Kurt/Ernesto, guys,
Must admit to surprising self with the CUT OUT WHOLE CABINTOP /INSTALL BEAM /RECONNECT. That's what I meant, anyway. It allows a more substantial beam which my prejudice goes for. It's not an impossible scenario.
If the job was a frp layup it would be easy (and absolutely necessary) to key the cabin top right back into the new beam. The idea means that the internal truss part of the beam (if it can be called that) can use the whole depth of the beam (3 - 3 1/2") for stiffness. Maybe design it so it humps up outside as well as in. The mast would stand on it.
I can see the arch done this way, but I would not cut open the cabin sides. The side compression struts seem just as important as the beam to me but they don't have to have the same depth or thickness. Well, of course, maybe they do, I no engineer. If possible it would be smart to run this by one, tho. All interior, but cutting back the liner for more room and to paste them in, if necessary, for the width you want.*
If you agree with me that the side struts are necessary to support the beam even tho it is built in (I think the cabin sides should be beefed up to eliminate any bulging, or flex and the stuts anchored as far down in the boat as they can go.) then they could be constructed first and the box-form for the beam layup made to connect them as part of the beam layup. They should be very stiff, imco, to resist any torsioning of the bridge, changing of shape, that rig and mast pressure could produce.
Then, your keepers, the extra supports, pipes, whatever could be removed for convenience when the sails are not flying.
Then again, they may be totally unnecessary. That arch is less than 4' across - it should be a piece of cake to make a rigid curve that will take 2 1/2 sponberg tons of point load. H m m m m m . That IS a lot to ask.
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* The cabin sides on the Ariel are flat, maybe around 1/8"+ thick layup. Tho the front curves so nicely around and also the sweet transition of sides to top - and is therefore a strong shape - the flat sides seem vulnerable to me to being deflected. I can't imagine how mast forces could do it, but anything is possible. Beam supports coming down the cabin sides as 338 has and being part of the remaining bulkhead under the deck ought to keep the sides from moving. They are kind of like arms and have a full lapjoint with the beam ends. If I did it over and became convinced a glass or carbon structure could be made strong enough (and perhaps it could be by tabbing and incorporating it totally into the cabin) I would do it. Because it is consistant with and a logical extension of the Ariel's monocque construction.
That wood beam is a left over from the past.
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