Roof Spar Mounting

[RunnerDuck]

I've been thinking about which method is the best for mounting the roof spars.

I've see at least four different methods:

1. Cut a single dado on the inside walls all the way from the front to the "hatch hing".

2. Cut dado's for each spar into the side walls.

3. Screw and glue the spars to the inside of the walls with "Pocket Screws", no dado.

4. Screw and glue the spars to the inside wall from the outside with flat head screws before the outside skin goes on, no dado.

Any thoughts on which method or methods from the above list is best?

By the way I'm building a Grumman 2 design.

http://www.tnttt.com/viewtopic.php?f=50&t=64385&start=15&hilit=sort+of

[KCStudly]

I like to build from inside out, so any variation on the Steve Fredricks' method where the ceiling sits on rabbets at the tops of the walls and the spars go on top of that makes the most sense to me.

Then filler blocks are added between spars and you have everything locked in and plenty of meat to fasten the roof skin to, but best of all you don't have to shimmy the ceiling in, prop it up, or scratch the prefinished walls doing so.

[tony.latham]

I like what I think you are calling a "single dado." It's Steve Fredrick's "inside out" method and allows for installing the pre-finished ceiling before the spars are installed.











The material removed for the "dado" is saved to be used for blocking later:



Tony

[RunnerDuck]

KC and Tony, I believe I'm sold.

I'd been struggling in my brain as to how, exactly, I was going to put in the ceiling. This method solves a whole bunch of problems.

Thanks so much!

[tony.latham]

I'd suggest you get a copy of Fredrick's Teardrop Builder's ShopManual. It's about 250 pages with lots of photos.

http://www.campingclassics.com/shopman05.html

Tony

[jonw]

I used solid 5/8in. marine plywood for my walls and .040 aluminum for the roof (floating, attached only at the edges underneath side and bottom molding). My spars were 1x2 poplar (whose actual dimensions are 3/4 x 1 1/2in).

Because they would be exposed (my exterior was not covered with anything) I didn't want to drill thru the wall into the end of the spars. But also because that is a very weak joint that will cause the wood to split over time.

Instead I used Kreg pocket screws and glue to attach the ends of the spars to the plywood. No end grain on either the ply nor the poplar to weaken and split. Has held up fine for 4+ years so far and I wouldn't hesitate to use this method again under the same circumstances.

[RunnerDuck]

I'd suggest you get a copy of Fredrick's Teardrop Builder's ShopManual. It's about 250 pages with lots of photos.

http://www.campingclassics.com/shopman05.html

Tony

Thanks Tony, I've got it on order. I figure every bit of information I can read and roll into my design will make for a great first time TD.

[RunnerDuck]

I used solid 5/8in. marine plywood for my walls and .040 aluminum for the roof (floating, attached only at the edges underneath side and bottom molding). My spars were 1x2 poplar (whose actual dimensions are 3/4 x 1 1/2in).

Because they would be exposed (my exterior was not covered with anything) I didn't want to drill thru the wall into the end of the spars. But also because that is a very weak joint that will cause the wood to split over time.

Instead I used Kreg pocket screws and glue to attach the ends of the spars to the plywood. No end grain on either the ply nor the poplar to weaken and split. Has held up fine for 4+ years so far and I wouldn't hesitate to use this method again under the same circumstances.

Thanks Jon, I agree with the pocket hole screws. I think I'll end up with what's been called a "single dado" running front to back with spacers between the spars and I think I'll screw them to the sidewall with pocket holes.

[clock152]

I like what I think you are calling a "single dado." It's Steve Fredrick's "inside out" method and allows for installing the pre-finished ceiling before the spars are installed.











The material removed for the "dado" is saved to be used for blocking later:



Tony

Bingo!.... I like this.

[noseoil]

What Tony said, it's simple, easy & fast.

Also, you don't need a "forest" of sticks inside to hold up the headliner, just drop it in place & set the spars on top. Since I used exterior aluminum skins, I just drilled pilot holes from the outside of the walls & ran drywall screws in with some titebond to fasten the spars. I used unbleached canvas for the headliner "pre-finish" prior to dropping it in the rabbets. It worked out pretty well.

[aggie79]

I went down a different path. I used 1-1/2" deep, 3/4" ply "ribs". The ribs were temporarily held in place and spars were attached to the ribs via pocket screws. I added temporary straps to keep the framing from racking and then removed the assembly to the bench to glue and fasten the plywood and attach the hull liner with spray adhesive. Then I placed the assembly back in place. The ribs are glued to the sidewall with PL premium and are fastened using deck screws. At each rib, I used a deck screw from the outside of the sidewall into the sidewall, rib and spar.















It looks awkward but I found benefits to me for doing it this way were:

1. I made the assembly removable so I could add plywood skins and hull liner on the bench rather than working overhead.
2. The double thickness of the sidewall gives more "meat" for the screws used to hold the roof / sidewall trim.

Take care,
Tom

[RunnerDuck]

Thanks Tom for the concept and pictures.

Unfortunately I've got very limited space and will probably go with the "single dado" method.

[Strop]

Tony,

A couple of questions that might help me & RunnerDuck.

What is the glue you were using along the wall to fix the ceiling?
What size roof spars were you using?
What glue did you use to fix the ceiling to the spars - titebond or the glue in the tube?
What glue did you use to fix the spacers between the roof spars?
Did you use any bracing inside to hold the ceiling up against the spars till the glue set?

Now another question for which I am expecting the same answer. Did you use the same glue to arachnid the wall to the floor?

Thanks,

Laurie

[KCStudly]

My ceiling/spar to wall arrangement is similar to the Fredricks method (ceiling and spars attacth on top of wall). Rather than trying to hold the ceiling up to the spars or use temporary supports to keep the ceiling from sagging while attempting to attach it to the walls, I positioned and glued the spars to the top of the ceiling panel before installing the ceiling. Sort of a cross between the Fredricks method and how Aggie/Tom did his premade roof assembly.

I used some small temporary alignment tabs double tapped to the top of the ceiling to help locate the spars and keep them from sliding around in the glue; and a 2x4 beam and wedge shim arrangement clamped to the work bench to be able to clamp the spars fully out in the field of the panel (or you could use weights). This allowed me to avoid having any visible fasteners in the ceiling.

[RunnerDuck]

My ceiling/spar to wall arrangement is similar to the Fredricks method (ceiling and spars attacth on top of wall). Rather than trying to hold the ceiling up to the spars or use temporary supports to keep the ceiling from sagging while attempting to attach it to the walls, I positioned and glued the spars to the top of the ceiling panel before installing the ceiling. Sort of a cross between the Fredricks method and how Aggie/Tom did his premade roof assembly.

I used some small temporary alignment tabs double tapped to the top of the ceiling to help locate the spars and keep them from sliding around in the glue; and a 2x4 beam and wedge shim arrangement clamped to the work bench to be able to clamp the spars fully out in the field of the panel (or you could use weights). This allowed me to avoid having any visible fasteners in the ceiling.

KC,

I'd asked this question before but maybe you know the answer.

On Steve's build instructions he uses a "scrap 1/8" spacer" in the build of the galley hatch edge to the trailer wall. I'm trying to figure out exactly where that spacer goes and what the purpose is.

Any idea?

Thanks,