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Old 14-01-2013, 09:55   #16
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Re: Cored Deck and Hull Stories?

CT44. Thru hull leak:Cored to just above the waterline (according to designer) Cored to the waterline or a couple inches below by the Chinese builders. One thru hull leaked into the core. Had to have the hull skin removed on one side maybe 1 ft x 8 ft and the core replaced.
Foredeck rot : as best as I could tell, from a cleat or fitting just aft of the anchor locker bulkhead on centerline.. I removed all core from that bulkhead maybe 3+ feet aft from the inside and layed up new core.

Surveyor said the hull core was not "stuck", had shrunk away from the layup. So a few hundred 3/8 holes were drilled in the cored area of the hull and epoxy injected from the bottom up. The hull was so thick that, in retrospect, I wouldnt do that again. I could have just considered the balsa core as "insulation" and a bonus! Sometimes you need to stop, take a deep breath and ask yourself : "Does this really matter?" The yard was pretty fast at drilling those holes.... now I know why... once that was done they had me for $20k!!
One of the few boats I made money on... but it was a lot of work.
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Old 14-01-2013, 09:57   #17
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Re: Cored Deck and Hull Stories?

Quote:
Originally Posted by Dockhead View Post
If you want to take no risk that you'll ever have a problem, by a boat with a solid fiberglass hull, like an Oyster or a Beneteau or any of the production monohulls.

If you want a boat which is lighter, stronger, and quieter, and with less condensation/heat loss, buy a boat with a cored hull, like Swans, Hallberg-Rasseys, and all catamarans.

My present boat is my first with a cored hull. The outer skin is Kevlar, and the core is made of encapsulated balsa blocks. I was quite nervous about this when I was buying my boat, but the more professional advice I got, the better I felt. Apparently encapsulated blocks is a particularly reliable (and expensive) method which isolates the effect of any leak through the outer skin.

We shall see. I don't think it is without risk -- sometimes such systems just don't work out the way the designer intended. As someone said, if a cored hull goes really bad, you're really screwed. Ask any SeaRay owner from the 1990's.

I can say, however, that the difference in strength is remarkable. My present boat's hull seems like the Brooklyn Bridge -- no flexing, no creaking, groaning, or squeaking even under the most horrendous sea conditions, quite unlike my previous boat with its very heavy solid fiberglass layup (4" thick in the bottom). You could hardly open the doors below in a seaway in that boat.

Also makes a big difference in speed. Cored hull despite being stronger weighs tons less. That gives my boat a racy D/L ratio of about 200, which really shows in the sailing qualities.

A guess a reasonable approach might be to avoid cored hulls in cheaper and older boats, but maybe consider them in higher end boats, after a thorough survey.


As to cored decks, you have little choice. I haven't seen a GRP sailboat made in the last 30 years which didn't have cored decks. Here again quality is key. A well built boat will have plywood reinforcements in the deck in highly stressed areas, and will be solid glass in places where there are penetrations. A poorly built boat, or one which has had holes drilled in the deck in random places, will have problems sooner or later.
I think this pretty well sums it up.

There were a few boats that were built with no core at all. The CSYs are one that come to mind. Very heavy boats and the decks tend to be a bit bouncy since there is no core to add rigidity.
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Old 14-01-2013, 10:06   #18
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Re: Cored Deck and Hull Stories?

Horror story has yet to start.
1961 trintella with a balsa core deck and 18mm solid teak on top of that.
At 2 areas the teak deck has been worn down to the screws holding. Because of this you walk on the copper screws and the upper layer certainly started leaking.

The plan:

Number the teak deck plank by plank (it is still 15 mm thick and in great condition after 50 years, its just worn down to the top of the screws)

Take the deck off, see how bad the damage is and repair where needed.
Glue the deck back on without screws.
Sand it down till flat.
Expected work: at least 4 full weeks

I'll probably start in april - may , it is still freezing here now.
I keep you guys updated.
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Old 14-01-2013, 10:18   #19
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Re: Cored Deck and Hull Stories?

My Hans Christian deck came off in chunks the size of kindling. Many of the screws wouldnt budge or would break off. If your's is bonded with the same goo, you'll be needing a new plan. Have you condidered just rescrewing , recaulking etc and calling it good?
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Old 14-01-2013, 10:27   #20
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Re: Cored Deck and Hull Stories?

This is the correct way to add hardware to a cored hull or deck
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Old 14-01-2013, 11:13   #21
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Re: Cored Deck and Hull Stories?

Quote:
Originally Posted by Cheechako View Post
My Hans Christian deck came off in chunks the size of kindling. Many of the screws wouldnt budge or would break off. If your's is bonded with the same goo, you'll be needing a new plan. Have you condidered just rescrewing , recaulking etc and calling it good?
NO, mine is bonded with scotch M3 glue and is already coming off and I haven't started yet. The idea is to use my movable drill stand with a milling cutter to remove whatever screw heads are left. Most of them are gone already they are soft copper. Then remove the planks and take out the leftover from the screws with a vice grip or just grind them of and leave them.

I am assuming your Hans Christian was bolted with stainless? And maybe younger.
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Old 14-01-2013, 14:45   #22
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Re: Cored Deck and Hull Stories?

Lucky You! Mine had the black caulking goo under as well as in between. I ended up just having my whole deck and cabin repainted and non-skidded. I didnt miss the teak in the tropics and the HC could certainly live without the weight! It is nice non skid though. You will likely need to go a size bigger on your plug holes to get nice clean edged holes. Good Luck!
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Old 14-01-2013, 15:33   #23
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Re: Cored Deck and Hull Stories?

Having owned 2 cored boats in the past, a C&C 40 and a Puma 29 , both with core problems , i choose a Csy 44 5 years agoo, here no core at all, the deck is solid and thick, the hull to, so my worrys about core stuff are gone forever ,,,
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Old 14-01-2013, 16:03   #24
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Re: Cored Deck and Hull Stories?

Quote:
Originally Posted by minaret View Post
Have replaced acres of rotten core professionally. Organic materials , poor construction and fitting fitment and water don't mix.
Corrected for you.
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Old 14-01-2013, 16:05   #25
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Re: Cored Deck and Hull Stories?

Quote:
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This is the correct way to add hardware to a cored hull or deck
And I'd even be suggesting that the epoxy bushing is a bit on the thin side.
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Old 14-01-2013, 16:23   #26
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Re: Cored Deck and Hull Stories?

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And I'd even be suggesting that the epoxy bushing is a bit on the thin side.
No suggestion needed. The picture is there to convey the principles of proper hardware fitting.
If the user has a tool to undercut the coring deeper then go for it.

The right tool of course has to fit through the hole so both top and bottom fiberglass is left un-touched.
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Old 14-01-2013, 17:06   #27
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Re: Cored Deck and Hull Stories?

Quote:
Originally Posted by neilpride View Post
Having owned 2 cored boats in the past, a C&C 40 and a Puma 29 , both with core problems , i choose a Csy 44 5 years agoo, here no core at all, the deck is solid and thick, the hull to, so my worrys about core stuff are gone forever ,,,
Yeah, I think if the companies would think it through and spend a little time it wouldnt be hard to eliminate one of the biggest, most expensive failures in boat design..... but you know how it is... "we've always done it that way...."
I can envision a rectangular stiffening product that gets glued to the bottom of the deck with maybe 4" square bracing or hex even better! (kind of a lace structure) Pre cut to fit the shapes, and placed on the wet layup just before vacuum bagging.... something along those lines...
Someone I knew had an old (60's)Hinckley Bermuda 40. Cool old boat with a centerboard. No core in the deck at all.
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Old 04-05-2013, 17:26   #28
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Re: Cored Deck and Hull Stories?

Anyone heard of any problems with yachts built by Windship Yachts Inc. built in foam core hull above and under waterline....?
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Old 04-05-2013, 18:20   #29
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Re: Cored Deck and Hull Stories?

Whenever it would rain after I bought my boat a few of the nuts holding the handrail onto the coach roof would have a single drop of moisture on them. After awhile I decided that wasn't good (to tell the truth at first I just thought it was routine "condensation",) so I took them off to varnish them and use MaineSail's procedure for rebedding them. After removing the nuts, a few of the bolts didn't want to come out of the holes so I used a rubber mallet to persuade them. When I wapped one of the leakers it sprayed water on me ha!!!

Following the mandate of one thing leads to another, I had to remove the headliner gelcoat, and repair a fairly large area of plywood core under my traveler. No big deal, and I noted after cutting out the plywood the fiberglass deck was still pretty sturdy, about 3/8 inch thick.

When doing a preliminary survey on a cored deck boat, tap around every deck penetration with the plastic handle end of a screwdriver and listen for a hollow sound. Also look for any tell-tale brown leak stains, the brown is from tannins in the wet plywood. Additionally, look for any signs of prior woodwork repairs, warped wood under stanchions, painted bulkheads, delaminated tabbing; leaking vents, portlights, companionways...

The first thing to do after buying a boat is to remove every deck penetration and check it for yourself, then use the proper methods (MaineSail's primer is excellent, google Compass Marine) to rebed everything. Otherwise, even a boat that is only a few years old may be leaking into the deck core. The wood acts like a sponge and a lot of damage may occur before you realize it. Don't trust the prior owners, in my case three engineers with deep pockets (new diesel and other expensive mods) managed to improperly install the traveler and the companionway leaked for about 47 reasons.
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Old 04-05-2013, 19:31   #30
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Re: Cored Deck and Hull Stories?

Lived through the "horror" with a C&C landfall 42. Cored hull. Delaminated to the point that where the balsa core once was-remained only a black mush. Thin layer of glass, black wet mush, thin layer of glass. When I say thin, it was cut it open with a razor knife (below the waterline). We refer to the boat as "the landfill".
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