How do you hold material in place on convex curve?

[Oregon Brew]

I've been told to skin the inside of the trailer first (the concave side of the curve) but can't really figure out how to hold the material in there while the glue sets.

Although my curved surface is not as large as some, it is a little more severe. Here's a picture of the curve.

[Gage]

Improvise It's not as hard as you may think. Just think about it. The ply will always try to flatten out so just block the upper and lower edges so they can't move.

[Oregon Brew]

Thanks Gage. That's kind of what I was thinking. Block where the plywood will go at the bottom. Force the plywood into the curved shape and mark where the top will hit. Remove the plywood and install blocks at the top. Put glue on everything and force the plywood in between the two sets of blocks... Since the top edge and bottom edge can't move, the plywood has to follow the curve of the braces...

[pohukai]

You do have a tight radius. For mine, i applied glue along the inside spars with scarp of wood, placed the luan and used a 2x4 the width of the camper to prop it in place. It was a 'T' type brace; the bottom of the 'T' jammed into the floor of the camper. It was not easy, but eventually it worked fine. Butting the adjacent luan was also a challenge, but it all worked out fine.

[jeff0520]

I snapped chalk lines to mark where my ribs were, attached one end, and just leaned on it. As the ply bent into place, I ran screws into the ribs to hold it into place. I'm covering the skin in fiberglass and painting it white so I don't have to worry about screws showing.

[CarlLaFong]

Even before I found this site, I figured the best way to do a roof in a trailer would be to build it as a separate unit with spars connected to stringers that are cut to the same curve as the trailer profile. The ceiling could then be installed in the spar/stringer assembly on the workbench, where forming and clamping would be much simpler. Then the, partially completed, roof assembly could be joined to the walls as a unit. You could then insulate and skin as usual. I see that my idea was not unique, as others have done it.

[markhusbands]

I just woodglued the bottom of the spars and then shot the 1/8 ply with pneumatic staples. I'll go back later and cover the staple lines with trim and wood putty a couple holes I left from misfires. I suppose if you can't tolerate banded trim then your technique gets a lot trickier.

I also cut the plywood sheet in half, bent the plywood parallel to the grain so it was really flexy, and avoided letting the 4x4 sheet end on the curve, which is 18" (less on the inside, really). I let the end of the sheet dictate the placement of the final spar, started with the sheet fixed on two planar spars (I have a flat roof section), and then pushed the sheet down with the spar, and attached the spar in place.