7' wide Tear roof spars

[plbecker]

I am working off an old 7' x 10' trailer. It was an old caned ham that had rear & roof rot. So, I wanted a smaller, lighter trailer anyway.

I am wondering if I should use laminated spars for the roof. I intend to give it a slight dome it to give it strength.

Has anyone built a wide drop. I see 4' to 6', but I'm wider yet.

Thank you for your input...

Pat

[angib]

Whoah! Depending on how slight a 'dome' you mean, you could be getting into big problems unless you've got a long section of otherwise flat roof.

If a panel is curved front-to-back and you add curvature from side-to-side, you are making the panel have 'double curvature' and you cannot bend a flat sheet of something like ply or aluminium into (significant) double curvature.

If you mean putting 1/8" or 1/4" dome in the middle of an otherwise-flat panel that's 6ft long and 6ft wide, then that's no problem. If you make the dome, say, 1" then you'll start to have problems as the edges start to try to wrinkle.

If you have the traditional teardrop or canned ham shape with a curving profile almost everywhere, then any doming will give you problems fitting the skin.

Andrew

[plbecker]

I mean a dome or curve from front to back. I was thinking of doing a metal L bracket and wood composition beam. Using them at the roof peak where the vent would be and at the front curve. My sides are straight. Though it would be really cool to do an dome. Maybe a geodesic dome.

Pat

[angib]

OK, Pat, forget what I wrote!

I don't see the need for complex beams - particularly if you are going to have inner and outer skins (which become the top and bottom flanges of each spar).

People here have built 5ft wide trailers with 1x2 lying on its side (ie, 3/4" high), in which direction it's fairly weak, so standing the same 1x2 up vertically (ie, 1-1/2" high) for 7ft span is quite reasonable.

Look at Len's (len19070) Shasta build photos for a similar-sized trailer built by a trailer expert - they look like 1x2s to me.

(Drat - can't link to his Yahoo album photos here)

Andrew

[plbecker]

I was going to use 2x2 is that too big? I was going to use them in the wall section so I can reuse the old trailer windows.

Pat

[angib]

I was going to use 2x2 is that too big?

Seems too much to me, but hopefully some builders will add their thoughts - I'm just a designer and this is a practical/experience question.

I'm surprised that your existing windows are designed to work with a wall around 2" thick. Here is the sidewall construction from some home-build 18ft trailer plans that Len mentioned in another thread:



So they're using 1"x1-5/8" (I take 'net' to mean actual) with the 1" in the thickness of the wall. So with a 1/4" plywood exterior skin and 1/8" interior, this is 1-3/8" total thickness. It appears they use exactly the same construction for the roof.

Andrew

[Jst83]

I was going to use 2x2 is that too big? I was going to use them in the wall section so I can reuse the old trailer windows.

Pat

I built 6'3" by 11'2" my roof spares are 2x2 I think for that size it's not to big Mine worked out good my walls are 1 3/4" (just my opinion)
So my thoughts are go for it

[Ira]

If you're running 1 by 2s the tall way and not flat for a 1 3/4" height, do you really need 2 by 2's?

[Jst83]

If you're running 1 by 2s the tall way and not flat for a 1 3/4" height, do you really need 2 by 2's?

Just my thoughts again but I think the longer the span the beefier it should be a 1x2 would be 3/4 x1 3/4. I would think the 3/4 width would get wobbly over the 7' span and wouldn't remain as stiff as needed . again just the ramblings of an amateur

[Miriam C.]

If you're running 1 by 2s the tall way and not flat for a 1 3/4" height, do you really need 2 by 2's?

Just my thoughts again but I think the longer the span the beefier it should be a 1x2 would be 3/4 x1 3/4. I would think the 3/4 width would get wobbly over the 7' span and wouldn't remain as stiff as needed . again just the ramblings of an amateur

Beefier won't hurt but I cut mine for a real 1" x 1 1/2". Mike and I have both been on top of it. We didn't bounce up and down on it. I only have a 1/8" skin on top and it is sturdy. 1/4" would probably be better.

GitRdun

[steve wolverton]

I used 1x2's in my camper (6 feet wide) and doubled up on the curves. I only have 6 or so spars though.

[Ira]

If you're running 1 by 2s the tall way and not flat for a 1 3/4" height, do you really need 2 by 2's?

Just my thoughts again but I think the longer the span the beefier it should be a 1x2 would be 3/4 x1 3/4. I would think the 3/4 width would get wobbly over the 7' span and wouldn't remain as stiff as needed . again just the ramblings of an amateur

Scott...I had a total brain fart:

I totally forgot that for mine, I laminated 1 by 2s for each spar for a 1 1/2" square spar.

And that's for just FOUR feet wide.

(I hate getting old.)