Homebuilt Kayaks in Fiberglass-no mold

I have been messing around with not only building boats, but ones of my own designs for the simple joy of doing it. One thing that I tried was seeing if I could build a glass boat without first making a plug then a mold then laying the boat up after that. What I hit upon (I am sure others have done it also) was to build a strong back with stations as if I was going to do a stripper. Next was to run molding trim or small diameter pvc pipe on all the corners where two chines meet as if I was going to turn it into a skin on frame boat. I then wrap it in shrink wrap plastic (what Home Depot sells for covering sliders to make a poor man’s storm window) attatch it to the frame then shrink it with a hair dyer. I then lay the glass over that, pre cut it to fit the boat shape then wet it with resin and lay it over the shrink wrap which the resin doesn’t stick to. Let it cure then pop it off. I am now looking at ways to use as many off the shelf products from Dept. stores or Home Depots to reduce the building cost for any other backyard builder that might want to put together a full fledge, but safe boat. My last two seem to be succesful. A 15’ Greenland style that I first built hoping to lure my kids “on board” (no such luck) and the second was a 17+’ Baidarka influenced style of a boat. I am always looking for suggestions and new ideas. Posting pictures on Web Shots.


Why not try your shrink wrap trick over a lashed together SOF frame? Seems like you would be able to glass the hull and deck as a continuous piece, then pull the frame out.

I didn’t do it that way as I thought it would be easier to install the bulheads to the hull first, then do the deck, but in the long run I think your suggestion is the way to go. After the cockpit is cut open, one could install the bulkheads through that opening plus you wouldn’t have to deal with the seaming of the hull to deck as the deck layup can slightly overlap the hull after the hull has already been layed up.

Cockpit AND hatch openings…
… should make it easier to get those bulkheads in if you do it monocoque.

My concern with the process would be surface finish, Mold and gel coat takes care of this normally - as you can work from outside layer in.

Your way goes inside out - so should entail a lot more sanding and refinishing the outside to get even close to the same result. Your boats look good, but even in online resolution photos I can see surface irregularities. Call me Mr. Picky.

Got shortcuts/techniques to address this?

Finish work
Yes it did require a fair amount of sanding. A belt sander makes fairly quick work (messy so doing it outside is the best) followed by a drill/disk sander for the more contoured surfaces then a palm sander to smooth it out. I do want to make it perfectly clear that you aren’t going to have a boat or finish that looked like it was from a mold. This was simply an attempt to see if a home/backyard builder could build themself “one” boat in glass (and in my case epoxy) without going through all of the time consuming and much greater expense of doing a plug, then making a mold from that before laying up their boat. From a distance my boat looks fairly good, but you would have no problem seeing that it most likely is “homebuilt” when one does a closer inspection. What it does allow is for some one to build a 17’ kayak for something in the $500 range. Less if they want to use a little more ingenuity and keep the extras to a minimum and more (as I did) if they want to start adding aftermarket features (rudder,seats,hatches, deck harware etc.) I look at it this way, the first 5000+ years of kayaks were homebuilt so for anybody who likes to work with their hands it isn’t a bad club to join.

Building monocoque
Is probably the way to go. I think if I had done it that way it would have sped up the process even more and allowed a little less of a visual ripple where the seam is. I initially didn’t do it that way so that I would have no problem removing the frame shrink wrap structure, but with a little ingenuity in how that part is put together, it should be able to be designed to snap apart and pulled out of the cockpit opening. That is why I think it is great to hear the pros, cons and suggestions of others.

Good scrounging and a nice looking boat. Keep at it!

Consider one of Tom Yost’s designs
His folding designs are well regarded and a slightly modified frame would allow easy removal after glassing, but be completely reusable if you want to make more than one boat. I’d hate to go through all the time and effort of making a wood SOF frame, just to cut it up to get it out after glassing. If you were going to go through that amount of effort for one boat, it would be faster and cheaper to simply buy panels or plans and do a S&G boat.

Building on Greyak & Bnystrom’s ideas
Sorry. No pun was intended. I’ve been knocking the idea of a folder around in my head for some time now. A one piece shell will solve some issues, but will create a couple more. You’ve already touched on the bulkhead issue, and I can’t see an easy solution there. The other problem may be in the stems. If you make upswept ends and adapt Yost’s methods, consider devising “break away” stem peices just in case. It would be better to have the stems as permanent residents than to try to cut them out later.

Stems and sterns
I have already thought about how to do things like upswept bows and the “breakaway” pieces are what I also thought would be the answer. What I’ve considered is shaping the bow out of easy to carve foam. I would have this “breakaway” piece start probably where the last station would be and have that station to also be a piece of foam identical in shape to the last wood station. At this point I would consider glassing the whole foam shape including the station side. This being glassed in its’ entirety would create an additional safety feature as it would create an extra air tank on either end of the boat. It would also make the rest of laying up the boat much easier as you wouldn’t have to contend with the more difficult task of overlapping the full boat length piece of wetted out glass over itself along the keel line when it starts to rise towards the top of the bow or stern. Instead you would only have to have your full length pieces overlap the already glassed ends of the boat and then fair it with sanding or autobody putty later.

I also have done a stitch and glue boat and by no means feel that my attempts are a superior technique. With strippers or s&g construction you still have to glass both the inside and out plus do your fair share of sanding. Wooden boats are light, strong, great lines and probably the best looking ones out there. My experiment along with the ideas, imagination and creativity of others may prove the old adage “That there is more then one way to skin a boat” in what hopefully might be a reasonably cheap and functional way.

Try the “Lost Foam” Trick…
I have never tried this for anything as large as a Kayak, but wanted to point this out as something to think about. I have done this to make cowlings for Large Radio Controled Airplanes, and it works well.

Buy some large long pices of white foam, and carve your entire kayak to full size. Lay the fiberglass and resin over the entire Kayak to the thickness and degree of finish you want.

CAREFULLY, VERY CAREFULLY,(Outside away from any flames) pour gasoline into the Kayak, and it will dissolve the white foam. You will then have your entire Kayak in one piece. (White foam dissolves quickly)

Note the inside of the kayak will need cleaned out from the gasoline, and the inside of the glass will be a bit rough from the foam. But this does work very well making objects that are around the size of 12" cube. You might want to try making a 36" model first to see how this works for you. AND you may want to try different solvents that will dissolve the white foam, and not be SO FLAMMABLE. The Modeling people use this process all of the time when building a design of their own.

Have Fun, and be carefull!

And Yes, I know Gas is dangerous…
And Yes, I know Gas is dangerous… I am hoping that if you are “handy” enough to design and build your own fiberglass Kayak, that you are intelligent enough to understand how dangerous this could be. You may want to carve out as much foam as you can, then finish removing the rest of the foam by dissolving it with gas or another solvent that won’t harm the fiberglass itself…


Just curious…
Home depot has resin by the gallon, but where did you acquire sheets of F/G cloth? All I find is patch-sized repair pieces.

Marine suppliers will have glass
Try www.raka.com. They also have the best prices on epoxy.

http://www.johnrsweet.com is another good source.

More sources
Raka and Sweet are excellent. Here are two more.



I only use the polyester resin from HomeDepot to do cold pours into the bow and stern of the kayaks otherwise I use epoxy because it is safer to work with. I also have a marine store that sells to commercial fisherman near where I live so I can get stuff there as well.

Fairing Compound
You should be able use fairing compound to smooth out those surface irregularities. It would add some weight, however. However fair your hull is is just a matter of how much time and effort you’re willing to put into it. I’ve seen 30’ hand glassed sail boats with hulls as slick as anything you’d see out of a big yard, just because the builder was willing to put the time into getting that perfectly fair surface. A lot more sanding, a lot more time, but IMHO, a much better looking result.