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Q: Gluing a radiused fretboard

pilotjones

pilotjones

Nov 8, 2001
9,246
893
US-NY-NYC
#1
I will soon be receiving my fretboard back from CNC, with a compound radius already on it. I haven't yet done a glue-up with a pre-radiused board, and I do want some strong and even clamping pressure so that my laminations will continue to look right, and consistent.

The back of the neck will still be square.


So...

What are your methods and tips for getting a good clamp down on a radiused fretboard?


 
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#4
I can't find any photos, so here's a rough drawing of how I did it last time I had a pre-radiused board:

Link Removed

Basically, I used 3/4" wide, 1/2" thick strips that ran the length of the fingerboard. I taped them to the fingerboard and then clamped them using the slightly wobbly face of the F clamps I use touching the maple strips. I suppose they are designed for clamping things that are slightly not flat. I also ran a maple strip down the center and clamped those with the flat face of the clamps on the maple.
 
#5
Surgical tubing, stretched and wrapped around the length of the neck. It will put as much if not more pressure than clamps. Use cauls like HaMMerHed suggests on the body where the surgical tubing cant be wrapped. I have used surgical tubing to re attach a broken head stock, or in other areas where clamps are not easily attached, it works very well.
 
#6
I bought some of that latex tubing but never could get satisfactory results with it as a clamping mechanism. I know a lot of people have used it with success, so I assume I'm just not doing it (whatever *it* is) right.
 
#7
HaMMerHeD said:
I bought some of that latex tubing but never could get satisfactory results with it as a clamping mechanism. I know a lot of people have used it with success, so I assume I'm just not doing it (whatever *it* is) right.
Click to expand...

The trick to it is to pull it around, stretch it as far as you can, and wrap it around again. You cant let it loose tension. Also it has to be wrapped pretty thoroughly, pretty much with no gaps in the wrap.
 
#8
I've seen people put kerfs in a piece of wood or plywood that is the same length and slightly wider than the fingerboard. These kerfs allow the board to bend and mold into the radius of the fingerboard. Then you clamp the same way as done on a non-radiused board.
 
#9
WorktheWood said:
I've seen people put kerfs in a piece of wood or plywood that is the same length and slightly wider than the fingerboard. These kerfs allow the board to bend and mold into the radius of the fingerboard. Then you clamp the same way as done on a non-radiused board.
Click to expand...

This is an excellent idea.
I made my own clamping cauls though
 
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#10
I always glue a radiused board. Mostly the clamping is done with radiused blocks. Matching radius is probably best. But I don't think it is absolutely necessary as the blocks should distribute the pressure evenly on the flat glued surface anyway. I might be of course wrong. Sometimes however I have to glue two fret boards concurrently and have to clamp one with slightly mismatching blocks. Can't say that there is any difference in the final result.

Hopkins tip works very well too. I use bike rubber tubes cut into long strips and tied together. Being flat they wrap well around the neck. Either cases the board must be secured in position - especially when using rubber strips. That thing loves moving around.
 
#11
I saw once a video of Dan Erliwine doing what I can describe as a "little pool" made from wood then filling it with bondo and when starting to set he pressed the fretboard (using some kind of waxed paper) leaving a mirrored impression of it. Then he trimmed and used it to clamp and glue the board.
 
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#12
joselorellano said:
I saw once a video of Dan Erliwine doing what I can describe as a "little pool" made from wood then filling it with bondo and when starting to set he pressed the fretboard (using some kind of waxed paper) leaving a mirrored impression of it. Then he trimmed and used it to clamp and glue the board.
Click to expand...
Very interesting idea, sounds like it would work. It's basically a bondo mold of the board your gluing. Bondo does get pretty hard. I'm probably the oddball here in saying "I like a good old 9-9 1/2" radius. Compound boards are great for those who bend a lot and solo.
 
#13
Thanks for the ideas. There are more of them than I had expected.


Multiple radius blocks - good idea, but sounds like a heck of a lot of work to make multiple blocks. This board is going from roughly 9-1/8" radius at the HS end to 26" radius at the tail end.

Three strips w/clamps - I had thought that might work, it's in the running.

Surgical tubing / bike tire strips - I always wondered how you can ensure it has enough pull. What you've posted makes sense.

Kerfed caul board - I can see how that would conform to the FB, but it seems like unless you got the clamps all the way to the edges, the edges would have no clamping force applied. Unless I'm misunderstanding something.

Bondo mold - I had been thinking of that, too. It's good to know that someone has already done it, successfully. It's a possibility.

Vacuum bag - no one mentioned this, but if I already had a setup I might try it. But I don't.

There's also another possibility, which I will enquire about tomorrow.
 
#14
Kerfed caul board: yes you would put clamps on either edge. Because of the width of the fingerboard and the width of the pads on most clamps, this will exert enough pressure on the edges to the middle of the fingerboard to get a great joint.
 
#15
pilotjones said:
Vacuum bag - no one mentioned this, but if I already had a setup I might try it. But I don't.
Click to expand...

I was going to mention this, but I have no actual experience with it. I saw a youtube video of a guy gluing up a drop top with a garment vacuum storage bag, a shopvac and a wine bottle vacuum pump. It seemed to come out all right and the guy seemed to know what he was doing.
 
#16
I was watching a video of a violin repair, where the guy was gluing cleats to repair a crack in the top. He had a pretty genius clamping solution. He had a canvas tube filled with flour, and used that with a wooden caul on top of it. The bag formed to the shape of multiple cleats and provided ample pressure to get a good glue joint. A larger version of this would work very well on a radiused board.
 
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