Epoxy/Polyester resins

[tobble]

sory for minor fred rift, although relevant in the broader context/question;

Polyester to wood is a no-no though.

I've read this a lot, unfirtuantely after I found out the hard way. Luckiliy it was sheathing a locker lid so not critical. My question is this; if, or as, Polyester is so poor at bonding to wood, why is it used to glass in ply bulkheads? should we be worrying about this more?

 

[Tranona]

Well, I might as well parade my ignorance further...

How much of the weight of a typical 32 footer is in the hull anyway? Ballast, engine, rigging and fit out must dwarf the fibreglass surely?

The whole point of a lighter hull is that you can then put the displacement into areas where it is more effective such as the keel or fill the inside with heavy creature comforts such as watermakers, gennys, etc. Clearly not a big issue with heavy displacement boats like the older style HRs, but they also produce much lighter hulls now - foam cored and better engineered so that they can keep the creature comforts and improve sailing performance.

 

[snowleopard]

I've read this a lot, unfirtuantely after I found out the hard way. Luckiliy it was sheathing a locker lid so not critical. My question is this; if, or as, Polyester is so poor at bonding to wood, why is it used to glass in ply bulkheads? should we be worrying about this more?

It works for a while. I followed the instructions and did it that way with the first boat I built, painting the bond area of the wood with cobalt accelerator for better adhesion. Some people drill large holes through the ply and put glass through them to form a mechanical bond. The adhesion lasts fine as long as dampness doesn't get into the wood.

 

[JimC]

Polyester to wood is a no-no though.

Also noteworthy is the fact that Epoxy will bond to timber buy poly resins will not at least not in the long term

What about all the Mirror dinghies whose plywood panels are bonded together with polyester resin & glasscloth. The oldest of these are nearly half a century old. I have seen an ancient one filled with soil and used as a municipal flower display in a seaside town. It was rotting and warped from the weight of damp earth inside it but the seams were all holding together perfectly.