Rim Width

[Ron Nossaman]

>Not the universal template, but likely one of the wider rim bevels - just 
>want to have the cauls wide enough to accomodate the widest I could 
>reasonably expect to encounter.

Which doesn't do much for the narrow rim in the treble, especially if you 
are using a tighter crown rib and a higher bevel angle.


>What I was getting at here is that I think most rim bevels are a pretty 
>consistent angle - let's say 1.5 degrees. I can cut the bottom of the 
>cauls at 1.5 degrees. But if my board is 3 degrees from horizontal at the 
>edges, and the rim bevel is only 1/2" wide, my 1.5 degree cauls will go 1" 
>out over the 3 degree board, and hence smoosh the near-edge of the board 
>down. But read on, this concern has dissipated.

Yep. I understood.



>Ok, I'm convinced. I like it. Your method eliminates any concern regarding 
>bevel width (cut the ply the same width), the EXACT angle of bevel, and 
>angle of the near soundboard edge (caul won't touch it).

Almost. Approximately match the width (a couple of mm either way isn't a 
big deal) and ignore the bevel completely. The plywood will flex and rotate 
enough to automatically accommodate pretty much anything.



>I trust you use some type of 2x4 or whatever block between your plywood 
>soundboard caul and your clamp - or do you have some type of clamp that 
>reaches down into the piano - like Ron Overs - but knowing you (a little 
>bit) you found some great regular F clamps at a garage sale for 50 cents 
>apiece!

No, I use 1x blocks. They're about 6" wide, and 5" tall, shaped like this.

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With the plywood caul bridging between the "legs", I get clamp points every 
4.5" with clamps spaced 9" apart.I only need to use half as many clamps per 
foot of rim perimeter this way as I would just using bevelled blocks. 
These, incidentally, aren't beveled anywhere. When I was shopping for 
replacement clamps for the cheapies I had bought long back, I wanted 
Besseys, and was prepared to spend the $25 (or whatever) apiece for them, 
but I couldn't find any in stock locally. That's a garage sale I really 
would have liked to find. I ordered some, but they never did come in. The 
place that "carried" them at the time was more interested in selling $1 
sanding belts for $9.95 to putterers, so I suspect there wasn't enough 
markup involved and they never even ordered the clamps. I considered 
Record, which is a good clamp, but still preferred the Besseys. I finally 
found some nice F clamps in New Mexico Woodworking catalog, ordered a 
couple to test torture, and finally bought 24 of them at about $12 each. 
They aren't quite Besseys, but they are the best clamp for the money I've 
seen, and I've been very satisfied with their performance under the abuse 
I've subjected them to. I also bought a dozen small Besseys for the belly 
rail and miscellaneous shop stuff. I never considered Jorgenson because I 
wanted quick slide coarse adjustment both ways without having to fight the 
clutch. Good clamps, but they don't fit my style. I didn't make custom 
clamps because I wanted general purpose clamps I could use more and store 
less than dedicated.


>All concerns resolved.........except maybe one. Let's say rim bevel 1.5 
>degrees. Make block cauls with 1.5 degree bottom. Perfect. Next we have 
>piano with 1 degree bevel, but we have blocks with 1.5 degree cut angle. 
>Obviously we now have the block pressing firmly on the outside-most edge 
>of the soundboard, but not so much at the inside edge of the rim bevel. I 
>suppose this difference is about 0.000000000000001 inches.

That's why I used 3/4" stock for the blocks. Placed against the inside of 
the rim, it's outer edge is about in the middle of the caul - just where I 
want it.


>I further suppose that the board will unnoticably crush that tiny bit and 
>in fact you will get excellent even clamping pressure across the full 
>width of the rim bevel.

That's the idea. If the system design takes care of the worrisome details 
for me, then I won't have to tie myself up with them and can get on to 
other things.


>I even further suppose this is all much ado about nothing.

Yes and no. To a point, it's important. I've installed a board or two in 
the past that I wasn't happy with, and I think the problem was primarily 
not having gotten the rim joint clamped down adequately. This isn't a 
concern for me any more.

I hope some of this makes sense.

Ron N