Gored: Crack repair

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Gored: Crack repair

Postby GreenLake » Thu Aug 18, 2011 12:19 pm

Well, it happened.

The smallest boat on the lake had it in for us, it's an El Toro, and true to its name it gored us good. :(

1035

Now we have a nice, not quite foot-long gash, on the port side, right above the bow flotation tank. Luckily no chop that night, or we might have taken on water. There are areas of weakened laminate around it as well, there's a shorter, vertical crack running up from the gash. That means the area above the crack was bent fairly far in during the collision and I would consider the laminate there suspect.

Before I commit on a particular repair approach, anyone who'd like to weigh in with a suggestion on how to make it easiest?

Sawing out the damaged laminate and rebuilding would be the straight forward approach, but I would imagine that matching the hull curve wouldn't be an easy thing to do. If I cut out all the damaged/suspect laminate, I may have a hole the size of a stack of copy paper.

It occurred to me that I could simply apply a "patch" from the back (for strength) and, leaving the laminate otherwise in place, just do gap-filling and cosmetic work on the outside. The added weight wouldn't seem a problem, and it would cut down on the area that would need to be faired.

The damage is forward of the "bulk head", which would hide a patch from view, but also makes it much more awkward to work from the inside. (Still far enough back to reach in).

Am I worrying too much about getting a fair repair? Any other approaches that I should consider?
~ green ~ lake ~ ~
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Postby Alan » Thu Aug 18, 2011 5:42 pm

I'm far from a fiberglass expert, but if that were my boat I'd try patching from the inside. If it turns out not to be strong enough, it seems to me you wouldn't have done any real harm, and that you could then try plan A - cutting out the damaged area and replacing it.
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Postby GreenLake » Thu Aug 18, 2011 7:11 pm

Good point, Alan.

Well, the good news is that the area seems plenty strong. We had no indication that the "bump" had been violent enough to actually break the laminate. We continued around the course that night. To really stress that area probably requires beating into significant chop.

I was joking with someone that I should install a view-port there. Seems like it would be a prime spot from where to view an impending collision with a port tacking boat ... 8)

I looked at it again, and no matter which way I proceed, I'll need to cut away a bit of the laminate, because in the crack it snapped back overlapped the wrong way.
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Postby GreenLake » Thu Aug 18, 2011 7:19 pm

Google ads on the forum helpfully suggested "Sewage Damage Repair". It's not that bad, surely :D
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Postby GreenLake » Thu Aug 18, 2011 8:11 pm

Inside view, after widening the gash with a saw to remove overlapping laminate plus all laminate that looked damaged from the outside. This inside view shows how much further the damage to the laminate has spread. I suspect that the area of weakened laminate (stressed so that some, but not all bonds have weakened) extends even further. A large patch on the inside seems indicated.

1036
Last edited by GreenLake on Sat Aug 20, 2011 10:04 pm, edited 1 time in total.
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Postby K.C. Walker » Thu Aug 18, 2011 9:53 pm

My, that's a nasty little gash! I think you're on the right track with putting a patch on the inside. You could laminate up the patch on a flat surface and after curing pull it into place through the crack itself and then you wouldn't need clamping on the inside. I don't think the patch would need to be very thick.

Fairing the repair will not be that difficult. Once you have the patch in place just grind down through the laminate from the outside until you just get to the patch, using an angle grinder. Those 36 grit or 24 grit flap wheels work really fast. Feather it out and then build back your laminate leaving some room for fairing compound. Use as long aboard as you can to sand out your fairing compound. Use your hand to rub over the repair area to check for fairness. You will be able to feel when you are fair. You can also use a batten to check your work but this is not a very large repair so you may not even need one.

I don't know anything about gelcoat repair so to me that would be the tricky part. It might be just easier to repair all the rest of the dings on that side and just paint it with linear urethane. Or just paint your patch for now and do the rest of the work off-season.
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Postby TIM WEBB » Thu Aug 18, 2011 10:23 pm

Holy <beep> GL, that's a nasty wound! If that happened to one of our DS2's, given the completely closed off area forward of the floatation bulkhead, we'd be royally up the proverbial creek sans paddle!

Hope ya get it repaired OK - sorry I have no advice in that area ...

THIS is one of many reasons why I don't race! 8)
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Postby GreenLake » Fri Aug 19, 2011 1:17 am

@Tim - thanks, yes, I love my DS1. I tested the laminate for bending, and it's firm everywhere except above and forward of the gash, which is an area well supported structurally by the rubrail. So, I'm hoping I'll be in good shape.

The "racing" I do is really far from extreme. It's not even very competitive, and the other sailor involved has a reputation of being careful and experienced. It was a very unlucky set of circumstances, not a result of a macho, devil-may-care stunt.

We were on starboard, but upwind of a larger boat which completely hid us from anyone coming from port. Our collision partner managed to cross safely in front of the other boat, but was as surprised to encounter us as we were to encounter them. A faster boat would have cleared us as well as the boat blanketing us - and with better training we might have have had the chance to react more quickly and possibly been able to help mitigate the situation.

@K.C. - yep, I think you've described it. After cleaning up around the edges a bit more, and looking at it from both sides, my plans are now "jelling" around something very close to your suggestion. (Flat plate patch is really appealing over a floppy wet patch). I don't have an angle grinder, so I'll fair the edges of the laminate using an orbital sander. 40 grit disk seems to be working well (I've started this already), but I think with that tool it is best done before the patch goes on from the inside - the laminate seems to be firm enough to allow sanding while unsupported.

For those interested, the laminate seems rather not uniform in thickness, even where it's sound. I'll measure it and post some numbers, if I remember, along with some photos showing further progress.
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Postby ctenidae » Fri Aug 19, 2011 10:01 am

Nasty bump, but does seem repairable.

Instead of a view port, maybe you should put a cannon port there to ward off other crashes.
Formerly 28 cents
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Now, sadly, powered boating...
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Postby K.C. Walker » Fri Aug 19, 2011 11:20 am

ctenidae wrote:Instead of a view port, maybe you should put a cannon port there to ward off other crashes.


...or an extendable bowsprit for ramming purposes.
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Postby GreenLake » Fri Aug 19, 2011 1:46 pm

ctenidae wrote:Instead of a view port, maybe you should put a cannon port there to ward off other crashes.

What I forgot to mount that day...
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Postby GreenLake » Fri Aug 19, 2011 4:13 pm

I promised I would post a measurement or two of laminate thickness. The results are interesting. I get readings from 3/16" to 5/16" with the former predominating. The forward side of the area where the crack is seems to possibly have thinner laminate than the area to the aft, which is closer to the bulkhead.

I thought at first that this could be random, but then I noticed the reinforcements that have been applied around the bulkhead - at least as far as visible from inside the cuddy, that is directly aft of the bulkhead. If these extend equally far forward, that would explain the variation in laminate thickness

The undamaged area above / forward the crack on the port side shows a lot more flexing than the same area on the starboard side, all the way up to the rubrail.

Here's a picture showing the patch being laminated.

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I decided on three layers, cloth, mat, cloth. For a patch of approx 9" x 12" I needed 4oz of mixed laminating epoxy.
Last edited by GreenLake on Sat Aug 20, 2011 10:09 pm, edited 1 time in total.
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Postby GreenLake » Fri Aug 19, 2011 4:18 pm

K.C. Walker wrote:I don't know anything about gelcoat repair so to me that would be the tricky part. It might be just easier to repair all the rest of the dings on that side and just paint it with linear urethane. Or just paint your patch for now and do the rest of the work off-season.


The hull is already painted, and, as these things go, could stand being repainted everywhere. Whether I get around to that this year is questionable. I'll probably slap a bit of the paint left over from my rudder project to protect the epoxy, and leave the rest for a later day.
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1000 posts! Congratulations!

Postby K.C. Walker » Fri Aug 19, 2011 7:33 pm

Congratulations on breaking 1000 posts! It's time to break out the champagne for a toast.

White paint is amazingly forgiving. Even if you're just reasonably close on the shade it's not going to show that badly. If you want to be a little picky about it you can wet sand the edges and give it a buff and it will blend even better.
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Re: 1000 posts! Congratulations!

Postby GreenLake » Fri Aug 19, 2011 7:55 pm

K.C. Walker wrote:Congratulations on breaking 1000 posts! It's time to break out the champagne for a toast.

Yeah!! !!
(I think)
8) :D

K.C. Walker wrote:White paint is amazingly forgiving. Even if you're just reasonably close on the shade it's not going to show that badly. If you want to be a little picky about it you can wet sand the edges and give it a buff and it will blend even better.


So true. Tried that with a white car some time back, and, unless it had just been back from the car wash, the off-color wasn't all that noticable. Still a drop of tinting might improve things.
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