plywood question

[Ian9365]

Hi, my fishing dinghy has painted plywood seat bases some of which need replacing. The boat will be used in salt water and normally I wouldn't consider anything but a good quality marine plywood. However the original plywood is 21 mm and I just cannot find that in marine ply, 18 mm and then 25 mm yes but because of the way its fitted I need to get it as close to original as possible. I can find 21 mm Birch Ply, would this be Ok if it was painted in a 2 pack epoxy paint.

 

[Wansworth]

Why not use solid wood?

 

[Refueler]

Good quality WBP and then treated with a good 2 pack epoxy paint would be OK.

Ordinary ply is not recc'd ......

 

[RJJ]

It wouldn't be that hard to cut the seat in 18 and 3 and then epoxy them both together. Which is basically what marine play is anyway.

 

[lw395]

You might find that 'exterior' birch ply lasts fairly well if you make a good effort of sealing it.
Ideally we'd use the best materials, but sometimes that's expensive.
Another possibility is to use thinner marine ply and add some stiffening with solid wood if needed.
Sometimes even expensive marine ply is disappointing.
Why did the original fail? Poor material, or left wet for too long due to the design of the seat?
Whatever wood you use, if you can avoid it being left wet, it will last longer.
Maybe economise on the ply wood and buy a cover for the dinghy?

 

[coopec]

Welcome to the forum Ian.

It is hard to answer your question without knowing your location. Are you from Bermuda?

In Australia we have a ply called "Exterior Quality Ply" which is the same as " Marine Ply-board" except it may have some knot holes and filled in holes. (both use the same glue). It would be very hard to justify paying the extra cost for Marine Ply. (Obviously lw395 is talking about the equivalent type of product)

 

[Refueler]

The suggestion of ply with a wood brace under is not a bad idea in fact.

You could use a thinner Marine ply and then have a square section wood bar under ... tapered at ends so it supports out to the ends.
Coated with a good paint or varnish .....

But if you go for anything other than Marine Ply - make sure it is at least WBP or better ... its not only the veneer layers - but also the bonding agent used to create the WBP ply to resist weather.