secondary bonds with peel-ply

[Ian]

We have used vacuum bagging and peel-ply for a while at the yard where I work, but untill recently always sanded after removing the peel-ply. We work in wood and some fairing was usualy necessary. Not long ago we applied a layer of carbon fiber to a hull-- and went with the idea that the peel-ply removes all the amine blush and leaves a roughened surface that needs no sanding to acheive a good secondary bond with the next layer. I have since read a letter to Multihull magazine (old issue) in which the author claims that he has had failures going with this method and that he has conducted tests that prove that sanding after removing the peel-ply vastly improves the bond. A internet search turned up some results from test that a college conducted that seemed to confirm this. They claimed that there was some contamination from the surface treatment on the nylon cloth. Has anyone out there had any problems? Most experience seems to be positive.

[Ilan Voyager]

It's true that it saves a lot of work (and money) if you can glue directly over the footprint left by the peelply.

The answer depends on the brand of peel ply.

Some peel ply have silicone or other stuff surface treatment and you have to sand heavily as silicone is the worst contaminant you can have on a resin.

Good peel ply is pure and cleaned nylon cloth and you can bond directly after taking it out We have done it very successfully with a peel ply fabricated without any surface treatment. You have to be sure at 100% of your peel ply!

The best is:
1/ Getting technical info and a written statement from the peel ply manufacturer .
2/ Making several samples and scientific trials.

If you have the least doubt, it's better to sand...

[Ian]

Thank you for your reply. I will check on the product we are using. Much obliged.