: Good morning,
: what would happen to a strip built if you didn´t glass the inside, like in a
: S&G.
: Would it be too weak??
: Just wondering:)?

It would be too weak. Remember that you have a big force -- the outside water pressure -- which is squeezing the hull. The more you load the boat the deeper it sinks and the more water pressure pushes in on the hull.

For each foot of submersion it is roughly 1/2 pound per square inch, or about 72 pounds of pressure per square foot. You'll have a pressure on the outsid of your hull squeezing the boat in which is equal to the displacement of the boat and its contents. So, If you weigh 160 pounds and the boat is 40 pounds,, then it is like havingg your boat trapped in a vise which is squeezing it with 100 poinds of pressure from each side. If you add enough weight to the boat the sides could buckle.

In a whitewater boat you would have additional problems from from "heavy water", or the hydrodynamics of rushing currents. A boat which was not well reinforced and that was caught in such conditions, perhaps by being snagged on a rock and turned braodside to the current, could squeeze tightly around the paddler, trapping them inside -- a potentially lethal situation.

I asume that your question is just about not having the glass cloth for reinforcement, and that you would still consider sealing the inside with two coats of epoxy resin. While the glass cloth is expensive, so is the resin, so if I guess that you are thinking of saving money, and might foolishly try to save a bit more. Without the coating of epoxy on the inside the wood would absorb moisture, whether from the humidity in the air or anything that splashed into the boat. This moisture would cause the wood to swell. since the swelling on the outside edge of the wood would be constrained by the external layer of glass cloth, all the swelling would be on the inside, bending the hull in as if it were being squeezed. The situation MIGHT reverse itself, and the wood shrink, back to "normal" if it was allowed to thoroughly dry, but that is not guaranteed. a few cycles of swelling and shrinking would put undue stress on the exterior glass skin, and the moisture in the wood could cause early failure of the outside skin through delamination. This could be in a matter of days if the boat interior was damp, and the boat was stored in direct sunlight, allowing the water vapor to move through the thin wood strips and accumulate under the fiberglass. You might even see large blisters filled with moisture forming within hours of such storage. Definitely not a good situation.

Since most of us use glues that are water resistant, but not waterproof for gluing together our strips, the constant immersion of the bottom of the boat with water in the bilge could cause the wood strips to separate. Since the water pressure on the bottom of the boat is higher than anywhere else on the hull (the botom is further under water than any other part of the hull) this is where you might see failure first and soonest.

If glass cloth and eposy resin are a finacial problem, or simply difficut to obtain, use a completely waterproof glue, seal the wood with several coats of a good varnish or paint, and strongly consider adding closely spaced ribs, which you can bend to fit the hull curvature if you steam the wood first.

PGJ