Trouble! "Blisters" on the underside of my canoe

[doe4rae]

I'm still trying to work out the "why" of this. 1. Is there anything that could have acted as a solvent on cured epoxy? (Lacquer thinner, acetone, something in my tack cloth, mineral spirits?) or 2. If I would have sanded down to the cloth before varnishing could it have caused this?

I chipped away some of what I could pry loose around the edges of the bubble (after I cut the bubble off). I think I've reached the limit of what lifts off easily. (Last picture in the album).

I'm bracing for the worst (uncured epoxy... too cold lay up, improper ratio of mix) -- but won't know that for a while.

[Denis]

Dawne did you wipe down the hull between coats of epoxy with anything? Mineral spirits on the epoxy before varnish shouldn't be a problem.

Denis

[doe4rae]

The first 3 coats of epoxy I did all the same day about 5 hours apart. I didn't do any wiping down in between because the epoxy was still green between coats. It was pretty chilly in the basement tho... right around 60 degrees. Then about 5 days later I scraped some of the drips and runs with a cabinet scraper, sanded the hull and added another 2 coats of epoxy. I am sure I wiped down the hull with something at that point but I can't remember what it would have been. I had both Acetone and Laquer thinner at my disposal .

I don't doubt that the final thing I would have done is to go over the entire thing with a tack cloth before adding either epoxy OR varnish. Its a mystery to me what's in those things but they are very tacky.

[Mac]

I read that using a tack cloth can cause problems with epoxy cure, so I avoided using one. Could that be an issue?

From the building tips section on http://www.michneboat.com/Fiberglassing%20-%20101.htm "DON'T wipe the hull down with a tack cloth or acetone - any contamination can effect the curing; in fact, acetone is a solvent for mixed epoxy and will soften cured epoxy."

[pyrofly73]

Sometimes we need to match thickness when doing repairs in older boat hulls. In order to do this we would cut out a small section(1" hole saw) of hull and burn it. The epoxy goes away in smoke and leaves behind the glass. It's a smelly nasty procedure, but after careful examination of the remains you could figure out exactly how many layers of what material was used.

To be 100% certain of what your problem is I would burn that chip instead of breaking it with your fingers. If there is any cloth left in the remains you know what needs to happen.; sand to 1" outside the sticky zone and do the patch. If there is no cloth I would wipe the area with acetone or mek to remove stickiness sand and apply more epoxy.

If the cloth looks like it's not fully adhered this may be the one time where you may want to thin the epoxy a bit to try and get it to flow under and into the poorly adhered cloth. Cuttinf a small slit or injecting the area will obviously improve penetration. I would heat the epoxy to reduce the viscosity, but this speeds up cure quite a bit. The epoxy can also be diluted with a bit of MEK(although most mfg recommend against this)

Good luck... It's not a big deal.

Xavier

[unix_r_us]

I'm not the original poster but would like thank everyone for their replies anyway as I've just run into a similar situation. I was going over the hull on last time before varnishing it, and found a troublesome spot. I know for sure it's the second epoxy coat, as my brother's "Oh oh, I forgot to mix this batch" comment after a few brush strokes is coming back to haunt me. We furiously mixed and went over that spot many times, but I guess it didn't solidify properly. The outer layer is solid, the middle layer of epoxy is still sticky in a roughly 4" diameter circle.

I'm planning on scraping out what I can without touching the glass, and use acetone/laquer thinner to clean out the rest, then re-apply epoxy. Not sure if I can make my August 2nd launching any more. :(

thanks
mike

[doe4rae]

I just wanted to post a short follow up on the repair that I asked advice on last month. It went very well and after several hours and miles it is holding up fine. I would post a picture of the repair but you really can't see where I made it. I think that it must have been a spot of uncured epoxy in a 2nd or 3rd coat. I was fortunate the cloth stayed intact. I also have decided not to use the tack cloth to wipe down the hull. I did this after sanding the epoxy and I noticed once that there was some sticky residue left on the hull. I keep going back to that moment in my mind and wondering if it was the cause. So... good news... we are back on the water and trouble free. No picture of the repair but here is a link to a recent image on a trip to Voyageurs National Park. I have every confidence in this boat after that trip! She can handle a load as well as any canoe I've paddled even at a seemingly shorter length of 15' 5".

http://picasaweb.google.com/olson.dawne ... 4464520258

[Glen Smith]

It's great to hear everything worked out for you. Nice photos, thanks for sharing.

[Gomer]

Dawne, Not only are you a great boat builder, your quite a photographer as well. Looks like a fun trip. I'm going to float several rivers in Texas this Fall. I can hardly wait for it to cool down! :twisted evil

[doe4rae]

Hey thanks! Best thing in the world on a hot day is to be on the water! Enjoy your canoe and thanks for the nice comments on both my boat and photographs!

[jpowers123]

I have not read the board in a while and read your recent back and forth about the blisters. I tell you, I had a similar situation and in my opinion you should have followed Rod Tait, of Orca Boats advice. I'l bet you the blister changed a bit once it was not as hot as that day you first noticed it and if you did not remove the fiberglass and epoxy all the way down and check for uncured epoxy, like Rod recommended, you will see it again in the future. I just did a couple of repairs following Rod's advice and I could not be happier with the results. Not to mention the fact that I know for sure that I got all of the uncured epoxy out of there. Just my own two cents. I have only done one stripper and am definitely no expert but I try hard to learn from my mistakes. If there are some soft epoxy spots anywhere on that hull, you will know about it eventually. Mine started like yours and before I knew it. there were a few more, nothing big, but definitely in need of repair. Good luck.