I'm looking at a disk of hull I just cut out. My trailer "missbehaved" and I have a spot of hull to replace about 1 foot below the waterline.

The piece I have here is just shy of 1" thick. Call it 0.95". About 0.12" for the outer skin, 0.10 for the inner, and 3/4" balsa. May not seem like much, but it's strong stuff!

I can't find the J30 laminate schedule anywhere. Found this for the Tartan 10 and imagine it's similar:

The laminate schedule for the hull is as follows:
1. A highly flexible Glidden gelcoat
2. 1 oz. mat (1 layer)
3. 12 oz. unidirectional cloth laid longitudinally
4. 1 oz. mat
5. 12 oz. unidirectional cloth laid transversely
6. 1 oz. mat
7. Balsa core
8. 1 oz. mat
9. 24 oz. woven roving (Fabmat)

The inner core on the T-10 looks a bit thinner than I'm measuring on the J30 but I could easily be off by 0.02.

Anyway, it doesn't matter that much, just curious I guess. Plan to put three layers of 1708 on the outside and two on the inside with some 9# balsa in between. Seem OK?

Indirectly related...the way the keel sump is bonded to the hull is amazingly heavy! Don't know what they were planning for, but you'd have to put a BIG hole in the bottom to detach the sump in a collision. Like 4 by 8 feet BIG. I bet you could drop one off a hoist onto a parking lot, pick her up, brush her off, and go sailing.

I am not volunteering my boat for the test.

Mark - your layup schedule is similar to what I used when I recored Rhapsody. I used 2 layers 17oz bi-axial fabric with the build in 8 ounce mat on one side for both outer and inner skin, strengthening the outer skin because it was paper thin in spots. The built in 8 ounce mat makes it easier to get a smoother surface for fairing.

I also used a product called Core-Bond instead of thickened epoxy to bond the balsa to the skin. It comes the consistency of peanut butter and you just mix in the hardener and trowel it on. It's much easier to work with and is easily sanded.