Weight support for bench

[TorreyT]

I am wondering which design would be better for weight support for the front bench/ bunk for the Trillium. I am using 3/4" plywood for the top of the bench and 2x2's for support.
The pic below shows:

Design 1) 2x2 Frame supports (walls side) resting on wood adhered to fiberglass wall.

Design 2) 2x2 Frame supports to floor

Ideally I would like to use the first design as it would allow for the maximum size of the storage space however I am wondering if this puts to much stress on the outer wall or is there enough distribution between the supports and the plywood areas attached to the fiberglass.

If this is confusing please let me know and I will try yo explain better. Thanks

[Rob S.]

Your first method will work fine as long as you get a good bond to the fiberglass wall. I will say however that you are a little over engineered and loosing space as a result. The bench in my Boler 17' consists of a solid 5/8" plywood top with hatches cut out. 1/2" ply strips are glued and screwed to prevent the hatches from falling in and stiffens the top. The side is a frame of 1/2" ply x 2.5" strips - top, bottom and middle suporting strips. Over that is the 1/8" panel. The base is screwed to the floor using galv angle brackets and the top is simply more angles riveted through the shell about 18" centers.

[Frederick L. Simson]

I am wondering which design would be better for [b]weight support for the front bench/ bunk for the Trillium. I am using 3/4" plywood for the top of the bench and 2x2's for support.

I will say however that you are a little [b]over engineered and loosing space as a result.

I agree with Rob. I think you will be creating a lot of weight [b]to support. My Fiber Stream's benches are engineered like your design #1, but use much smaller sized framing, more like 1" x 2" with 3/8" thick sheeting on top, and they support plenty of weight.

[TorreyT]

Yeah I have tendency to do that. OK, so I am going with the pic below (L-brackets on bottom, plywood strip supports (x3). This will lighten things up a bit and it still seems strong. I am 6' 0" and 195 lbs and just want to make sure the bench will support my weight.

I'll go with the 5/8" plywood if you think the 3/4" top is too much weight, however how much of a difference is it going to make vs 3/4". Unfortunately I had already purchased, and cut, a nice piece of 3/4" plywood for the face and top. Will the difference in weight between these two make a significant difference?

[Frederick L. Simson]

Unfortunately I had already purchased, and cut, a nice piece of 3/4" plywood for the face and top. Will the difference in weight between these two make a significant difference?

For one bench, maybe not.

[peterh]

Unfortunately I had already purchased, and cut, a nice piece of 3/4" plywood for the face and top. Will the difference in weight between these two make a significant difference?

Couple of things. First, the weight difference for that one part won't bee too great, but it's way too easy to add this little bit of weight and that little bit of weight and some other little bit of weight and wind up with quite a lot of dead, useless weight to haul around. I'd ditch the 3/4" ply and drop down to 3/8" ply for the top, quarter inch ply or hardboard for the front.

As for framing, I might well keep the 2x2 stock for my attachment points to the fiberglass shell walls, but would use a tight-grained, finish grade (something like Hemlock, but wood types available vary region to region) 1x2s placed on roughly 16" centers for most of my framing. If you glue these 1x2s to the underside of the 3/8 plywood they'll be more than strong enough to support your weight; tight-grained woods are both stronger and lighter than the more common 2x2 stud grade stuff. Also, remember that, as long as the wood doesn't have any rot or knot holes to compromise it's integrity, wood is really very strong. So strong that cheap, stud-grade 2x10 lumber on 24" centers supported 12' apart can comfortably handle the weight of a refrigerator, king-sized water bed, or grand piano.

--Peter