Spar slots

[Forrest747]

Working on a few ideas for the next trailer which is a couple of years off.
I am thinking of using a pattern router to cut out the profiles and one thing i am thinking about is making pockets for the spars. not sure its worth rounding over the square edges but hey why not try it now. . benefits more gluing surface and few other things.the plan right now is a 3/4 inch cookie cutter design

[tony.latham]

I think that's a good idea, but I really like Steve Fredrick's method of having a shelf for the ceiling to sit on, and then attach the spars to the top of that. It sure makes for a perfect seam on the inside.







You have to add blocking between the spars once they're in place. But If you cut that off of your internal skeleton material before you laminate your walls, it goes quickly.



T

[noseoil]

I like the idea of a "shelf" as well, so that's what I'm using on mine. Basically, it's just a rabbet joint to include the thickness of a headliner, spar & top skin. In my case it's about 1 3/4" wide X 3/8" deep along the edge of the panel. I added an extra 1/2" of meat to the 3/4" plywood frame, to get a bit more strength for the skeleton. A router with an edge guide makes short work of the cut. Here's the cut being made on the 3/4" plywood & 1/8" Baltic birch in place on the inside. The edge guide pilots along the outside edge to make the inner shelf ledge.

[tony.latham]

With a sandwiched wall, you can cut your skeletons out (both at the same time) leaving the shelf area "on" the skeleton, and then cut the shelf portion off. Save those two pieces for your blocking that'll go between the spars. (Ignore that red text, that was for another post)


Once you've got your inside wall glued to the skeleton, you can use a router to flush trim it using the skeleton as a guide for the interior's incorporation into the shelf.


T

[ACK]

My walls are solid 3/4 " ply. I routed a "ceiling shelf" 1/3 of the thickness then routed spar slots another 1/3 of the way through. Instead of rounding the bottom of the spars I used a chisel to square off the bottom of the slots. Put glue in the slots and ran screws through from the outside. Seems strong enough but then it hasn't left my driveway yet...

[woodywrkng]

Another vote here for the shelf method. There's absolutely no gap where the walls meet the ceiling as seen from the inside. You certainly could rout in notches for the spars as well, as long as you only go about 1/4" deep. Anything like this you can do to make your trailer more rigid is a good thing.

[mikeschn]

Putting slots in for your spars makes your spar alignment much easier, and much more precise!

I wonder if you could combine your spar slots with a shelf for the ceiling?

Mike...