String Tension

[Geddys nose]

Got a Yamaha BB Bass with a very slight convex bow thats bordering on flat, The truss rods a one way one and is slack as it can go.

I'm hoping with very high tension strings this  will create a bit of a concave bow. 

I have Lo Riders on that I've been told are high tension being hex cores but still not enough.

Any Advice?  Cheers

[hooky_lowdown]

I've never heard of a slack truss rod causing backbow. However, hex core are higher tension, some high tension roundwound brands include Fender, D'Addario and Rotosound.

Avoid brands like Ernie Ball, Warwick, DR, Elities, Dunlop, GHS, Picato and LaBella - all medium tension.

[peteb]

I would take the bass to a tech to check out the truss rod 

[Supernaut]

2 minutes ago, hooky_lowdown said:

I've never heard of a slack truss rod causing backbow. However, hex core are higher tension, some high tension roundwound brands include Fender, D'Addario and Rotosound.

Avoid brands like Ernie Ball, Warwick, DR, Elities, Dunlop, GHS, Picato and LaBella - all medium tension.

GHS Booomers are definitely higher tension than 7250s, XLs. Probably equal to Rotos.

Lo Riders are medium-low tension for a hexcore round... not sure why people think they're high tension. 

The highest tension roundwounds I've had experience of are the OLD Fender 7250s in the sky blue packaging. 

Honestly if I were you, I would just try a higher gauge string, think 50-110. 

[Geddys nose]

Might have got the convex bow bit wrong, it’s a slight forward bow in the middle with the truss rod released. With the Lo Riders on it is flat. Cheers

[hooky_lowdown]

If the neck is flat with the strings on, whats the problem? With strings off there should be a upward bow in the middle, thats normal.

[PlungerModerno]

Is the "convex bow" matching the upper neck in this diagram?

I interpret what you're looking for in the strings is something to add more tension and add more relief/bow to the neck since it's a single action truss rod and can't be turned to force forward/concave/relief into the neck.

I'd try tuning up beyond concert pitch a whole step or maybe more, depending on what happens and how confident I was in the hardware. It might not budge as much as you like with even very high tension strings.

[Geddys nose]

The neck was in a mess when I got it, The truss rod was maxed out to a convex bow for some reason. Just trying to help it along with some higher tension strings really.

It has got a bit better in a week TBH and has a slight Convex bow now with only a bit of string rattle in the middle. 

Thanks for the advice.

[PlungerModerno]

12 minutes ago, Geddys nose said:

The neck was in a mess when I got it, The truss rod was maxed out to a convex bow for some reason. Just trying to help it along with some higher tension strings really.

It has got a bit better in a week TBH and has a slight Convex bow now with only a bit of string rattle in the middle. 

Thanks for the advice.

Maybe it was set up years ago for high tension strings (e.g. James Jamerson Cables), then somebody switched out for lighter tension flats or rounds and didn't adjust it enough (or at all!) to back off all that unnecessary truss rod tension and quickly it developed a semi-permanent back bow. They may have increased the string height to permit some sort of playing at the first few frets. Might also have been used with alternate tunings with high tension, then switched back to concert pitch without proper setup.

When the truss rod is way too tight or just loose, often the saddle height and other details have been neglected or messed with so it's anyones guess what happened & when.

[Reggaebass]

Could it be that the rod is jammed ?

I had a 414 with the opposite problem, with the strings off it had back bow but with the strings on it had a big concave bow 

[Andyjr1515]

On 23/03/2021 at 22:50, Geddys nose said:

The neck was in a mess when I got it, The truss rod was maxed out to a convex bow for some reason. Just trying to help it along with some higher tension strings really.

It has got a bit better in a week TBH and has a slight Convex bow now with only a bit of string rattle in the middle. 

Thanks for the advice.

Yes - it sounds like either the truss rod has been overtightened in the past, or maybe tightened properly but then the strings left slack or removed for a longish time and the wood has eventually taken on some of that shape. 

There are more dramatic ways of sorting this, but often the same process is reversible by broadly doing what you are doing...but it will take time.  So, if you have the time, I would go for thicker strings as @Supernaut says, and tuning up two semitones as @PlungerModerno says with the truss rod completely slack and leave it for at least a week then see if it gets you where you want it, because flat is very, very close to where it needs to end up and so it won't take a lot to give just that smidgen of relief...   

[Geddys nose]

Yes the strings where slack when I got it, I’ll over tighten them for a bit and see  what happens. Great advice 👍

[Reggaebass]

If the truss rod nut is completely loose, it would have back bow , right?   wouldn’t tightening it with the strings on help, or is it not that sort of rod 🙂

[Andyjr1515]

1 hour ago, Reggaebass said:

If the truss rod nut is completely loose, it would have back bow , right?   wouldn’t tightening it with the strings on help, or is it not that sort of rod 🙂

No - not quite.

The strings pull the neck into a bow and arrow kind of bow - and the trussrod's job is to counteract that by trying to pull it into a backbow.  If the two tensions balance, then the neck ends up straight.

So if the truss rod has been left in its tightened state, but the strings are left slack, then the neck will indeed take on a back bow.  Left too long like that and the back bow sort of sets into the wood.

So if @Geddys nose does the opposite - leaving the trussrod loose but tightening the strings, then the strings will pull the neck into a bow and arrow forward bow.  The plan is, if he leaves it like that for a while, then the back bow set into the wood will be corrected and the neck will be straightish when neither the truss rod nor the strings are tightened.

That's the hope, anyway

 

[Reggaebass]

Thanks Andy, so if the strings pull it forward, do you then tighten the nut to hold it there 

[Andyjr1515]

50 minutes ago, Reggaebass said:

Thanks Andy, so if the strings pull it forward, do you then tighten the nut to hold it there 

Do you mean in normal use or to solve @Geddys nose's problem?

[Reggaebass]

Just now, Andyjr1515 said:

Do you mean in normal use or to solve @Geddys nose's problem?

Both really , I just wondered how the single action rod worked on the Yamaha, thanks 

[PlungerModerno]

1 hour ago, Reggaebass said:

Thanks Andy, so if the strings pull it forward, do you then tighten the nut to hold it there 

I know for the dual truss rod Rickenbackers, especially the older ones like the 4001's, many of those experienced with them advise something like that for general adjustments:

http://www.rickenbacker.com/forum/viewtopic.php?t=2752

http://www.rickresource.com/rrp/basstrussrods.html

Using the truss rod to hold the neck in it's shape, rather than to adjust it's curvature.

Edited March 25, 2021 by PlungerModerno
Links now instead of just the text.

[Andyjr1515]

4 minutes ago, Reggaebass said:

Both really , I just wondered how the single action rod worked on the Yamaha, thanks 

If you envisage the strings at the top of the neck pulling the neck in a bow shape as tightening the tuners make them shorter, the single action truss rod is doing the same at the back of the neck as the nut is tightened, making the trussrod shorter.

I'll try to get a moment to draw a picture tomorrow.

[Reggaebass]

I think I understand what you’re saying Andy, My fender jazzes and precisions adjust both ways , but I could never quite get my 414 rod to work  properly, I later found out that it had a fault 

Edited March 25, 2021 by Reggaebass

[Andyjr1515]

10 hours ago, Reggaebass said:

I think I understand what you’re saying Andy, My fender jazzes and precisions adjust both ways , but I could never quite get my 414 rod to work  properly, I later found out that it had a fault 

I've never worked on a Ric but I know their trussrods are a bit unusual (I think the lefty loosy, righty tighty is reversed?).

But of the two physical principles used:

- one is where the rod independently curves one way or the other based on the nut adjustment (typical of a modern two-way rod) and the neck simply follows the curve of the rod

- the other is where the rod is clamped either end to the internals of the neck and shortening the rod 'pulls' the headstock towards the back of the heel (typical of a traditional one-way rod)

- in both cases, the strings are trying to 'pull' the headstock towards the bridge  

 

[Andyjr1515]

12 hours ago, Reggaebass said:

Thanks Andy, so if the strings pull it forward, do you then tighten the nut to hold it there

 

11 hours ago, PlungerModerno said:

I know for the dual truss rod Rickenbackers, especially the older ones like the 4001's, many of those experienced with them advise something like that for general adjustments:

http://www.rickenbacker.com/forum/viewtopic.php?t=2752http://www.rickresource.com/rrp/basstrussrods.html

I see where your original question comes from @Reggaebass .  The link that @PlungerModerno includes above say that pre-1984 Rics need the neck to be physically bent and then the truss rod nut tightened to hold it in that bend.  In reality, the rod will be doing exactly the same thing but simply will not be physically capable of actually moving the neck by itself, but nevertheless is strong enough to hold it there once the bend has been induced.

For completeness, I'll see if I can find a few photos that illustrate the two truss rod types.  And while all that is going on, hopefully @Geddys nose 's neck is gradually assuming its original shape 

[Andyjr1515]

OK - in hope that this will clarify rather than further confuse...and with thanks to the folks whose photos I've purloined from Google:

Objective:  For buzz-free playing at decently low action of the strings above the fretboard, the neck needs to be pretty much flat

However:

In the absence of a trussrod, the string tension is going to do this -

The string tension is pulling the headstock towards it and, because the neck is flexible, it bends.  This would play buzz-free...but the action would be unplayably high.

Common Solutions

- Build the neck completely rigid and so the string tension cannot bend the neck.  This can be done.  Vigier guitars do not have a truss rod - the necks are very stiff.

or

- Fit a trussrod that is capable of trying to bend the neck in the opposite direction and, counteracting effect the string tension, leaving the neck straight.

Truss-rods - the two common types

So the trussrod's job is to resist that bending leaving the neck straight, even under full string tension.  There are two commonly used designs of truss rod:    

Trussrod Design 1 - the (usually) two-way self bending trussrod

This rod will bend independently of being in a neck or not.  Turn the allen nut one way, it bends one way; turn the allen nut the other way, it bends in the opposite direction:

It is fitted straight in a slot in the neck and, in the absence of any strings, adjusting the nut will make it bend, and the flexible neck  has no option to bend with it:

It doesn't matter whether the adjuster is at the headstock or the heel - the effect is just the same:

 

Trussrod Design 2 - the single-acting rod

Here, if the rod was not fitted, tightening the nut would not make it bend.  But the way it is fitted, where the rod is anchored at both the heel and at the headstock end and the slot it sits in is, in itself, curved...

...means that as the nut is tightened, the rod tries to straighten itself.  This makes the neck bend downwards.  

 

Ref the Ric issue on the pre-84 models (although their actual design is different to either of the above but the principle will be the same).  You can imagine what stresses are on both the neck and the trussrod thread trying to get the turning nut to bend that stiff maple neck!  But, of course, if you helped it along by physically bending the neck downwards at the headstock, the rod would straighten and the nut would feel looser.  So, to take some of the stress off the rod and thread, you could pre-bend the neck, tighten the nut until it seated against the neck wood and then when you took the pressure off the neck, it (the neck) wouldn't be able to straighten again because the shortened trussrod wouldn't let it. 

Hopefully makes some sort of sense

 

 

 

[Reggaebass]

29 minutes ago, Andyjr1515 said:

OK - in hope that this will clarify rather than further confuse.

Thanks very much for this, very well explained 👍

[Reggaebass]

@Geddys nose, how’s the neck coming along