Bottom Cracks
Moderators: Tim Bosma, Tom Elsen
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normbue
Bottom Cracks
Hull #284 has serious cracks in front of, and behind the centerboard opening. Rather than cut the external skin to repair it, would it be possible to cut out the inner skin and fill the area with glass and epoxy? It seems like it would make a stronger patch. I'm pretty sure the balsa is gone. Externally, the cracks start about 6 " in front of and behind the center opening and are about 8" long, but I can't tell if they overlap the centerboard trunk or anything else on the inside.
Re: Bottom Cracks
Norm,
While you can get at the front of the trunk via the V Berth, the back is difficult form inside without destroying the cabin floor pan. And as Stef said, these areas are already solid glass. This is one repair I would do from the outside, but I am sure Dave will have some good comments about how to do this.
Thanks,
While you can get at the front of the trunk via the V Berth, the back is difficult form inside without destroying the cabin floor pan. And as Stef said, these areas are already solid glass. This is one repair I would do from the outside, but I am sure Dave will have some good comments about how to do this.
Thanks,
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normbue
Re: Bottom Cracks
If it is solid glass, why can't I see the cracks from inside in the bilge?
Re: Bottom Cracks
Are you seeing just gelcoat cracks, that might explain it? Picture might be worth a 1000 answers or something.
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normbue
Re: Bottom Cracks
These are big open cracks, Its on a lift so I can't get to it yet. to get pictures.But when you let it down, water comes into the boat. When you raise it up, water runs out of those cracks. A local marina filled them with something.... but it didn't stay.
I thought if I could get to them from the inside. and flood the area, it might be stronger than applying epoxy over the skin from the outside.
By the way, how do you post a picture here
I thought if I could get to them from the inside. and flood the area, it might be stronger than applying epoxy over the skin from the outside.
By the way, how do you post a picture here
Re: Bottom Cracks
I put a short lesson on attaching pics in the pic thread.
thanks,
thanks,
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LarryE-old
- Posts: 233
- Joined: Fri Jun 27, 2003 12:06 pm
Re: Bottom Cracks
Love the last line of your replyTim Bosma wrote:Norm,
While you can get at the front of the trunk via the V Berth, the back is difficult form inside without destroying the cabin floor pan. And as Stef said, these areas are already solid glass. This is one repair I would do from the outside, but I am sure Dave will have some good comments about how to do this.
Thanks,
Purr-Fect
262
262
Re: Bottom Cracks
Just now seeing this, haven't been on here since January or so, sorry if that set the poster back.
Even though the front and back of the boatd trunk/hull area is "solid glass", it's not very well done (in my experience) as far as the layup goes, and most importantly, the builder used Polyester resin, like all prodcution boat builders did back then and 99% still do. Two things here; Polyester is very stiff and brittle compared to Vinyl Ester or Epoxy, and this type of area is one of those which often get a fairly lousy layup in boat production factories. When the going gets tough, as in getting anything besides chopped strand matt to lay smoothly in tight corners with very sharp radii, the industry standard practice (for the average laminators at least), is to slop more resin to it! See the brittle and stiff thingy again!!!!
These fore and aft joints take a LOT of load, and flex more than one might think just sailing upwind in moderate to high winds with lots of waves and chop. Throw a few groundings in and then add the above info and you can see why the cracks develop, and on my boat they were REALLY DEEP! Only a comparitively deep grind job to cut away the cracked laminate and resin, followed by GOOD layup using really good glass like Knytex 1708 in many layers with at least Vinyl Ester resin, done over a fairly large surface area to spread the loads and the adhesion, will usually fix this.
On the interior, you could always install 6" ispection ports, or even larger if needed, but this doesn't address the exterior cracks. There are some nice ones out now that are rectangular, giving more working space and reach. These would be perfect for the gudgeon problems too, when installed in the back of the cockpit.
If you have done it already, sorry that I missed it.
Even though the front and back of the boatd trunk/hull area is "solid glass", it's not very well done (in my experience) as far as the layup goes, and most importantly, the builder used Polyester resin, like all prodcution boat builders did back then and 99% still do. Two things here; Polyester is very stiff and brittle compared to Vinyl Ester or Epoxy, and this type of area is one of those which often get a fairly lousy layup in boat production factories. When the going gets tough, as in getting anything besides chopped strand matt to lay smoothly in tight corners with very sharp radii, the industry standard practice (for the average laminators at least), is to slop more resin to it! See the brittle and stiff thingy again!!!!
These fore and aft joints take a LOT of load, and flex more than one might think just sailing upwind in moderate to high winds with lots of waves and chop. Throw a few groundings in and then add the above info and you can see why the cracks develop, and on my boat they were REALLY DEEP! Only a comparitively deep grind job to cut away the cracked laminate and resin, followed by GOOD layup using really good glass like Knytex 1708 in many layers with at least Vinyl Ester resin, done over a fairly large surface area to spread the loads and the adhesion, will usually fix this.
On the interior, you could always install 6" ispection ports, or even larger if needed, but this doesn't address the exterior cracks. There are some nice ones out now that are rectangular, giving more working space and reach. These would be perfect for the gudgeon problems too, when installed in the back of the cockpit.
If you have done it already, sorry that I missed it.
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normbue
Re: Bottom Cracks
Haven't done it yet. Waiting for the weather to break.... But if water is getting in, shouldn't I be able to see those cracks from the inside? Or could the leak be somewhere else, like the inside of the trunk.
Re: Bottom Cracks
Normbue,
I try to work smart, not hard. Still, things almost always seem to be hard no matter what. On that note: the best way to find suspected bottom leaks is to pull the boat out of the water, let the bottom dry completely, then start adding water to the interior. If you have the boat level then the keel trunk will be the lowest part, and and true leaks will be very apparent.
Understand though, that just because you have cracks in the exterior, that doesn't mean they go all the way through into the interior.
Something that I forgot to mention about Polyester resin is that it shrinks a good bit after curing. The higher the exotherm of the specific resin, in a specific spot, at a specific time of year and of a specific thickness can mean anything from not much problem all the way to cracking like hell in months or years to come. The hotter it gets at cure, the more it will shrink post cure. Thick areas of Polyester resin are infamous fir becoming to hot, then cracking. The introduction of fiberglass slows this to some extent, but.....
This is one more great reason to use epoxy. Even though it to creates heat at cure, one can use tye appropriate cure time for the weather and the laminate thickness so that it doesn't "smoke". Plus, Epoxy resins and hardeners are 100% solids, while Polyester and even Vinyl Ester have a lot of VOC's that evaporate upon cure. This evaporation means that there's less resin mass left at the end of the cure than before the cure, so when added to the info above, it should be easy to see that you never want to make any laminate really thick all at one time (no matter the resin), and that this too adds to tye shrinking and eventual cracking of areas that are laid up too thick, too fast, too hot, or all of the above.
I try to work smart, not hard. Still, things almost always seem to be hard no matter what. On that note: the best way to find suspected bottom leaks is to pull the boat out of the water, let the bottom dry completely, then start adding water to the interior. If you have the boat level then the keel trunk will be the lowest part, and and true leaks will be very apparent.
Understand though, that just because you have cracks in the exterior, that doesn't mean they go all the way through into the interior.
Something that I forgot to mention about Polyester resin is that it shrinks a good bit after curing. The higher the exotherm of the specific resin, in a specific spot, at a specific time of year and of a specific thickness can mean anything from not much problem all the way to cracking like hell in months or years to come. The hotter it gets at cure, the more it will shrink post cure. Thick areas of Polyester resin are infamous fir becoming to hot, then cracking. The introduction of fiberglass slows this to some extent, but.....
This is one more great reason to use epoxy. Even though it to creates heat at cure, one can use tye appropriate cure time for the weather and the laminate thickness so that it doesn't "smoke". Plus, Epoxy resins and hardeners are 100% solids, while Polyester and even Vinyl Ester have a lot of VOC's that evaporate upon cure. This evaporation means that there's less resin mass left at the end of the cure than before the cure, so when added to the info above, it should be easy to see that you never want to make any laminate really thick all at one time (no matter the resin), and that this too adds to tye shrinking and eventual cracking of areas that are laid up too thick, too fast, too hot, or all of the above.
Re: Bottom Cracks
Sorry for a few typos, wish there was an "edit" icon somwhere!
Re: Bottom Cracks
To add to Dave's comments, another great thing about epoxy is West System has a dozen tech advisors on staff ready to take calls and/or emails if you have questions or need assistance with their products. I should note that I am not completely objective as my wife works in their marketing department (hence the boat name).
Drew
Bond Girl - Hull 007
Drew
Bond Girl - Hull 007