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Old 11-06-2015, 12:34   #1
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Bow GRP repair after hitting a rock island

Sailing from Cuba to Florida we hit a rock island on Cay Sal Bank, just south of Elbow Island.

Windpilot was on, we are a couple and we're very tired felt a sleep and didn't wake with the timer for route check. Wind changed a little and course taking us to the rocks we should have crossed north.

Thing is Trintellas are more solid than rock, so we are fine, reached Ft Lauderdale after sailing through Bimini, boat does not make water and we were lucky damage was above the water line.

Now I want to fix it before sailing north to Boston. Have been looking for info to make sure I do it right. I will remove all loose fiberglass and redo layers to recover/ remake the area damaged.

Any tips, tutorials, sugestión on material to use are useful and will be highly appreciated.

Bellow some pics.

Best,

Gus
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Old 11-06-2015, 16:26   #2
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Re: Bow GRP repair after hitting a rock island

This may help you.
WEST SYSTEM | Projects - Boat Repair
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Old 11-06-2015, 16:46   #3
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Re: Bow GRP repair after hitting a rock island

When you get a chance to do it, photographs showing the damage will help. There are a few shipwrights who are CF members, and PM's will get a response, so there's no lack of wisdom.

Sorry about the accident; you've been fortunate, no one injured, and a good (albeit brutal) learning experience.

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Old 11-06-2015, 17:02   #4
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Re: Bow GRP repair after hitting a rock island

Thanks guys. Just uploaded a good photo.

Just inspected under water and no signs of any impact bellow. Much relieved!

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Old 11-06-2015, 17:33   #5
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Re: Bow GRP repair after hitting a rock island

That's a bad one. I'd recommend hiring a pro, this is beyond the scope of most amateurs. No insurance?
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Old 11-06-2015, 18:53   #6
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Re: Bow GRP repair after hitting a rock island

Quote:
Originally Posted by gtpinhei View Post
Sailing from Cuba to Florida we hit a rock island on Cay Sal Bank, just south of Elbow Island.

Windpilot was on, we are a couple and we're very tired felt a sleep and didn't wake with the timer for route check. Wind changed a little and course taking us to the rocks we should have crossed north.

Thing is Trintellas are more solid than rock, so we are fine, reached Ft Lauderdale after sailing through Bimini, boat does not make water and we were lucky damage was above the water line.

Now I want to fix it before sailing north to Boston. Have been looking for info to make sure I do it right. I will remove all loose fiberglass and redo layers to recover/ remake the area damaged.

Any tips, tutorials, sugestión on material to use are useful and will be highly appreciated.

Bellow some pics.

Best,

Gus
A solid built fibreglass hull is readily repaired.

The advice to follow the west system text is good.

Its a little hard to offer specific advice but here are some general tips.

1) there are no shortcuts
2) feather all repairs back to undamaged glass. No abrupt additions of glass or resin.
3) carefully inspect throughout the interior for companion damage from the impact.
4) you want to repair in layers. No voids, no gaps and make sure every surface is cleaned properly.
5) wetting out properly is crucial

Post pics of your repairs

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
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Old 11-06-2015, 19:58   #7
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Re: Bow GRP repair after hitting a rock island

OP, minaret is a marine professional that offers good advice on this forum. I would advise you to follow is suggestion.
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Old 11-06-2015, 20:17   #8
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Re: Bow GRP repair after hitting a rock island

DpFrz,

I agree, as well. minaret has done absolutely gorgeous work on his Nauticat 52 (about which there is a CF thread, so the OP can see the quality of work that can be done); and he has given advice generously here as long as I've been on the forum.

Good luck with your repairs, gtpinhei.

Ann
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Old 12-06-2015, 10:02   #9
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Re: Bow GRP repair after hitting a rock island

Also recommend Minaret as a very qualified expert to consider in this case.

From the photo it looks like the bow is split right up and down. Cannot tell from the photo but I'm guessing that split goes very deep, probably all the way through the hull to the inside. Also, as other's have mentioned, damage to a fiberglass can spread far from the visible damage, causing delamination and weakness in a wide area.

I would highly recommend you get a professional survey or inspection by a yard very qualified in fiberglass repairs.

Very possible that to repair this properly you might need to rebuild a fairly large area of the bow. It would not be a good idea to just patch it up and seal the damage just to keep out the water. The forestay exerts a good bit of force on the stem and a bad repair could result in bigger problems in the future.
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Old 12-06-2015, 10:31   #10
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Re: Bow GRP repair after hitting a rock island

Capt. John Banister, AMS®
SAMS® Accredited Marine Surveyor
Palm Beach Gardens, Florida



You may wish to contact him? He just posted a very interesting post on thermal imaging.
He may be able to detect damage not visible.
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Old 12-06-2015, 11:22   #11
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Re: Bow GRP repair after hitting a rock island

This thread is located at:
http://www.cruisersforum.com/forums/f55/some-recent-thermal-images-from-surveys-147741-new-post.html


Sorry I didn't include this.
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Old 13-06-2015, 00:49   #12
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Re: Bow GRP repair after hitting a rock island

Having built my own fibreglass foam sandwich 48ft yacht along with good advice already provided note the following:

Being the bow and forestay pressures involved You will need to feathery this repair into at least 100-200mm of undamaged glass in all directions.

Sand thoroughly and clean with acetone before any glass lay up commences.

Prepare all your fibreglass strips beforehand precut to size. Don't try and fibreglass large areas all at once. Use typically 80-100mm wide and 300mm -400mm long.

Use following layup of cloth mat/cloth/mat together Chopstrand Matt 600gsm+ then use biaxial or triaxial cloth or woven rovings
Never lay up more than 3 layers as above at a time and use more rather than resin when wetting out.

Roll the glass out always leaving no bubbles or voids.

Ideally ensure the previous layers of glass layer up has gone off allowing 6 -12 hrs at least before next layup and provide a light hand sand before applying next layup of glass. Never do fibreglass in direct sunlight if you can avoid it as it affects catalyst timing and chemical reaction

Always wear gloves try and clean any drips as you go with acetone cloth beware of surrounding gel coat or paint as the acetone will cause runs or Matt a gloss finish.
Finish repair with filler or micro balloons /resin mix and sand to using increasing fine sandpaper to 240g then apply two pack hi build epoxy paint and sand with 240 sandpaper and or wet and dry yen paint or spray gel coat to finish job.
Remember prepare ,clean as you go and always clean roller and brushed in acetone after every layup or use cheap brushes and dispose (I prefer cheaper than acetone)
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Old 13-06-2015, 05:51   #13
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Re: Bow GRP repair after hitting a rock island

Glad that no one got hurt, & that the boat's fixable vs. being a new artificial reef.

Um, maybe it's just me, but I can't get the pic to enlarge by clicking on it. And thus, can't offer up specific wisdoms. Well, other than "the usual", aka the reference already mentioned. Plus, if you're serious about doing it right, a core sample burn down test helps (in solid glass hulls). That, and one other iest. Call it a laminate "CAT Scan" (the true names escape me @ the moment).
I’m fairly certain that it’s something other than a thermal test. For example, the racer PRB had the integrity of the fibers in her keel structures checked with it after a grounding, prior to being splashed again for an ocean crossing.

In a burn down test, the "boat lab geek" takes a sample of the hull near the damaged area. And then it's literally burned until no resin's left, as the glass (and many other fiber types) in the extracted sample piece of the layup don't burn.

From there, an expert/lab can determine; fiber type, weight, orientation, & layup schedule. Or get pretty close to it. So that then, you can match what's there when doing the repair. And assuming that you get the resin right, between that, & the fiber matching (weight, weave or stitch pattern, & type), it's an almost perfect clone of what was there, pre-impact.

All of this is, after, of course, you get someone to do some fancy tests to tell you how far the damage is, beyond what the eye can see. IE; some NDT to tell you how big the "owie" is. As unlike say, sheet metal in a car, damage in composites can spread out far further (sometimes) than meets the eye (is visible).
The "CAT Scan" part/tests.

Ah, & of course, both of these tests are Far from cheap. And the 1st one especially, is usually reserved for boats with laminates that are rather svelte when compared to a boat's size. And or, she's made with semi-exotic fibers, & a layup designed with FEA/Load Path Mapping (like in a "string sail").
These kinds & levels of testing are done when for some reason, the original layup can't be tracked down via the builder, but the above, fancy construction methods are known to have been used.

Although, as a reality check. Unless you're super concerned about rebuilding to as new status, there are simpler fixes which are plenty strong. But one has to be able to see, and know, what they're working with.



PS: Using the right resin(s) is also vital. Both in terms of strength, & in that some resins don't stick well to some other cured ones.

Plus, ideally, you want to match the physical strength, & flexural characteristics of a resin to that of the reinforcements that you're using. As different brands & type of glass (and other reinforcements) can have vastly differing physical properties. Even though in essence, & in labeling, they're the "same thing".
IE: Quite literally, one can be more than twice as strong as another. Much as the "same" alloy of a steel from 2 different smelters can have vastl differing properties.

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Old 15-06-2015, 06:31   #14
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Re: Bow GRP repair after hitting a rock island

Quote:
Originally Posted by Cadence View Post
Thank you Cadence. This thermal image seems very interesting. I'll look after it.

Best

Gus
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Old 15-06-2015, 06:36   #15
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Re: Bow GRP repair after hitting a rock island

Quote:
Originally Posted by foletti View Post
Having built my own fibreglass foam sandwich 48ft yacht along with good advice already provided note the following:

Being the bow and forestay pressures involved You will need to feathery this repair into at least 100-200mm of undamaged glass in all directions.

Sand thoroughly and clean with acetone before any glass lay up commences.

Prepare all your fibreglass strips beforehand precut to size. Don't try and fibreglass large areas all at once. Use typically 80-100mm wide and 300mm -400mm long.

Use following layup of cloth mat/cloth/mat together Chopstrand Matt 600gsm+ then use biaxial or triaxial cloth or woven rovings
Never lay up more than 3 layers as above at a time and use more rather than resin when wetting out.

Roll the glass out always leaving no bubbles or voids.

Ideally ensure the previous layers of glass layer up has gone off allowing 6 -12 hrs at least before next layup and provide a light hand sand before applying next layup of glass. Never do fibreglass in direct sunlight if you can avoid it as it affects catalyst timing and chemical reaction

Always wear gloves try and clean any drips as you go with acetone cloth beware of surrounding gel coat or paint as the acetone will cause runs or Matt a gloss finish.
Finish repair with filler or micro balloons /resin mix and sand to using increasing fine sandpaper to 240g then apply two pack hi build epoxy paint and sand with 240 sandpaper and or wet and dry yen paint or spray gel coat to finish job.
Remember prepare ,clean as you go and always clean roller and brushed in acetone after every layup or use cheap brushes and dispose (I prefer cheaper than acetone)
Thanks Foletti, your advices are very useful!
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