Waterproofing the bottom of the walls...

[mikeschn]

Exactly... that's what the gap is for in the Generic Benroy plans!

Mike...

Dale,

Yes, very similar.

A thing I'll add here is that I spent a long time working in shipbuilding and one of the principles was that no welded structure is ever perfectly right. Even if you cut it just right (and steelworkers' tolerances are not the same as engineers' or joiners' tolerances), it will distort when welded. So I would never design the wood to sit tightly on the side of the frame as you've shown - I'd leave a 1/4" gap. Then the floor ply can be cut to the right width and doesn't have to be 'adjusted' to fit the actual width of the frame.

[cracker39]

angib wrote:

Dale,

Yes, very similar.

A thing I'll add here is that I spent a long time working in shipbuilding and one of the principles was that no welded structure is ever perfectly right. Even if you cut it just right (and steelworkers' tolerances are not the same as engineers' or joiners' tolerances), it will distort when welded. So I would never design the wood to sit tightly on the side of the frame as you've shown - I'd leave a 1/4" gap. Then the floor ply can be cut to the right width and doesn't have to be 'adjusted' to fit the actual width of the frame.

Is there any other reason to leave a gap between the skin plywood and the side rail of the chassis other than possible frame distortion? I'm not going to cut any wood until after the frame is finished. That way, I'll measure the frame and to make the wood fit. If for some reason, it is wider at one end, then I can adjust the spar lengths to fit. Same goes for length, i can make one side a little longer if necessary, but I intend to do all I can to make sure all metal pieces are the same size, and my son-in-law is an experienced welder.

I do want the side extensions tight against the side rails of the chassis with glue or roofing emulsion inbetween to keep moisture out. But, the skin will be sealed outside, inside for the lower two inches that will be agains the rails, and double sealed on the edges. After the sides are in place, I may spray inside the skins with varnish, just not on the frame members where I will glue the inside skin.

Building Hint:

If your sides will extend down to the bottom of the chassis side rails, you can make a "helper" to keep the plywood in place. A couple of concrete blocks placed on end, or even a couple of 5 gallon buckets turned upside down, placed under the side rail near the front and back will support the side skin while putting it in place. If you do any fitting before the floor is in place, just clamp a couple of piceces of wood under the rail, sticking out a few inches as a support. If I used the concrete blocks, I'd still put a piece of plywood on top to keep from scratching the chassis paint and risking early rusting.

[mikeschn]

Dale,

That is "THE" reason I left the gap. It ensures that I bolt up to the floor, and it ensures perpendicularity.

If you are going to custom fit all your wood, and build it snug, and make sure it's perpendicular, you shouldn't have any problem...

Mike...

[cracker39]

I'm not concerned with perpendicularity (wow,,what a word). Since my sides are nearly 7 1/2 feet high (from bottom of chassis rail to roof peak) and nearly 12 feet long, I'm cutting 3 vertical sheets of ply for each side. That leaves 2 corner pieces cut from each end of the front and rear plywood pieces. That gives me up to 4 90 degree corner pieces to use on each side to brace it perpendicula to the floor. No matter if the chassis isn't sitting on a level surface, the sides will be at 90 degrees to the floor due to the bracing until I get front and back skins on to keep it rigid. Now, working inside that maze of plywood to apply the inside skins, which will go on first, will be a fun job.

[bledsoe3]

angib wrote:


Building Hint:

If your sides will extend down to the bottom of the chassis side rails, you can make a "helper" to keep the plywood in place. A couple of concrete blocks placed on end, or even a couple of 5 gallon buckets turned upside down, placed under the side rail near the front and back will support the side skin while putting it in place. If you do any fitting before the floor is in place, just clamp a couple of piceces of wood under the rail, sticking out a few inches as a support. If I used the concrete blocks, I'd still put a piece of plywood on top to keep from scratching the chassis paint and risking early rusting.

If you're building your own frame, weld small metal tabs to the underside of the frame. They just need to stick out far enough to set the side walls on. They're hard to see in the picture cause I painted them already. Look at the bottom right. You can kinda see where it is by the dust on it and a shine on the corner from the flash.

[angib]

Is there any other reason to leave a gap between the skin plywood and the side rail of the chassis other than possible frame distortion?

Nope, welding distortion and 'steelworker accuracy' was the whole reason. If you're using square tube frame rails, the weld distortion won't be great (it would be more with welded angle or channel).

I'd still worry about 'distorting' the body to fit the frame - making the doors seal, out-of-square interior cabinets, etc - but it might well be no problem in reality.

Andrew

[cracker39]

Is there any other reason to leave a gap between the skin plywood and the side rail of the chassis other than possible frame distortion?

Nope, welding distortion and 'steelworker accuracy' was the whole reason. If you're using square tube frame rails, the weld distortion won't be great (it would be more with welded angle or channel).

I'd still worry about 'distorting' the body to fit the frame - making the doors seal, out-of-square interior cabinets, etc - but it might well be no problem in reality.

Andrew

Your first statement above is the answer I was looking for. I will be using 2"x1/8" square tubing for sides and ends, each cut at 45 degrees on the ends for a mitered weld. In between the side rails will be either one 2" square and two 2"x2" angle cross members (or maybe just three 2"x2" angle cross members) distributed between the ends (approximately 25" apart). These cross members for stiffening and floor support will be cut to fit inside the side rails after the outer perimeter is welded. That's why I'm not too worried about frame distortion.

As to the 2nd statement, as I don't anticipate any distortion in the frame, the body should be free of distortion as well. Keeping my fingers crossed though.