Fiberglass repair

[oded kishony]

Working on my boat last weekend I noticed some gouges that I think should be repaired- with so many knowledgeable folks on this list, can someone suggest how to repair some deep scratches and while we're at it, there are some spiderweb cracks on the transom that I'd like to take care of.

Thanks,
Oded Kishony

[s/v Faith]

Don't know if I fit the knowledgeable part, but I have been doing a bunch of this kinda stuff.

Regular fiberglass resin is good for construction projects, but most sources say it is not ideal for repairs.  It seems as though it does not want to stick to anything other then fresh fiberglass.

Some may recommend bondo..... I do not.  I had to chip quite a bit out of my boat with a hammer, as it seems to absorb water and get flaky or swell over time.

Epoxy is the material of choice, it can be used to 'wet out' fiberglass mat for structural repairs, or mixed with fillers to fill scratches and small holes.

I use West systems epoxy, but only because I got a great deal on a couple gallons of it.  It is a 'blushing' epoxy, which means it leaves a waxy coating when it dries that you must remove before painting, or adding more epoxy.

Non-blushing epoxy is considered to be 'better' by most who report to have studied such things.  FCGI.com is a good source for non-blushing epoxy and fiberglass mat.

If you click the link above, there is a users guide that will tell you all you ever want to know about using west system epoxy.

The classic plastics forum is also filled with experts on all matters fiberglass.

[AllAboutMe]

Oded,
It depends on whether the gouges are into the sub-strata or not. If they are, then they need to be ground out a bit, filled with thickened poly or epoxy, and then sanded or ground down to the depth of the gel-cote. Then, with a kit that you can purchase from West, or the hardware store in Urbanna, mix up a color matched gel-cote repair. This is applied to the crevice, and covered with plastic til it cures. Then you can wet sand, and polish the new surface. It's easier to do, than to write about. West Marine has a free or almost free pamphlet that gives the entire process in detail.
Larry Wilson

[Triton218]

Hi Oded,

From your post, you have two problems that require different solutions. The gouges and the stress cracks should be treated differently.

The deep scratches can be ground out and filled with thickened epoxy. I'd recommend a filler that's easy to sand and fair. If you use West System, that would be number 407 or 410 filler; if you use a different epoxy, it will be a filler with microballoons. From there, I wouldn't reapply gelcoat - just prime and paint.

The stress cracks, though, are a bit different. They're common on old boats and some new ones and they result from either a degradation in or inherent weakness of the surrounding laminate. For example, on my Triton, I've had them at the forward edge of the cockpit as my cockpit sole needs reinforcement. The use of thickened epoxy to effect this repair will only provide a short term solution, as the flexing that created the stress cracks will still be there. If it is an area, such as a cockpit, that can be easily reinforced, then I'd advise strengthening the area prior to repairing the cracks. Or you can apply stringers and/or a few layers of fresh glass to an area to provide greater rigidity. From that point, just fair, prime, and paint.

[psyche]

I have used Marine Tech to fill some gauges or deep scratches. After it hardens I have sanded it smooth. Depending on the area I may use a burr in a dremel to make the scratch/gauge more receptive for the Marine Tech. Dan