Plywood Boat Design Question

Is the hull of a boat built using the stitch and glue method as strong as one built using conventional frame timbers and plywood planking?

Would a stitch and glue hull be able to withstand an impact on a rock shoal as well as a conventionally framed boat?

I am considering using the stitch and glue method of construction and would welcome any comments from builders with such knowledge or experience.

3 replies:

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RE: Plywood Boat Design Question

There's a bit more to that question. Stitch & glue is only the way the boat bits are assembled and fastened. Its main advantage is easy home construction. Although gluing is typically stronger than screwing or nailing, what really determines the boat's strength is the type of construction. There are 2 main styles:

1. Plank on frame; and

2. Monocoque

Plank on frame (the traditional boat in your question) uses the frames for structural strength and the planking to keep out the water and shape the flow. Monocoque uses the skin for both structural strength and to keep out the water. The number of frames is a bare minimum. In some small boats, there are no frames. Since there are no frames, the boat weighs less. Since it weighs less, it can use thinner skins for structural strength. Since the skins are thinner, the boat weighs less. Since it weighs less, ... (you get the picture)

By making the skins out of composites (such as plywood with fiberglass on both sides) the skin can be made even lighter while staying just as stiff as thicker plywood. So monocoque boats are typically much lighter than plank on frame boats of the same strength. Think of the difference between WWI biplanes and modern jet fighters. The biplanes were essentially skin on frame, while the jets are monocoque.

This strength is the resistance to bending and twisting. In your second question you're asking about puncture resistance. That can be achieved by locally thickening the area you want to protect by increasing the wood or glass thickness.

So if you went with a composite monocoque boat that was designed to be assembled with the stitch and glue method, with local reinforcements to protect against punctures, you would definitely have a winning combination that you could easily build at home. It would be stronger than a traditional plank on frame boat of the same weight.

Hope you stayed awake :-)




RE: Plywood Boat Design Question


 Thanks so much for taking the time to address my question. I have a stitch and glue CLC plan for a small 13 foot kayak which I am sure will work out great and perfectly as designed. I have also been looking at plans from other designers for a much larger power boat which I am contemplating, in the 23 to 25 foot range, much heavier of course but the design calls for a stitch and glue hull construction. Having grown up with a 2 by 4 background and everything being heavily built and of workboat structure, I am slow to accept the "light" but still very "strong" way of doing things. Your answer has given me more food for thought and guidance. Thanks again! 

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