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Old 08-04-2013, 09:21   #1
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New Core for Foredeck

I know there are 100 threads on this topic but I havent found one yet to answer this question. Has anyone used polycarbonate as a core replacement? I need to replace the core in my foredeck, and I dont like the idea of using wood again (marine ply or balsa). Im not a professional so I'd like to use something that wont get soft or rot if water does happen to get in there again. I have used the polycarbonate for backing plates, etc., but would it be too rigid? I can either install in thinner layers and epoxy together or one 1/2 piece, but im not sure how much flex the material needs to have to move with the hull.
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Old 08-04-2013, 09:39   #2
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Re: New Core for Foredeck

There is plastic honeycomb too....
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Old 08-04-2013, 09:44   #3
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Re: New Core for Foredeck

Coosa 26 lb Bluewater Foam core is the answer you're looking for.

Keep it clean and out of the sun. Hit it with acetone before glassing. Beautiful for coring decks
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Old 08-04-2013, 12:00   #4
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Re: New Core for Foredeck

Is the Coosa foam one piece or do you install in layers? Do you know the cost?
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Old 08-04-2013, 17:01   #5
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Re: New Core for Foredeck

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Is the Coosa foam one piece or do you install in layers? Do you know the cost?
Coosa is the brand name. It comes in different thicknesses and weight. The 26lb refers to the weight per cubic foot. It is extruded polyurethane with integrated fiberglass. Waterproof and strong. Needs to be glassed. Can be sized and cut into any shape or thickness. Expensive as is all good quality core.
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Old 08-04-2013, 17:25   #6
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Re: New Core for Foredeck

I looked up the brand but having trouble finding dealers. Also, is it a material I would be able to cut myself or do I have to have the dimensions sent to them for a custom cut? Seems like they sell it standard in 4x8 sheets.
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Old 08-04-2013, 18:45   #7
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Re: New Core for Foredeck

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I looked up the brand but having trouble finding dealers. Also, is it a material I would be able to cut myself or do I have to have the dimensions sent to them for a custom cut? Seems like they sell it standard in 4x8 sheets.
Revchem. 4 x 8 sheets. You cut it yourself---it cuts like butter
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Old 10-04-2013, 07:29   #8
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Re: New Core for Foredeck

Depends on what you're replacing and how much shape. Coosa is a great core material for replacing ply core, it has similar weight and stiffness. However, if you are replacing any other core material, I would recommend rigid urethane foam core with Coosa block outs for hardware penetrations. This will give you a much lighter deck that is 100% rot proof. Coosa can be difficult to get in large orders, but a few sheets is no problem. Rigid urethane is much easier to come by. If your foredeck has a lot of shape, you may find it fairly difficult to get Coosa to conform to that shape without a vacuum bag. Working in foam is much faster as well.
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Old 10-04-2013, 07:52   #9
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Re: New Core for Foredeck

Do you have a brand name for this urethane foam core? Im replacing the foredeck on an Island Packt 26', so not a huge area. I may be able to cover it with one 4x8 sheet, if I cut properly, but definitely with two I would think. My plan of attack was to remove the top skin, and epoxy or 5200 the new core to the bottom skin, screwing it in from underneath until the glue cures so that the new core will form to the arch of the foredeck. It doesnt have a lot of arch to it, but some. Is the Coosa too rigid to conform to any kind of shape?
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Old 10-04-2013, 07:59   #10
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Re: New Core for Foredeck

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Do you have a brand name for this urethane foam core? Im replacing the foredeck on an Island Packt 26', so not a huge area. I may be able to cover it with one 4x8 sheet, if I cut properly, but definitely with two I would think. My plan of attack was to remove the top skin, and epoxy or 5200 the new core to the bottom skin, screwing it in from underneath until the glue cures so that the new core will form to the arch of the foredeck. It doesnt have a lot of arch to it, but some. Is the Coosa too rigid to conform to any kind of shape?


Try Divinycell or Core Cell. Sheet materials will bend some in a single plane, if the shape is very compound you need to use a contourable core. These are blocks of material bonded to a fiberglass backing. You will probably have no trouble with sheet stock on a small foredeck like that.

http://www.jamestowndistributors.com...ne=1&page=GRID
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Old 10-04-2013, 08:08   #11
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Re: New Core for Foredeck

I would definitely go with a contourable core. I would stay away from rigid foam for compound curves even with a vacuum bag, it's too easy to get voids.

Minaret is a professional, what he can pull off is beyond the abilities of most of us... so I would make it as easy as possible towards a good solid result instead of using more difficult techniques and materials. But it would be a reason for me to start using vacuum bagging I think...
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Old 10-04-2013, 08:34   #12
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Re: New Core for Foredeck

Is 5 lb./cu ft. suitable for a foredeck? Why is there such a large difference between that and the Coosa 26 lb/cu ft.? Also, in regards to conforming to the shape of the deck (without getting into vaccuum bagging) would it be better to buy 2 1/4" sheets and install in two layers, or would I have no problem with 1 1/2" sheet conforming to the deck shape?
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Old 10-04-2013, 08:36   #13
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Re: New Core for Foredeck

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Originally Posted by Captndan714 View Post
Is 5 lb./cu ft. suitable for a foredeck? Why is there such a large difference between that and the Coosa 26 lb/cu ft.? Also, in regards to conforming to the shape of the deck (without getting into vaccuum bagging) would it be better to buy 2 1/4" sheets and install in two layers, or would I have no problem with 1 1/2" sheet conforming to the deck shape?
Contourable: just buy it in the thickness you need; it will lay in the right contour by itself, no forcing required
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Old 10-04-2013, 08:40   #14
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Re: New Core for Foredeck

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Originally Posted by Captndan714 View Post
Is 5 lb./cu ft. suitable for a foredeck? Why is there such a large difference between that and the Coosa 26 lb/cu ft.? Also, in regards to conforming to the shape of the deck (without getting into vaccuum bagging) would it be better to buy 2 1/4" sheets and install in two layers, or would I have no problem with 1 1/2" sheet conforming to the deck shape?


Yup, 5 lb. is standard core density. Coosa is dramatically stronger and heavier than most core materials, this is why I said it makes a good replacement for ply core. If your foredeck was originally balsa, replace with foam. I have done this job a great many times, and its extremely rare that I have to go to a contourable core, especially in thinner thickness like 1/2".

You might consider a primitive vacuum bag for a better job. You can bag with visqueen and a shop vac on thinner cores like this.
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Old 10-04-2013, 12:00   #15
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Re: New Core for Foredeck

Can you recommend a good source to learn about vaccuum bagging? I know of it, but I dont know much about it.
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