Originally Posted by mitiempo
Not that I've personally seen but maybe Morris?
No, not Morris. Foam works fine for building and retrofits and as you mentioned Tim L. uses it, as it helps you hold a gap without a specific jig but many production builders use jigs to keep the bulkheads off the hull slightly when tabbing. I have normally just used 1/8" thick pieces of wood shims to hold it away from the hull and keep it in place then done some spot tabs, let cure, remove shims and finish tabbing.
The gap does not need to be big 3/32" - 1/8" is plenty for actual tabbed bulkheads. Screwed bulkheads...well I won't even go there.. My problem with some foams, like weatherstripping used by some, is that they can absorb resin and also just become another hard spot or extension of the bulkhead.
From what I have personally witnessed, and seen in use during construction, Morris uses dead air space, about 3/32" - 1/8" and the bulkheads are held by a jig while getting tabbed. Below is a Morris bulkhead for the anchor locker before the tabbing begins. You can see the gap all the way around. If the hull comes in contact with the plywood, then they did not tab it right.
It would be very tough to tell if a dead air gap or foam was used in the production after the fact and in a survey. Morris, in particular, gelcoats the entire inside after they tab in the bulkheads, not that you could ever see the gap through the tabbing to begin with. My CS-36T has air gaps, as I have had to dig into some of it..
Pretty tough to see that gap now..