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Hi
Having the worst day, just finished my latest OM acoustic and did an initial setup and it looks like I have made a big fat screw-up.
I have got the saddle level set for a low action 2.0mm(0.08)+ 1.5mm(0.06) measured at the 12th fret and the 1st,2nd,3rd strings are all hitting the top frets above the 14th fret
It must be the dreaded hump I have heard mentioned on here before.

I know it's a low action but I only have 0.5mm(0.01) clearance at the last fret so I guess it was never gonna work. Absolutely gutted

Any ideas please gratefully received





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Over set neck? Lets see a pic with a straight edge right down the middle?

50% of the guitars coming into our shop for repair have strings on the frets because it's very cold and dry here.

Do you control your humidity?

Hi Hesh, I have kept the humidity between 50-55 during the whole build, I reckon this is builder error. I tried to build two guitars at the same time and must of taken my eye of the ball at some point



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Will do a picture now, when you say overset do you mean too much relief?

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Picture with straight edge over 7th and at bridge. Have about 1-2mm clearance over the bridge, have always added a bit of extra clearance, but not had this problem before

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That looks like a lot of relief...what is the measurement? You might set relief at .005” to start and shim your saddle to move action to a .063/.096 generic action, then see where the clearance over the extension goes.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower

Perhaps instead of creating a "hump" you created a dip at the 14th fret. When you joined the neck to the body was there any fallback of the fret board to the body at the last couple of frets or did you have to force the fret board down to meet the body at the 14th fret? If it was the latter, you may have created a situation in which the fret board is rising up from the 14th fret on. If that is the case, and if the problem is severe enough, you may have to do a neck re-set.

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

Hi Pat,
Yes I had to force the fretboard down as it was bending back, I assumed this was because it was fretted.
A neck reset would probably give me to much height over the bridge?

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Thanks Woodie, am I right in thinking that the height over the 14th fret upwards should be slightly higher than the height over the 12th

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Tune to pitch and adjust the neck so that you have near zero relief. Lay a straight edge on the frets from 1st to the 14th. The straight edge should lay on top of the bridge or just above it, with slight fallaway of the fret tops from the body joint to the last fret. If you had to force the fretboard down when installing the neck, you probably created a high tongue. Resetting the neck will correct this, just don't over-correct and end up having to make a high saddle. This is called over-setting the neck, referenced above. Level the frets after you correct the neck angle. You will probably need to make a new saddle as well.

Don't beat yourself up. This is how we all learn and it is part of the process.

_________________
It will probably be alright.

Thanks Greg, will try that now

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If the relief is set properly, there will likely be a few thousandths more clearance over the 14th than 12th; excessive relief may result in decreasing string height over the frets above the body join, and the saddle will be lower than it should be, dropping string height over the body and resulting in less clearance for the strings (and possible buzzes when fretting much above the 7th). Other issues which might cause the issues you are seeing would be inconsistent fret work (high/incorrectly leveled/loose frets...very common), fretboard distortion due to incorrect fit of the extension and body (extension appears to bend upwards), and a few others that are less likely, but can be explored once the easy fixes are exhausted.

Start by setting relief, then look down the fretboard from nut to saddle...a slight amount of curvature (nearly straight at .005" relief), with a straight or slight fall-away to the extension would be good, while a kick-up/ski-jump would suggest that there is a geometry issue with the body. Should that be the case, other steps may be required to resolve it, but let's get the relief and action at 12th set so we can start figuring out where the actual problem lies.

For what it is worth - a sheet of copier paper is .0035" in thickness, so about 1-1/2 sheets of copier paper worth of relief is a decent place to start...fret at the 1st and just beyond the body fret (the 15th) and check at the 7th or 8th (wherever max relief occurs). If in doubt on estimating the measurement, capo at the first and fret just past the body fret and use a feeler gauge or nut setting gauge.

_________________
A constellation only takes shape when one maps the whole.
- Beth Brower

So I have adjusted the truss rod so the neck is flat 1st to 14th fret and I definitely have an upward ski slope from the 14th onwards, also the height above the bridge with a straight edge has increased to about 3mm (higher than I would like)
The ski slope is more pronounced on the treble side, but this maybe due to an extra half fret extension.


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More pics

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How is the neck attached? You may need to machine out the ski ramp by either removing the neck and planing some material off the bottom of the fretboard extension, or pulling the upper frets and planing out the ski ramp.

I've done something similar to this before. Your fret board is def rising after 14th fret. In the future, to avoid this, do not curve the transverse brace and flatten kerfed lining in upper bout (above soundole)

To a certain extent, depending on how bad it rises, you can fix this in place by removing frets above 13, radius sand in place - carefully - then replace frets, hopefully slots are deep. As Barry said. The second option is preferable I think given how much work the neck reset will be. The down side is you are working close to the finished top.

Mike

Looks over set to me.

The strings in the last two pics that you posted look like they get closer to the frets over the fret board extension, this is an over set neck if that's the case.

What I would be looking for is with the truss rod adjusted so that the neck is super straight (strings or no strings, makes no difference to me for this look we want no relief) and a straight edge resting on all of the frets and projecting out to the bridge where does the straight edge intersect the bridge? This has to be done with the neck adjusted super straight, no relief or string tension pulling it into relief.

What you want to see is the straight edge coming in just over the bridge approximately the height of the frets. Some over set more, some less, what I am suggesting is a middle of the road look and how I set my necks. A properly sized (height) bridge is part of this method of setting the neck too.

If it is overset it needs to be properly set and there is no getting around this.

I just reread your post with the straight edge, yep over set.

The prior post where you have a straight edge and way too much relief is pulling the nut region of the neck forward and masking that it's over set. Always do the straight edge check with as straight a neck as you can.

If there is too much dome in the top, it won't matter. It looks like dome to me. You really think changing neck angle will solve that?

Hey Mike, Happy New Year to You!

I'm not sure why you think there is too much dome. I may be missing something here but when I set a neck I don't really care what dome there is, how much, etc. I set the neck angle to a properly sized (height) bridge shooting for about 1/2" of string height over the top at the front of the bridge.

Sure there may be body humps and issues with the fret board extension transitioning over the body but in the pics that show the neck and body the neck angle is way too far back. In one of the pics the neck looks like it's pointed at the top of the window all indicating neck angle is at least one of the issues, there certainly may be more and you could be right.

This is an example of where a PLEK would be handy. You could then just pull the upper frets, have the PLEK shave off the top of the fretboard, re-do the frets slots that have gone too shallow and, after a little touch-up sanding, be good to install some new frets and you'd be good to go.

One little ray of good news in this is that if you choose to go the route of planing or sanding off the ramp rather than doing a neck re-set, at least you didn't bind the fret board so making any fret slots that get too shallow from the planing/sanding deeper should be doable.

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.

It is unusual to have both a hump/ski jump at the top extension and an overset neck at the same time.

If, in fact, you do have a ski jump, the straight edge test may not be accurate. This is because the upward trajectory of the extension will lift the straightedge up giving a false reading, assuming the straightedge is touching the first and last fret. With no relief, is there a gap under the straight edge, or does it touch all frets along the way? If it has a ski jump I don't see how it could.

So a more accurate assessment may be to determine the trajectory of the neck from nut to body join. You can do this with a piece of scrap wood sanded nice and flat with the section where the extension is scooped away so it doesn't ride on it.

I agree, the rising extension is probably giving a false neck set reading with the straightedge.

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Thanks for the replies
It definitely does have a ski jump/rising extension as with a straight truss rod 1st-14th fret the straight edge is only resting on first and last fret. I agree this is probably giving the false reading at the bridge, although it may still be a bit over set. I'm like the idea of checking with a straight edge with a recess skipping the fretboard extension, this will give me and idea of what neck angle I actually have.
Then I guess it may be a case of pulling frets and sending? This makes me nervous as I have never pulled frets before, open to any other suggestions



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