Straightening T39 before gluing on the last side

[el_ingeniero]

turns out that my first T39 is a bit skewed.

I've got 2 solid oak 2x2 cauls 4 feet long going from top to bottom across the front and the back of the cab, 1/2" down from where the side is going in. I have a bar clamp near the top, and bar clamps at the top and bottom of the mouth.

Unfortunately, after getting everything solidly clamped down, the panels where the side is getting glued are making a parallelogram, so that the bottom back and top front corners extend about 3/16" past the top and bottom of the side.

In the plans, Bill mentions using bar clamps to straighten the cab, but not sure how to deal with this.

Help!!!

[Gregory East]

You're screwed

Just kidding. I would try to pull the long axis of the parallelogramme towards the middle. Failing that lots of bondo.

[fitzwaddle]

Not sure if its quite the same situation, but one of the side panels to my THT LP had quite a warp to it - but I was able to pull it in line just by getting some screws on one end, then using pipe clamps to pull the next section in line to screw it down, continuing down the line every foot or so. Then finished up with the screws in between.

[Grant Bunter]

Check a few things:
That panel 1 is flat/square, more so towards the back heading towards panel 8 and 9 ( I had to screw a 2 x 2 to my panel 1 on one cab and fill with PL when finished, to flatten it out. It helped remove some overlap)
That panel 8 is flat/square.
I also screwed a 2 x 2 to panel 8 to straighten it up before putting on the final side, that lost a bit more.
After that my dry run consisted of drilling a screw hole in the front left hand corner (the panel 1 panel 7 corner) and putting the screw in. That gives you a pivot point to start working off to get your top edge lined up with panel 1 and then you can start working down the cab. I then also go immediately to the side/panel 10 front corner and put a screw there, that sets your side to length on the front edge totally. I use a few large sash/bar clamps to pull things into shape, checking for square as I go. This ended up with less than 1/8" overlap for me, which I just trimmed up with the router.


Hope this helps...

[el_ingeniero]

I got it figured out.

Everyone has a different method, I am sure, but what I did was to make sure the side was lined up with the back panel, putting in about 8 screws. I do the same with the bottom, putting in about 5 screws. Then I put a short caul across the top and use pipe clamps to wrestle the top into place, then I put one of my 4 foot 2x2 oak cauls in front across panel 5 and the bottom, and use bar clamps to get that lined up. Once I get everything screwed in around the perimeter, I mark panels 6 and 7 by reaching into the horn path with a pencil, and panels 2, 3 and 4 by reaching into the speaker chamber.

Then I unscrew everything, remove the side, drill pilot holes for the inner panels, push the screws back through until the the points are 3/8" through, wet down the play, and lay a bead of glue all around.

At this point, I repeat everything I did before, except I leave the side standing off about 3/16" on the screws (that's why I sent them through 3/8" before putting one the side). Once everything is lined up again, I tighten everything down on the perimeter, then extend the pilot holes for the inner panels and screw those down. As a precaution, I also laid a big fat bead of PL and then fileted the bead like Syney does where the side met panels 6, 7, 8, 10 and 11 in the horn path, and did the same inside the speaker chamber along panels 2, 3 and 4.

Two other things:

1. I picked up a 7/64" countersink bit from Rockler's this morning, and it's a big improvement on using a 3/32" bit. The tip is easier to place where I want it, it doesn't feel as fragile, and I can set the depth where I want it.

2. I mistakenly bought 4 tubes of PL Premium Advanced, and used one on the second cabinet I did today. I'll return the 3 remaining tubes tomorrow, but I sure hope it hangs together after I take the screws out tomorrow.

[Grant Bunter]

No biggie!
If you're worried about the hold, just leave the screws there, in fact sink them deeper and bondo them in. Job done.

[el_ingeniero]

No biggie!
If you're worried about the hold, just leave the screws there, in fact sink them deeper and bondo them in. Job done.

Took the screws out this morning. Everything's still hanging together.

Today was a nightmare though. Routers can be such a PITA. I did OK with a caster relieve, but the template I made for setting the caster flush with the surface got messed up when the router went a little crazy.

[Grant Bunter]

No biggie!
If you're worried about the hold, just leave the screws there, in fact sink them deeper and bondo them in. Job done.

Took the screws out this morning. Everything's still hanging together.

Today was a nightmare though. Routers can be such a PITA. I did OK with a caster relieve, but the template I made for setting the caster flush with the surface got messed up when the router went a little crazy.

Ouch!
More work then...