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Old 15-02-2019, 14:54   #1
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Join Date: Sep 2016
Location: Chesapeake & southern new jersey
Boat: Eastward ho 24, Downeaster 32, scarab sprint 18
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Corecell and balsa core decisions decisions decisions

Dear Abby,
among the other things going on I have a recore job coming up yay! I’ve recored smaller areas using corecell a500 with great results. I cant attest to its longevity, but it’s easy, light, and initially strong( before taking years of abuse). My Downeaster has a foam core roof and deck ( I think it’s a corecell type of foam but can’t be sure what specific type is used ) the whole coach roof has delaminated. Not from water intrusion. Its a poor design lacking, knees, compression posts, and proper stiffness to hold up the roof of the spacious cabin. Lack or a proper compression post caused masts to crush the roof,bouncing and flexing on the roof or what ever it was but the whole entire roof is delaminated. I’ve added knees ,a compression post under the mast ,and held up the roof a bit with posts .Now I plan on recoreing hopefully saving the old skins. Gonna cut them strategically remove the old core, recore ,replace. If I can’t reuse the old skins I’ll use 1808 or triaxail and west system epoxy. So, that’s what I’ve got going on. I’ve been back and fourth about wether the delamination was because of a foam core or some excesses Loading flexing and bounceing or combination of a bunch of things, but I’m now focused on fixing it since I feel I have sured up,the roof from inside. Now I’ve had balsa core boats and it’s very stiff and as long as it stays dry it seems to be a far better core material for a cruising boat not concerned with a few extra lbs. I’m using 1/2 “ core looks like the weight difference will be 2 or 3lbs for every 2x4’ section but it does add up. And I’m not looking to detract from the boats characteristics. I do like the extra r value of the foam ( since I’ve already spent a lot of time and money insulating the cabin from inside)And form what I’ve read balsa has way higher sheer and delamination numbers. From what I’ve seen most of the closed cell foam on my boat has waterlogged and delaminated. Do,I just have a bad taste of foam core? should I be concerned of foam core delamination again if properly laid up?The builder used foam core and I’m reluctant to go balsa because he used foam, but it seems that it will help stiffen up my coachroof( or the extra weight up there actually cause more flexing) ,be a little cheaper, and be a better core material. So I’m on the fence here. The deciding factor for me is strength and longevity not ease or price. I just want to sail away already😀! So does anyone care to weigh in on these thoughts or correct me if my assumptions are wrong?


Here’s some charts I was looking at but dont really understand Hahaha!
https://www.researchgate.net/figure/...fig5_323312996


Once again I thank everyone for all the input and help I’ve gotten over time!!!
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Old 15-02-2019, 16:00   #2
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Re: Corecell and balsa core decisions decisions decisions

Without seeing the damage it's impossible to be sure, but reckon (besides inadaquate support for the mast) it's was also due bad ponding between the skins and core. Foam core shouldn't be that bad if done correctly.
Anyway foam or balsa you must rip one skin completely and lay the new core in place with care to be sure of good bonding. There's no need to do everthing at once, and it's actually better to do in sequenced so there's enough stiffness on both sides of the area currently under work. Use small enough core pieces to be sure of good bonding or have vacuum bagging. When it's done some sanding and new skin on top..
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