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Old 01-24-2019, 09:00 AM   #21
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I'd suggest you contact a Marine Surveyor in your area. The entire hull should be checked and a grid (blue painters tape) installed on the exterior with readings recorded and noted for each area. This will give you a better idea what you are facing and the extent of the intrusion which you need to stop. Additionally see if you can find a local Surveyor with an Infrared Camera. I won't comment on the repairs as they are well addressed already.
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Old 01-24-2019, 09:06 AM   #22
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Originally Posted by CNRules2 View Post
You might take a look at Carribean Sealife's blog, where he redoes the bottom of a Krogen 42 that had a wet core: the full blog is in the second link below, https://photos.google.com/share/AF1Q...ZfZ25zMG1ONlZ3

Full refit blog:
https://caribbeansealife.com/about-our-boat/refit/

Wow, that's an eye opener.
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Old 01-24-2019, 09:52 AM   #23
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Wow, that's an eye opener.
Yup - that's what we have seen as well. Just not on a KK42.
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Old 01-24-2019, 11:01 AM   #24
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Saw the same, a two year job at the yard.

What kind of core was that? Balsa or synthetic?
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Old 01-24-2019, 11:07 AM   #25
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Originally Posted by bayview View Post
Saw the same, a two year job at the yard.

What kind of core was that? Balsa or synthetic?
Synthetic, pvc. Krogen switched to solid fiberglass below the water line on the KK42 in about 1993.
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Old 01-24-2019, 11:29 AM   #26
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So even though the pvc core wouldn't rot the problem was essentially the same as if it was balsa.

I have now changed my mind about any core. previously I thought synthetic would limit the intrusion to a small area because or resin in between the blocks and there would be no rot migration. Now I see that, in that boat at least, water covered a huge area.

Any report on the source of the water?
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Old 01-24-2019, 12:29 PM   #27
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Foam core does not limit water migration, as the kerfs required to make it conform create water channels throughout the hull. Builders will tell you they fill the kerfs with resin, but this is provably false, which can be verified by cutting one apart. Even infused hulls have channels in many types of cores, as the resin is too viscous to fill the tight kerfs. Many foam cores are structurally unaffected by water though, so there is no damage. If the skin is delaminated from whatever cause, then stripping and relaminating is about the only cure. Water by itself does not dissolve this bond.

Very rarely, cored boats are built by vacuum forming large foam sheets into the mold. These sheets do not have kerfs, usually only an array of holes. In that case, water migration should be severely limited. I've only seen that construction in recently built, very high end sailboats. It could be done fairly easily in a hard chine powerboat - at least over large areas - but I've not seen that either.

I mostly agree with Boatpoker's article. A moisture meter gives you some information, but not definitive information, absent other measures confirming. Thermal imaging can be incredibly revealing, but is even much more difficult to do properly than a moisture meter. If you can get conditions just right, you can see each individual block of foam, the resin in the kerfs between them, etc. Getting those conditions to happen on command it nearly impossible.
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Old 01-24-2019, 01:35 PM   #28
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After viewing those photos It appears that there was delamination is that what caused the water ingress? if so... is this caused by poor manufacturing practice, bad resin or?
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Old 01-24-2019, 01:55 PM   #29
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A friend of mine for years managed QA QC for a major boat builder. As well, he traveled overseas to monitor new builds for the buyer.

His stories on what could screw up the molds, resin, the layup process, core, etc were fascinating. One thing he mentioned was the guys working in the molds and doing the layup sweat a lot dependent upon humidity and temperature. Any dripping sweat, building roof leaks, bird poo, condensation from water bottles or spilled tea/coffee onto the work in process created ideal spots for blister formation and potential delamination.
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Old 01-24-2019, 01:58 PM   #30
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Originally Posted by Ka_sea_ta View Post
After viewing those photos It appears that there was delamination is that what caused the water ingress? if so... is this caused by poor manufacturing practice, bad resin or?
Generally from what I understand, it's water ingress that causes delamination in this context. I'm sure twisting/structural deformation can cause it as well, but that's not the subject of this thread.

I'm also curious what caused it though, how'd the water get in?

I suspect I know some of the possible suspects:

1. Thru hulls
2. Construction technique
3. Gashes/holes
4. Osmosis?
5. Thru hulls
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