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30-04-2009, 09:59
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#1
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Registered User
Join Date: Jun 2008
Location: Corpus Christi Texas
Boat: boatless atm
Posts: 762
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Fillling in holes in hull,
What is the best way to remove a thru hull and ensure a good repair on a fiberglass boat?
I have 13 Thru hulls, and would like to reduce that number.
Thanks
Bob
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30-04-2009, 15:21
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#2
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Registered User
Join Date: Nov 2005
Location: At the intersection of here & there
Boat: 47' Olympic Adventure
Posts: 4,852
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30-04-2009, 15:30
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#3
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Registered User
Join Date: Aug 2006
Location: Skagit City, WA
Posts: 25,482
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It is said that you want at least 3 times the hole size tapered with a grinder around the hole. The outside would be the most important as the water pressure is "in". So for a 1" hole grind a tapered circle maybe 3" all the way around. Fill the hole with epoxy saturated disc's of fibreglass graduating from 1" to the maximum size. Ditto on the inside, albeit it is less important to go so big on the grinding. Once hardened, grind the outside off flush. fair and coat. I did this on my 44 footer, what with all the odd ball fittings I had to make into manifolds etc in order to use less throughhulls, as well as the extra length of hoses running everywhere, I was then worried about the weight of all that bronze hanging on the remaining seacocks when I was done, Frankly, unless you have shorts runs, lots of room and a good plan..... I dont think it was worth it....
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30-04-2009, 15:37
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#4
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Registered User
Join Date: Nov 2005
Location: Tasmania
Boat: VandeStadt IOR 40' - Insatiable
Posts: 2,317
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I filled a few holes from unwanted thru-hulls on Insatiable. The hull is solid fibreglass / kevlar about 20mm thick. I ground out a bowl shaped recess about 150mm diameter both inside and outside. The "bowl" was only 1-2mm deep at the edge and about 5-6 deep in the middle. I made a plug to fit into the hole (marine ply, coated with 3-4 coats of timber preserver, then laid glass / resin both inside and out. The point of having a tpered bowl recess is that you can cut circular pieces of glass mat of increasing diameter. We used about 4 laters of glass each one larger than the last, with the last one being the diameter of the outside of the recess.
when the glass/resin was nice and hard, we sanded it back smooth. On the inboard side we laid flowcoat straight over the top. On the ouside we laid a screed of filler over the area, and indeed over a bigger area and sanded / faired it back to smooth before painting.
Whether the above method is strictly the professional way to do it; I don't know, but it worked fine for us.
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01-05-2009, 03:22
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#5
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,139
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Quote:
Originally Posted by Cheechako
It is said that you want at least 3 times the hole size tapered with a grinder around the hole....
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I think that the laminate thickness (not hole diameter) determines the amount of bevel, according to the ratio 12:1.
Accordingly, a hole through a 1" thick laminate will be bevelled out (tapered) 12" beyond the circumference of the original hole.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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01-05-2009, 14:36
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#6
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Registered User
Join Date: Feb 2008
Location: Eastern Seaboard
Boat: Searunner 34 and Searunner Constant Camber 44
Posts: 949
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Quote:
Originally Posted by bobfnbw
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Solid or cored?
__________________
Regards,
Maren
The sea is always beautiful, sometimes mysterious and, on occasions, frighteningly powerful.
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01-05-2009, 23:37
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#7
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Registered User
Join Date: Nov 2006
Location: Back in Northern California working on the Ranch
Boat: Pearson 365 Sloop and 9' Fatty Knees.
Posts: 10,466
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Quote:
Originally Posted by Cheechako
It is said that you want at least 3 times the hole size tapered with a grinder around the hole. The outside would be the most important as the water pressure is "in". So for a 1" hole grind a tapered circle maybe 3" all the way around. Fill the hole with epoxy saturated disc's of fibreglass graduating from 1" to the maximum size. Ditto on the inside, albeit it is less important to go so big on the grinding. Once hardened, grind the outside off flush. fair and coat. I did this on my 44 footer, what with all the odd ball fittings I had to make into manifolds etc in order to use less throughhulls, as well as the extra length of hoses running everywhere, I was then worried about the weight of all that bronze hanging on the remaining seacocks when I was done, Frankly, unless you have shorts runs, lots of room and a good plan..... I dont think it was worth it....
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This is the way I do mine too. It seems every boat I have bought except this latest one had waaaaay too many thru-hulls. One thing I will add to your good description Cheech is to use X-Mat cloth. It is one of the strongest for weight and quick build up.
__________________
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming: Wow - what a ride!"
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02-05-2009, 06:13
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#8
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Registered User
Join Date: Jun 2008
Location: Corpus Christi Texas
Boat: boatless atm
Posts: 762
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Thanks all for your reply s.
I understand now what to do.
I think I can get rid of 4 Thru hulls. Now if I can just get my boat out of the #$@&^%$# damn marina where they won't let me on it cause its a "contractor only" yard and into the do it yourself yard a 25 miles north... I will be happy.
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02-05-2009, 06:40
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#9
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Registered User
Join Date: Oct 2008
Location: Princeton, NJ
Boat: Challenger Anacapa 42
Posts: 2,097
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I was told that when filling in the ground out 12:1 area, the LARGEST piece of cloth should be placed first, followed by the smaller. Reason is you will have a much larger surface area bond, compared to just the edges of each sequentially larger patch. BTW, Gord is right...@12:1 your cone is gonna be close to 12" for a 1" thick hull, 6" for a 1/2" er.
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02-05-2009, 10:31
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#10
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Registered User
Join Date: Nov 2006
Location: Back in Northern California working on the Ranch
Boat: Pearson 365 Sloop and 9' Fatty Knees.
Posts: 10,466
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Hate to be a stickler about this subject but I feel doing 12:1 when using epoxy is ridiculous. 4:1 at the most.
__________________
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming: Wow - what a ride!"
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