Fiberglass bubbles.... how and why???

[saltfly]

That chemical reaction Bob is talking about, is out gasing. You add a catalyst to the rosin it causes a chemical reaction that heats the rosin so it will cure. The best example I can give you is this. Dry ice just sitting their doesn’t do much except make something cold. Put it in water and watch the bubbles. that’s out gassing, the chemical reaction. Put it in a closed container and add water before closing tight, and you get an exposition. Out gassing happens every day and in almost every thing, we just don’t see it so it doesn’t effect us under normal every day life. When we designed and built anything going in to space, we had to be concerned with everything  we used. Out gassing could destroy an expensive piece of electronics. When you saturate the cloth with rosin and it doesn’t adheres to the parent material, the gas that can’t escape because of the serration, builds and pushes up to form a bubble.

[seabob4]

I had some beans with lunch.  Out-gassing occurred...

[kaptainkoz]

Thanks again everyone. Who knows what was in that keel after all these years. It could even still be wet despite being covered for about a month now and fairly dry weather. That glass over the keel was definitely porus. The keel was still solid as I walked on it every day. So if there was a weak spot I would have felt it. The whole post and all the suggestions does make me more conscious of surface prep. Everyone talks about it but at least heres an example of the consequence.

[gran398]

Everyone is big on vinylester, for good reason.

The job you've achieved is strong. Dave, Saltfly, and Seabob may be on the money regarding outgassing issues; mixing resins on horizontal surfaces.

I'm thinking play it safe and easy....poly on poly for the next layup....your vertical surface transom.

[saltfly]

Hey Bob, the students in my class, made me promise not to eat beans or chili, before coming to class. They said it was cruel and unusual punishment.  

[Group W Bench]

It looks from the picture like the mat backing on the biax is not fully wet out. It takes a few minutes for the styrene in the resin to break down the starch binders holding the mat backing onto the cloth. First liberally wet the dry surface to which you are glassing and then wet out the cloth from the top. Use squeegees and hard rollers to work out the air which will pull excess resin to the surface. Roll up excess resin with your dry nap roller and these dry mat spots will go away. Brushes are for overlaps, corners and chines. Use a nap roller when wetting out long sections as in the picture. It will save you a lot of time and frustration.

Another tip is to lay 3/4 mat down on any ground surface prior to the biax. It will greatly promote adhesion and it is much easier to roll out the cloth with the mat underneath. The mat backing on biax is not very consistent.

[kaptainkoz]

Another tip is to lay 3/4 mat down on any ground surface prior to the biax. It will greatly promote adhesion and it is much easier to roll out the cloth with the mat underneath. The mat backing on biax is not very consistent.

Great Points group W. I have picked up a few rollers and will start using them. I was wetting out the surface first than laying the biax. The biax is very thirsty and I think all are correct in leading me to the roller for larger sections. I have to agree with placing the chop strand first as the biaxial seemed to have wet out really good in areas that went over the chopped strand first. It worked kind of like a sponge to hold the resin in place. Roller or brush, there is only so much resin you are going to get to stick to a non horizontal surface so the chopped strand would probably do the trick much better. I never thought of making that protocol but that sounds pretty bulletproof.

There isnt anything I have done so far that is super critical even if it is a bit starved in places. Im not worried. I am very glad I posted the question before getting into the transom. Thank you and everyone for your great input.

[Callyb]

Koz, I was just looking back through your rebuild thread and I noticed a pic that made me wonder if it has something to do with this issue.

Are you sure you have 1708?

But if this is the label from your roll of 1708, and you are applying resin for that weight, your lam may be a little dry which would cause what you have experienced. Because the label says it is 2408.

[kaptainkoz]

Carl, wow, you are probably right. Based on the label that makes sense. I didnt even know there was such a thing as 2408. I asked for 1708 and do not have the experience with the fabrics to know the difference. In a way im glad its heavier because I ended up having to do less coats to get the thickness I needed. Moving forward I have paint rollers now and will try to resin the fabric on plastic sheets when ever possible... or at the very least hit the chopped strand side with the paint roller first. Now im curious to get a piece of 1708 to see the difference.

Thanks again Carl thats great looking out!!!