Coosa

[El Dorado]

I’m starting to build the structure for a new deck and purchased some 3/4” Coosa 26 to replace the original one by lumber. This is the first time I’ve used anything synthetic. I plan to skin any bulkheads with glass but wanted to know what everyone was doing with other pieces. Can it just be painted with whatever I’m painting the bilge with, sealed with thinned epoxy or does it need to be glassed?

[Ironworker]

Coosa needs to be glassed before painted especially its going to be exposed to view. Otherwise its pretty impervious. Its a great product. I just rebuilt my 31 with it.

[El Dorado]

Thanks, I was surprised how porous it is. Everything is below deck so I’ll just skin it with one layer. I followed your build and look forward to seeing pictures when it’s out of the yard.

[Tony Meola]

Thanks, I was surprised how porous it is. Everything is below deck so I’ll just skin it with one layer. I followed your build and look forward to seeing pictures when it’s out of the yard.

Screws will hold better in it if you cover it with a couple of layers of cloth.

[Hutch]

I agree with Rick and Tony.

In addition, here's what I've done rebuilding my blackfin 24.
Get a good respirator and eye protection. A supplied air respirator is even better if your dealing with resin or paint in the bilge.

Sand good w/80 grit and any brown or yellow areas need to be sanded back to gray.

If you're using epoxy, wet out Coosa good with 2 coats of unthickened epoxy, and while still wet, apply stitched glass, wet on wet, followed by release fabric. Release fabric will save you a lot of time in removing the blush but you'll still have to sand some before bonding or painting.

You'll need resin laminating rollers (metal disks) in addition to thin nap rollers and brushes. Get an air tight container to keep your expensive laminating rollers in acetone. (Tip from the Duracell sailboat project on youtube)

With West Systems epoxy, use stitched glass only (no mat) mat soaks up a lot of resin, could result in a bad bond and will make the part heavier

45/45 for bulkheads, 0/90 for stringers, Airx or similar between bulkhead or stringer and hull (Gerr)

For fillets and bonding the bulkheads and stringers to the hull, I use six10, wetting out the coosa and AirX spacers with regular unthickened epoxy first. Six10 doesn't heat up as much as handmade 105 thickened epoxy and is a lot safer on your lungs. I try to bond, tab in the bulkhead wet on wet in one operation, otherwise I bond the bulkhead, AirX spacer with six10, and apply a wide strip of release fabric to the fillet, and then sand and glass the next day.

You'll need the same glass thickness on the coosa as was originally on the plywood. (West Systems)
If you're replacing solid mahogany with coosa then you'll have to calculate the additional glass thickness required to match the original strength, in my opinion.

Probably more info than you asked for but this worked good for me and was based on a lot of good info on this forum, West Systems tech info and Dave Gerrs book, Boat Strength.

Good luck with your project!
Hutch

[El Dorado]

Thanks, I appreciate the advice and experience. I only want to do the project once. Verticals will be FRP from McMaster and the horizontals will be Coosa. Most connections will be thru bolted.

[CamB25]

Good advice here. The only thing I would add is to blow/vacuum the dust off the Coosa before you apply the adhesive. This opens up the pores and allows the adhesives to penetrate further into the material.

For coating below decks we used some sort of epoxy (see link). It has held up very well. I can get the product name if you are interested.
https://www.amazon.com/photos/shared/sv ... 1mVez7r53t

Good luck!

[DCJ]

If you go to utube and search Verneese boat resto
, not sure on the spelly, this guy gives one of the best
tutorials on coosa along with some handy tips. It’s great stuff to work with once you learn the does and donts. Good luck

[Ironworker]

I blow off my coosa as well then wipe it down with Denatured alcohol. I find that one coat of resin is enough to fill the pores on the coosa then add glass as normal. Since I used epoxy, I used 1708 which is pretty easy to work with.

The Carolina Reaper comes out of the boatyard August 23rd at 8:00 am!