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Old 09-04-2017, 09:46 PM   #1
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Transom soft spot smoking gun

Hi All,

One of the items found on the survey for our 40 year old Taiwanese 36 was a soft spot on the transom (amidships and around the hull zinc). What I found today was 90% of the bolts holding the swim platform brackets are spinning. The heads are encapsulated in the transom, i.e. don't go all the way through. I'm going to have to cut through the inside fiberglass to expose the heads.

Question is, do I try to re-epoxy them in place, or remove the bolts, glass the area back up solid and then drill new holes and install the bolts from inside the lazaretto to the outside?

Discussion - Dave
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Old 09-04-2017, 11:01 PM   #2
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Take a flush ciut vibrater saw cut the glass away, remove the bolts almost certainly "waisted" corroded where they go thru the hull. You may be good to just replace the bolts, or redrill and move up a size, rebolt and caulk, cover bolt heads neatly with filler and reglass. Good for the next 30 years.
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Old 09-04-2017, 11:27 PM   #3
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Originally Posted by Dave_E View Post
Hi All,

One of the items found on the survey for our 40 year old Taiwanese 36 was a soft spot on the transom (amidships and around the hull zinc). What I found today was 90% of the bolts holding the swim platform brackets are spinning. The heads are encapsulated in the transom, i.e. don't go all the way through. I'm going to have to cut through the inside fiberglass to expose the heads.

Question is, do I try to re-epoxy them in place, or remove the bolts, glass the area back up solid and then drill new holes and install the bolts from inside the lazaretto to the outside?

Discussion - Dave
Your last option is your best bet, new bolts (preferably 316 SS) after doing your repairs and either in something like 5200 , when installing be sure to place large size washers or better still doubler tabs under the bolt heads,

If sealed correctly with 5200 or similar there should be no need to glass over at all thus giving you access should you ever need to remove for any reason


Cheers Steve
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Old 09-05-2017, 12:49 AM   #4
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Hmm, you said 'soft spot'. Perhaps the bolt heads are spinning because the core of the transom has a lot of rot?

The transom is likely multiple layers of ply with 'glass skins, albeit the skins may be quite thick as well. If the swim platform boltholes were not properly prepared (drilled oversize, thickened epoxy filled and re-drilled for bolts) then those boltholes may well have allowed enough water entry to rot significant amounts of the ply.

Check it out thoroughly! Hope for the best, but be prepared for the worst!
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Old 09-05-2017, 04:34 AM   #5
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Yep, as Insequent just said, you had better prepare to do some core replacement & glass grinding.
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Old 09-05-2017, 09:41 PM   #6
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Hi All,

Found the problem... the two through hull studs for the hull zinc were loose and when I removed all the hardware one of them started leaking like crazy. When I got the bolt out, brown water literaly ran out of the hole. I had to cut out a good foot of glass on the inside before I got to good wood. It was concentrated around the hull zinc. The PO used a diver every year and it's my guess the diver may not have used two wrenches to tighten up the bolts and every time the bolt moved just enough to break the sealant. Will let the area dry for a few days before glassing in the new wood while I replace the PSS shaft seal.

Dave
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Old 09-05-2017, 10:35 PM   #7
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Suggest not putting wood back in there. Use solid fiberglass stock from a source like McMaster-Carr. Been there this past spring.

If your whole transom is cored, cut the inner 'glass back 'till you find dry wood (balsa or plywood). Grind things clean, epoxy solid 'glass in where the swim platform goes, epoxy core in elsewhere, laminate new 'glass in, scarphing onto the rest of the interior 'glass. Then drill new boltholes from outside and reinstall the swim platform and the zincs, platform brackets and zinc bolts all properly bedded.

No fun, but not that tough, either!
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Old 09-06-2017, 09:23 AM   #8
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Suggest not putting wood back in there. Use solid fiberglass stock from a source like McMaster-Carr. Been there this past spring.

If your whole transom is cored, cut the inner 'glass back 'till you find dry wood (balsa or plywood). Grind things clean, epoxy solid 'glass in where the swim platform goes, epoxy core in elsewhere, laminate new 'glass in, scarphing onto the rest of the interior 'glass. Then drill new boltholes from outside and reinstall the swim platform and the zincs, platform brackets and zinc bolts all properly bedded.

No fun, but not that tough, either!
Yes and add the largest backing plates that you can fit in there.
Material choice is up to you but I like to use exterior or marine plywood.
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Old 09-06-2017, 09:56 AM   #9
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A few days may not be enough. Get some heat lamps and aim them at the area. A fan or two to force a low breeze to carry off moisture but not enough to negate the heat effect. Good and warm, not hot.
If there is too much residual moisture not driven off the process will start again.
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