3-ply versus 5-ply

by Eddie Gregory

Hi folks.

I need to pick your brains.

My new 60s style 21-foot Sea Hawk cabin Cruiser is coming on well but I have a bit of a problem.

I have been using 5-ply 3/8 marine ply for the underside and the bow planking.

I still have the upper hull planking midships to stern to cover.

Check out pictures on my website.

My supplier has run out of 5-ply but has plenty of top quality 3-ply marine, what do you think, should I use this or source 5-ply?

Eddie Gregory

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Comments for 3-ply versus 5-ply

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So good
by: Verlamo

I am very much happy to know the differences between the 3-ply and 5-ply.

I think 5-ply is better and more efficient when compared to other types.

Thank you for sharing this post here!

Keep sharing!

by: Eddie

Thank you very much lads, I appreciate your help. Bearing in mind I will be covering the whole hull in 2 layers of glass I will indeed go out and buy the 4 sheets of 3-ply I need.
Thanks again,

Three/Five ply Plywood?
by: Mike

Hi Eddie,

Good to hear that you are getting some work done on her despite the weather.

Well I think the previous posts have just about summed it up.

Unless you are intending to go ice breaking on Belfast Lough the three ply should be fine.

The more piles there are the more the lengthwise and crosswise strengths and stiffness increase.

With three ply the strength is greatest along the surface grain axis, as there are two layers with grain in that direction but only the one, the core with its grain running at right angles.

And the three ply will have thicker surface veneers.

The five ply gives you two more veneers running at right angles so the cross strength/stiffness increases.

But for your application three will be fine especially if you have the surface grain direction running across the frames, along the length of the hull.

Happy boat building,


by: Anonymous

yes , use 3 ply

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