistance unless one uses a really >hard filler like metal powder etc. I'd agree with John on that. From what I've heard from others (I've not tried it meself), abrasion resistance seems to increase with the addition of the graphite powder. Personally, I think it's just the slipperyness of the graphite, rather than any increase of hardness of the resin (that last is probably nil). John's the last word on slipperyness in the water as far as I'm concerned, so heed his info on that. Long ago and far away (20+ years ago in Chicago) some slalom racing kayak building friends of mine dumped some metalflake glitter into the resin used for the first layer of one boat and later noticed a remarkable increase in the abrasion resistance of that one over the others they had built at the same time. Probably is something to the carborundum or aluminium oxide (both are used in sharpening stones for knives, etc.), but is it worth the added weight in the boat? High concentrations of any filler degrade resin strength properties, but I don't know what the "high concentration" limit for stuff like that is. Probably higher than most people would use, anyway, so may not matter. Good luck with it and let us know how the experiments turn out for you. Hank Hays Lightning Paddles *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
At 07:23 AM 11/9/98 -0800, Hank Hays wrote: >John's the last word on slipperyness in the water as far as I'm concerned, >so heed his info on that. > > >Hank Hays >Lightning Paddles > Hank are you saying that John is a slippery type character??? Dana *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Hi, I added graphite (and collidal scilica -- West Systems stuff) to the epoxy used on the bottom (below the waterline) on my cedar strip canoe. This does seem to create a more scratch resistant surface. Also this coat does not need to be protected from the sun and water like the plain epoxy (which clouds up). These were the reasons why I tried it. I have been using this canoe for about 5 years and am glad that I took this approach. If I had varnished the bottom I would be constantly touching it up due to scratches from rocks. I don't really have to worry much about sliding over rocks in rivers (or those in the BWCA where they hide in that dark water). Since it is below the water line you don't notice it except when the canoe is on the car. I don't know how "low resistance" it is (is that the resistance against the rocks or the water?). Henry On Nov 8, 6:17pm, Bob Washburn wrote: > Subject: [Paddlewise] Graphite for Bottoms >Chesapeake Light Craft's shop notes discusses adding graphite to the epoxy >used to finish the bottom of the boat. The Notes indicate it creates a >tough scratch resistant, low friction surface. My knowledge of fluid >dynamics tells me a low friction surface has minimal effect on boat >performance, but does it make the finish more scratch resistant? Anyone >have any experience with adding graphite to the epoxy finish? >-- End of excerpt from Bob Washburn -- henry o_, _at_ ------------ [\/ o,/ Henry Davies (`-----/----') <-----</-----> OASIS, Inc. ~~~~~~~~_at_~~~~~~~~~~~~~~~~~~~~~~~~/~~~~~~~~~~ phone: 248.952.1490 x210 fax: 248.952.1493 email: henry_at_orion-sim.com *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Regarding scratch resistance and friction reduction- The original post on this mentioned the reduction of fluid friction. (Actually, I'm not sure he meant fluid friction, maybe it was sliding friction on the beach. I assume fluid friction.) Many years ago, I did some research on the drag reducing qualities of visco-elastic fluids. These fluids were essentially water with the addition of a small amount of polymer (say 5 to 500 ppm) and great reductions in the drag were noted. At that time, it was claimed that the injection of small amounts of this fluid in the boundary layer next to ships could yield a decrease in the frictional drag. Boats could operate at the same speed with less horsepower expended and less power would be needed to bring hydrofoil boats to "takeoff". Fire hoses could discharge more water with the same pumping power. So why do I bring this up? A year or so ago I was having a conversation with Robert Morris of Brewery Creek Small Boats, who teaches the construction of skin covered baidarkas, Greenland kayaks, etc. Robert claimed that traditional baidarkas paddled faster than many people would think. We discussed the fact that the original seal skins might have had an effect like adding some oil (or whatever) to the boundary layer and working like a visco-elastic fluid. Does anyone have any definite knowledge of this? Have there been any efforts to use visco-elastic fluids to increase the performance of human powered vessels? Does anyone know if there are coatings that might "ablate" and effect the drag performance of a kayak or canoe? Enquiring minds want to know! Bill Leonhardt *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Since the typical application procedure for graphite powder and epoxy involves sanding, it is doubtful that that material gets all that hard, but the lubricating properties of graphite may help rocks slide off instead of cutting in. BTW, remember that graphite is conductive and can have a severe galvanic reaction with some metals such as aluminum. Aluminum footbraces on a boat with graphite could corrode badly in certain situations. At 6:17 PM -0600 11/8/98, Bob Washburn wrote: >Chesapeake Light Craft's shop notes discusses adding graphite to the epoxy >used to finish the bottom of the boat. The Notes indicate it creates a >tough scratch resistant, low friction surface. My knowledge of fluid >dynamics tells me a low friction surface has minimal effect on boat >performance, but does it make the finish more scratch resistant? Anyone >have any experience with adding graphite to the epoxy finish? > ,,, > (o o) >==================oOO--(_)--OOo========================== > Bob Washburn >whiterabbit_at_iw.edwpub.com or rwashbu_at_siue.edu >The only difference between a rut and a grave is the depth. >========================================================= >*************************************************************************** >PaddleWise Paddling Mailing List >Submissions: paddlewise_at_lists.intelenet.net >Subscriptions: paddlewise-request_at_lists.intelenet.net >Website: http://www.gasp-seakayak.net/paddlewise/ >*************************************************************************** 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
At 11:40 AM 11/9/98 -0500, Bill Leonhardt wrote: >Regarding scratch resistance and friction reduction- >We discussed the fact that the original seal skins might have had >an effect like adding some oil (or whatever) to the boundary layer and >working like a visco-elastic fluid. Does anyone have any definite >knowledge of this? Have there been any efforts to use visco-elastic fluids >to increase the performance of human powered vessels? Does anyone know if >there are coatings that might "ablate" and effect the drag performance of a >kayak or canoe? > >Enquiring minds want to know! I'd think the America's cup sailing people as well as the sprint kayak and canoe racing section of the US Olympic committee would know if anyone does. My theory on the superiority of skin boat speed is that the contemporary proponents of it are over reacting to early reports of quickness that the little boats seemed to have. Look at a little bug running around on the ground. Seems fast doesn't it? It's just so small that it looks to be fast. You can outrun (out walk?) it easily. Smaller boats were more maneuverable than the bigger whiteman boats, and I think that made them seem so fast to people not used to them. I sure haven't seen any olympic kayakers paddling skin boats. Be nice if I were were wrong, though.... a whole new world to explore. Hank Hays Lightning Paddles *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
> >knowledge of this? Have there been any efforts to use visco-elastic fluids > >to increase the performance of human powered vessels? Does anyone know if > >there are coatings that might "ablate" and effect the drag performance of a > >kayak or canoe? > > > >Enquiring minds want to know! > > I'd think the America's cup sailing people as well as the sprint kayak and > canoe racing section of the US Olympic committee would know if anyone does. Whether they do or do not, it is against the Olympic and international canoe racing rules to add any gunk or slime to the hulls of canoes or kayaks. As it is illegal to pitt the surface of the hull in an attempt to reduce surface drag (they apparently scrutinize the hull with a microscope at some races). Apart from unfair advantage, we do not want any more chemica grot in in our waterways jim *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Bill wrote; (SNIP) >So why do I bring this up? A year or so ago I was having a conversation >with Robert Morris of Brewery Creek Small Boats, who teaches the >construction of skin covered baidarkas, Greenland kayaks, etc. Robert >claimed that traditional baidarkas paddled faster than many people would >think. We discussed the fact that the original seal skins might have had >an effect like adding some oil (or whatever) to the boundary layer and >working like a visco-elastic fluid. Does anyone have any definite >knowledge of this? Have there been any efforts to use visco-elastic fluids >to increase the performance of human powered vessels? Does anyone know if >there are coatings that might "ablate" and effect the drag performance of a >kayak or canoe? Many years ago I coated the bottoms of my sailboats with Lux liquid detergent believing it would reduce friction (as did others). We also tried a lot of other goops that supposedly imitated fish slime. I doubt if any worked but the psychological benefit may have been high. Some tests on long chain polymers did show some friction reduction (Catchpole,Canham,and Lon-Trans.RINA 1971) but problems existed. The polymers had to be replenished constantly and the resulting pollution would not be desirable in these enlightened times. Also the weight of the polymers you had to carry offset the benefits of the reduced friction. Paint manufacturers have been claiming all kinds of stuff over the year to gull the rich sail boat owner. Unfortunately, independent tank tests have never been able to confirm their claims. That does not mean that some ingenious inventor won't solve the problem some time in the future but so far only the advertising writers have it licked. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
One commonly cited quote for great speed in a baidarka is: "We supposed the strong tide to run near 8 knots per hour, for on heaving the Log once We found ourselves going thro' the water above 6 knots, yet falling fast astern by the land. At this time the Indians in their Seal skin Canoes kept way with us very easily." this is from James Trevenen a midshipman on Cook's expedition in 1778. Notes from the ships astronomer noted that: "the ebb tide met us from the north--running so strong that we could not stem it tho we had a fine breeze at SSW... ...which makes a very great Race, & Rough Sea..." While it may have surprised someone used to large sailing boats that a small canoe could keep up with them in a high current with rough waves, it should not surprise a kayaker. An out-flowing tide with an on-shore breeze sets up the ideal situation for some excellent surfing. With these conditions, a skilled paddler should have no problems moving up against the tide even if their kayak is not exceptionally fast. These feats of great speed are still obtainable. I've passed a 40' sail boat going wing-on-wing in a 15 to 20 knot wind without working too hard. You just need the right conditions. It is quite possible the other historical accounts of extraordinary baidarka performance have reasonable explanations that have nothing to do with lost secrets of the Aleuts. The Aleuts were extraordinarily strong and skiled. There is no doubt that they were consistently able to make their boats do things that most of us modern paddlers can only dream of. It would be mistake to assume their performance was primarily due to some magic property of their boats. The Aleut paddlers were quite capable of taking advantage of favorable conditions. >Bill wrote; >(SNIP) > >>So why do I bring this up? A year or so ago I was having a conversation >>with Robert Morris of Brewery Creek Small Boats, who teaches the >>construction of skin covered baidarkas, Greenland kayaks, etc. Robert >>claimed that traditional baidarkas paddled faster than many people would >>think. We discussed the fact that the original seal skins might have had >>an effect like adding some oil (or whatever) to the boundary layer and >>working like a visco-elastic fluid. Does anyone have any definite >>knowledge of this? Have there been any efforts to use visco-elastic >fluids >>to increase the performance of human powered vessels? Does anyone know if >>there are coatings that might "ablate" and effect the drag performance of >a >>kayak or canoe? 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
I have done a little research lately into Aleut boat design, and there is no doubt in my mind that... 1. The Aleuts were stronger and better paddlers than practically anyone living today. Imagine a race of Greg Bartons... 2. Their boats were capable of extremely high performance due to special technological innovations developed over the course of several thousand years of R&D. The aspect of decreasing viscous friction of the water because the boats were made of oily sealskin makes perfect sense. George Gronseth and I once theorized of creating a special oil-dripper that could be mounted on the front of a kayak. We decided that it would be neat to test speed gains used by this method. Even better, this might be a good way to get jet skiers to switch to kayaking. Imagine... "This kayak pollutes almost as much as your jetski. You'll love it." Of course, then we would also have to add a leaf blower on the back deck to make it almost as loud. :) Kevin On Tue, 10 Nov 1998, Nick Schade wrote: > > The Aleuts were extraordinarily strong and skiled. There is no doubt that > they were consistently able to make their boats do things that most of us > modern paddlers can only dream of. It would be mistake to assume their > performance was primarily due to some magic property of their boats. The > Aleut paddlers were quite capable of taking advantage of favorable > conditions. > > > >Bill wrote; > >(SNIP) > > > >>So why do I bring this up? A year or so ago I was having a conversation > >>with Robert Morris of Brewery Creek Small Boats, who teaches the > >>construction of skin covered baidarkas, Greenland kayaks, etc. Robert > >>claimed that traditional baidarkas paddled faster than many people would > >>think. We discussed the fact that the original seal skins might have had > >>an effect like adding some oil (or whatever) to the boundary layer and > >>working like a visco-elastic fluid. Does anyone have any definite > >>knowledge of this? Have there been any efforts to use visco-elastic > >fluids > >>to increase the performance of human powered vessels? Does anyone know if > >>there are coatings that might "ablate" and effect the drag performance of > >a > >>kayak or canoe? *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
I have used the west epoxy/graphite mix on the bottoms of the last three kayaks that I've built and have been happy with its durability so far. I believe that it is also claimed in some places to have a positive effect on hull speed. I can not vouch for that. mark *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
#ifdef WISE_ASS I wonder if I had put "graphite" on my "bottom" when I was a kid and had gotten in trouble and was "paddled" by my dad if there would have been less "abrasion"? #endif Sorry folks, I apologize profusely. I just couldn't resist. :) Mel --- There are three types of people, those who can count and those who can't. -----== Sent via Deja News, The Discussion Network ==----- http://www.dejanews.com/ Easy access to 50,000+ discussion forums *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
The Irish pub where hang out in Ft. Lauderdale is a center for the sailing and yahting crowd. I ran into a fellow who designs racing hulls and he stated that they use teflon in the gelcote. Then they sand it with either 200 or 400 grit to roughen it up. It was his opinion that an 18' kayak should gain 1/4 knot with a similar sanding. cya *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Mary Denton wrote: > > The Irish pub where hang out in Ft. Lauderdale is a center for the sailing > and yahting crowd. Do you know any excellent kayak instructers using the BCU syllabus or something similar in the area? Workshops would be ideal. -- gabriel l romeu http://members.aol.com/romeug studio furniture http://members.aol.com/romeugp paintings, photos, prints, etc. http://members.xoom.com/gabrielR a daily photo journal *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Mary wrote; >The Irish pub where hang out in Ft. Lauderdale is a center for the sailing >and yahting crowd. I ran into a fellow who designs racing hulls and he >stated that they use teflon in the gelcote. Then they sand it with either >200 or 400 grit to roughen it up. It was his opinion that an 18' kayak >should gain 1/4 knot with a similar sanding. Ahhh Yes, the old naval architect in the pub bit. Having been one of those I can say with complete confidence that the worst place in the world to get information on fluid dynamics is a pub where naval architects hang out. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
John Winters wrote: > Mary wrote; > > >The Irish pub where hang out in Ft. Lauderdale is a center for the sailing > >and yahting crowd. I ran into a fellow who designs racing hulls and he > >stated that they use teflon in the gelcote. Then they sand it with either > >200 or 400 grit to roughen it up. It was his opinion that an 18' kayak > >should gain 1/4 knot with a similar sanding. > > Ahhh Yes, the old naval architect in the pub bit. > > Having been one of those I can say with complete confidence that the worst > place in the world to get information on fluid dynamics is a pub where > naval architects hang out. > > Cheers, > John Winters > Redwing Designs > Specialists in Human Powered Watercraft > http://home.ican.net/~735769/ > Its not the architects, its the shaggy dogs they hang with. As a serious young dinghy racer (Geary 18, OK Dinghy, 505, Int. 14), I tried everything in the book. 1/4 knot is a HUGE increase, even at v=1.2(LWL)^.5, and the best goop we tried never showed an improvement beyong the systematic error of the model basin balance at David Taylor. My point was that graphite decreases the friction over sand and gravel, causing less scratching of the bottom. I don't think it makes the epoxy harder, just more scratch resistant due to the lower friction over the abrading surface. Roger *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
What a great group! Not only do I get several thoughtful and experienced answers to the question, but also a treatise on baidarka speed and a discourse on navel architects. Thanks to all for the help. <CLIP> >Its not the architects, its the shaggy dogs they hang with. > <CLIP> >My point was that graphite decreases the friction over sand and gravel, causing >less scratching of the bottom. I don't think it makes the epoxy harder, just >more scratch resistant due to the lower friction over the abrading surface. > ,,, (o o) ==================oOO--(_)--OOo========================== Bob Washburn whiterabbit_at_iw.edwpub.com or rwashbu_at_siue.edu The only difference between a rut and a grave is the depth. ========================================================= *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
John Winters wrote: > > Ahhh Yes, the old naval architect in the pub bit. > Having been one of those I can say with complete confidence that the worst > place in the world to get information on fluid dynamics is a pub where > naval architects hang out. > I should think that depends a lot on the particular fluid being discussed, non? Steve -- Test Scoring & Reporting Services Sometimes, you never can University of Georgia always tell what you Athens, GA 30602-5593 least expect the most. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
In a message dated 11/10/1998 9:50:52 AM EST, rkorn_at_europa.com writes: << My point was that graphite decreases the friction over sand and gravel, causing less scratching of the bottom. I don't think it makes the epoxy harder, just more scratch resistant due to the lower friction over the abrading surface. >> You ae absolutely correct! John *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Actually, these guys don't hang out at the pub, they were here for the Whitbread around the world race, and had designed one of the leading boats. They were only around for a week or two. cya > -----Original Message----- > From: owner-paddlewise_at_lists.intelenet.net > [mailto:owner-paddlewise_at_lists.intelenet.net]On Behalf Of John Winters > Sent: Monday, November 09, 1998 6:21 AM > To: paddlewise_at_lists.intelenet.net > Subject: Re: [Paddlewise] Graphite for Bottoms > > > Mary wrote; > > > >The Irish pub where hang out in Ft. Lauderdale is a center > for the sailing > >and yachting crowd. I ran into a fellow who designs racing > hulls and he > >stated that they use Teflon in the gelcote. Then they sand > it with either > >200 or 400 grit to roughen it up. It was his opinion that an > 18' kayak > >should gain 1/4 knot with a similar sanding. > > > Ahhh Yes, the old naval architect in the pub bit. > > Having been one of those I can say with complete confidence > that the worst > place in the world to get information on fluid dynamics is a pub where > naval architects hang out. > > Cheers, > John Winters > Redwing Designs > Specialists in Human Powered Watercraft > 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.gasp-seakayak.net/paddlewise/ > ************************************************************** > ************* > *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
In a message dated 98-11-10 15:18:04 EST, kwhilden_at_u.washington.edu writes: << 1. The Aleuts were stronger and better paddlers than practically anyone living today. Imagine a race of Greg Bartons... 2. Their boats were capable of extremely high performance due to special technological innovations developed over the course of several thousand years of R&D. >> At times like these and with great information like this before us, one wonders (aloud) if Professor Inverbon will return to sort it all out? Jack Martin *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Try this experiment, paddle your kayak for 8 hours a day, 5 days a week for, say, 6 months and see if there is a difference in your ability. :-) When I was driving a harbor patrol boat at Catalina Is., many people would comment on how they wished they could handle their boats the way I handled the patrol boat. I would tell them to just practice for 8 hours a day, 5 days a week and see how quick they get there. In my job I was constantly putting my boat next to either a boat or a dock and moving away again, I was not just cruising around. Also it was considered very poor form to ever let the patrol boat touch a guest boat. At the Isthmus, the main job of the harbor patrol is to assign moorings and collect fees, you had to get within arms reach of the guest boat to get money, and return change and receit. Lots of great boat handling practice. The skin of many aquatic creatures seems to be very well adapted to moving through the water with minimum drag. There may very well be real advantages to using real skin for boats. There are also disadvantages, like getting the skin, processing it, attaching it to the boat, and maintaining it in working condition. Most of us don't have the time for that level of commitment. :-)( Anybody here have the sewing skill to sew the pieces of skin together without making needle holes through the skin? I don't. I think I could get there with a few months of practice, but I hesitate to even use the animal skins for my boat, let alone the practice. OTOH If I were hunting the animals for food and other materials as a matter of life, then it would be natural to use every bit of the animal in some usefull way. BTW Are there any Aleuts living fully in the old traditional way now? The kayak is a better hunting vessel only as long as you consider the materials used to make and operate the boat as well as the actual hunting. Outboard motor powered, aluminum boats are better, but require outside materials that come at great cost, both in money and environmental terms. michael kwhilden_at_u.washington.edu wrote: > > I have done a little research lately into Aleut boat design, and there is > no doubt in my mind that... > 1. The Aleuts were stronger and better paddlers than practically anyone > living today. Imagine a race of Greg Bartons... > 2. Their boats were capable of extremely high performance due to special > technological innovations developed over the course of several thousand > years of R&D. > > The aspect of decreasing viscous friction of the water because the boats > were made of oily sealskin makes perfect sense. George Gronseth and I once > theorized of creating a special oil-dripper that could be mounted on the > front of a kayak. We decided that it would be neat to test speed gains > used by this method. Even better, this might be a good way to get jet > skiers to switch to kayaking. Imagine... > "This kayak pollutes almost as much as your jetski. You'll love it." > Of course, then we would also have to add a leaf blower on the back deck > to make it almost as loud. :) *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Steve wrote; ->> >> Ahhh Yes, the old naval architect in the pub bit. >> Having been one of those I can say with complete confidence that the worst >> place in the world to get information on fluid dynamics is a pub where >> naval architects hang out. >> >I should think that depends a lot on the particular fluid being >discussed, non? Never seemed to matter. I believe a good naval architect in his cups can lie with equal facility about any fluid. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
Got to see the test case for graphite bottoms at Chesapeake Light Craft (CLC) today --- it was an observation on Chris Kulczycki's Fall '98 "Notes From Our Shop" at CLC that started this thread. Specifically, Chris said that mixing graphite powder with epoxy "make[s] a smooth, tough and, most importantly, a low-friction coating." Typically, Chris uses only about half of a six ounce, $6 can of graphite per boat, so we're not talking major cost or weight here. The bottom is tougher and more scratch resistant than painted epoxy, can easily be faired when it's needed, and, therefore, probably provides some increase in hull speed --- or, at least, minimizes the develoment of drag from scratches in the surface. Downside is that it is a dull dark gray color. Okay for the bottom --- pretty boring for the whole hull. But tough and very smooth. Jack Martin *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
This reminds me of an engineering course I took a while ago. If I remember correctly, fluid friction against a solid surface can be reduced if the solid surface has some roughness to it. The principle, as I remember, is that a smooth surface allows laminar flow to occur near the wall, while a rough surface creates turbulence near the wall. The smooth wall (boat) has to drag along a thick boundary layer of water, while the rough surface will carry only a thin layer. Similar to why dimples help a golf ball fly far. So maybe roughing up the surface with sanding, or by creating a bumpy coating with various fillers, could reduce drag. Since I'm not practicing hydrodynamic engineering right now, I have no idea whether this would work or what size "bumps" are required. Any ideas? Doug Diez >Mary wrote; > > >>The Irish pub where hang out in Ft. Lauderdale is a center for the sailing >>and yahting crowd. I ran into a fellow who designs racing hulls and he >>stated that they use teflon in the gelcote. Then they sand it with either >>200 or 400 grit to roughen it up. It was his opinion that an 18' kayak >>should gain 1/4 knot with a similar sanding. > > >Ahhh Yes, the old naval architect in the pub bit. > >Having been one of those I can say with complete confidence that the worst >place in the world to get information on fluid dynamics is a pub where >naval architects hang out. > >Cheers, >John Winters >Redwing Designs >Specialists in Human Powered Watercraft >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.gasp-seakayak.net/paddlewise/ >*************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Douglas wrote; >This reminds me of an engineering course I took a while ago. If I remember >correctly, fluid friction against a solid surface can be reduced if the >solid surface has some roughness to it. The principle, as I remember, is >that a smooth surface allows laminar flow to occur near the wall, while a >rough surface creates turbulence near the wall. The smooth wall (boat) has >to drag along a thick boundary layer of water, while the rough surface will >carry only a thin layer. Similar to why dimples help a golf ball fly far. Laminar flow is the exception rather than the rule on kayaks (and other surface vessels as well). Typically the flow becomes turbulent only a short distance from the bow as the Reynolds number rises rather rapidly with length. In theory laminar flow can be retained for the full length of a kayak but in practice this does not occur due to yaw, particulate in the water, surface condition (mostly rough bows), wave turbulence, etc. To date the only "rough" surface that reduces friction (for boats) comes in the form of microgrooves commonly called structuring. These grooves work only when oriented properly to the flow and if they have the right depth for the speed. This requirement for precfision makes them impractical for kayaks. There was an article in Scientific American about microgrooves but I don't know if it is still on their web site. It explianed how they work and had some nifty pictures of the flow. Try this URL although some of the stuff ddi not come up for me http://www.contrib.andrew.cmu.edu/~zu22/html/supercomp/0197moin.html The golf ball business pops up a lot but does not apply. The dimples on the golf ball reduce the wake size not the surface friction of the ball. In the case of streamlined bodies like kayaks, the wake size has already been reduced to the near minimum and separation drag rarely amounts to much. > >So maybe roughing up the surface with sanding, or by creating a bumpy >coating with various fillers, could reduce drag. Since I'm not practicing >hydrodynamic engineering right now, I have no idea whether this would work >or what size "bumps" are required. Any ideas? There have been a number of research projects into this and some interesting configurations have surfaced but the problem of flow alignment with grooves or bumps seems to foul up the works. Cheers, John Winters Redwing Designs Specialists in Human Powered Watercraft 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.gasp-seakayak.net/paddlewise/ ***************************************************************************
Mac McCarthy (Feather Canoes, Sarasota, FL) says that graphite is inappropriate down there. A boat on a parked car gets far too hot. He uses a WEST material which I think is aluminum powder, and finds that it strongly reduces wear/scratches when going over an oyster bar (no, the kind where oysters live). Bruce Bruce Winterbon bwinterb_at_intranet.ca http://intranet.ca:80/~bwinterb Carpe diem -- crastinum! *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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