Andyjr1515

Unless you have massively thick strings (I'm talking size of a bishop's finger) I am pretty sure it would be sonically undetectable and probably immeasurable. And even if it was, you could file a small flat at the top edge of the nut with a needle file. It would be pretty invisible - you would only be squaring off the edge of the groove for half the width of the string. But personally, I reckon even that would be more trouble than its worth

The last couple of days have been about the final knockings - final shaping and refinishing of the neck, set-up and strap buttons I had built a couple of tweaks to help the balance but the main one - fitting Axesrus' wonderful lightweight aluminium tuners - was dashed because of (presumably Covid-related) non-availability. Instead, I have fitted some really, really nice open gear Hipshots - but, honestly, they are quite a bit heavier than the Axesrus ones. But when Matt tried it out. I watched how he played and we discussed that yes - he does want to get to that 24th fret..and with his thumb wrapped round and so the back button wanted to be in the 'traditional' place if at all possible. But what I do (with all of my builds) is first fit the back button, then pop a slippy strap on it, over my shoulder and, holding the strap in various positions while supporting the guitar, gauge where the balance was going to be. And it looked like we could get there. So on went the back button (and nowhere near the 'goldilocks' zone of 12th -13th fret I always recommend!): ...and then popped a slippy strap on and hands off... So, whatever position Matt likes to play, it should be absolutely fine Final bit of polishing up tomorrow and it's ready to go to Matt. So one last glance before it goes into the gig bag: Yup - that'll do Thank you all again for your kind words and encouragement along the way - always immensely appreciated

Not sure what problem this is trying to solve...?

Splendid on all counts

Thanks again, folks. And now we are onto the final knockings. Firstly, suitably masked and gloved (which used to be the tip to the police to stop and search...how times have changed!) I popped the pickup across to Matt for him to reverse the phasing, which he did while I waited. I took the guitar along, fully strung up and watched from the regulation 2m while he tried out the neck profile. I noticed how much he uses the thumb wraparound - even at the very top frets. He was happy with the feel but this morning - with both pickups now in phase and sounding good, I played it for real, also trying more thumb wraparound. My conclusion was that there is still too much bulk either side of the centre line, and that the spine thickness could lose a mm also. So, having checked with Matt that he would be OK with it, I set about the profile one more time, concentrating on playability in the style Matt prefers. And - boy what a difference! I also took more away from the bass side of the heel: I'm sure his guitar teacher won't thank me for it, but he should now be able to thumb wrap all the way up the fretboard until the body stops him So now the final danish oil slurry sanding has been started and the next three days will see the final slurry and buff finish completed. Two final jobs while that's all going on - final set up and fixing the strap buttons. So I reckon Wed / Thur should see it ready to hand over

No - you are not overthinking it. You have to stop it sliding around - it's like a skater on ice - otherwise it will slide out of position as the clamps are tightened. But there are a number of cunning ways of doing that when the time comes

Well, to return the gushing bonhomie that apparently is a side effect of covid-19 cabin fever, I would like to point out, reference the following two posts - and that you, @stewblack , performed the surgical operation of removing the fretboard and trussrod like a Harley Street Consultant. That's pretty awesome in my book But let's get back to criticising each other - it's much more fun

So for the elimination of doubt...are you saying that directly underneath the slot at that point there is 7mm of wood before you hit fresh air? And so the original rod was also acting on this same thickness of wood. Well, given the above, if this was my bass, and as long as I made sure the trussrod was positioned correctly at the nut end (and 'correctly' means in relation to that thicker area of the neck, which will put the rod just a touch further forward than normal), I would be keeping it simple and putting a modern two-way truss rod in. Anyone disagree?

Actually, though, following @3below 's suggestion of putting a full length fillet in the bottom of the slot: if there isn't already enough thickness at the nut (and there might be), there is a variation on his theme. You could put a short strengthening/thickening fillet at the nut going back, say, just an inch. That would raise the nut end of the trussrod (assuming modern) top face a mm or so above the neck face for a short length back from the nut. You could certainly file or chisel a clearance slot in that short bit of the underside of the fretboard - and it wouldn't need to be overly accurate as long as it cleared the bit of the rod that was standing proud! I think that could be plan B if the thickness under the nut isn't quite enough at the moment

Not a silly question, but exceptionally difficult without the right equipment and the new piece wouldn't match what is a full length centre splice. Also wouldn't give you a structural advantage as the only critical point is at the nut end, and there, the thickness is the thickness...

Yes - a valid solution. But a tricky rout even with experience and an absolute no-no for someone with no experience. It's possible, though (see above) it doesn't actually need those extra steps. We'll see what the other clever folks think

Yes - absolutely. See above

Right. I hope you can see this - pesky Microsoft! 'Modern' trussrod (at the top) Starts off straight and when tensioned bows down at either end and up in the middle. Because the heel end is rigid, the force is transmitted to the nut end trying to bend it down (which counteracts the string tension which is trying to bend it up. So the main forces are suffered upwards at the centre of the fretboard and downwards at the nut. There is a critical thickness needed of wood under the nut end of the rod so that the end doesn't burst through the bottom. Here, a volute is your friend Traditional Trussrod (at the bottom) Starts off bent - pressed down by the shaped packer shown hatched in the drawing. Because the heel end is held rigidly, as you tighten the nut, the rod tries to straighten. This produces an upward force on the packer in the middle of the fretboard and a downward force at the nut end of the rod. There is a critical thickness of wood needed under the nut end just like with the modern rod. However, in most cases - because the circular rod goes through a drilled hole, you have a greater wood thickness So - and this was the bit that confused me because many makers curve the bottom of the slot - actually, other than at the nut end, the strip underneath the rod takes none of the forces ( see @Maude 's comment above reaching the same conclusion). So my view is that, as long as the nut end has enough thickness, your cracking - even if it is in the wood itself - is not structurally important So, @stewblack - a couple of questions. 1. In this shot: ...the rod appears to be sitting is a slot rather than a hole drilled through. Was this how it was, or has any material underneath the rod end immediately behind where the nut and washer used to be been removed? 2. See where the broken end of the rod is in this pic. Are you able to work out relatively accurately how thick the wood is here, including any thickening due to meeting the headstock? My suggestions, to be thrown to my knowledgeable peers are: a) If this area was never thicker, then the original rod was placing as much force on this spot as a modern trussrod would, providing the main body of the rod reaches at least this point. b) Other than in this specific area, any cracking of the back strip is structurally insignificant What do folks think?

Microsoft Office update has screwed up Powerpoint, email, etc,etc so I'll have to draw it by hand. Give me 1/2hr

Actually, just sussed it how a single action can work OK with these dimensions and why, even if the centre strip has split, why that might not be a problem. I'll draw it up in the morning and see if the wise sages around here agree

Yes - good point. Let me sleep on it - there's something that doesn't quite add up at the moment in the way I'm interpreting the measurements. I may need to sketch out how I am seeing the various thicknesses in the various positions and check if I'm right. At the moment, I can't see how the truss rod was working properly in the first place (which, of course, it might not have been )

Goodness! Wasn't expecting that! In fact, like @Maude can't think what could have caused that at all!? Does it look like it's the wood or could it be just the lacquer? If it's the lacquer, you have a bit of extra finishing work to do, but the options on the neck remain as they were. Assuming I'm right - those measurements tell me you need to be sticking with a single action. There might be just 2mm under there - and that's not enough, really

A traditional single acting trussrod sits in a curved slot: So - assuming that the top face of the neck is flat then, as @songofthewind says, the slot should vary in depth, with the deepest in the middle. If it doesn't - or if it does but only by a tiny amount - then this might be why the rod broke in the first place. If it does, then you could fit a single action rod in the slot, and then you will need to carve a curved packer (to replace the one you had to remove to get the rod out) shaped like in the photo above. A single acting trussrod is fitted curved in a curved chamber like in the photo. They will only work if the channel and packer are curved the right amount But if the slot is at least 9mm deep at either end, then that is deep enough to fit a double acting trussrod. These are fitted straight and they will bend whether or not they are in a channel: Untensioned: Tensioned: So, if the channel is deep enough at both ends, one of these would fit. And it's a lot easier than worrying about the amount of curve in the channel and creating that curve. So then the remaining question is the one that @Jabba_the_gut raises. That is: Because we know your fretboard is very thick, it implies that the neck itself is quite thin. So how thick is the neck at around the first fret (or closer to the nut if it is clear of any volute)? If it is at or more than 13-14mm, then you have a channel at 9.5mm and that would leave you 3.5 -4.5 mm wood below the slot - which would be plenty. If, say, the neck at the 1st fret is 12mm, then that only leaves 2.5mm of wood under the slot and, when a 2-way truss rod end starts applying the pressure, it is possible that it might crack the bottom of the neck under the nut. So if it is thick enough, a 2-way rod would be much easier to fit. If it's worryingly thin, then a single action replacement would be safer, albeit a little trickier to fit properly.

Ooooohhhhhhhh! How embarrassing is that...clean forgot about GC!! I shall go down to the pond and stand on my head in the middle of it for an hour in penance! I'll post the pics and link this afternoon...

As mentioned above, I have to take a touch more off the neck haunches and I need to get the neck pickup back to Matt to swop the internal wires round, but externally this is done. So forgive the self-indulgence, but here it is:

Great progress so far! Another question @stewblack - in relation to the top face, is the channel the same depth all the way along (ie is it parallel with the top face) or - more likely - does it get deeper the further you go along towards the heel (ie a curved bottom to the slot along the length). Either way, I'm pretty sure that a two-way modern rod would fit - they are generally 9mm deep - and, personally, that's what I would fit. Tonetech do good ones in a variety of lengths. As @3below says, you may need to put some packing strip in the bottom if it is curved and deepens but we can send you some if necessary

^ Wot he said

Forgive the dust on the headstock - I promise to give it a wipe-down before I do the fancy photos - but I put a couple of magnets on the trussrod cover: Which hold it secure and straight: Underneath the tip there is a tiny bevel sanded so that removal is just fingernail stuff: Pickups and electrics are in and the 'first fit' is being done today and tomorrow. Two things I've already picked up that need tweaking: - now I've tried it with strings, the neck needs just a bit more shaving off the haunches - the two pickups are out of phase in the middle position (although they sound great individually). As they are single conductor jobbies, it's an internal swop rather than just swopping the hot and return that you can do with a two-wire setup so I'll get one of them back to Matt to do the surgery. But it's close enough to do a gratuitous photo or two If the light is good in the morning, I'll do the arty-farty photos before I take the neck pickup out again as it won't really change in outward appearance from this point on

@stewblack - how deep is the channel from the top face to the bottom?

That made me laugh out loud. MrsAndyjr1515 muttered something similar