Marine Ply Bonding

[jon and michie]

Hi - I have been asked by a Friend of mine to ask this question so please bear with me

The Ply on his Speedboat is rotten and Plans to change it out for 12mm Marine Ply - What is the best type of adhesive to stick it down to GRP and what prep is required.
Many thanks In advance

 

[Bobc]

Use West epoxy resin.

 

[Graham376]

Polyurethane adhesive.

 

[geem]

Epoxy will bond well to the ply and the existing grp

 

[MikeBz]

It would be advisable to key the surface of the GRP, and if if it's not smooth (i.e. not the product of a mould surface) then thicken the epoxy - which of the myriad of fillers to thicken it with I'll leave to others to advise (there is a guide here: Filler Selection Guide | WEST SYSTEM).

 

[Hacker]

What is the replacement ply for? If it’s just a pad on the inside of the boat (to screw something to) then an adhesive such as Sika 291 would be fine. If it’s to replace a structural piece then epoxy and thickened epoxy (as in post above). If it is an internal pad then give it a couple of coats of epoxy to seal the surfaces before sticking it down.

 

[jon and michie]

Many thanks for your replies so far much appreciated

What is the replacement ply for? If it’s just a pad on the inside of the boat (to screw something to) then an adhesive such as Sika 291 would be fine. If it’s to replace a structural piece then epoxy and thickened epoxy (as in post above). If it is an internal pad then give it a couple of coats of epoxy to seal the surfaces before sticking it down.

From what I gather its full boarding that has rotted not a pad.
Jon

 

[neil_s]

I have been using West epoxy resin, colloidal silica filler and woven bandage to make repairs to my own boat. It bonds very well to roughened GRP and wood.

 

[B27]

Epoxy is good, but expensive.
If we are talking about bonding large areas of ply, e.g the core of a deck or bulkhead, there are cheaper adhesives which can be entirely adequate.

Some of the 'builders' adhesives in mastic gin tubes stick very well to wood and GRP.

If the ply is to be 'glassed in' or laminated over, then doing the whole job in polyester layup resin could be good, if done right.

 

[Hacker]

But if the original layup was epoxy then polyester has poor chemical bond characteristics. Usually easier to use epoxy as that bond to both polyester and epoxy.

 

[PCUK]

CT1