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Acoustic guitar - neck pitch, bridge height - Help

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Acoustic guitar - neck pitch, bridge height - Help

Postby Darren Lynch » Thu Oct 12, 2017 12:30 pm

Hello All,

I have a Yamaha FS720s, acquired from the epitome of fair dealing that is Cash Converters.

The guitar has a high action, despite the following:

Nut - the gap between nut and third fret is business card thin, no obvious issue
Neck - Relief appears OK, gap at 6th fret with first and 14th frets depressed is, again, business card thin

So I viewed some online vids on setups, which led me to examine the neck angle. The plane of the fretboard is well down against the top edge of the bridge. The bridge itself is a chunky affair, way taller than my two other guitars (Yamaha FG420, Tanglewood TW15)

My thinking goes - To overcome the unusually high bridge, I'll have to shave the saddle excessively. This risks placing the strings in contact with the top edge of the bridge during energetic strumming. Lowering the saddle will also reduce the break angle of the strings, reducing tension and tone.

Long story short, is it time to back slowly away and admit that without serious treatment of the bridge, a low action is not possible?

I appreciate that without seeing the instrument it may be hard to give an opinion, but I do think this is beyond the usual nut>trussrod>saddle solution to high action.
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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby zenguitar » Thu Oct 12, 2017 1:04 pm

There are two ways to do this. The proper way is to get someone skilled to remove the neck and refit it with the correct neck/body angle. But this WILL be expensive.

The kludge is to plane some height off the bridge and then deepen the saddle slot. However, there is a risk you will lose tone/volume. Ideally, you want to keep the strings at no less than 10mm from the front of the guitar. Once you go below that is when you riskproblems.

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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby Darren Lynch » Fri Oct 13, 2017 11:16 am

Thanks for the reply, Andy.
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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby CS70 » Fri Oct 13, 2017 12:20 pm

Darren Lynch wrote:Hello All,

I have a Yamaha FS720s, acquired from the epitome of fair dealing that is Cash Converters.

The guitar has a high action, despite the following:

I don't have a .0001 of Andy's expertise, so just my experience.. I had a old japanese Precision bass which I wanted to use for demos, and it had the same problem, way too high action on high frets, the neck was at an angle.

What my tech did was to warm the neck up and bend it back in shape, leaving it that way for a few days (not sure about the details, of course). After that, a little relief adjustment and it's now super-playable.

Obviously was an electric bass and it might be difficult with an acoustic, but he did do the job with the neck attached..
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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby BigRedX » Fri Oct 13, 2017 12:54 pm

CS70 wrote:I don't have a .0001 of Andy's expertise, so just my experience.. I had a old japanese Precision bass which I wanted to use for demos, and it had the same problem, way too high action on high frets, the neck was at an angle.

What my tech did was to warm the neck up and bend it back in shape, leaving it that way for a few days (not sure about the details, of course). After that, a little relief adjustment and it's now super-playable.

Obviously was an electric bass and it might be difficult with an acoustic, but he did do the job with the neck attached..

That sounds like a warped neck problem. If it had simply been the neck angle on P-Bass your tech could simply have unbolted it and fitted a shim (or adjusted an existing one).
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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby CS70 » Fri Oct 13, 2017 1:08 pm

BigRedX wrote:That sounds like a warped neck problem. If it had simply been the neck angle on P-Bass your tech could simply have unbolted it and fitted a shim (or adjusted an existing one).

Funny you say, that's what I actually was proposing at start (and I actually went all the way to unbolt the neck, got hold of a shim and fitted it myself, getting to a somewhat better playability) but he wanted to go the warm up way.

As as I said, not an expert tough - I just play the stuff.
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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby Wonks » Fri Oct 13, 2017 4:23 pm

You need the right solution for the problem in hand. Sounds like CS70 had a problem with the truss rod not being able to correct the neck bow. Sometimes there's not enough thread on the truss rod to correct a large concave bow. If the neck wood isn't quarter-sawn (the most rigid and warp-resistant way to cut wood), then as the wood dries out over time, it can create more of a bow than the truss rod can deal with.

In these instances you free the truss rod right off, then try and bend the neck back to near-flat using heat and pressure, Sometimes it works, sometimes it doesn't. But if it does, you can then adjust the truss rod to get the best neck relief for your guitar/bass and you've got a working neck again.

If you can get the neck back to flat or near-flat but you still can't get the saddles low enough to get a low action without loosing a decent break angle across the saddles, or the saddles are right up in the air, then that's the time to look at adjusting the neck angle. With a bolt-on neck, you can use shims under the front or rear of the neck joint (depending on whether you respectively want to lower or increase the neck angle). With a set neck guitar or bass, its a question of steaming the neck joint apart and shaving wood away until the neck sits at a better angle before gluing it back together again.

It's not always the neck that is the reason for a high action. Sometimes uneven or proud frets that mean you can't get a low action without some of the strings catching on the high frets at certain points on the fretboard. Adjusting the neck bow can only mitigate this to a very limited extent (and it does depend on where the high frets are). Sometimes the high frets can be tapped back into the fret slots so the fretting is level again.

Other times this is insufficient and the frets need to be levelled. This is certainly the case where a lot of playing has worn grooves into the frets, which mean that the next fret up is now sitting comparatively higher and the string buzzes on it unless you raise the action up.

To level the frets, the neck first needs to be set flat (a notched straight edge is required as you want the fretboard flat, not the frets, to do this). Then you stone or file the frets flat, then you re-profile them with a fret profiling file. Then you run up through the sanding grits (MicroMesh pads or sheets are great for this and is far less messy than using wire wool) and polish them so they end up mirror smooth again. Then it's just a case of fitting new strings and going through a standard set-up procedure.
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Re: Acoustic guitar - neck pitch, bridge height - Help

Postby adrian_k » Sun Oct 15, 2017 8:09 am

Re forcing the neck back into shape, isn’t there a risk it’ll just move back to where it wants to be over time?

If the bow isn’t too bad and you think it’s stopped moving you could whip the frets out and re-level the fingerboard. This would also address any slight neck twist, which (in my limited experience!) often comes with a bow.

Re action height in general, some older inexpensive guitars I’ve seen with this problem it’s due to the top pulling up over time because the bracing wasn’t good enough. You can see a very slight bulge, with the bridge at the crown.
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