extra fiberglass layer on the bottom

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Dave G
Posts: 7
Joined: Thu Oct 06, 2005 8:17 pm

extra fiberglass layer on the bottom

Post by Dave G »

:thinking

I have a question regarding the direction of the weave when applying a second layer of 6 oz. cloth to the exterior bottom of a canoe ( or any other boat I guess if it is going to be finished clear).

My wife and I just finished a mahogany Whitehall using the WEST system. The architect and supplier of the plans was Glen L. Everything turned out especially nice even though this is a fairly involved craft to build. My current question evolved from that boat to the current one, a 17' mahogany canoe.

The canoe is ready for glassing. On the Whitehall we were instructed to wrap the 6 oz. cloth around the stem, keel, and corners of the transom ( no easy feat with the wineglass shape). Overall, the boat is stuning. The areas of the doubled up glass however are somewhat evident if the sunlight is at a particular angle, producing a more noticeable presence of glass sheathing.

As we intend to build many more canoes and smaller craft such as kayaks, I would like to find out about the best direction for the weave when applying the second layer. I am probably correct in assuming that if any canoe or small craft that is 17' is more likely to try to be loaded heavier by the customer, and because of its overall size may be more affected carrying a load through rougher waters with regards to torsional twisting or bending.

I can see at least three posssibilities for the second layer on the bottom. (1)- same lengthwise direction as the first, (2)- 90 degrees to the keel, (3)- an angle somewhere around 45 degrees to the keel. If anyone has any thoughts, I would love to here them !!
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Bryan Hansel
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Location: Grand Marais, MN
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Post by Bryan Hansel »

I just run them same as the first. I've never thought as an extra layer as stiffening the canoe or kayak, but more as a sacrificial layer to guard against rocks and abrasion from going into shallower areas than you would with a powerboat.

As for torsional twisting in rough conditions, I'd assume that there is some, but not much. The gunwales on a canoe and the deck of a kayak serve to stiffen up the craft. I've noticed slight flexing of the floor of the canoe before, but never any twisting in heavy conditions in fully loaded boats. Cedarstrip/epoxy canoes and kayaks tend to be some of the stiffest boats of their kind.
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Glen Smith
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Location: Baie-St-Paul, Quebec, Canada

Post by Glen Smith »

Don't take this as gospel but I believe I read that to obtain maximum strength when using two layers of glass, you should apply the first layer at 45 degrees to the keel-line and the second layer at 45 degrees in the opposing direction. This puts all the threads at an agle to the keel-line and to the strip seams providing more strength. For a strip-built canoe or kayak this would normally be considered as overkill.
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