Bulk Head Material

[78Hondo Cruiser]

Ok guys I am a bit of a lurker here and have picked up some great ideas and tips from you all in the past year of so. I am finally starting to work on my project and was wondering if I could use regular ply to replace my existing bulkhead. I plan on slathering a bunch of resin on it but would be open to any other ideas.
Kyle
P.S. I am replacing the green 70's shag that is under the bow.

[Icarus prospector]

For the small amount of space you have there, yes, a piece of AB or ACX grade fir would work. The ONLY difference with marine grade is that the cores are "A" quality which makes it stiffer, the glues are the same. If you can find a piece of AB with 5 or more cores, you're good to go.
Remember too, that there needs to be a 1/16 or so actual gap between the edge of the ply and the daeck, side, whatever. Laminating the wood right against the deck will cause a hard spot and you'll suffer gelcoat cracking. Just run a generous fillet or bead of putty(cabo-sill+ resin+hardener) so the glass can have as gentle a transition as you can. The radius of a quarter works, and for tooling the putty, take an old shifter ball on a long bolt.

[jimsplace]

It is my understanding marine plywood is allowed fewer air gaps than conventional plywood. Aircraft plywood is allowed even less.