Constructing cabin roof

[EStaggs]

So here I sit trying to figure out how I'm going to build out my cabin roof. Thought I'd come to the pros to see what ideas they might have.

Need to build a hard top over an open cabin. Will have 3 panel windshield, two hard sides, and open aft to the fish deck. This will be built on a 23 foot Clippercraft sportfisher, and needs to have enough strength to not be destroyed by a 200lb person. Typically will only have rods, crab pots, and a radar on it, don't intend it to be a platform for spotting or anything.

Walls will be 6mm ply, forward panels as well.

Considering doing laminated beams with a 6mm panel over them, laminating 3 6mm panels together and doing a single aft beam on the exterior (to preserve headroom) for support, or possibly foam core with 3mm skins on the outside.

Any and all advice/ideas are accepted. This needs to be something relatively quickly built, as I am on a deadline.

Here she is in templating stock:



The roofline will come down around an inch or two before the final sheets are cut.



Thanks for your input.

E

[alan white]

You've got enough crown to laminate a roof from thin plywood. You could laminate plywood or strip-build it. If plywod alone (no beams), try to achieve 1/2"-9/16"" total. If strip-built over a form, use red cedar 1/2" thick and 10 oz fiberglass cloth inside and out.
With low headroom, you can run EXTERNAL longitudinal stringers 2"-2 1/2" tall incorporated (bonded) into 3/8" plywood (good mounts for handrails) a foot or so in on each side. This would stiffen up the plywood enough to obviate the need for any internal beams.
I like this approach for speed and because the hand rails can be mounted on the external stringers (which can be wider at the base (1 1/2") and angled to a narrower top surface (3/4"), more or less keystone-shaped in section.

[EStaggs]

Alan, I was out of town and wasn't able to access this, thanks for posting.

So laminating 2 sheets of 1/4" okoume and sheathing it in 6oz woven fabric would be plenty.

I had thought about just doing full length hoop style hand holds cut from 2"x4" dimensional lumber. Wasn't sure if I was going to do a longitudinal member underneath it or if it would be enough strength as-is, epoxied down and backed with #12 SS screws.

Thanks again.

E

[alan white]

It's impossible to advise without seeing plans, but it's probable that 1/2" would be okay. The problem can be where a hatch is located, the break in the ply tends to straighten the curve leading up to it. Then transverse frames would help. Alternately, as said, strip-building the cabin top will work well in such a situation.
You needn't glass plywood---- epoxy alone will be fine.

Alan, I don't see where he said a hatch will be put in it. There are boats here with external frames but I like it internal if necessary. Because it will carry a crab pot, etc., it needs glass fabric.
You can get the Shelman Marine ply in Spokane - It has a fungicidal glue and is wonderfully rot resistant. E, I took a peak at your site - Nice ice box but if you dont put a drain with a P-trap, you will be sorry. No big deal, copper tubing with flare epoxied in place. The P-trap keeps the cold from flowing down and out. Tryt not to drain into bilge if you have another place to drain. IMO, the cabin does not look too tall, if fact, when they are cut down too much, they look chopped;


Nice work, E.

[alan white]

I'd say that without a hatch, plywood will be consistant in curvature, but if there's a sliding type hatch, a single curved frame could be installed externally, located just across the forward end of the hatch. Alternately, two partial frames could be put inside, and the forward hatch frame could sit above the roof and control the curvature of the roof in the middle. That way there's no head-bumper in the middle when going below.