Coosa composites

[wetnwild]

Anyone used any of the Coosa composite foam with the woven roving for structural uses? Product specs say that it can be used in transoms. Plan on giving it a try on the transom of an XF-20. I used some of the less denser Coosa without the roving for lifting strakes on our 54 footer and it's still on the bootom of the boat. Very easy to work with. I couldn't even dent the un-fiberglassed foam with a full swing from a hammer.

[jacquesmm]

Too heavy, too brittle.
No boat manufacturer uses Coosa for transoms.
Use real transom foam instead:
http://boatbuildercentral.com/proddetai ... cell_E2402
The XF20 should be kept light. If you use Coosa, it will trim by the stern.

[wetnwild]

Are you sure about that weight issue? It's 25 to 30 percent lighter than plywood. The lighter density inch and a half I used weighed a considerable amount lighter than ply.

[tech_support]

Coosa is PU foam with glass roving pressed inside. Its used as a replacement for plywood in production boats. There are now a couple other similar products on the market, we saw them at the last IBEX in Feb..

You could use it in a transom as a placement for the wood core, but you would still need glass on each side. I priced it a years ago and it was a lot more than regular high density foam core (see Jacques' link above). Because you still need glass on each side, its going to be heavier than standard transom foam.

There may be some boats using it in transoms, but it does not make economic sense vs. other cores. I have seen it for interior structural parts, still with lighter glass on each side. Because it has the roving, it hold screw really well, which I suspect is the reason for using it in production boats vs. regular foam. With regular foam core, you need a special insert where you will have screws/bolts. With the coosa, it will be heavier, but a lot less work. Saving work it critical for production boat building.

Joel

[Old E.]

I have used Coosa extensively in a production boat rebuild. They make a 1.5" 20-25# density board for transoms. Lighter weight stuff for other parts depending. It holds a screw pretty well, but not as well in the lighter stuff. It is light, but not as light as divinicell/Kledgecell. It is also much stiffer. Good for bulkheads stringers, etc... Not good for bending. Never rots!!

[tech_support]

One other thing. Its PU foam which has very poor sheer and peel properties relative to PVC foams - so you would never use it in the hull

[jacquesmm]

Joel knows more about Coosa than I do. He studied the possibility of using it and gave me the specs.
I would never use PU foam in the structure: less shear and peel strength.
And it cost more than good proven foam like Divynicell. Why pay more for something inferior?

[Old E.]

Can one of y'all explain peel/shear strength? Sorry for my ignorance.

When I used coosa, it seemed so much better than the kledgecell that I had been using.

[tech_support]

Polyurethane (PU) foam is “weakerâ€

[Old E.]

Thanks!!

I could tell, just by working with it, that the peel strength was less. I had never heard of that term, but found that sometimes I got a good bond and other times it wasn't so good.

As for the compression. If I understand you correctly - 2 samples of foam core, each at 6# density the pvc will compress less than the PU? Wow. Handling the stuff, I never would have guessed that. That 25# Coosa was tough stuff.

I have been to Diabs site a few times before, but I will check it out again.

Thanks for the insight.