: Point of view #1: Probably none. A lot depends on some variables you have not
: mentioned, and perhaps not even thought of.

: Bulkheads, for example. Where are they placed, and how thick are they?

: How big are the fillets?

: Think about what the boat would look like if you removed all the wood parts
: at this time. What you would have left are the fillets, which would create
: a skeleton, which would resemble the frame of a skin-on-frame kayak. What
: would be missing would be the ribs and bracing and of course the skin.
: Let's ignore that skin for a minute as it does not add a lot to the
: structural properties of the frame.

: If your fiberglass fillets are big enough to match the strength of a wood
: chine on a canvas skinned s-o-f kayak, and then wood panels provide as
: much stiffness and bracing as the ribs on this hypothetical s-o-f boat,
: then (theoretically) there is no reason to bother with glass at all.

: Point of view #2: Glassing the bottom is good for scratch and ding
: resistance. A layer of 6 ounce, or two layers of 4 ounce cloth would be
: wonderful protecton against sand and gravel abrasion. If your area has
: mostly sandy beaches, then a single layer of 2 or 4 ounce would work. If
: your goal is only abrasion resistance you could save some money, though,
: by gluing on 1 to 2 inch wide "rub strips" along the bottom. Cut
: the strips from your doorskin panels.

: Point of view #3: If you want to add structural strength to the boat then
: your greatest improvement would be in reinforcing the interior of the
: hull. The way that hulls flex seems to make the most out of the strength
: of the glass cloth when the cloth is placed inside the boat. it has
: something to do with the difference between how glass cloth handles the
: forces of tension and compression.
: with this theory in mind I'd put the 6 ounce cloth on the inside of the hull,
: 4 ounce on the outside, and 4 ounce on both sides of the deck. Assuming I
: had all those different sizes and lengths. Almost as good would be 4 ounce
: cloth on all surfaces, in and out.

: You can also add strength to the boat by epoxying in ribs, or their
: functional equivalents. You can cut ribs from 3/8 inch plywood but making
: a piece that is shaped to fit like a bulkhead, but has the center removed,
: leaving behind a "donut" with 1 inch to 1.5 inch thick walls.
: Or, you can make 1 inch high forms from cardboard, and cover them with a
: couple layers of glass cloth and resin, thus molding them in place. Or,
: you can mix up some of the stiff glop you used for the fillets and seams,
: and build up rings on the interior of the boat.

: Minicell foam bulkheads provide some structural strength, too.

: Point of view #4: There is a lot to be said (and it HAS been said) for using
: multiple layers of thinner and lighter fabric. For example, instead of
: using a single layer of 6 ounce cloth you would use three layers of 2
: ounce cloth. One feature of this approach is that if you should ding the
: boat so deeply that the cloth layer gets snagged, you have a chance of
: snagging just the outer layer, or layers, of cloth, and leaving the inner
: layers completely intact.

: Hope this helps you understand that there is no single "right"
: answer. Best thing for now is to build according to the plans, and if it
: breaks, fix it and make it stronger.

: PGJ

Excellent points Paul. I forgot all about the compression/expansion factor. The multiple thin layers of fiberglass are also a great idea.

Let me up the anti a little. We have 3 nephews which of coarse have 2 friends which are all hyped about building S&G’s. Ages 13,13,16,17,17. I’m imagining ultra sensitive care the first 2 trips. After that, no holds bar. At least that’s how my brother and I treated our boats at that age. Any special areas that will need special reinforcement?

Roger