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Core Thickness #18990
05/03/22 02:18 PM
05/03/22 02:18 PM
Joined: Oct 2005
Posts: 8
Sudbury, Massachusetts, USA
andrewware Offline OP
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andrewware  Offline OP
Forum Newbie
Joined: Oct 2005
Posts: 8
Sudbury, Massachusetts, USA
Hi all -

I'm embarking on my first core replacement on hull# 539 after 17 years of ownership, looking forward to it! Looking for guidance on core thickness.

The worst location is near the bow cleat, vent and pump out access. Does anyone know the thickness of the core in that area? Is it consistent everywhere including the transom? I may address that at some point, luckily the problem is limited but there is evidence of moisture near the exhaust tube (as well as anchor locker area and cabin top).

Thanks in advance.

Andy Ware (Mystic)

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Re: Core Thickness [Re: andrewware] #18991
05/03/22 02:26 PM
05/03/22 02:26 PM
Joined: Oct 2005
Posts: 8
Sudbury, Massachusetts, USA
andrewware Offline OP
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andrewware  Offline OP
Forum Newbie
Joined: Oct 2005
Posts: 8
Sudbury, Massachusetts, USA
Should have searched first, I think I have my answer from another post:

Greetings Phil,

3/4". This is the same for the main deck including under the winches, cockpit deck, transom, hull and on at least some boats, the bulkhead to the left and right of the companionway. The 45 degree section connecting the cabin top to the main deck is 1/2", at least on my boat. Under the primary winches, expect to find a 12"x24" section of balsa cored deck that is doubled with extra layers of glass between the main deck core and a lower 12"x24" 3/4" marine fir plywood doubler.

Numerous people have used foam core instead of end grain balsa and there is no short supply of people touting the virtues of each with arguments ranging from never wanting to smell decomposing balsa again to wanting to keep the flexural modulus the same across to sections that did not get re-cored. While I chose balsa, my opinion is that either is just fine as long as the common workmanship topics are addressed such as grinding out 12-to-1 scarf joints to the adjacent FRP, never using polyester or vinylester on top of epoxy, fully scrubbing the blush off of cured epoxy and properly epoxy isolating the new holes you drill to remount the deck hardware.


Re: Core Thickness [Re: andrewware] #19000
05/14/22 11:09 AM
05/14/22 11:09 AM
Joined: Oct 2009
Posts: 77
Belmont, MA
Georges Offline
Senior Member
Georges  Offline
Senior Member
Joined: Oct 2009
Posts: 77
Belmont, MA
I used this 3/4 https://www.jamestowndistributors.com/product/product-detail/1586 for similar work on my boat.
It ended up slightly thicker overall that the old one... but then I had no concern being marginally thicker and that hidden area...
good luck ... hope you have a good vacuum pump... and working with a mask against gravity in such a cramped place... it IS truly exhausting.

Hope to see you in the water around Boston, soon :-)

-- Georges
Foot Loose #467 - CPYC - Winthrop

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