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Old 25-07-2017, 12:32   #1
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Hull crack

I have a crack in the hull at the bottom of the keels leading edge. The construction of the boat is the hull came together in 2 halves with the cast iron ballast encapsulated between the halves. I thought this was a rock solid design until Practical Sailor had an article on this design. Their article pointed at possible problems if you had ever gone aground. We have in the ICW. Yesterday the boat yard sent me a couple of pictures showing either motor oil or diesel fuel leaking through the keel. The fuel tank is in the keel. Here's the pics. Any ideas would be appreciated.
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Old 25-07-2017, 16:52   #2
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Re: Hull crack

Photos are a little confusing. One would think if oil is leaking, it would run down face of the keel to the wood blocking. From these photos there is no witness marking on the cribbing. Maybe a few more photos from other angles and close up shots. There is a huge amount of experience in this blog that should be able to help.
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Old 25-07-2017, 23:11   #3
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Re: Hull crack

OK, first have a read from the Gulfstar 37 web site Quote:

delamination around keel joint and if there's any engine oil around where the keel is sealed by FG inside don't buy it. This is because some stupid GS owners just dropped their engine oil in the bilge to change oil and this works its way to the aforementioned joint and - delaminates it over time - this is almost impossible to repair. Other things are - water getting into the balsa core of the decks/cabin top - I was lucky here and mine was perfect - stress cracks in the outside fg ...,

1) Confirm if it's diesel or oil (to me looks like diesel?)
2) Remove tank replace/repair out of vessel if feasible
3) Check if oil where from? repair/ clean
4) As above once confirmed what you are dealing with (Diesel or oil) try to flush from the top and let drain thru the keel and out of the crack
5) Once flushing shows no sign of further dripping of oily waste, grind back the crack and feather back the bottom and side of keel area around crack, I would recommend a good water blasting or even better hot water detergent blasting finishing with fresh water,(Dont use water combined with acids when blasting(quite a few yards do this now!) as it will eventually degrade the GRP!
6) Once confirmed dry and free from contaminants proceed with the repair, due to the possibility of contaminants remaining in the GRP material I would personally look around for a Vinyl-ester resin rather than conventional poly ester then use an alternative layer system of chop strand Matt and uni directional,(Below for reference)

Vinyl-ester resins are stronger than polyester resins and cheaper than epoxy resins. Vinyl-ester resins utilize a polyester resin type of cross-linking molecules in the bonding process. Vinyl-ester is a hybrid form of polyester resin which has been toughened with epoxy molecules within the main molecular structure.


I offer the forgoing only as advice with no preconception, with no legal implications and without prejudice.

Cheers Steve (MIIMS Surveyor)
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Old 26-07-2017, 10:40   #4
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Re: Hull crack

Hello Steve and thank you for your knowledgeable input. The diesel tank is just a void in the fiberglass in the aft section of the keel. It is roughly a trapezoid shape about 42" deep. It holds about 75 US gallons. I strongly suspect the leak is diesel. We have had a few hard impact groundings. My plan is to cut open the top of the tank (void). Have all the fuel pumped out. {your idea} Have the tank hot pressure washed. Have a custom or close as I can find tank inserted into the void and epoxy foam into place. As to the hull the repairs would be done in carbon and epoxy. I'd like your opinion of my plan.
The boat is kind of irreplaceable because I've never found on like it.
Thank You,
Michael
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Old 26-07-2017, 10:57   #5
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Re: Hull crack

To start, drain the tank, wash it out (detergent/soap type washing), along with steam cleaning, & pressure washing. Which somewhere along the way you may wish to drill some drain holes in the bottom so that ALL of the petroleum products, as well as the oils suspended in the detergent cleanings, have an easy way out.
Then grind any areas in question back to bare glass, & assess the area of damage. Followed by repairs with epoxy, & triax. Plus having a removable tank for that void, fabricated.

You really do want to go full on OCD when it comes to getting things clean, & free of contaminants. Perhaps even to the point of having someone test the laminate after you're "done" cleaning. And prior to doing any glass work repairs.

Also, since it is leaking, that's a sign that there are cracks which extend fully through the laminate in some areas. So given how thick keel laminates tend to be, you're in for doing a lot of glass work... that's fairly professional in quality. And one tricky bit will be when grinding in order to get your bevels for applying new glass, is not to remove so much material during this phase of the repair so that the internal ballast is less than adequately supported.


There's some great, albeit semi-scary, information & pics in the thread by Hooked & minaret when they repaired his keel stub/sump. It's several pages long, with lots of pics & descriptive captions, dealing with repairing serious structural laminates to a boat's keel mounting stub. Some/much of which will apply here.
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Old 27-07-2017, 00:06   #6
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Re: Hull crack

Michael, agree with all the above post, obviously dont be tempted in using mild steel for your new tank, custom Stainless Steel 316 grade/GRP -( using correct materials)/or custom plastic!

Cheers Steve
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