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I have a cutaway that I'm working on, I glued in the neck and end blocks this past weekend. When I remove the rim from the mold it want to rotate the neck block out of square, as in pointing the neck away from the cutaway. I think this has to do with the tension caused by the soft cutaway, and my question is - is this normal, and do you defeat this by adding the kerfing and gluing on the back, or top? I assume this will hold everything true.

Thanks



Yes - I decided to go with the standard neck block, not the tapered dealy LanceK38482.5210185185

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Lance@LuthiersForum.com

it's the cutaway springing back that's pushing the block out of allignment. could have benefitted from a couple more cooking cycles in your bender perhaps.

as long as you can keep the alignment correct whilst glueing the linings and the plates it shouldn't pose a long term problem.

however it looks like the mold you have it in is a normal non-cutaway mold leaving the cutaway area unsupported/uncontroled. if you are doing a cutaway i think you would be better served building a cutaway mold (really only need to build one half) or an infill block to support the cutaway and control that spring back. going to be fiddly to get everthing aligned without.

crazymanmichael38482.552037037

Thanks - Ill make an in fill block -good idea

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Lance@LuthiersForum.com

Lance I use a fill in block. It hols that cutaway area true. Reverse kerf linings will also stiffen everything up. I don't see a problem.

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Lance,

This shoudn't be a problem in the long run. The important thing is to make sure that you get everything the way you want it in the correct position before putting the top or back on. If it is not...well...you can imagine the results.
Another trick is to make a spreader that runs from heel block to end block to make things stay in position. Check out my copy of the steel string or classical DVD that you have to see how I make the spreaders.

Thanks Robbie - I actually do have spreaders - side to side and neck to heal, my concern was when I took the rims out, the neck block went wacky on me! I guess its to be expected until its sured up with kerfing and either a top or a back plate - thanks again guys for the reassurance.

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Lance@LuthiersForum.com

The way to solve this problem is to never take the sides out of the mold until
the back and top are glued on. Everytime you take the rim out of the mold it
changes-in my opinion never for the better. I devised molds that allow me to
do all of the work on the rim while the rim is in the mold-then there is never
any problems like you describe. My rims don't come out of the mold until
the top and back are glued on and everything stays perpendicular and
square.

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lance, you may also want a diagonal spreader that holds the cutaway firmly in place in addition to the normal longitudinal and lateral spreaders. traffic gets messy in there and you have to plan where your adjusters are going to be.

re the infill block: if you go that route rather than making a cutaway half mold, cut it out based on the drawings and not the bent side. it also needs to be positively located in the mold. it can be held in place with dowels, screws, splines, whatever, just so it doesn't shift and holds everything firmly in alignment.

i find the blocks fiddly so use the half mold.crazymanmichael38482.7674768519

Lance, did you just bend the sides for a straight cutaway and then force them into the compound shape? I am doing one now also but I made the form and cutaway cawl so the side would conform to the compound cutaway and it worked pretty good. Both halves of the form are identical except where it straightens out to meet the neck block them of course the back side has a larger radius.

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