''PVC Skin Material by Hendrik Maroske''

Skin Material (HHM)

For the first prototype I sewed two strips of PVC onto a zipper and glued these zipper strips at the middle of the deck piece. This feature was as strange as convenient; it eased assembly and loading of the boat.

With some grief I dropped this idea and the actual design now has hatches instead of the zipper. These hatches serve the same purpose except that it is a lot more difficult to assemble the boat. Also I do not have these sponsons any more that had to stretch the skin.

My most recent Baidarka still is the one from the 1999 Toronto trip. The Baidarka skin was finished late summer 1998 and I must confess I did not use the boat very much since Toronto. I have moved the workshop since, and with it the boat, and since that move the lake is a little more difficult to get to (without car).

Anyway, the pics on this website with several closeups of that particular skin have been made during Christmas holidays January 2002, so you have a guess at how good the skin actually is. It still looks "new enough", is tough as ever and still waterproof. No seams broke.

The skin is nearly four years old, the "unprotected" Stamoid, and ready to go on any trip. I'm satisfied with it. Always cleaned stains before they could wear in (with water only), because without the protection I am afraid to use chemicals to clean the skin.

I see that Tom Yost used polyester material, and then coated with hypalon, which worked well for him, but I wanted to avoid having to use toxic coatings, and the pvc material seemed quicker to skin.

To each one his way looks as the best afterwards. But I would still do it again. It took some time to learn to use a good balance of techniques, stitching, glueing, welding. Basically, my experience with Stamoid and Pattex and Acetone is that if the glue doesn't hold within the first five minutes, it never will. Throw away the pieces that you can and restart. If it holds, it always will. And by "holds" I mean you rip the pieces apart and not the glue fails, but the Stamoid goes apart.

Practice good bonds before doing the skin.

And even more basically the only advice I can give is to really do a few practice runs on the stem and stern pieces with the intention to keep them as samples. This will pay out in the end. Use double sided tape for the first practice run to have a good chance to rearrange things and if you don't want to wait for the glue to settle.

And, talking about abrasion, I cut Stamoid in strips and these were formed with a heat gun to match the curving of the hull before glueing them on over the stringers and where the skin pieces meet.

Tom writes:
This temporary folding skin is made of PVC to test the viability of the material as a one piece hull. In this test, I've pulled the skin fairly tight using squidding line but am careful not to over stretch. There are still a few wrinkles in the skin, but to this point no heat has been applied. The "Real" skin will be made of higher quality, thinner, Stamoid PVC.

I feel that a one piece PVC hull is workable, as it has been done by others. The problem I had was trying to do it with Stamoid. The black PVC had multidirectional cloth , the same that I use on my sewn skins, so it had the ability to conform to the stringers. I didn't have enough of it for the entire boat so I purchased Stamoid thinking it was made the same way. It wasn't.

The Stamoid has unidirectional fibers which would only conform in one direction, so it wouldn't take the shape of the hull without getting all wrinkled at the stringers. In addition, and the thing that bothered me the most, was the fact that the Stamoid was easy to tear when I pulled on the stitching that I used to stretch the skin. This happened in only one direction , parallel to the fibers. I've never had a skin material tear before, so it really caused me concern.

About the Stamoid tearing easily when sewn; that is a good point. If I recall correctly, the thicker 0.6mm variant would not tear as easy as the 0.4mm one. Anyway, I had no other comparison and was satisfied with the 0.6mm stuff. Although I have never seen a skin tear on my boats, even on tar or stone beaches. And back then I simply took it as normal, but shame on me, I have used only a small amount of really thin Stamoid, mostly using the 0.6mm material. I stand corrected in having said the thinner material is better. Maybe the thicker material has a stronger cross weave respectively more cross weave?

Here are a few measurements on tearing strength on 0.55mm Stamoid. To me the difference doesn't look so alarming, but yes the Stamoid actually is not at all multi/bi directional.

During my boat building runs I noted a rather large variation in quality even in a single roll. Also, the material sample I just have tested is 0.55mm thick instead of the supposed 0.6mm. The resistance to tearing with a strong line also varied a lot and was kept at bay in using a small distance between stitches. In the end I glued everything anyway. Also I used to use a thinner, weaker 10kg line that would rupture before the skin would tear and would not interfere with glueing.