As it turns out, for our modified Narai MKIV crossbeams: 1.25 gallons of mixed epoxy, two quarts of fillers, one sheet of 18mm plywood, 48 feet of 3"x3" Douglas Fir, 96 feet of 5/4"x6" Douglas Fir, 48 feet of 5/4"x6" White Oak, 100 or more stainless ring shank nails, half a gallon of paint, 50 man hours of labor, and a little blood, sweat, and cursing. And we did that four times to complete the 24-foot long "I" beams.
Of course, it is not as simple as just slapping together some lumber and plywood. Each step was meticulously planned out to optimize time and materials. Had I not had the help of two other experienced people, and been working alone instead, I would have used nearly twice as much epoxy and fillers and it would have taken me nearly three times as long to build each one. Why is that? Squeeze out and dry time.
Since we built modified beams, what did we do? The original beams are made from layers of laminated lumber, and provide for a maximum overall beam of 19'. With hulls that are 7' wide each, that leaves very little room between the hulls, especially considering my plans. The Tiki 38, which by weight, WLL, etc, is actually quite similar to the Narai MKIV (or vice versa), and it has a 22'4" beam overall on only three primary beams, and one mast beam. The considerably larger and heavier Tiki 46 has a beam overall of 24'. So I concluded that because the Narai MKIV has a larger cruising payload than the Tiki 38, but is otherwise similar, that I could extend the Narai MKIV beam out to 23.5' provided I made stronger beams.
I am not creating any new idea here. Strengthening and widening the beams has been done before. In the case of the Narai MKIV, Don Brazier with his modified Naria MKIV widened his overall beam. For my purposes, I simply took the basics of the Tiki 38 "I" beams and added to them. The webs of the "I" beams are still made of two layers of 18mm ply, but I did not cut a curve in the top - they are just straight top and bottom. Instead of square supports, I took pieces of 3"x3" Douglas Fir and ran them through the saw so as to be cut off at an angle to create two pieces in mirror image - right triangles with the top cut off. And instead of just two layers of 5/4"x6" Douglas Fir, I added an extra layer of 5/4"x6" White Oak to the top and bottom. The Tiki 38 has three full beams with two layers top and bottom, and I have four full beams with three layers top and bottom. I cannot imagine that this will not be strong enough, especially compared to the original laminated beams.