Whoa!!! What happened to my fiberglass???

[PiratePast40]

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Laid in the mat in the engine compartment late yesterday. Came out to take a look today and there's bubbles everywhere. It was smooth as a baby's bottom when I left it yesterday - in fact, I was pretty darned proud of the job. What the heck is going on?? Any ideas?

 

[zach103]

Re: Whoa!!! What happened to my fiberglass???

not enough resin maybe.. i put some resin down than glass than more resin

 

[Mark42]

Re: Whoa!!! What happened to my fiberglass???

I had that happen to me before. For some reason, as it hardened it lifted in a few places. Now I watch until it starts to set before leaving. I keep the paint brush in some acetone to keep it from hardening and just touch up where the cloth lifts.

You can grind off the bubbles and lay a patch over it. Also make sure the surface is smooth, little bumps will cause it to lift after you mash it all down. And make sure all the air is out. Use a bubble buster roller.

 

[PiratePast40]

Re: Whoa!!! What happened to my fiberglass???

I can't imagine not being enough resin but it's definately something I'll keep in mind. I brush it on, lay the mat and then dab in resin with a brush unitl the mat is opaque. Maybe I didn't apply enough to the surface first in this instance. After about an hour of being bent over working with your face in the stuff, you start to see pink elephants - even with a respirator and goggles. Waiting for a few minutes with a brush ready in acetone is a good idea too. I'll give that a shot next time. I've been gently using plastic spatulas and a bubble buster as well but it's a delicate dance working the mat and laying in the resin without the mat pulling up.

Just curious about poly resin use. I've used about a gallon of resin on each of the 11' stringers on the first layer of mat. The stringers were totally coated with resin and it cured for a few days before being bedded in. Does that sound like the right amount or does it seem like more than normal?

Thanks again for any advice.

 

[Mark42]

Re: Whoa!!! What happened to my fiberglass???

I can't say if that was typical coverage of the stringers or not. If you go to fiberglasssite.com they have a coverage chart by resin type and fiberglass cloth/mat by weight. That should give you a good idea if your coverage meets the suggested coverage.

 

[PiratePast40]

Re: Whoa!!! What happened to my fiberglass???

Sorry, I should have been able to figure that out myself. It's funny how sometimes you get stupid and forget the basics. I had to do the calculations originally when I was figuring out how much resin and mat I was going to need.

To answer my own question - I'm using about double the amount of resin I originally calculated. I wish there was a way to thin resin for better saturation. I'm wondering if adding acetone be acceptable or would it upset the chemical balance? The reason I ask about thinning is that it's extremely difficult to get good saturation and workability on large areas like stringers.

 

[Bondo]

Re: Whoa!!! What happened to my fiberglass???

Also make sure the surface is smooth, little bumps will cause it to lift after you mash it all down. And make sure all the air is out. Use a bubble buster roller.

Ayuh,... It sounds like you're just draping the mat over wet resin,... It's gotta be IN the resin...
Get a Bubble Buster,+ Work it in...
Or,... Put the mat into the resin bucket,+ drape it on Wet, then smooth it...

 

[Mark42]

Re: Whoa!!! What happened to my fiberglass???

.... I wish there was a way to thin resin for better saturation. I'm wondering if adding acetone be acceptable or would it upset the chemical balance? The reason I ask about thinning is that it's extremely difficult to get good saturation and workability on large areas like stringers.

Yes, resin can be thinned with acetone or styrene. I think styrene is preferred, but acetone works well also. I read somewhere (probably here or on a label) that thinning up to 10% is OK. I would start with about 3 oz of resin thinned about 5%, and see how well it goes. Too much thinning leaves the resin weak as all that thinner evaporates leaving space where it used to be. Thinning at 30% is probably going to make a weak lamination.

I cast boat emblems and rail ends from polyester resin with powdered metal filler. I have to thin the resin so it will capture all the fine detail of the mold. When I thin too much, the result is a floppy emblem that takes days to cure fully. Then its brittle and junk. I put about 1/4 to 1/2 table spoon of acetone to 3 oz of resin. It still takes the detail, and makes an emblem flexible enough to take banging when mounted and won't crack years later.

So, experiment until you get something that works for you.

 

[Robert D]

Re: Whoa!!! What happened to my fiberglass???

I discovered the answer was to thicken things up a little. Some chopped micro-fibers or something similar, really keeps it stuck down. (not too thick, we're not filleting corners) I think if you thin it further, the problem will likely get worse. Lower temperatures plus too thin resin I suspect. Also, did you wipe the hull with acetone beforehand? As stated above, clean up the lifted area's and patch, no problem.

 

[PiratePast40]

Re: Whoa!!! What happened to my fiberglass???

thanks for all the recommendations. I don't see how adding any material to the resin would make a difference, it's going over CSM anyway. As far as I can tell, I'm not just laying it on resin -I'm painting a little resin on first to help keep the mat in place and then dapping on more with a brush and pushing it into the mat until it's saturated and turning opaque. There is some brushing involved but not too much - for obvious reasons. Temperature might be a factor, it was in the mid 50's when I finished up and then in the 40's overnight.

I've been doing small sections at a time. I cut a 12 to 18" wide piece of mat from the rol - that fits over the stringer and extende a little over 2 inches on the hull on each side.

Will take everyones recommendadions into account and see how it comes out today - after first grinding and sanding out the bubbles

 

[salty87]

Re: Whoa!!! What happened to my fiberglass???

nothing like grinding off your own work.

hard to see any seams in the pics, you might try working with smaller pieces.

i think robert d was saying a thicker mix might fill in the voids a little better, hold the mat more. i haven't tried that but i can see the idea behind it. if there are any bumps, and it looks like there were, it could fill them in a bit. best to have the flattest surface possible though.

i can't remember the ratio i was told for resin:mat but i was surprised at how thirsty it was too. more being better than less, within reason.

 

[ondarvr]

Re: Whoa!!! What happened to my fiberglass???

Did you coat the wood thoroughly with resin and let it cure before glassing? If you don't and the temperature changes as the air starts to expand it will raise up off the wood leaving bubbles.

 

[PiratePast40]

Re: Whoa!!! What happened to my fiberglass???

Yes - coated the wood quite thoroughly the weekend prior to glassing in. I let the PL and the tabs cure for about a week before doing the major glass work so that shouldn't be an issue. Now I see what is meant by thickening things up to fill gaps - I have big globs of "yetti fur" laying around that I can use for that

I just finished grinding things down again and laying in a bulkhead for the engine area. The area showing in the picture is the only glass over glass area so far. I am seeing some bubbles near the tops of the stringers. That's why I've been working from the top down in small pieces.

Yes - grinding out your own work is sooo much fun. Then there's the feeling when the resin is just beginning to gel in the paint pan. You know you've got to really hustle or quit right now to avoid grinding it back out again.

I also realized that I don't have an actual "bubble buster" roller. It's a "marine fiberglass roller" so it doesn't give the same effect or advantage as the big rollers on the bubble buster - just means more work with the spatulas.

I'll go on out and wipe down one more time and clean with acetone, then give that same area a try again. BTW - the wife thinks it's pretty weird that I'm spending so much time on the internet talking to the "boat people"!

 

[jonesg]

Re: Whoa!!! What happened to my fiberglass???

I cast boat emblems and rail ends from polyester resin with powdered metal filler. I have to thin the resin so it will capture all the fine detail of the mold. When I thin too much, the result is a floppy emblem that takes days to cure fully. Then its brittle and junk. I put about 1/4 to 1/2 table spoon of acetone to 3 oz of resin. It still takes the detail, and makes an emblem flexible enough to take banging when mounted and won't crack years later.

So, experiment until you get something that works for you.

whatcha really need to make a detail mold is tool resin, the stuff I use is bright orange color, spray it over the plug then let it gel, cover any corners and dips with cabolsil'd resin and apply a veil of glass and unwaxed resin, then build the mold thickness with matt and finish with a coat of waxed resin. Tool resin can be brushed but it can tend to crinkle up if not done just right. The details it will capture are minute, even a hair will show in the mold.

To pull a detailed part from the mold just paint the inside of the mold with epoxy paint then lay the part up with epoxy resin and cloth.
If you want to stick with poly then use gelcoat instead of epoxy paint.
I made some very detailed parts like this.

 

[danond]

Re: Whoa!!! What happened to my fiberglass???

sh and pushing it into the mat until it's saturated and turning opaque. There is some brushing involved but not too much - for obvious reasons. Temperature might be a factor, it was in the mid 50's when I finished up and then in the 40's overnight.

It's not the temp. I just did an entire bilge/stringer/tray/transom job in 40 degree weather over 4 weeks and had no bubbling problems.

 

[PiratePast40]

Re: Whoa!!! What happened to my fiberglass???

It didn't seem as bad today after a thorough cleaning with acetone. I was seeing some separation during curing so used a brush to push the mat back in. Still having problems with bubbles at the top of the stringers. I've been wetting out the top first and then pulling down with the brush but still seem to get the bubbles just before the top of the stringer. I think I'll just sand those down and lay in a cap of mat and resin. I know that's not the best way but it's got to be better than leaving the voids.

Since I'm allmost out of regular resin will use finishing resin for the final coat of cloth in the engine area - at least that section will be done.

Thanks to everyone for all the help.

 

[Tail_Gunner]

Re: Whoa!!! What happened to my fiberglass???

Did you coat the wood thoroughly with resin and let it cure before glassing? If you don't and the temperature changes as the air starts to expand it will raise up off the wood leaving bubbles.

Pay close attention here..perhaps the most knowledgeable glass man you will meet

 

[Robert D]

Re: Whoa!!! What happened to my fiberglass???

Bubbles at th etop of the stringers.....are you wrapping the fiberglass over too sharp a corner? I usually grind/sand the top edges of my stringers so I have a nice, smooth rounded edge. Too sharp a corner and the glass will lift. Same theory as fillets, just the opposite. As for the thickening, it doe shelp when you have a surface that's not perfect, as well as provides an allowance for reactions to temperature changes.

 

[oops!]

Re: Whoa!!! What happened to my fiberglass???

i seee qiute a few things going on there......

first off.....the reason you are using so much resin is because of the cold temp.......search glassing in colder temps.....you will triple your coverage area.

im also sorry to say.....i really dont think your substraight was clean......i can see by the black stuff under the glass that the area was not propperly prepped.....

the area you are glassing is the engine compartment right?....the shot we are looking thru is the transom cut out.....that area will be full of contaminates

you need to really clean the area by rough and scuffing it and also cleaning it with aceitone before any glass is applyed.....

cheers
oops

 

[PiratePast40]

Re: Whoa!!! What happened to my fiberglass???

I know the picture shows different colors but it's the color of either the filler or paint used previously. I had ground through the filler in most places but didn't really think it was necesary to remove all the chop glass underneath. I realize it looks like it might be grease or stains but it's not - the area has been thoroughly ground and sanded. However, I will say that I probably didn't prewash this area with acetone enough for that time. I did when tabbing in the transom and again when bedding and tabbing the stringers. but may not have washed as thoroughly before this layer.