Chris,

I built a skin Putz Walrus this summer and researched it a lot before I started, so I will pass on what I have learned.

> Using canvas for the skin and Elast-o-Seal and Snow Roof for the coating:

> should the surface which will be the inside of the skin be coated with the
> Elast-o-Seal before stretching the fabric on the frame?

I did not do this when I built my skin kayak, now my kayak has untreated canvas on the inside. I am thinking of pouring a sealer on the inside and sloshing it around. I am not too woried because I store my kayak in a very dry semi-heated basement.

> I have used Snow Roof in another application, without Elast-o-Seal, and
> was not impressed by its gripping ability. Does anyone have experience
> with it in this application?

I primed the canvas with the Elast-o-Seal first, adhesion was good, but it took about a month for the Snow-Roof to harden and get full abrasion resistance.

> For boats of the same design, will stich & glue or skin on frame
> produce the lightest boat? (I built two rigid Folbots, a 17' single and
> the 14' Glider, back when Folbot marketed kits. The boats were anything
> but light - about the weight of comparable plastic boats.)

Give me a month and I will answer you question. I built a skin Walrus 17 (33-1/2 lbs.) this summer, and am currently building a stitch & glue version.

> I have seen references to using cedar for the stringers. Cedar is light,
> but not very strong, i.e., a 3/4"x1" stringer of cedar can be
> easily broken by hand. Unless I am missing something, I should think a
> stronger wood would be advisable if the boat is to be banged around a bit
> (as all my boats are).

I used cedar for mine, but it is not a traditional frame structure, it is a trestle frame(ala Putz). The cedar appears to be strong enough for my purposes. It will flex a lot before it breaks. If you want to use cedar, just increase it's width. It is a good wood for skin kayaks because it is light, and naturally rot resistant. You might want to use yellow cedar for the ribs, it is signifigantly stronger and takes well to bending. Red cedar is lighter but cannot tolerate extreme bending easily. Stresses on a skin kayak ure usually distributed over a large area, so a lighter flexible, but weak wood works fairly well for the frame. I have not banged mine up too much yet, so I cannot say how strong it really is.

> For what it is worth, Daniel Smith, an art supply house with free catalog,
> carries a wide variety of canvas duck and also linen in various weights.
> They only have one synthetic fabric. Defender Industries carries some
> vinyl coated nylon cloth. Would the vinyl coating be a sufficient
> waterproofing?

I would stay clear of the vinyl, I don't think it is very strong for it's weight. Check into tent and awning suppliers. My local tent and awning supplier had a very good selection of frabrics, including kevlar, polyester, coated nylon, and cotton duck, all in various weights.

Hope this helps,

Mike