Fiberglass Creep

Put a newly built boat into the sun for the first time the other day and this developed along the interior scarf joint that was in the sunshine.  It feels like braille. West System claims it's called "fiberglass creep" which can develop when the panel was glassed while flat as opposed to when it was in its final hull shape. The surface temperature passed 120F, the epoxy softened, and the fiberglass "creeped."  Has anyone experienced this and how have you avoided it?  Anyone have ideas as to how to fix it.  West System suggests scraping the heads off the "bubbles" and filling with thickened epoxy.  Thoughts????  Bummer of a situation, particularly since I've never heard anyone speak of such a thing!

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Permalink Reply by Eric Loudenslager on July 29, 2016 at 3:29pm

Also called "fiberglass print through". Not uncommon with an epoxy/fiberglass laminate. Cosmetic problem, not structural. Is that a final paint top-coat, or primer in the picture? If primer, can you wait a couple weeks, then sand, fair, etc re-prime if necessary, before top-coating? If top coat, use the boat for a year or so to let everything settle in place, then scrape, fair, sand, prime and repaint.

Don't worry to much. No one else will even notice. Devlin's Boat Building (book) has several pages of discussion of print through, so even the pros have unresolved challenges.

Permalink Reply by Craig Campbell on July 30, 2016 at 8:00am

Thanks for the response Eric but what I'm experiencing is not fiberglass print through.  Unfortunately, this is an entirely different beast. 

Permalink Reply by tungsten on July 30, 2016 at 10:08am

Not sure if you really need to do it but the only way to tell for sure is grind out a little area and see if the glass has lifted or if its still bonded.You'll     sleep  better knowing exactly what it is.

Permalink Reply by Craig Campbell on July 30, 2016 at 2:13pm

Scraped off the heads and the fiberglass is still bonded securely.  West System says fill with thickened epoxy and continue with finishing.  This has happened on all of my scarf joints that saw direct sunlight.

Permalink Reply by Craig Campbell on August 1, 2016 at 3:05pm

Since I'm not the only person who has laid fiberglass on a flat panel (as opposed to on a completed hull) I can't be the only person this has happened to.  Has no one else experienced this?  Really want to figure this out!:)

Permalink Reply by David Witton on August 3, 2016 at 6:47am

I store my boat outdoors, part of the day in the full sun, under a cover, so temps get pretty high. I haven't seen anything like what you describe. I'd guess it's dependent on the epoxy type that was used. 

Permalink Reply by Craig Campbell on August 3, 2016 at 9:11am

I use West System 105/207.  What brand of epoxy do you use?

Permalink Reply by Mike Thomas on August 3, 2016 at 3:34pm

I could see how glassing a flat panel then bending it could cause issues, somethings gotta give, and with the epoxy and no uv protection in 100+ temps too. Maybe post some pics of the damage. Interesting though on just the joints. I used 105/207 to seal and glass my boat, sealed all the panels flat, but glassed after it was assembled

Permalink Reply by David Witton on August 4, 2016 at 6:50am

For an explanation of epoxy behavior at elevated temps you may want to look at 

http://www.westsystem.com/ss/if-you-can-t-take-the-heat/

I used Resin Research 2000 series. It has an HDT (HDUL) of 122F - although that figure doesn't indicate a failure point, as explained in the article above. 

Permalink Reply by James Prepura on August 12, 2016 at 3:40pm

I think West System is right about that, it almost looks like what I would call gas off its when you trap air under something in your case it might have been air trapped in the fibers of the glass that didn't release when you epoxyied over the glass and extreme heat brought it to the surface through expansion we have had that with auto paint before after glassing I could be wrong, have been wrong before hope it works out for you

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