bulkhead material?

[yourmomm]

hi-am just about to make a structural bulkhead to be bolted to the frames of my beloved wooden boat. the bulkhead will be completely internal and will be faced on both sides with 12mm mahogany T&G planking (glued and screwed). i was going to use marine ply but is this absolutely neccesary? wouldnt any ply, or even MDF do? many thanks...

 

[Keith 66]

If you use any old ply the risk is water will get in and it will delaminate, likewise, MDF which has no place near any boat unless it is part of the building jig.
If you don't believe me put an offcut in water overnight and see how it soaks up water like blotting paper and swelling alarmingly!
In truth is it worth compromising on your "beloved wooden boat". For something like a bulkhead marine ply should be used or maybe the very best exterior if its source can be trusted.

 

[Blueboatman]

And saturate the end grain with epoxy x 2 before installing

 

[roly_voya]

If you plan to face each side with 12mm mahogany why not just build the whole job in 25mm T&G? Also has the advantage that it can move with the rest of the boat. Unless you are looking at something the size of a theams barge I am sure this would be strong enough and much eaisier to build. If you do need the ply core to stabilise it then 6mm marine ply with the T&G glued to it would do it.

 

[yourmomm]

many thanks....marine it is then!! but epoxied, as suggested by blueboatman? the ply im pulling out now (with great effort) following fire damage has never been epoxied, and is still as fresh as it was laid some 15 years ago!