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Peel Ply Versus Ordinary Plastic sheeting

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To paraphrase Jan Brady, it seems all I ever hear on this board is, "Peel ply, peel ply, peel ply!" https://www.youtube.com/watch?v=-yZHveWFvqM

Ok, I've never used peel ply. But a retired shipwright who has probably gone through more epoxy in his life than the collective builders/repairers on this board once taught me to use ordinary plastic sheeting (like the kind that comes with the heavy duty plastic drop cloths from the big box stores), when trying to smooth/fair epoxy/fiberglass repairs on the hull of my canoe. I've done it and it works astonishingly well, leaving a no drip, glass smooth finish that fairs almost perfectly without sanding, fuss or muss.

So, what is the advantage of peel ply over using an ordinary plastic sheet that epoxy won't stick to?
 
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Since it's woven peel ply will take curves, especially compound curves, better than plastic. Peel ply doesn't get all slippery when it's covered with epoxy. Peel ply leaves a light texture that gives the next coat something to grab onto but is easily sanded away if you want to smooth it out. Peel ply allows entrapped air to escape when you put pressure on the laminate. Peel ply absorbs excess resin. Since amine blush forms on the very outer layer of epoxy it will be removed with the peel ply.

I've used plastic before and it works fine in some situations and no doubt the more you use it the better you get at using it, just like anything.

Alan
 
In my early learning days before I heard of Peel Ply I used plastic wrap, Saran Wrap, and then taped it down. It worked but often left a wrinkle in the cloth. I have become a fan of Peel Ply for a lot of the reasons Alan mentioned. What I really like is the smooth finish it provides. Just my .02.

Doug
 
In my early learning days before I heard of Peel Ply I used plastic wrap, Saran Wrap, and then taped it down. It worked but often left a wrinkle in the cloth. I have become a fan of Peel Ply for a lot of the reasons Alan mentioned. What I really like is the smooth finish it provides. Just my .02.

Doug

In my experience, Saran is too thin a plastic and does wrinkle. A thicker plastic doesn't wrinkle.

The technique I was taught is to cut the fiberglass to size, lay it out on a piece of plastic several inches longer/wider than the fiberglass, then wet out the fabric. Pick up the plastic with the wetted-out cloth still on it, and invert over the repair, smooth and work out air bubbles. If done correctly, the fabric doesn't require additional fill coats or fairing.
 
I haven't had the best of luck with PP ! It's fine on a flat, or a curve in one direction, but say over a stem, where there are compound curves ? No. I was unable to work out the wrinkles.
Alan and I discussed this once, and concluded, that cutting the PP into strips might solve. I'm afraid it would leave marks, where it over lapped.

I know they use it in vacuum bagging, and infusion.

It may have something to do with the type of PP I was using. At $8/yd. I feel it is too expensive, for me.

Jim
 
I haven't had the best of luck with PP ! It's fine on a flat, or a curve in one direction, but say over a stem, where there are compound curves ? No. I was unable to work out the wrinkles.

Jim

Yes, stems are tough with that tight curve. I cut darts in the fabric. The seams do show where the cloth overlaps at the darts and there will still be spots where it doesn't make contact but overall I still think it's worth it since there are only a couple spots that need the weave filled and it's going to all get sanded anyway.

It's not perfect but I still like it.

I don't remember if I've ever tried the thick 4 or 6 mil plastic but I can see where it would work much better than something like saran wrap. The method of wetting out on the cloth on plastic and then transferring the whole thing to the patch area is a good one.

Alan
 
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