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fiberglass bubbling and peeling away

Submitted by KEPPEL, ANDREW - Sat, 7/20/13 » 3:05 PM

Hi all. Thought we were done with our Shearwater Sport, my girlfriend took it for a paddle and we put it on the kayak rack for a day or two. Next time we went for a paddle, there were several areas where the cloth seemed to have pulled away from the wood, anywhere from an inch to several inches in diameter. I figured the best thing to do was cut these bubbles out, sand around them, and patch with new cloth. Started cutting them away and found that, in some areas, the cloth around the bubbles just pulls away from the wood in big sheets, leaving a tacky residue on the wood beneath. Any ideas whats going on? Any ideas what we did wrong? I have a sinking feeling we're going to have to pull all the cloth off and start over, but I'd at least like to have some idea what went wrong last time before I try again. Thanks for any input!

11 replies:

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RE: fiberglass bubbling and peeling away

» Submitted by Old Yeller - Sat, 7/20/13 » 4:49 PM

My guess is the epoxy used to wet out the glass didn't completely cure either because the resin:hardener ratio was way off, or it wasn't mixed thoroughly enough. And yes, I think the only thing to do is to peel off the glass (careful use of a heat gun helps), scrape the surface as clean as you can, clean it with lots of denatured alcohol or lacquer thinner, sand it smooth, and start over.

But first you should hope that I'm wrong, and wait a while longer for more encouraging input. I feel your pain. Good luck to you Andrew!

Old Yeller

RE: fiberglass bubbling and peeling away

» Submitted by twofootartist - Sun, 7/21/13 » 9:08 AM

Gotta agree with Old Yeller. Mixing epoxy is more critical than many people realize. First, the ratios need to be correct. Throw away the pumps and use one ounce measuring cups. And second, the mix has to be thorough. Stir it for at least a full minute, and be sure to get into the corners of the cup. It's a bummer, but we've all learned the hard way too, so you're in good company. -Wes

RE: fiberglass bubbling and peeling away

» Submitted by Meyer, Robert - Sun, 7/21/13 » 9:23 AM

I guess most everyone who has worked with fiberglass and epoxy long enough will experience this same problem. After having to peel off an uncured layer from the bottom of my last boat (I KNOW I mixed the ratio correctly and stired well..... well....maybe not) and sand and scrape for two wasted days I can only concure with the above advice. I now stir for two minutes and never use pumps.

RE: fiberglass bubbling and peeling away

» Submitted by Laszlo - Sun, 7/21/13 » 7:49 PM

There's nothing wrong with pumps. I've used them for over 10 years and never had a bad mix. The only time I had a peeler was when I accidently washed the surface with lacquer thinner instead of denatured alcohol. (The containers were very similar in appearance and I was wearing a respirator and couldn't smell the liquid).

Good luck with the fix,

Laszlo

RE: fiberglass bubbling and peeling away

» Submitted by Duuane - Mon, 7/22/13 » 10:18 AM

I noticed what appears to be a contradiction in two posts. Yeller recomended using denatured alcohol or lacquer thinner to clean the problem areas before reapplying the glass, but in Laszlos post he said that his one peeling issue was when he accidentally cleaned with lacquer thinner instead of denatured alcohol. I don't personally know the difference, so I am just pointing out what I noticed. Duane

RE: fiberglass bubbling and peeling away

» Submitted by Old Yeller - Mon, 7/22/13 » 11:21 AM

I noticed that too, Duuane, and was a bit surpised to see that. I use denatured alcohol myself, but have also heard others recommend using lacquer thinner to remove uncured epoxy, so that's why I mentioned it. The best advice regarding solvents might be to consult the epoxy manufacturer.

Old Yeller

RE: fiberglass bubbling and peeling away

» Submitted by Laszlo - Mon, 7/22/13 » 1:07 PM

I think that the issue has to do with when you use the lacquer thinner. I used it on bare wood and I believe that the wood pores sucked in the petroleum distillate. Also, I did it as the last step before glassing and Grant recommended sanding afterwards before applying the glass.

It could also be the brand of thinner. Mine was not the premium stuff, so it may have had contaminants in it that did not get along with epoxy in it.

The long and short of it, since I accidently used lacquer thinner when I was in the point in the process where I should have been using alcohol, my incident should not be taken to contradict Grant's advice.

Laszlo

RE: fiberglass bubbling and peeling away

» Submitted by Old Yeller - Mon, 7/22/13 » 1:31 PM

Laszlo, that's a good (but disturbing) point about the brand and quality of the solvents. I've also heard some other very experienced people advise against using solvents to prep surfaces for epoxy or painting, because they sometimes contain contaminants themselves. It's always best to work clean, and not use them when they're not needed. In the cases where they are needed, it helps to use enough solvent, and to change to clean rags often, so the contaminants are actually removed from the surface rather than just being spread around.

Old Yeller

RE: fiberglass bubbling and peeling away

» Submitted by careybob - Mon, 7/22/13 » 7:34 PM

I don't consider myself an expert on fiberglass, although I'm about done with my kayak and I feel like I've been living with the stuff for days. Let's just say I've gone through a box of 100 latex gloves.

Anyway, I just wanted to point out that my mixing instructions for MAS resin and hardener specify mixing it for two full minutes, not one. It also recommends going slowly as you pump to make sure the pumps have had time to rise back to their original position.

Good luck.

RE: fiberglass bubbling and peeling away

» Submitted by careybob - Tue, 7/23/13 » 9:24 AM

I was thinking about this thread and took to the Internet for possible answers. I found this FAQ on a fiberglass/resin supply company in Florida at: http://www.uscomposites.com/faq_epoxy.html

The one thing I haven't heard before is the need to shake up hardener if it's been sitting a long time. I received my kit in March and worked on my kayak since then, and so my hardener sat in its box for four months before I used it. I'll bet this is typical for kit builders...so think about shaking your hardener before fiberglassing.

1. My epoxy is taking forever to dry. What went wrong?

The reasons listed here cover 99.9% of possible scenarios. One or more of them should ring true to your situation.

The ratio for resin to hardener was not correct. This is most commonly a function of poor or imprecise measuring. Eyeballing the epoxy for your ratio is not good enough. A graduated cup should always be used for measuring.
Improper usage of the pumps. If you did not prime the pumps properly it can throw off the ratio. An indication of an improperly primed pump would be when small amounts of air are expelled when dispensing. It may also be a result of losing count of the number of pump strokes.
The resin and hardener ratio was reversed. Odd as this may sound, we've heard about this happening many times. If your hardener is a 3:1 ratio, this mean 3 parts of resin to 1 part of hardener.
The batch was too small. Often when customers are testing epoxy for the first time they will only mix a few teaspoons of epoxy. We encourage testing but when done in such small batches a slight deviation in ratio is greatly magnified. We therefore recommend that your test batches be at least a few ounces, be accurately measured and be thoroughly mixed.
The resin was applied too thin. Very thin applications take longer to cure especially when applied without fiberglass. In these cases patience is required. If the epoxy still does not cure refer to the other scenarios listed in this section.
Something was mixed into the batch. We have heard of people mixing strange things into their epoxy, with water being the strangest. Always use uncontaminated containers and clean stir sticks when mixing the product.
It just wasn't mixed thoroughly. This is more likely to occur if your epoxy is cold. Ideal mixing temperature is about 75 to 80 degrees. If you can't meet these temperatures just be certain your are getting a complete mix.
Low air temperature increases dry time. Temperature plays the biggest factor in the speed of drying. Even when you are using our fastest hardener low temperature always increases dry time. If the resin can be kept between 75 and 80 degrees, i.e. indoors, before mixing, a lower working temperature is not a problem. But again patience is required.
The hardener may need to be shaken. If your hardener has not been used for a month or more, we recommend shaking it at least 45 seconds to agitate any settling that may have occurred. This is not necessary for the resin.
Epoxies cure slower than polyesters. If you are used to working with polyester resins, epoxy cure times will seem to be dramatically longer. They are! And unlike polyesters, there is nothing you can do to speed up the process. Epoxy ratios must be accurate and consistent.

RE: fiberglass bubbling and peeling away

» Submitted by careybob - Wed, 7/24/13 » 7:18 AM

The MAS epoxy web site is at:

http://www.masepoxies.com/index.html

I notice they have a FAQ at:

http://www.masepoxies.com/Epoxy_School_/Tech_Support_FAQ.html

There's a chart on curing times. With the slow epoxy, curing times really slow down as the temperature drops. At 95 deg. F the curing time is 2.5 days. At 77 deg it's 5 days. At 55 deg it's 10 days.