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Glassing technique


Joe Nelson CS#35

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For those of you who are Duckworks paid subscribers...there is an article about glassing that is worth reading. The author uses 30 mil clear plastic and a rubber roller to work out bubbles. He goes directly over the wet glass with the plastic. Peel it off after it dries and the surface is glossy smooth and requires not sanding or filling of the weave. From my past experience with filling and sanding it sounds like a great idea!

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Funny you should mention John Blazy's site and technique.

I am currently doing that on a small classic style runabout. Getting the 30 mill polyester material was fairly easy although it had to be ordered. Fishing out the bubbles is the most difficult part of the process and I found that chasing them to the edges with a small wood block held on edge was better than the roller. One concern is getting enough epoxy over the fiberglass to prevent early print through of the fabric. This will eventually happen anyway but I'm trying to work out a way to get more epoxy over the cloth before laying on the plastic sheeting.

Time will tell how it works out. There is definitely a learning curve.

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Tom,

I saw Tom Blazy's site as well and was impressed with his results. I wonder if a regular guy with 10 thumbs can get as smooth a finish?

Where did you get the 30mil plastic in rolls? Is it available in different widths? I think I'll give his technique a try on some scrap material and see how well I can do...

Roger

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Roger,

There is no doubt that the technique works. Many of us have used it for repairs for many years and I saw it being used in manufactureing on a large boat in the 1970's with gel coat and celophane plastic.

I got the material from the nearest supplier of Cadillac Plastics in Raliegh, NC.

It is too early for me to give any pointers or advice but on the topsides of most of the boats we discuss here, it should do very well. I may try it on the topsides of this boat without the layer of fiberglass.

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:( With all respect to John Blazy, I can't endorse the plastic leveling technique for the whole side of a boat.

There are two major problems.

The first is that the plywood deforms in making the twists found on the panels of our boats. The amount of this stretching/compression becomes very clear when we attempt to lay a sheet of stiff plastic over the plywood. The plastic will not take even fairly simple twisting movements without buckling and refusing to follow the surface of the plywood. It might accept following the side panel of some of our boats but, if you have to torque the plywood even a little, the plastic will not follow smoothly.

The second problem is that it is very - very hard to get the air bubbles out. In previous uses, I had applied a dollop of epoxy or gel coat to a small repair and laid the plastic sheet on. Then the epoxy was rolled toward the edges and the large (relatively) blob of goop would chase the bubbles out completely. This is not possible on a large area. Maybe if several workers were used it could be easier. After the plastic sheet is removed, the surface looks just as good as the one on Blazy's website - from a distance. Beautifully smooth and fair. Up closer, the bubbles become craters and they are there by the hundreds, if not thousands. Getting these things covered is at least as much trouble as fairing in the usual way.

If someone finds the secret to these problems, then this may be a worthwhile finishing method. In the meantime, I am going back to normal epoxy coating with a foam roller and dry brush for plain coating and peelply for fiberglassing which does work and does not have these problems.

That's my story and I'm sticking to it -- until someone shows me otherwise.

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Thanks Tom, for bringing us back to the "real world". It would figure that such a technique wouldn't work for the boats we build. I never thought about the twists in the ply that the plastic wouldn't conform to. :shock: I have never been able to get away with "quick and easy"anything. I guess I should get out the old fairing board and sandpaper...

Thanks again for keeping me from making a king size mess. :wink:

Roger

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What about using Peel Ply instead of plastic. I haven't really tried it before, but it might be good here. I am not planning to glass my hull, but do plan on using Peel Ply. I would welcome the experience of other.

John

CS17#102

ps: I think I am going to name my boat "Three Ladies" instead of "Catherine and Elizabeth," because my daughters will react to the order of the names and my wife would be left out. Three Ladies may lead to greater family harmony.

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I afraid I don't understand why you would want to use Peelply on a boat that wasn't being glassed? The reasons for using peel ply are several, but getting a finsih on an unglassed boat isn't one that I would think of.

I would use it in a situation where I needed to prep a surface for later bonding to another surface. The Peelply contributes to a much better secondary bond.

Another reason would be in vacumn bagging to allow excess resin to bleed through and be removed when the peelply was removed. This could also be done when squeegeeing the resin into the glass, by squeegeeing the peelply down, then lifting it once the epopxy cured.

Seems to me a waste of money and effort, when you could just roll on thin coats of epoxy and finsih sand.

Am I missing something here?

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I'm with you Charlie -- I don't see the point either.

I've used peel ply (actually, the cheap alternative: taffeta nylon from Fabricland) for vacuum bagging my oars, and for the outside edge tapes on the mini-paw.

Its huge benefit is that epoxy doesn't stick to it at all. In both cases above, I used a thick layer above the peel ply to absorb the excess epoxy. In one case, breather fabric (or felt from, you guessed it, Fabricland), and for the edge tapes, I used newsprint.

The entire point of the peel ply is to allow excess epoxy to bleed through. For epoxying a surface, I would simply not put so much epoxy on if that was an issue. For glassing, it's more difficult to get just the right amount of epoxy to wet out the surface AND the glass, and push down the glass so it doesn't float in a thick layer of epoxy.

Michel

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I agree Charlie. Can't see any reason to use peelply on an epoxy only finish.

John, as I stated in my post, peelply does work ok on glassed surfaces. It may be a bit hard to understand this unless you have tried it. What normally happens is that the first coat of epoxy on a fiberglass surface leaves the surface pretty rough with glass fibers standing proud when it sets up. No big deal though since adding more coats of epoxy will smooth it out, after sanding or scraping of course. What the peelply does is force the glass to level out more, so that when stripped off, the surface is much smoother than without the peelply. This allows a smooth surface with less epoxy, less weight as well as less sanding and zero chance of amine blush. We usually use a serrated metal roller to roll the air pockets out of heavy glass layups or peelply but, in this case, the serrated roller should be followed with a smooth roller to avoid the ridges that will be left in the final surface by the serrated roller.

If all this has talked you out of using peelply, that is ok since you can get along just fine without it.

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Interesting topic, as I am waking at night thinking about the construction process of the Blue Jacket 24! :)

First to biuld an additionm ot the shop, then, maybe I start the Blue Jacket... Too many projects and wya too little time. ;) I wanted to start the blue Jacket yesterday, but.. :roll: :roll: That was yesterday in about a year ago! :) Soon.. I hope! :)

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There have been some discussions about peel ply and its use in finishing off epoxy coated glass on plywood. It is well documented in vacuum bagging operations but not for "in the open" covering of glass/epoxy layups.

I've been doing some research about it and came across this article from Jim Michalak in Duckworth magazines Way back archives.

http://marina.fortunecity.com/breakwater/274/2003/1115/index.htm#Glassing%20Plywood

In the article the writer is building a large plywood sailboat and is epoxy coating/glassing both sides of plywood panels prior to cutting them out to save labor when assembled and inaccessible. He talks about using Lexan film to cover the epoxy/glass layup. There are some photographs and tips on elimination of bubbles, etc.

Interesting material and maybe food for thought. Although I still have some doubts as to the validity of applying this on formed hull surfaces or other surfaces after they are inplace. But I'm willing to be convinced and to give it a try. It won't work on any compound curved surface however. Only flat or curved on one plane.

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thanks for the information. Frankly, I will be happy not to have the added expense of peel ply. I'll just make my coats of epoxy as smooth as possible.

One question...for doing vertical surfaces, are you finding using a roller the best to apply the epoxy ie, to minimize drips?

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The one advantage other than saving sanding time that I can see if it can be used successfully is that it has the potential to save a lot of epoxy and thus cash outlay. However there is one caveat that isn't covered in these articles that has to be considered. Glass telegraphs its weave thru the epoxy layers. As the epoxy cures over time it shrinks. And that telegraphs the weave of the glass thru the surface.

One of the uses of the peel ply in vacuum moulding is to create non-skid surfaces on the glass by telegraphing the weave thru the surface layer. So think about that nice smooth glass surface when you peel the film off. It is likely to become a nice weave impression overall as the epoxy shrinks with curing over time.

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