Cubby roof: Aluminum only over spars?

[tvlawyer]

The Cubby plans show the aluminum sheet being laid over the spars. However, I feel like there should be a sheet of 1/8 ply laid over the spars and then float the aluminum over that. Using a sheet of ply should increase the overall integrity of the roof and decrease the number of dents and dings that would form between the spars. Am I over-engineering?

[GuitarPhotog]

My 1948 trailer has aluminum skin riveted directly to the angle iron frame, so I think you could attach directly to roof spars without problems.

Mine has held up for 63 years that way, so it seems to work

<Chas>

[down under tech]

tvlawyer: I used 1/8" ply over the spars and attached it with PL Premium construction adhesive and screws on my Cubby. After it set up, I removed the screws and filled in the holes with wood filler. Then I floated aluminum on top of that. The side trim holds it all down.
Over kill ??? "I don't think so, Tim".
It will add some more weight and it will be stronger and the aluminum will not bend in on high speed maneuvers.

[madjack]

...applying over a substrate will certainly be stronger BUT, I put mine directly over spars on 8"centers and after 4yrs, the only dents are from rocks hitting the front box...which is over 1/2" ply........
madjack

[ssrjim]

I've done both and I don't think they turned out any different. I guess we will have to wait 20 years and a 100000 miles and compare them

[Lgboro]

Very soon I'll be installing my aluminum roof directly over my spars and insulation. Any dings I accumulate will be because I have been camping . Not a particularly bad thing.

[tvlawyer]

tvlawyer: I used 1/8" ply over the spars and attached it with PL Premium construction adhesive and screws on my Cubby. After it set up, I removed the screws and filled in the holes with wood filler. Then I floated aluminum on top of that. The side trim holds it all down.
Over kill ??? "I don't think so, Tim".
It will add some more weight and it will be stronger and the aluminum will not bend in on high speed maneuvers.

Tim:

What's your reason for removing the screws?

[down under tech]

They were used to hold things together until the adhesive had time to set up. Less weight with out them, too. It also gives a flat surface for the aluminum to lay down on.

[Lgboro]

Weight -- I don't have a metal fastener in my build yet. Only metal on mine will be to hold the tear to the trailer frame and hold the trim on. I used both dowel pins and biscuit joints to hold my build together and it is super strong. All my framing is a T or L with opposing grains - a lot of work but really strong to be made of cedar. I did buy about 50 good clamps to allow me to bypass metal fasteners.

[toypusher]

The Cubby plans show the aluminum sheet being laid over the spars. However, I feel like there should be a sheet of 1/8 ply laid over the spars and then float the aluminum over that. Using a sheet of ply should increase the overall integrity of the roof and decrease the number of dents and dings that would form between the spars. Am I over-engineering?

I did mine exactly as the Cubby plans say and it has been fine since June of 2005 - not dents or dips or anything of the kind.