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bubbles under fiberglass, how to get rid of?
I am having a continual problem getting the glass fully wetted out on my Chesapeake. In order to get the glass fully wetted out I am having to put so much epoxy on it that is is running everywhere before it kicks so now I am going to have to go back and grind all the runs down to get it smooth. If I don't put enough on there I get spots where it is not fully wetted out.
I thought the problem was the several year old MAS epoxy that came with the kit , so I went to West Marine and bought a gallon of West System with 205 Hardner that I have used before with success on fiberglass boat repairs and it is the same deal, I still have a bunch of tiny bubbles that are going to show through the varnish.
I have decided not to fiberglass my deck and just paint the hull to cover all the bubbles so I can be done with it, but what is the secret to getting a clear finish when glassing over wood? Is there any way to thin the epoxy so it will soak through the glass cloth easier? I just can't figure out what I am doing wrong? The temperature in my shop was about 65 degrees.
3 replies:
RE: bubbles under fiberglass, how to get rid of?
Building my chesapeake in the fall, I routinely heated the epoxy containers with a 100 watt shop light for a while before using. Might be that your mix is just to viscous to fully penetrate the fiberglass. In cooler weather, I have an electric portable baseboard heater that I set under the boat to warm it up. If the wood is getting cold at night and things warming up in your garage during the day, maybe the wood is outgassing. Warm up the hull first, then epoxy. That might do it.
RE: bubbles under fiberglass, how to get rid of?
Good points, ludwigd. If you're seeing tiny bubbles in the cured resin rather than localized areas of resin-starved cloth, outgassing could be the cause. That can be avoided by always coating bare wood with epoxy when the temperature is falling, rather than rising. You can warm up the hull first by putting a portable heater under it, and draping a tarp over it. Don't set the tarp on fire. Heat can also be carefully applied with a heatgun to speed up the warming process. Turn off the heat a bit before you start applying the epoxy, and make sure that the temperature will not rise again before the epoxy has set. Shield the boat from the the sun and keep it away from other heat sources. Outgassing will not affect subsequent coats, because once the wood is sealed, air trapped in the wood is then not able to escape.
Pre-warming the epoxy a little in cold weather does make it less visous so that it will wet out the cloth faster. But don't overdo it, because warming it up also shortens its working time, and it won't wet the cloth properly if it is starting to gel. Using slow hardener is a good idea also, because it helps prevent that.
Oh, it looks like I committed a typo in my last message. It should read "squeegee", not "squeeze", at the end of my first paragraph. Sorry ...
RE: bubbles under fiberglass, how to get rid of?
» Submitted by Old Yeller - Mon, 4/29/13 » 11:24 PM
The secret, I think, is to apply enough epoxy to completely wet out the cloth, and then squeegee off the excess . A small slit in the top edge of a cardboard or plastic cup makes it easy to remove the excess epoxy from the squeeze after each stroke.
It might be possible to add filler to the waste epoxy for glueing or filleting, but it probably should not be used for wetting out fiberglass. Air bubbles get mixed into it, which tends to make it foamy. I normally just discard it.