First solo build - neck angle problem

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First solo build - neck angle problem

Post by dotbot » Sat Aug 08, 2015 9:06 pm

Hi folks,

I was desperately close to finishing my first solo build, a tenor uke. I'm really happy with it so far, except . . .

I glued on the bridge yesterday. Tonight I put on a couple strings (low G and high A) just to hear it before I go away for a week on a work trip, and :toi. Now I'm just desperate.

There's a bit too much neck angle and every fret below the 9th sounds like the 9th. Plays fine above that but, like I guess most people, I spend a lot more time below the 9th than above it. There is no adjustable truss rod, just a carbon fibre insert. I tried jacking the saddle height up dangerously high and that made the strings play nice. (It did sound nice!) But that's not a permanent fix.

My best thought at the moment, other than drinking, is to heat it up, pry the fretboard off and reshape it. It was glued on with epoxy.

Any advice? I haven't taken any pictures or measurements yet but would be happy to if that would help.

Thanks,
Aaron

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Re: First solo build - neck angle problem

Post by kiwigeo » Sat Aug 08, 2015 10:21 pm

I assume the uke was built spanish method...with a spanish foot. When you lay a straight edge along the top of the frets how high is the straight edge off the top at front of saddle?

Possible fixes:

1. A new thicker bridge.

2. Whack off the back and trim the spanish foot to reduce the neck rake angle.

3. Another fix might be to remove fretboard and install a new fretboard with a wedge under same. This is pretty how Gore and Gilet achieve a positive neck rake on the bolt-on bolt-down classical in their books.
Martin

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Re: First solo build - neck angle problem

Post by charangohabsburg » Sat Aug 08, 2015 11:12 pm

dotbot wrote:There's a bit too much neck angle and every fret below the 9th sounds like the 9th. Plays fine above that but, like I guess most people, I spend a lot more time below the 9th than above it.
Just place a capo at the 9th fret and you'll be fine. :mrgreen:

If this fretboard is thick enough you can taper it towards the bridge without taking it off. I have done this many times as a repair of older instruments, and I find it is easiest to use a block plane. Start at the bridge-end of the fretboard and keep planing an incrementally increasing area extending towards the nut-end. You can use the plane with the grain or, if it is a very hard or stubborn wood across the grain with a temporarily glued on strip of wood to the exit edge to prevent blow-out. In any case take very light shavings and check progress often in order to establish a flat and not a crooked fretboard surface. When I have established the desired taper I use long sanding block (100 grit followed by 180 and/or 240 grit) to even out eventual irregularities, especially after planing across the grain.

You could also only use sanding blocks (60 or 80 grit) to create the taper. I have done it this way too, but I found it much more difficult to create a straight, not crooked surface. Regardless of whether you use a plane or just sanding blocks, checking progress frequently is very important or you very quickly might overshoot your goal at one or another corner of the fretboard. You must be conscious of how fast work is progressing to be able to take off the exact amounts of wood you want and where you want it to come off.

If the fretboard is too thin to taper it down you still have three options:
As yo said you could take it off completely and then make a new one. most epoxies start to release at about 180 -200°C. I have never de-glued off such a large epoxied surface, but it should be possible. Pull the frets so a clothes iron will make full contact with the fretboard. Planing off the greatest part of the fretboard will help too. The faster the heat penetrates the less deep it will have penetrated at the point the board will release. This can be important to not put in danger other glue joints (head/neck and heel/sides).

The second option would be to plane off the fretboard completely. I had to do this once with a fretboard that apparently was glued on with PU glue (heat would have charcoaled the wood before releasing the PU glue). I don't know what soundboard wood you used, but I see a bit of a problem when thinking of planing epoxy off a softwood surface.

The third possibility would be to plane down the fretboard until fret slots disappear, then glue another (correctly tapered) piece of wood on top of the thinned down old fretboard. With some woods (especially dark ones) it will hardly be noticeable that there is actually a "laminated fretboard", but on figured or light coloured woods it may show quite clearly.
Markus

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Re: First solo build - neck angle problem

Post by dotbot » Sun Aug 09, 2015 1:27 pm

Hi Martin and Markus,

Thanks to you both for the suggestions. I didn't give enough details the first time but Martin is right: it's a Spanish heel construction. I'm going more or less with Martin's #3 as the frets are already in place, otherwise Markus's idea would be simplest.

I put the heat blanket on it today at 100 and the fretboard came off without any trouble. So, when I get back in a few days I'll plane and sand it down. If that is enough, great. If not, I'll try adding a shim. The board is flamed WA sheoak from TimS and densely figured.

This being my first solo build, I sure am learning a lot from my mistakes. Thanks again for your guidance, gents.

Aaron

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Re: First solo build - neck angle problem

Post by kiwigeo » Mon Aug 10, 2015 11:24 am

Aaron,

When I do my builds I keep a close eye on neck geometry at all stages of the build.....especially critical for me as I'm usually doing a bolt on bolt down neck.

Building Spanish method the first chance you have to check neck geometry is when the instrument comes off the workboard and prior to the fretboard and bindings going on. At this stage it would be worth laying a straight edge along the fretboard (sans frets) and measuring height of same at saddle position. Note the measurement and then do some calculations to see how high the strings will sit above top of bridge at desired action.....ie add fretboard thickness + fret height plus lowest expected action at saddle (twice that at 12th fret). I do a little drawing to make sure its all clear in my head. If string height is a bit low then you have the option of making a lower bridge (within limits). There's also the option of shaping the fretboard or installing a wedge under same. Worse case scenario not having the bindings in place means taking the back off to adjust the spanish foot is not a hugely difficult process...I've done it a few times on earlier classicals I've done using Spanish method.
Martin

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