Commander 147

[ebb]

2 cents worth.
Early on in A338 I decided to replace the original sawn beam with a laminated one out of white oak and epoxy. Not the best choice.
On the last current page in ebb's gallery thread you can read what I later decided to do
because I really don't think that white oak can be glued.....totally, including with resorcinol.

If I was to do it over again and I couldn't find the scantlings in a piece of oak to band saw the single piece out like the original
I would definitely do the beam with vertical pieces as you suggest.
BUT also mechanically lag the pieces together with BRONZE screws.
Iron is a notorious enemy of oak, so I would not use even 316.

I really can't imagine the arch being bent by the downward pressure of the mast.
If the arch is non-bendable even when supported by partial bulkheads then the arch must be made immovable.
Gluing it to the roof is a good idea. So to the bulkheads with thru fastenings.
You might think about adding gussets on the inside, on the other side of the beam.
This can be done by adding a piece of solid oak as a strut along side the cabin down to the hull.
The struts would completely immobilize the ends of the support beam.
Imco I would not depend on the bulkheads alone to hold the beam in place.
If you do you are only adding support off the side of the beam even if you thru-fastened it to the bulkhead.

Since you are band-sawing the vertical beam pieces out you don't have to have a parallel sided
lamination. You can increase the thickness of the beam as goes toward the ends. Yousometimes see bridge structures that do this.
In other words the exposed part of the beam would LOOK like it got skinnier in the center of the span. But you could keep the scantling you are happy with but increase the height of the beam as it goes toward the bulkhead supports - essentially loosing no head-room.

Could also add extra width to the beam, an extra vertical lamination.