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Bolt Down Fingerboard Extensions
http://www-.luthiersforum.com/forum/viewtopic.php?f=10102&t=2885		 Page 1 of 3
Author:  RussellR [ Thu Aug 18, 2005 9:12 pm ]
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Hi All

I use a bolt on neck system with cross dowels, as designed by William Cumpiano.

It seems to me it would be a great idea if I used a bolt down Fingerboard extension too.

I wondered if anyone would be prepared to give a bit of insight into how this system is executed.

Many Thanks


Russell
Author:  Dave White [ Thu Aug 18, 2005 9:53 pm ]
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Russell,

John Mayes does a version based on Dana Bourgeois that I'm sure he'll chip in with. I've used some very simple (but effective) low tech methods. One was to get a couple of M6 bolts with washers/nuts, cut off the bolt head, drill 2 6mm support holes on the underside of the fingerboard, expoxy them in, drill corresponding holes through the top, and then tighten down with the washers and nuts from the inside. I've also just used Duck double sided tape!

Now I just leave the extensions free-floating and this works fine for me too.
Author:  LanceK [ Thu Aug 18, 2005 10:07 pm ]
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Dave- free floating FB ext? Do you ever get vibrating sounds from it? Buzzes etc?

Russell - John Kinnaird also uses a bold on extension - I'm sure hell chime in here too
Author:  Wade Sylvester [ Thu Aug 18, 2005 10:15 pm ]
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Russell,
I am in the same boat as you. However, I have recently bolted the extension down on a smaller scale instrument I made that seemed to work well.
I drilled a hole through the top at relative center to the fretboard extension. The trick is to position the hole so your not too near a brace. You want to have room for a washer and the “bolt” (in my case, I used a 4-40 thumb screw with the proper length to “bottom out” into the fretboard extension and yet tighten the extension enough).
After the hole is drilled, bolt on the neck and mark the hole onto the inside of the extension from inside the body. Now you want to drill into the underside of the extension without going through and use a bottom tap give the thumb screw something to grab on to. This was a bit tricky but seems to work and I will likely try it on one of my guitars.
I would be interested in what others come up with also.

Wade
Author:  John Kinnaird [ Thu Aug 18, 2005 10:24 pm ]
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Yup sho do

I make a "L" shaped neck block. Part of that "L" extends out and touches the brace thats just above the soundhole. (In fact the only reason I put that brace in there is to make the guitar look as traditional as possible looking in from the soundhole)

I route a 1.5 x about 3 inch pocket into that block that is 3/8 inch deep. This depth includes the top because I route through the top too.


I lay in a piece of mahogany that just fills that cavity (But is about 1/16 inch shallower, an important point) and drill a 1/4 inch bolt through it and partway into the internal block. I drill a 3/8 inch hole in the block below that 1/4 inch hole.

Countersink and attach a 1/4 inch brass flathead bolt to the mahogany filler and use a female furniture bolt under the block on the inside coming up through the 3/8 inch hole to tighten down the mahogany fill piece.

At this point I release the bolts and shim the mahogany piece just a hair proud of the top. (I use cardboard for this but it is important to have room between the mahog filler and the internal block) Make sure you have a piece of plastic wrap under the shim piece so you don't accidentally glue everything to the guitar and at this point bolt on the neck and glue on the fingerboard extension to the mahogany filler piece. I used JB weld for this project since it is the strongest adhesive I can find that has good gap filling properties as well.

When it is all set up, you can unbolt the mahogany fill piece from inside the guitar, unbolt the neck, and remove the shims that kept that mahog filler just proud of the top. You should have a little space between the mahog and the pocket it rests in so you can clamp that extension down with no gaps showing.

It is really pretty easy and it makes sense if you bolt on a neck that you bolt on all parts of it.

I'll post pics if I have any and if you are interested.

John
Author:  Colin S [ Thu Aug 18, 2005 10:45 pm ]
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Russell, I bolt down my extension as well, it bolts on to the neck block extension, same as John's. When I make my necks I glue the stacked heel back from the end so that the extension of the neck carries the fingerboard and that bolts to the neckblock is a continuation of the neck. This extension gets thinned down and has captive nuts fixed in it. It's then just a matter of routing out the top and heelblock to match. Don't forget the angle.

A number of guys on the forum bolt there extension down, Jimmy Caldwell is another that comes to mind, take a look at his site. (He's the only other one I know that also uses zero frets) Taylor of course also have a bolt down system , which is adjustable, but probably needs CNC capabilities, or at least woodwork skills higher than mine.

Bolt downs mean you can do resets even change necks and scale lengths (if you don't mind the fret not exactly at the body end). My name isn't Martin so I don't see why I should build my guitars the way they do!

ColinColin S38583.3246875
Author:  LanceK [ Thu Aug 18, 2005 10:48 pm ]
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John
How thick is the neck block extension? Not including the top thickness?
Author:  LanceK [ Thu Aug 18, 2005 10:53 pm ]
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I can see a HUGE advantage here reguaring finishing work too - no need to scrap down to wood to glued down the FB Ext! Im going to do this on my current project! John - Would a neck block extension of 1/2" be thick enough? with a 3/8ths pocket, plus the thickness of the top, ill have around 1/4" of meat for the bold to tighten against.
Author:  Wade Sylvester [ Thu Aug 18, 2005 10:55 pm ]
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John,
I think I get it but a few pics would be greatly appreciated.
Thanks,

Wade
Author:  Colin S [ Thu Aug 18, 2005 11:31 pm ]
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I should have added that I do most of the shaping to the tenon and face of the heel before gluing the block to the neck. I'd prefer to do it after but haven't worked out an easy way of doing it. On my next guitar I'm going to do away with the mortice and tenon altogether. I don't think it's necessary with the bolt on extension, as that acts as a kind of mortice and tenon itself.

Colin
Author:  RussellR [ Thu Aug 18, 2005 11:32 pm ]
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Hi Guys

Thanks for all of the help, very much appreciatted.

John - I would appreciate some photos if its not too much trouble.

The thing that was baffeling me was how you got a decent fix into the fingerboard, It didn't occure to me that there was an additional bloack there.

Just one question can you still use a truss rod with access from the soundhole with this system ?

Many Thanks

Russell
Author:  Dave White [ Thu Aug 18, 2005 11:51 pm ]
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[QUOTE=LanceK] Dave- free floating FB ext? Do you ever get vibrating sounds from it? Buzzes etc?

[/QUOTE]

Lance - yes I had some buzzing once but this was easily fixed by attaching a thin piece of card to the top under the part of the f-b where the vibrating was occuring with double sided tape - not visible at all. I like to have the ipper bout as free as possible to contribute to the guitar's sound. I'm not of the view that this is a tonally "dead" part of the guitar - I think it does contribute in "subtle" ways. Also I have a pronounced arch in the upper bouts of my guitars - here's a couple of pics of one to give the idea:

Author:  RussellR [ Fri Aug 19, 2005 3:48 am ]
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Dave

Thats a really interesting approach, what would your judgement be on what this area contributes to the sound ?


Many Thanks


Russell
Author:  Dave White [ Fri Aug 19, 2005 4:56 am ]
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[QUOTE=RussellR] Dave

Thats a really interesting approach, what would your judgement be on what this area contributes to the sound ?


Many Thanks


Russell[/QUOTE]

Rusell,

I don't do glitter tests and all that sort of stuff, but I spend some time when playing guitars to place a hand on various parts of the top to feel what is going on. On the upper bout there is definitely stuff going on, particularly with the top 2 or 3 strings. I don't really know what it's doing but my "guess" would be that it helps the string balance in mids-trebles and contributes overall to the overtone complexity
Author:  Andy Zimmerman [ Fri Aug 19, 2005 5:10 am ]
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John

I would love to see some picts.

Andy
Author:  John Kinnaird [ Fri Aug 19, 2005 5:56 am ]
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Hey guys
I tried to post some pics and nothing happened.
   I'll try again Sunday
   I'm off to the mountains to work on a cabin

John
Author:  RussellR [ Fri Aug 19, 2005 6:00 am ]
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Thanks John

Have a good weekend

Russell
Author:  KiwiCraig [ Fri Aug 19, 2005 12:36 pm ]
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My thoughts were to have a 3/16" go from the F/B (capped with shell inlay) through the upper face brace.
This would leave room for (heel end ) truss rod adjustment
Can anyone see any problems with this?

     Kiwi
Author:  old man [ Fri Aug 19, 2005 1:44 pm ]
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I don't understand why you guys think it is necessary to bolt the extension down. Is it just to make removal easier or because the top curvature is extreme, or what? Seems if everything fits the glue should be adequate. Splain it to me, please.

Ron
Author:  RussellR [ Fri Aug 19, 2005 7:04 pm ]
Post subject: 
HI Ron

It is purely to make removal easier, as you say there is nothing wrong with the way a fingerboard extension holds down when glued and properly fitted.

My logic is if I use a bolt on neck system to make maitenance easier, then why not give the person doing the maintenance the added advantage of being able to unbolt the extension as well.

The other advantage I see is sometimes when you glue the extension down it does come out of level a fraction, so with this system you can fit it level your board, then remove the neck for fretting. This one is just theoretical as I haven't tried it out yet.

Russell
Author:  Colin S [ Fri Aug 19, 2005 8:47 pm ]
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[QUOTE=old man] I don't understand why you guys think it is necessary to bolt the extension down. Is it just to make removal easier or because the top curvature is extreme, or what? Seems if everything fits the glue should be adequate. Splain it to me, please.

Ron[/QUOTE]

Ron,

Russell's right it's mainly to make neck removal easier. But think about it logically, what is the point of bolting the neck system on, to facilitate easier removal, then gluing another part of the system making removal harder. There should always be an argued reason for every action we take. Simply because it's always been done that way is not good enough. The question could just as easily be why glue the fingerboard extension down so that the fingerboard is glued to two completely different woods?

With my system where the neck wood extends past the heelblock, the fingerboard is glued (with epoxy now following Mario's excellent advice) its whole length to the same piece of wood. I feel that this must help in keeping a straight fingerboard. Time will tell.

Dave's system is interesting, letting the fingerboard extension float. I may try a hybrid of the two and use my extended neck wood and simply not bolt it down.

I'm a scientist so I just love experimenting.

Colin
Author:  RussellR [ Fri Aug 19, 2005 9:08 pm ]
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Hi Colin

Under your system, how do you position the truss rod adjustment.

Thanks


Russell
Author:  Colin S [ Fri Aug 19, 2005 9:16 pm ]
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No different Russel, just continue the slot the full length and if necessary make a relief cut in the neckblock extension. You've got a nice guide for the allen key then!

On the next one I'm may try using the adjuster at the head.

ColinColin S38584.3778472222
Author:  RussellR [ Fri Aug 19, 2005 9:17 pm ]
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Thanks Colin

Russell
Author:  old man [ Sat Aug 20, 2005 5:12 am ]
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Thanks, guys.

Ron
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