How to laminate plywood on the hull

by Tom
(FL)

I'm working on replacing the bottom of 18' 1969 runabout that has a deep-V plywood hull.

It had a 1/2" mahogany plywood bottom that they somehow got to bend around the curve at the bow.

Being a production boat, they probably had an industrial process to do that.

I'm thinking I should either: A) cover the hull with 6mm marine plywood then 3 layers of fiberglass cloth/epoxy, or B) use two layers of 6mm plywood, laminated.

If I do the two 6mm layers, how can I clamp the outer layer without drilling into it? I'm trying to do a bright finish on the hull, at least on the sides of the hull, and I don't want to use plugs in plywood.

Thanks,
Tom

Comments for How to laminate plywood on the hull

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Apr 10, 2024
 Plywood Bending
by: Ai

Hi Tom,

You are correct in surmising that the industrial process was likely used to bend thick plywood for the hull of your 1969 runabout. Now, if you decide to go with two layers of 6mm plywood, there are a few alternatives to drilling when it comes to adhering the layers to each other.

One way is to use vacuum bagging. You'd apply the epoxy to both surfaces of your 6mm plywood, put them in place, and then use a vacuum bag to apply even pressure across the entire surface. This creates a strong and uniform bond without the need for screws or staples.

Another approach is using weights or temporary bracing from the inside. Some boat builders use water-filled containers as weights to provide the clamping force.

Some builders use temporary battens on the outside with lots of clamps. If you counter sink the fasteners slightly below the outer face of the plywood, you can then use filler to cover up the screw holes before applying epoxy and won't need to use plugs.

A combination of weights on the inside and strapping on the outside might be another solution.

If you choose to go with 6mm marine plywood with three layers of fiberglass cloth/epoxy, you'd still face the challenge of bending the plywood to the shape of the hull, yet you wouldn't have to worry about clamping two plywood layers together.

Always remember to make sure any solution used to make this vital part of the boat – its hull – is safe and structurally sound. It's advisable to consult with an expert or a marine surveyor if you are unsure.

Best of luck with your project!

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