Washburn AB20 Acoustic Save (fingers crossed)

[Andyjr1515]

Just now, 6feet7 said:

Oh, do tell

I will - just got to take a few photos first otherwise, as normal with my posts, nobody will have any idea what I'm going on about  

[Andyjr1515]

The original truss rod is one of these - a substantial aluminium three-sided box with the rod in the middle:

So this, actually glued in the equally substantial slot in the neck... :

...will indeed stop the neck from twisting.

Trouble is, this design can be highly troublesome.  The original, as well as breaking its way through the back of the neck, was doing this too - can you see how the nut is pushing its way into the u-shape, expanding it and almost certainly resulting in the fretboard splitting away from the neck:

 

So what I have done so far, it add a strip of silk fabric epoxied in to strengthen the very thin bottom of the slot where the crack has been mended (thanks for the tip, @6feet7 !)  :

...and then to keep the neck straighter (it had assumed a permanent bow) I've used rosewood strips as the trussrod packers (the strips are VERY strong in this direction) to help keep the neck straight:

 

But that's not going to stop it twisting.

So what I can do with the rock maple offcut packaging strip that  G&W sent in @Matt P 's parcel, is cut a capping strip that will fit over the two rosewood strips and make a hardwood U surrounding the trussrod to give it the same twist resistance as the original U of aluminium from the old trussrod.

But the difference is that the U is not integral to the trussrod operation, as it was in the original, and so each only has one job - the wooden hardwood U to stop the twist and the trussrod to stop the bow...

 

 

 

Edited April 18, 2021 by Andyjr1515

[Andyjr1515]

I have a bit of thinking and drawing to do on @Matt P 's singlecut before I do anything daft like cut or glue wood - working out control chamber size and position, weight relief chambering, back shape - so just to make sure that my hands don't seize up, a bit more progress on this.

AHAH!  I bet you thought I'd forgotten 

So, delving back in the memory, it was all about a potentially twisty neck.  And out comes one of those tools that I rarely use but boy are they useful when you do.  My mini hand router:

What I am doing is levelling the tops of the rosewood packing/strengthening strips, flush with the top of the truss rod:

 

Then I cut the free-bit-of-packing-waste rock maple to size:

 

Then ran a thread of Titebond along the tops of them both and 'you can never have too many clamps':

 

And finally, planed the strip flush with the top of the neck:

And the neck is SO much more resistant to twisting

So when I get another natural break from the single-cut, it'll be a refit of the fretboard - once I've worked out the best way to clamp it... 

 

 

 

 

 

[Andyjr1515]

Glueing the fretboard on is quite difficult.  The challenge is clamping evenly when the back caul along the straight part of the neck can, by definition, be only a thin strip teetering on the spine of the neck, and then the part over the body being able to be clamped without crushing the hollow body.  With a standard acoustic, you can pop a clamp inside the sound-hole for the upper frets, but this doesn't have a proper soundhole.

But, at the end of the day, it's still a case of just swamping it with clamps and radius blocks to try to give maximum even pressure on the board itself:

...and I think this is OK.  Not perfect, but probably better than I expected:

 

It looks pretty flat and twist free, but before I spend any time on refinishing and re-levelling/crowning the frets, I'm going to see if the basic break mend cuts the mustard.  So tomorrow, when I know the fretboard glue is fully cured, I'm going to string it up, bring it up to pitch and see what happens

 

 

 

 

 

[stewblack]

Fabulous thread. I can now clearly see just how far out of my depth I was trying to carry out a not dissimilar repair on my broken faker. 

[Andyjr1515]

Now, I know the phrase, 'he spoke too soon' very well, but nevertheless...

 

...

Certainly, 'So far, so good!' 

I find the same with any acoustic guitar or bass - you sense the enormity of the string tension much more than with a solid body.  And so those last few semitones to bring it to pitch... 

But it's there.

And so far it's lasted at least 20 minutes.

And, while I've not plugged it in yet, it plays and sounds GREAT

Just one buzzy fret position out of 87, which will be easily filed fixed.  No fret levelling or re-crowning to do 

And so - assuming it holds itself under tension for the rest of the day it should be just a case of tidying it up.  I'm probably not going to completely re-finish the neck - I think it's stained and getting the heel and headstock to match would be a bit of a nightmare on a glued in neck.  So, while that remains the fall-back position, I'm going to start off trying an 'as invisible as possible given the limitations of materials and the bloke using them' mend for the fretboard join and either the same, or even a 'if you can't hide it, then flaunt it' jobbee for the scarf joint mend.

But all of that will have to wait a bit because, with some more bits on the way, a certain single-cut beckons

 

[Andyjr1515]

46 minutes ago, Andyjr1515 said:

And so far it's lasted at least 20 minutes.

An hour and still no ominous cracking noises

 

[Frank Blank]

41 minutes ago, Andyjr1515 said:

An hour and still no ominous cracking noises

 

Apart from those coming from your knees?

[Andyjr1515]

1 hour ago, Frank Blank said:

Apart from those coming from your knees?

Well, you'd certainly be able to hear those from Essex 

[Andyjr1515]

Three hours, still in tune... 

(the bass, not me)

[Frank Blank]

2 hours ago, Andyjr1515 said:

Well, you'd certainly be able to hear those from Essex 

You can hear mine from space.

[Andyjr1515]

Well, two days under full string tension and it's still holding tune. 

So it's time to see if we can really break its spirit - by adjusting the neck relief

10 minutes after a required 2.5 'quarter turns' and still in one piece:

[Andyjr1515]

..and still OK a day later. 

Tuning holding; neck relief holding; fixed glue joints holding.

Just one buzzy fret position to file down a bit and then hiding all the new glue joints as best I can and then it will be ready to return to @Fishman 

 

And as a bass - I'm well impressed.  You could easily run this unplugged - it's louder than many acoustic basses I've used in the past.  And plugged in - excellent built in EQ.  Very impressed.

 

[BigRedX]

Interesting neck break...

I used to own a Washburn B20-8 (8-string bass) which had a very similar selection of cracks and breaks in the neck, and which had been fixed with a selection of what looked like rosewood wedges, plus a glued-in block at exactly the same point where it looks as though the truss-rod was coming through the back of the neck on this bass. I wonder if this was a common Washburn problem with their necks?

[Andyjr1515]

3 hours ago, BigRedX said:

Interesting neck break...

I used to own a Washburn B20-8 (8-string bass) which had a very similar selection of cracks and breaks in the neck, and which had been fixed with a selection of what looked like rosewood wedges, plus a glued-in block at exactly the same point where it looks as though the truss-rod was coming through the back of the neck on this bass. I wonder if this was a common Washburn problem with their necks?

Given the construction, I'm sure it would be.  It's fine when the trussrod is new and working OK because, as there is so little wood around it, the truss rod box IS the neck   But once the rod starts getting stiff, or is overtightened, or the glue holding it in the channel starts failing there really isn't enough wood there to stop it breaking out. 

Even if it had been maple, it would help, but this REALLY isn't enough wood for any meaningful strength with mahogany:

 

[PlungerModerno]

52 minutes ago, Andyjr1515 said:

...Even if it had been maple, it would help, but this REALLY isn't enough wood for any meaningful strength with mahogany

I think there maybe some woods out there sold as mahogany that are much much stiffer and tougher than the usual stuff, but I agree there is not enough there to be fully confident in any wood. Even the most consistent wood can hide a void or shake! Luthiers, especially those dealing with tricky and non traditional instruments like acoustic basses, should always err on the side of sturdiness when there is no issue with volume or tone, like the neck. Unless they like warrantee return work lol.

[6feet7]

4 hours ago, BigRedX said:

Interesting neck break...

I used to own a Washburn B20-8 (8-string bass) which had a very similar selection of cracks and breaks in the neck, and which had been fixed with a selection of what looked like rosewood wedges, plus a glued-in block at exactly the same point where it looks as though the truss-rod was coming through the back of the neck on this bass. I wonder if this was a common Washburn problem with their necks?

I used to own an AB45 (5 string version of this bass) and was sorely tempted to get one again as I really regretted selling it (it's the sound hole that just looks so wonderful), but after seeing this repair I've gone and bought an Ibanez electro-acoustic instead.

[TheGreek]

Good work Andy.

TBH I'd forgotten about this build. I remember being shocked by the lack of material in the neck - surprised that this could get through QC. At least you've managed to save this one.

[Andyjr1515]

I bet you thought I'd forgotten this

Well...MrsAndyjr1515 hadn't. 

With it still being in one piece, it's time to start tidying it up ready for return.

The easy bit was giving the fretboard a bit of love and attention.  Nice piece of rosewood:

 

Then it was the glue lines.  First job was getting rid of any glue and cracked finish.  I have started with a single-edged razor blade:

 

Next job - BEFORE I sanded that smooth - should have been filling any gaps with epoxy mixed with wood dust.  I forgot that was the sequence in my rush to get it smooth to the touch (there's some fine sandpaper glued to the back of that ply:

And why should I have filled first?  Well...see that fine white varnish dust...in the cracks. 

Anyway, after a happy half hour with a pin and a vacuum, I then did the first epoxy/wood dust fill:

Starting to look a bit better.

Then the repaired scarfe and back cracks.  Well the repaired cracks again is just a case of smoothing it off with the razor.  For the scarfe repair, it is going to have to be properly filled and so the first job is to start chavelling away the glue and lacquer to give any filler enough depth to get decent adhesion:

And, although I will need to talk to @Fishman for his view, looking at this...hmmm...you know the phrase, "If you can't hide it, then flaunt it!"?  

 

 

 

 

[Andyjr1515]

So sides are done, transition smooth to the touch and  ready for the final all over fine sand and a final couple of very light coats of gloss varnish which will restore the colour and should largely hide the repair:

 

But before I do that, I have to fill that scarfe joint repair.

And have the discussion of 'hide or flaunt' with @Fishman

And spend most of the rest of today doing some important but exciting stuff on Matt P's build  

(Which is a long way of saying I'll be doing the scarfe joint repair tomorrow  )

 

 

[mybass]

Just a thought....I use ‘micromesh’ after sanding.....found on eBay in packs, starting around 1500 ‘grit’ going up to 12000 (I think). It will both polish up and show off any leftover scratches before your final oil finishing, which can also then be micromeshed before further oiling.

[Andyjr1515]

2 hours ago, mybass said:

Just a thought....I use ‘micromesh’ after sanding.....found on eBay in packs, starting around 1500 ‘grit’ going up to 12000 (I think). It will both polish up and show off any leftover scratches before your final oil finishing, which can also then be micromeshed before further oiling.

Yes - I generally start with 2000 wet and dry emery used wet and then move onto micromesh.  It's great stuff and especially for fine finishing curved surfaces because it just follows the surface shape.  Fully washable too!

Great tip from @mybass if you've not tried it

[Andyjr1515]

For the scarfe repair, we've decided to flaunt it! 

So the fill is epoxy mixed with ebony dust:

@Fishman is going for playability rather than aesthetics and wants to go for a sanded neck silky feel rather than the flattering effect of a couple of coats of gloss (a little bit of gloss hides lots of things  ).  So the objective is a smooth-to-touch-and-no-sticky feel.

This is relatively easy to achieve because the old Washburn finish is, of course, rock hard and you do not start exposing uncured nitro as you sand through the outer skin (unlike some other makes where is can still be like it years later mentioning no names but Gibson please note!  ).  The challenge will be more about getting the transition at the headstock and heel looking OK.

After a scrape-flush of the epoxy, a progression of fine wet and dry, followed by progressively finer scotchbright has got me here so far:

Playability-wise, objective already met - it feels great!  

But just to finish off I want to get the heel and headstock transitions looking intentional and bring out the colour of the original out a touch more.  You see better what I mean in this shot here:

 

So I will spend a bit of time tomorrow continuing the same treatment up to a masked line at the heel and headstock joint, and also run through a number of grades of micro-web which will bring the depth of colour of the neck itself out without loosing the satin feel.

 

[Andyjr1515]

And done.  Hardly an invisible mend, but silky smooth to the touch, structurally sound and sounds great! 

 

[TheGreek]

20 hours ago, Andyjr1515 said:

the objective is a smooth-to-touch-and-no-sticky feel.

If he gets the feel I get from my Silk Bass, The Psilos or my Nanyo which you did he'll should be more than happy..

Great work sir.