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Learn From My Cutaway Mistake
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Author:  Terence Kennedy [ Fri Mar 18, 2011 8:13 pm ]
Post subject:  Learn From My Cutaway Mistake
I've built over forty guitars but am working on my first flat top acoustic cutaway. I just used my OM templates with a cutaway modification. I have a little arch at the headblock where the neck attaches so I just left that as is. When it came time to fit the neck I undercut the cheeks, bolted it on and the fit was great, the angle was perfect, and the fretboard fit nicely against the edge of the cutaway. I was feeling a little smug until I checked the longitudinal alignment. It was at least 1/4" off to the treble side!! ##%%$!! Then I realized that with an arched headblock the cutaway side is a lot shorter than the non cutaway and if the cheeks are sung to the sides the neck looks like a badly set fracture!
Luckily my tenon routing jig was still set for that neck angle so I routed about 3/64 off the treble side and with a little flossing all was well. In the future my cutaways will have flat neck blocks!
Author:  L. Presnall [ Sat Mar 19, 2011 8:36 am ]
Post subject:  Re: Learn From My Cutaway Mistake
Terry, I hate that happened to you...believe me, I've had many #$%^ moments in this luthierie thing! But, I am not understanding "arched" and "flat"...do you mean arched as in angle in the top of the block, (as in setting neck angle) or "angled" at the cutaway side of the block where the cutaway joins...? I just want to make sure that I don't repeat your mistake rather than learn from it, since I build fewer cutaways than most...

Larry
Author:  Terence Kennedy [ Sat Mar 19, 2011 12:06 pm ]
Post subject:  Re: Learn From My Cutaway Mistake
Rather than being dead flat in the area where the sides attach to the head block I've got a little radius on mine.

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On this guitar I did not rout the mortise in the headblock until after the box was closed and the binding was on. I think what happened was that with the cutaway the apex of the radius got shifted to the bass side and so the sides dropped off more that direction and the head block could have rotated a little too. I found a construction photo and I think in retrospect I can see it a little there.

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I've built two Benedetto style guitars with a tight cutaway and used a flat headblock with no problems. I think that's what I'll do in the future for all cutaway instruments. Hope that makes sense. I'd appreciate any input from those of you that do a lot of cutaways as to alignment issues and whether you pre-cut the mortise in the headblock or do it after the box is closed and bound and whether you use a flat or radiused headblock. Thanks a million.
Author:  Ian Cunningham [ Sat Mar 19, 2011 8:54 pm ]
Post subject:  Re: Learn From My Cutaway Mistake
Can't wait to do a cutaway.....
Author:  Beth Mayer [ Sat Mar 19, 2011 9:23 pm ]
Post subject:  Re: Learn From My Cutaway Mistake
When I grow up, I want to make a cutaway...just don't know if I'll live long enough to get that much experience and confidence!
Author:  Terence Kennedy [ Sat Mar 19, 2011 9:51 pm ]
Post subject:  Re: Learn From My Cutaway Mistake
On my adjustable mold the head and tail cauls have a radius to match the head and tailblock and slide in a routed track that keeps them on the center line so there has never been an alignment problem on conventional guitars and it's worked great. I think you are right Todd, there are asymmetric stresses clamping the headblock with a venetian cutaway that are not there with a regular body and a closed mold would be better. With the two Benedetto style archies I built I used a closed mold and they were fine but the headblock was flat too. Do any of you guys use a radius on the headblock with your cutaways?
Author:  Laurent Brondel [ Sun Mar 20, 2011 8:22 am ]
Post subject:  Re: Learn From My Cutaway Mistake
Terence, I've never had that problem but I see how it could happen. I don't use flat blocks, the curve is the same for cutaways on non cutaways, and I rout the mortise after the body is fully bound.
However, my rims are secured in the mould by a long 1/4" bolt at the tail block and a 5/32" long screw at the headblock, both dead centre. The 1/4" bolt at the tail block becomes the end pin receptacle, the 5/32" thread at the headblock is routed out with the mortise. Hope that makes sense, like this both blocks are pressed against the walls of the mould and can't slip one way or another.
Author:  L. Presnall [ Sun Mar 20, 2011 8:36 am ]
Post subject:  Re: Learn From My Cutaway Mistake
Got it now Terry! Thanks! I did use the shaped block on my latest which is still in progress...now I have ONE MORE thing to worry about! :D
Author:  Terence Kennedy [ Sun Mar 20, 2011 10:46 am ]
Post subject:  Re: Learn From My Cutaway Mistake
Thanks Laurent, that's a wonderful idea. Here are some pictures with the neck bolted on now in perfect alignment. The fretboard is not glued yet. I shimmed the bass side and found the difference in the width of the heel required to straighten it out was 5/64". After undercutting the heel I used my tenon routing jig to take that much off the treble side and it worked great. I'll just call it the "Kennedy wedge" or my Ergo heel. Actually I don't think it will look too bad after the heel is shaped. The 14th fret still is where it should be so I think all is well but it was a real learning experience. Thanks for the help and Larry good luck!! I'm sure you'll be fine.

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Author:  ChuckB [ Sun Mar 20, 2011 12:20 pm ]
Post subject:  Re: Learn From My Cutaway Mistake
Terry, I am sure you thought of this,,,it would be impossible to detect, if it's not too late to go to a tapered heel, and you are ok with the look. Guitar looks great BTW.

Chuck
Author:  Terence Kennedy [ Sun Mar 20, 2011 2:59 pm ]
Post subject:  Re: Learn From My Cutaway Mistake
ChuckB wrote:
Terry, I am sure you thought of this,,,it would be impossible to detect, if it's not too late to go to a tapered heel, and you are ok with the look. Guitar looks great BTW.

Chuck


Thanks Chuck, I did think of that and besides not liking how a tapered heel looks on a cutaway the thought of four more miters on the binding shut it down. As an interesting aside (and this is a problem when building more than one at a time) I was shaping three necks and while I was putting a taper on the heel of the neck for this guitar I thought "oh yeah this is supposed to have a straight heel" so I do have a tapered heel that will fit this instrument. I had to make another neck. I'll be glad when this one is done. Wonder what other tricks it has up it's sleeve.
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