I am building a double folding kayak, a Blandford PBK19, per plans from Clarkcraft. This will be primarily used in lakes, Long Island Sound, and until tested in warm water within swimming distance of shore (FYI the bottom is essentially done including endposts, the first two crossframes, and stringers and gunwales installed for the front quarter of the boat.) I am looking ahead to skinning and have three possible routes to follow. They are in order as follows: 1. Plans call for a rubberized fabric, preferably canvas and rubber ply. The hull is done in one piece, being stretched along the gunwales and sewn up along the endposts. I imagine this is done similar to that shown at the Folbot page at http://www.folbot.com/tour3.htm Notice the Folbot uses a thick hypalon material that I believe is not stretchy, which is why they use sponsons (like other manufacturers). Folbot and others connect the gunwale to the top stringer with little plates as shown at http://www.folbot.com/anatomy.htm which give the sponsons something to push against to tighten the hull. The pbk19 does not have these. If I follow this route I have to either find a stretchy material, or use non-stretchy material and somehow add sponsons to tighten. Questions for this route a) Since the pbk19 has a flat plywood bottom, can I put a sponson there? b) Does anyone know of a source for stretchable rubberized fabric? I have samples of PVC and neoprene fabric and none seem to stretch. 2. From the baidarka mailing archives, cut strips to match the keel, chines, and gunwales, glue and then heat to remove wrinkles. This can be found in detail by searching the archives at http://robroy.totalsports.net/baidarka/wgindex.html and searching for "hendrix mixture", will return two hits including "cutting the skin" which is what you want. This was done for the kayaks at (excellent site by the way!) http://robroy.totalsports.net/baidarka/slideshow/index.html by Hendrik Maroske. His brother Gerald advocates sewing as well, as mentioned in the other hit returned. I believe Hendrik used Stamoid PVC for his single aluminum kayak. I have a sample of 15 oz seems thin but smooth both sides, and looks like it would glue nice. Other samples I have, basically have one smooth side and the other side shows the fabric weave which I believe would not glue as easily, as when gluing an overlap. Additionally some PVC has special coatings, which must be cleaned before gluing. Questions a) Blandford advocates no seams below the waterline, and this route has a lot. Hendrik and his brother have had luck with this but is this really such a good idea? b) The neoprene fabric sample I have is 16 oz buff free(no coating), a little thin but looks fairly tough. Does anyone have any recommendations for/against neoprene fabric? Is there any particular flexible glue that should be used? c) Any recommendations for a particular PVC source? I have samples from Seattle Fabrics, of PVC, and neoprene (special order fabric). I am waiting on 16-oz hypalon sample (again special order). They have been very helpful. I also have Weblon samples, but they have coatings on them. 3. George Dyson, author of Baidarka, sells plans for aluminum kayaks that are skinned with one-piece nylon fabric. The skin is then heat shrunk and hand painted with thinned hypalon, to saturate the skin to the inside. It is then painted with neoprene, and finally finished in hypalon. Since this is sewn in one piece similar to route 1 above the question arose from another pbk19 plans purchaser if this could be tried. Questions a) Dyson’s method is meant for a non-folding boat so there is quite a thick layer of coating on this boat. I seem to recall that folding something this thick would result in cracking since much of the coating is on the surface. Is there anyway of getting by with just using thin coats of neoprene? I believe this is more flexible than hypalon, but Mr. Dyson used thin coats of hypalon because it thins easier than neoprene. b) Is there some way of covering the woodwork so that the paint that soaks through will not stick to the woodwork? I recall reading that removing skins painted in polyurethane results in wood coming off with it. c) Some boats done this way use polyurethane instead of hypalon/neoprene. Is polyurethane flexible enough for a folding kayak? 4. Okay I am sneaking in a forth route, basically meaning other. This assortment comes from Jim Heter’s really neat PakYak site at http://robroy.totalsports.net/boats/PakYak/ He uses multiple layers in his latest prototype, nylon pack cloth, a foam layer and a bottom liner. The pack cloth is waterproofed with urethane on one side and then he coats the outside with Thompson's Water-Seal. I’m not sure if there are seams below the waterline. He mentions that he has used cordura in the past. Questions a) Multiple layers sounds interesting. Some inflatable boats use two layers. Okay how about making an unsupported vinyl hull (no fabric) glued up as in route 2. Then sew up a nylon skin as in route 3 over the vinyl and coat with thinned neoprene? b) Thompson's Water-Seal? Can this be used on plain old canvas? Has anyone actually read this far? Feel free to offer any suggestions or comments. Thank you in advance, Paul. kayaker37_at_hotmail.com *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Paul Raymond wrote: > > I am building a double folding kayak, a Blandford PBK19, per plans from > Clarkcraft. This will be primarily used in lakes, Long Island Sound, and > until tested in warm water within swimming distance of shore (FYI the bottom > is essentially done including endposts, the first two crossframes, and > stringers and gunwales installed for the front quarter of the boat.) I am > looking ahead to skinning and have three possible routes to follow. They are > in order as follows Paul, You have a lot of detailed questions that deserve detailed answers. But I am leaving this morning for Paddlesports Show in NJ and out effectively until Monday nite (paddling plans on Monday) and so won't be able to go into this deeply. Still here are some thoughts. I sense, and I may be wrong, that you have not really been around folding kayaks and are working mainly from reading materials and websites. The reason I say that is your the focus on getting skin material that is stretchy and your misconception of how sponsons factor into a folding kayak's design. You seem to be taking the technology around non-folding skin boats and extrapolating on this for use on a folding kayak. If you follow that route you will have either one of two things: 1. a folding kayak that you will never be able to take apart (if you work on fitting the skin to the frame while making the skin) or 2. a folding kayak into whose skin you will never be able to place the frame. It is imperative that you have enough room inside the skin to slide in frame halves, which I assume is the assembly method you are after. There are others, like the new approach introduced recently in several Nautiraids and in the new Klepper Alulite in which the frame is assembled entirely outside the skin and dropped into the skin via a zippered back deck. So having a skin that will accept the frame easily and then stretch the frame is critical. There are some folding kayaks that do not employ sponsons and they are harder to assemble and they are very exacting to sew skins for. It would be okay to sew a seam below the waterline. Several models do that and have done well, the Klepper Aerius I and its smaller sister the 2000 have a seam directly along the keel line. But they cover it with keelstripping both inside and outside. You are correct in worrying about how any material you use will react over time to being folded. The materials classically used in folding kayaks have held up quite well even over 30 years of folding and refolding a skin or leaving it folded for years. This has tended to be rubber or hypalon. Other materials have done okay but the hypalon is proven over longer periods. I will try to get to your message on Tuesday and I hope some others will pitch in with thoughts. Frankly, though, in my experience constructing your own folding kayak virtually never comes up with something that is anywhere as good as even the run-of-the-mill factory one in terms of consistent skin fit and performance. The skin winds up, over time, being either too tight and screwing up the frame and popping stitches or so loose that it like a rumpled bed sheet and creates enormous drag and sluggishness. ralph diaz -- ----------------------------------------------------------------------- Ralph Diaz . . . Folding Kayaker newsletter PO Box 0754, New York, NY 10024 Tel: 212-724-5069; E-mail: rdiaz_at_ix.netcom.com "Where's your sea kayak?"----"It's in the bag." ----------------------------------------------------------------------- *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Perhaps we can combine this thread with another and talk about "Skinning a varmint to make a folding kayak" *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
John Fereira wrote: > > Perhaps we can combine this thread with another and talk about > > "Skinning a varmint to make a folding kayak" > Or, as the Feathercraft people might say (and stealing a pun from Ralph) "There's more than one way to skin a Khat." Steve *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
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