stringer damage

**Exador** · 5th June 2011, 06:34 AM

I refinished my fibreglass half-cabin topsides a few months ago and she's not been out much since, but I noticed a section near the bow where the paint had "crazed". Upon investigation, I found a crack in the glass around the top-most stringer, about 200mm back from where it fairs into the hull near the bow. This crack was there previously, seemingly sound, although I coated the area with epoxy when I first noted it. It's got a great deal worse, and i suspect that the timber is not in the best of nick inside, or it got a whack last time we went out, which is entirely possible, it was not long after the Brisbane floods and the water was very mucky. There is notable "softness" around the crack, although not for very far along the stringer. I suspect it's been flexing for some time, since there was some minor cracking which I ground out and filled in the same area that the crazing has occurred.

The problem I've got is that there is no access on the inside of the hull, thanks to the cabin seating, which is moulded as part of the hull, so I'll have to attack the repair from outside.

My question is, has anybody tried injecting epoxy in this sort of situation? I think it would be a major job to cut out the stringer and replace the wood and very difficult to achieve a good appearance. I though to contact someone who does grout/epoxy injection and see if we can't repair it that way. Any ideas?

**PAR** · 6th June 2011, 11:00 AM

Injecting epoxy into blind applications has two major drawbacks: the first is you can't see how much damage there is, so you don't know when to stop and the second issue is you have to drill lots of blind holes into something you can't real see.

Injection works, but honestly it's a Mickey Mouse way of doing things. Epoxy alone will not stabilize a crack, it needs reinforcement. Usually this means 'glass or other fabrics and/or filler materials like silica and milled fibers (there are others too).

If it was my boat, I would take a grinder and plow down through the plywood (my assumption) deck and expose the stringer (deck beam?) from above. Another option is to cut just through the deck, but set the saw blade to only to the thickness of the deck, so you can remove the deck piece intact (saving some work later). With the piece of decking removed, you'll see the extent of the damage and can make the hole bigger or another on the fly, decision about how to approach the problem. Once the stringer is restored to full load status, you feather the edges of the deck piece and the deck and patch it back down. Naturally, this is all preformed with epoxy.

**Exador** · 6th June 2011, 11:37 AM

Thanks for the advice PAR, but I think you've misunderstood the problem a little. The damage is to one of the stringers that runs along the hull, forming a strake or spray strip. This is the top-most strake on the port side, just below the chine. The crazing I mentioned is above the stringer/strake and slightly forward, just in front of the point the chine fairs into the bow. I wasn't very clear, sorry. As always, a picture would clear the whole thing up. I'll get one before I go any further.

**soundman** · 14th June 2011, 02:51 PM

If it is only a strake and possibly the meterial behind......probaly the safest option is to have it off.

Slice it off flush with the hull..... get a good look, then scarf a piece back in to replace it......(an 8:1 scarf with epoxy is equavalent to original material strength)
The make good over.

If you could take the dentist approach..if it does not seem structrual......hop in with a die grinder and hollow out the soft bit back to sound material and then bog up with thickened epoxy...then make good over.

next time i'm passing I'll drop in and we can poke it with a stick

cheers

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