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TheGreek's Mystery Bass Rebuild


Andyjr1515
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[quote name='roman_sub' timestamp='1462286662' post='3041779']
Is it me, or is the "spot the difference" answer is the 24th fret is now missing? :)
[/quote]
You win today's special prize, roman_sub. The prize is so special, you can't see it, hear it, touch it or smell it....but it's there all the same....trust me :lol:

I took the 24th out because it was loose and also raised right across its length, making lining up with a levelling beam inaccurate. All the frets will have to come out in any case - they are a very odd shape, most are raised at one or both sides and they seem to have been attacked by aliens. Also the fretboard needs straightening and re-radiusing.

Mick and I are pretty sure there have been two builders at work on this bass - the first, a skilled luthier, capable of producing a very fine, technically advanced instrument in an interesting variety of woods; the second, a over-enthusiastic boilermaker, using all the tools at his disposal with gusto (lead mallet, bolster, sledgehammer, plumbers-mate sealant). Those of you who are at the Midlands bash on Saturday will be able to see what we mean...Mick's happy for me to bring it along :)

Edited by Andyjr1515
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Mahogany body splice seems to be holding well. Only a thin glue line that will be pretty invisible once resanded and finished.

Today, I am giving the other peeling backpanel the same treatment - it's only coming off at the horn so should hold OK, glued with the same kind of clamping pressure (trust me - it's a different picture :D )




Once that has cured fully, tomorrow, it will allow me to flatten and re-square up the other fully removed back panel and hopefully get that glued back too.

Edited by Andyjr1515
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Clamps are off and the 'non-luthier' fix is holding:



Glue lines are generally pretty small but - more importantly - the panels are very securely held.

The manner in which this bass has delaminated has given an interesting example of differential properties in woods and the internal stresses and strains in a multi-laminate construction and the desirability to make laminates compatible. See the raised central neck splice in the above picture? It is [i]completely [/i]flat at the other side - it has simply expanded, because it could, more than the maple and mahogany either side.

You see it again here. The oak back panel (cross grained) is pretty well joined at the neck splice:


But overhangs by at least 1mm at the edges:



In both cases, the expanded wood is oak. I suspect when I look at the Wood Database for oak, I will find that the dimensional stability of oak with changing temperature or moisture is significantly worse than maple or mahogany.

This expansion and contraction can be all held together with decent glue, but can produce unexpected results if the glue holds (eg warped necks, etc) or strains on the glue joints if atmospheric conditions change, that can lead to failures of the joints, thus letting more moisture and exacerbating the movement.

If I'm right, then it's no surprise that the major cracks are at oak joints...

If I'm wrong....well...that would not be a surprise either :D

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Well, in light of the above, it is clear that the oak is actually a major part of the problem. Some of it is that it is cross-grained, but look at this, the panel I managed to remove and which was still solidly stuck at the join line before I removed it....here it is lined up with the front horn curves:


...and this is where it is at the back:


It's shrunk around 3mm since I took it off less than a week ago. Lengthways (ie along the length of the grain) it has actually GROWN by around 1.5mm.

With that kind of movement - and the evidence that most of the issues have been around the two oak panels - I have to revert to a more standard 'luthier' approach....the oak has got to go.

So yes - I now have to remove the one panel I spent the last 2 days fixing extremely securely, but basically they both need taking off and new panels need putting in their place that are the correct grain direction and whose properties are more compatible with the mahogany and maple.

I have agreed with Mick that we will use these lovely bookmatched walnut pieces:


It will look lovely with the quite deep carve of the panels...

But before I do that and add the additional cost, I'm going to test the strength of the neck. Mick has sent me some machine heads and strings, and so I will now fit the TOM stop tail, the tuners and nut and get it up to playing tension to see what happens...

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[quote name='TheGreek' timestamp='1462547199' post='3043960']
What a shame that the Midlands Bash has had to be cancelled this weekend...

Never mind, Andy can hopefully use the time to do a bit more work on my bass.. ;) ;) :lol: :lol: :lol:
[/quote]
:lol:

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There was great interest in this at the Bash.

Two things came out of it:

Confirmation that those oak panels have got to go. They almost move before your very eyes :)

I have seen the inspiration and aspiration....Norris's reconditioned Aria!

Let's hope it survives the stringing up test....

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The crucial test - the go forward or not test - is underway...and so far so good :)

If the neck is stable under string tension, we have a live rebuild. If not, then it's back to the drawing board.

Mick had sent me some nice Sperzel tuners, a brass nut and a T-o-M bridge and stop tail. For the string test, the only thing I needed to fit was the stop tail and tuners. The latter will need a bit of work, but good enough for this test - clearly a previous owner was indecisive where to fit them:



Next was a rough fret flattening - the frets are coming out but they need to be flat to be able to measure the relief and truss-rod effectiveness. You can see by the levelling beam swarf that it's a bit bowed!:




Next was fitting the T-o-M stop tail bushes. Mick's preferred string length is medium so the stop tail has to be a bit closer to the bridge than normal to ensure the strings are clear of the binding at the nut. This was one of those check, double-check, triple-check, double-triple check occasions:




Then loose fit the nut, loose fit the bridge and string her up!



And so far so good. No sign whatsoever of strain or movement on the neck, tuning holding so far. I'll leave it overnight and then do some checks of the bow, relief, effectiveness (and/or need) of the truss rod etc., before hopefully declaring an end to the first phase, that of feasibility and structural checks :D

Andy

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Good news!

The tuning held true. No sign at all of movement. Tuning held overnight so I think the neck is stable. I might add a cross-dowel in the heel just to be doubly sure the neck doesn't split from the body upwards but other than that, it seems strong enough.

In fact, very strong. The trussrod tightens fine but does nothing at all to the neck relief. But actually, releasing all the tension on the strings does nothing either. Basically, I think the neck is so stiff, it isn't moving at all. That might be OK. I will be taking off the frets, flattening the fretboard and refretting. As long as it never moves, it should be fine (a number of basses nowadays have carbon rods and no trussrod - same principle)...but of course there is no guarantee.

As expected, the action is very high due to zero neck angle paired with a T-o-M bridge. I think the bridge (and stop tail to some extent) will need to be recessed into the body and dropped by about 5mm to get a decent action. There's enough depth to do this although it will mean that intonation adjustments would require slackening the strings to lift the bridge out of the recess to get to the adjustment screws. I don't think that is a big issue as it is very rare for basses to need intonation changes once they've been initially set. Warwick bridges and stop tails are similarly recessed so it is not such an unusual state of affairs.

Mick and I are now starting to discuss the final shape, the finish and, of course, the pickup types and arrangements.

One question Mick has asked is whether it was at all feasible to put a curvature to the body cross-section similar to Warwick or my own bubinga fretless?

I think the answer is probably yes to a reasonable degree. The top can't be cambered any more than it is already because the control chamber is too close to the upper surface. However, it is feasible to scoop out the back by 5 or 6mm, reflecting the curvature of the top:


I actually think that might be a nice thing to do. It's a chunky old thing, as the folk at the Midlands Bash saw, and scalloped out at the back might look pretty cool and also take a bit of bulk out of it....

Edited by Andyjr1515
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Here's some info about the pick ups we're hoping to use:

https://www.youtube.com/watch?v=VV8MV9WzHaA

Not cheap, but hopefully will do everything anybody would want...with any luck the bass will be complete for the Herts Bass Bash on June 5th.

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It's going to be a fabbo sounding and looking instrument :gas:


Nick was round at my gaff over the weekend with his Enfield bass. Those pups are amazing, the combinations almost endless. Loved it.
Mind you, I can only really cope with a volume and tone knob these days :lol:

Edited by gary mac
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[quote name='Bastav' timestamp='1462562830' post='3044104']
That walnut will be putting the front of the bass to shame! Beautiful
[/quote]

Looks like I'll have to learn to play with the bass behind my head - a la Jimi Hendrix...

Actually we're looking at staining the front to complement the outside stripes...

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I'm praying for the rain to stop - I'd like to bandsaw the new back panels and rout off the remaining oak one later today :)

I still have to tidy up the new joint line, but this is broadly how the new panel will look:


In terms of both together - bearing in mind that the bandsaw guideline outlines you see are oversize and the walnut will darken from this - this will be the visible figuring:

Edited by Andyjr1515
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