I had the same issue on my LT17. The 3/8" gap is not a big deal, I bridged it with thickened epoxy alone, and did not use any tape on it.

On a larger gap like this I found it easier to do one side at a time. Apply some tape (adhesive, not fiberglass) on one side to keep the epoxy from oozing out there. When the first side is hard, remove the tape and do the other side. To get the rear side of the front bulkhead it's easiest to turn the boat upside down on saw horses and reach into the cockpit from underneath. Still a little bit of a contortionist act. Heats up nice and warm in there from the trouble light, too.

-- Dave

: First I would like to thank all of you for your help; I've been lurking
: around this site all year as I build my CLC Ches 17. Your tips and
: insights have been invaluable. But now I have my first real problem.

: I decked the boat and now find there is separation at both bulkheads;
: 1/8" at the rear and up to 3/8" in the front. Both deckbeams
: (ahead of the coaming and at the nose) have solid contact. For the rear I
: think a stout fillet will be okay. But what about the front bulkhead? Do I
: make a taped fillet, or try to shim the gap smaller first? The boat has a
: curved foredeck; I think the root problem was that the front bulkhead was
: not radiused correctly against the shapes of the deckbeams on either size.
: Thanks in advance.