Included is a quicky graphic* I did up to illustrate my current thinking. I'm with you on the stiffener thinking: Since the vertical component of an I-beam is what makes it resistant to downward bending, I have been trying to figure the best way to incorporate that into a 2" thick structure which could resist the compression forces put on it by the mast. I've ruled out wood, because I think that in what I'm going to do it will only add extra weight, w/out adding any extra strength. I'll be relying on glass for strength. Too bad, I like the look of wood! But it will be elsewhere in the cabin, so...
In a nutshell, to build the beam: Lay up the glass onto a sheet of 3/4" thick foam (one side at a time), putting a total of 1/8" thickness glass on each side of the foam. This can be done with the foam in a horizontal position, making it easy to control wetting out, and to control alignment of the glass fibers in the cloth to achieve maximum strength in the finished beam. Once both sides are glassed and cured, carefully cut the 1" thick individual "slices" of the beam to a template taken directly from the hull, then bond the 'slices' to each other. After the slices are assembled into a unit, glass on the outer layers (top and bottom skins of beam).
When this entire beam assembly is cured, it gets bonded into/under the deck, bedded in glass and "ebb's mishmash", drawn up into place with screws and/or bolts until cured. Use more mishmash to filet the edges of the beam to the deck for smooth transitions, and then, last, laminate on a final overskin of glass.
I plan to put 2 vertical stainless poles in place where the old doorframe verts were, they should give additional support and handholds. I 'mocked this up' yesterday to see how they would look visually, and they don't detract from the 'open' feeling the cabin has with most of the bulkhead removed (which I am loving!). At the bottom, they will tie in to reinforced floors similar to what you have done.
Whatcha think?
*(((As I was just making the graphic, the thought came to mind: "Hey, there's also the space between deck skins which could be incorporated!". Hmmm - doing so would give structure which would not protrude down into cabin space (good!), but it would involve much more work - remove outer deck skin once new beam was in place, build structure in where the current balsa core is, then replace deck skin. An idea which deserves further thought, and which someone else might be able to use at some point, so I've included it...)))
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