How do I cut a smooth rabbet for the headliner?

[tony.latham]

A 1/4" spiral up-cut bit with a router guide should work for this with a Fredrick's-style plywood skeleton. (Since he suggests boards, is it really a Fredrick's style skeleton?)

That 1/4" would remove the space needed for the two layers of 1/8" Baltic --and save trimming later after the blocking is installed.

I wouldn't be too excited about dragging an 1/8" bit at over 20,000 RPM even if it's a really shallow cut.



But looking at the headliner/wall joint in my current 'drop ––cut with a jigsaw–– it's nice and tight with no wobble.

Tom: I'll be curious to see how you chose to make this cut and how it came out.



Tony

[halfdome, Danny]

Here's how this Cabinetmaker does it.


You'll need a 1/4" piece of plexiglass 12" - 16" long and the width of your router base and make a straight fence as pictured.
The small "C" clamps hold the fence to the base.
When routing with the base and clamped on fence you'll need to hold down the long end of the plexiglass base/outrigger flat on your walls to keep a perfectly flat rabbet.
I keep working my way in to the fence in an orderly fashion, this makes a perfect edge, as long as the exterior profile is perfect.

I glue & staple my ceiling on the 1/4" rabbeted edge and then glue and screw the spars on top of the ceiling in the rabbet to the walls.
I use pressure from padded sticks to push the ceiling up (from the floor) to the glued spars from inside the teardrop.
I use a 3/4" stubby straight router bit with a 1/2" shank.

This method works very well for me.
Danny

[Tom&Shelly]

A 1/4" spiral up-cut bit with a router guide should work for this with a Fredrick's-style plywood skeleton. (Since he suggests boards, is it really a Fredrick's style skeleton?)

That 1/4" would remove the space needed for the two layers of 1/8" Baltic --and save trimming later after the blocking is installed.

I wouldn't be too excited about dragging an 1/8" bit at over 20,000 RPM even if it's a really shallow cut.

Wondered about that too, but that's what Steve Fredrick did to make his ledge. (He used a bushing vs a guide.) If I found the Rotozip adapter earlier I would have tried it his way. Now that I see them on Amazon (and elsewhere on the internet) I ordered one to play with. Probably wear a heavy shirt and face shield!

But looking at the headliner/wall joint in my current 'drop ––cut with a jigsaw–– it's nice and tight with no wobble.

Tom: I'll be curious to see how you chose to make this cut and how it came out.



Tony

Me? or Tearlurker (who may also be named Tom; don't know)?

I drew two lines on my wall template 1/8" apart using this thing made with two ball bearing wheels



Did the same for each of the plywood skeletons. Then I cut the template with a fine jig saw blade, and each skeleton separately with the stiff upcut jigsaw blade. Stayed between the lines for all. Sanded the template and trimmed the ledge flat with a router. Checked with a machine square and both ledges are good.

When I posted a few days ago, I'd thought that I used the cut out from the template, sanded that to the other line and trimmed the cutoff from the ledges with the router (as I did with the hatch sides). In fact, I mis-remembered slightly and haven't done that with the ledge cutoff yet. I may, or may bandsaw the correct lines for the cutoff (as I make them into blocking pieces to fit in between the spars. Or do what Tony suggested to me, just put the blocking in as is and rout to the edge of the blocking to the wall after that.

Tearlurker, let us know how you do this!

Tom

[KTM_Guy]

I must be missing something here because this is really not that hard.

I made my skeleton inner walls and cut it to the profile I wanted with a jig saw and cleaned it up with a belt sander.

Next I used the cut skeleton and marked the second one, rough cut 1/8" big and put the two skeleton walls together and used a flush trim bit to make two identical skeletons.

Next was to clam the outer skin to the skeleton and use a flush trim bit to trim it, I also marked the position of the skeleton on the outer shin. Did this to both walls.

Next was to mark the 1 5/8" line using a block of wood on the skeleton and cut it out with a jigsaw. Cleaned it up with a belt sander. Then marked the second skeleton cut it a little big and flush trimmed it. The pro to this is every piece is cut the same on both sides. The con is the the cut off piece is not the exact cut to put back in for blocking in the roof later. But it was easy to fit those pieces later with a little time with the belt sander or the bandsaw. Not a big deal.

Next step is to glue the skeleton to the outer wall using the marks from a few steps above. You end up with a rabbit that is your inner wall thickness plus your inner wall thickness. In most cases 7/8" or 1" if you use 3/4" inner wall and 1/8" or 1/4". I'll take a 1" ledge over the 1/4" or 3?8" rabbit cut any day.

I think I have photos of these steps in my build.

Also my outer wall on the bottom has what would be a 1 1/4" rabbit on the bottom edge that overhangs the floor. Screws were put through the outer skin 1/4" into the side of the floor while the glue dried and were then removed. Screws and dowel rods were put up through the floor into the skeleton to hold the walls to the floor.

Todd

[tearlurker]

I actually like Dad Rambles idea of routing first and finishing with the jigsaw. He dipped in a bit though when his router edge turned so maybe the URB would really help here. The more I think about it, The more I think I’m overthinking it. As long as I line up the blocking with the top edge of the template after it’s cut and it’s not sitting proud, I’ll be ok. Yes, I would like the headliner to be smooth but if I screw it up a bit so what? That’s what moulding is for, right?

[tearlurker]

[b][i][color=#4000FF]Here's how this Cabinetmaker does it.

Danny, very cool.

[halfdome, Danny]

Thanks, Tearlurker.
My ceilings to wall come out very nice and tight but I do mold between them with a glued up "L" profiled shape custom molding to run all my 12 volt wires from rear to front.
I can access the wires or add a circuit any time by just by unscrewing the molding.
Danny