Planking vs Ply and Glass for a trailered boat

by Alan DeForest
(Wilmington, NC, USA)

I am restoring a wooden Harkers Island (see Salty in 'Your Boats' Section).

The bottom needs replacing and I have been leaning towards plywood and then glassing the hull.

The purest would say you’re dooming the boat to a slow death.

I understand their concern, but I will be trailering the boat and if I plank conventionally the boat will dry and then need to take up again at the next use.

This would be most inconvenient and thus the ply and glass approach.

I was wondering about an alternative that would use an elastomer or caulk that I could use between the planks in lieu of traditional cotton and or oakum then putty.

The planks could move with the moisture content the hull would maintain its integrity.

When I first got the boat the gaps between planks was a 1/8 of an inch at worst.

Has anyone gone this route with success?

I’d like to hear suggestions.



PS: I posted a while back that I was going to use yellow pine for the floor frames and I got feedback that it was a bad idea.

Well, I’m going to use cypress instead and found a reasonably priced source.

Every project has a budget.

Comments for Planking vs Ply and Glass for a trailered boat

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Mar 13, 2012
by: Al

Thanks for the feedback Mike.

Mar 13, 2012
Bedding Compound
by: Mike

"Dolfinite" will be an excellent choice.

Pettit also do caulking/seam compounds.

Mar 08, 2012
Double Planking
by: Al DeForest

At this time, as it may change, I am going to put a 3/8 plywood bottom then bed in 3/4 planks.

I am leaning towards using Dolfinite as it remains flexible and repairs down the road are easier.

I will epoxy coat the plywood since it doesn't move as much as the planking.

I'll caulk the planks traditionally, cotton and a modern caulk.

If there is anyone out there that can recommend a caulk or has experience with one let me know.


Feb 25, 2012
Salty's Bottom
by: Mike

Salty was, I suspect, built as a work boat that would be kept in the water so a single planked carvel bottom was ideal.

Most of the classic woody runabouts that were designed to be trailered used a double planked bottom.

Two layers of planking with a waterproof membrane in between.

One of the ways these boats have been re-bottomed is by using what’s has come to be known as a 3m or 5200 bottom.

Some others have used and swear by the epoxy and ply solution.

There are a few comments and suggestions here and here and here.

One solution might be a plywood first layer, a membrane or bedding compound middle layer and an outer layer of planking.

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