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Forgive me for asking what may be a stupid question, but I'm trying to understand relevance of the neck angle in relationship to the top of the bridge.

It is my understanding that the neck angle of a guitar should be that a straightedge on the fingerboard (with frets) skims the top surface of the bridge.

If there is a standard set in place for the neck angle, is there a standard for the saddle height, or is the straightedge on the fingerboard skimming across the bridge just a good general point to where various saddle heights could be used to lower/raise the string action?

I guess the point of my question is what is the relevance of the bridge surface when in reality, the strings contact the saddle? If a straightedge skims the top of a .345 thick bridge with a .125” high saddle that would be the same as if a straightedge skims the top of a .375 thick bridge with a .095” high saddle? Or using the a .375” thick bridge with a .125” high saddle and having the straightedge go .03 below the bridge surface, and so on, and so on. There are many ways to get the relationship between the fingerboard plane and the top of the saddle the same regardless of the relationship between the fingerboard plane and the top of the bridge.

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Thanks,
Blain

http://www.ullrichguitar.com

"89.67% of all statistics are made up on the spot."

To understand this better you may need to make a drawing. In most cases we use a 1 1/2 degree neck angle. What you are doing is trying to hit a line so that you can create a string height at the bridge od 1/2 inch while holding a line so the action can fall into a relationship on the neck with string height at the 12th fret of 7/64.
If you do a 90 degree side you will have a fall off of the fretboard extension. check out this link http://bluescreekguitars.com/blog/ and see how I control this geometry

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

The reason to set the plane at just above the bridge, not the saddle, is that if it's just above the bridge then you know you can properly adjust the string height up and down with the saddle. If the line intersects too high above the bridge then the saddle will need to be super high, and if it's too low then there's no way to lower the action past a certain point.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

With my guitars at least .. there is no correlation .. the angle is whatever it is, I dont even bother to measure it by putting a number on it, I am shooting for just above the bridge with the lie of the fretted Fb .... I adjust the neck angle until I get it ....

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

John and Bob are correct.

Just remember that the neck extension (14th fret on up) needs to be on the same plane as the rest of the fingerboard. You don't want to end up with an angle there (the exception being a small turn down of the fingerboad at this point is ok. Never an up angle, not if you want the upper frets to actually work.

So the goal is, according to Cumpiano/Natelson, to end up with a 1/64" to 1/16" gap at the C/L of the bridge, at the saddle position, when a straight edge is held on the center of the fretted fingerboard.

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Joe Beaver
Maker of Sawdust

Shouldn't that be without frets?

No

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

That's how I do it. The straight edge on the board itself just barely kissing the top of the bridge.

And to drop a fly into the ointment here. I am finding that with a bit more saddle above the bridge I am seeing a huge difference in the power of the instrument. All things in moderation of course.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I actually like 1/32 or slightly less gap with frets on unstrung. When it's under tension I like the straight edge to kiss the top of the bridge and the above gap gives that to me on my stuff. The action's going to come up in the first year of life and a little higher saddle is nice at birth.
TJK

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

you will find many different answers for this.

I started with a small .025" "air gap" above the bridge with a fretted fingerboard.

That worked OK, but still when pulled up to tension a straightedge fell to just below the front of the bridge.

This has worked very well for me - but I am continually refining it.
neck with no fretboard at the saddle location - 0.090" air gap above the top.
With the unfretted fretboard on - Straight edge falls on top of the bridge.
With a fretted fretboard on - straight edge has a 0.040 to 0.60" air gap above the bridge.
Saddle height ends up to be about .120"

For a neck reset I wouldnt use near that much of an air gap, but on a new build the top pulls up quite a bit.

For each guitar you build take lots of notes of your measurements for future reference and dial it in to what works best for you.

I have used a standard martin belly bridge or stew macs pyramid bridge for all my guitars so far (5 of them).
Hope this helps.

I had asked a while back about builder's preferences for string height over the soundboard. I've noticed that the guitars I like best seem to have the strings higher than the norm. That can be from a tall bridge, lots of saddle showing or some combination.

Brock,

In addition to the difference in power, do you perceive any effect on timbre or tonal balance? In theory it would seem the greater leverage ought to have differential effects on the various modes of soundboard motion but I'm not sure how it plays out in practice.

I check my heights off of the height above the soundboard, not above the bridge. I like to see a straightedge sit .4 off of the top registered off of the fretted fingerboard. Generally my bridge is about .35 in the middle. Like Brock, I prefer a little more saddle showing. I think it is important to be very consistent with the string height off of the soundboard, even more than bridge height. That said, sometimes I will take the bracing and top thinner than normal trying to maximize response. I am trying to do that less but if I do I will reduce the string height off of the soundboard slightly when I set the neck.

I didn't do full scale drawings on my first 5 or 6 but once I started it made a world of difference. The side drawing is the most important, it will show you where everything should lie, including the arches and back taper. Things rarely ever come together perfectly, but usually they are very close and doing the drawing will allow you to either know what to expect, or alter your plans slightly to make fitting the neck and extension easier.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

I suspect a taller saddle leads to a greater break angle of the strings as they make their way to the pins. That could be a large factor in volume increase.

Just a guess.

Joe

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Joe Beaver
Maker of Sawdust

I like to use the term 'neck extension at the bridge', since 'angle' is something different. In fact, you can get the proper neck extension with a whole range of neck angles, depending on how much 'overstand' (the height of the neck surface above the top) you use.

String height off the top can effect the timbre, and, possibly, to a lesser extent, the power of the guitar. When the string vibrates it produces two major force signals on the top of the saddle, a 'transverse' signal and a 'tension change' signal. If the string is vibrating vertically with respect to the top, the transverse force is also vertical, pushing the top in and out like a loudspeaker cone. The tension change signal tugs the top of the saddle toward the neck twice for every full vibration of the string, so it's an octave higher in pitch than the sounding note of the string. Since part of the top is coming up while another is going down there will always be some 'phase cancellation' from this sort of motion, and it's not as effective at producing sound as the 'loudspeaker' type motion. Generally speaking the transverse signal is the stronger of the two as well. However, the tension change signal does influence the timbre of the guitar, and may add some useful power.

The higher the strings are off the top, the more leverage the tension change signal has, and th emore of the frequencies it produces there are in the signal. You have to balance that agianst the higher static torque that is trying to fold the top up and peel the bridge loose.

The 'optimum' height for the strings off the top is probably something that each maker has to work out for themself. It's lilely to vary somewhat with things like top thickness, bracing, and so on.

I think so. The most immediate/notable difference that I see is power (both loudness and long range projection) and the perceived "speed" of the sound. I find a taller saddle gives a bit crisper, faster sound in addition to the volume.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

That's one more thing I like about the adjustable neck joint. I cut my tenon at 1 1/2 degrees and then just dial it in to set it up.
it's a easy set up. If you all are doing bolt on necks then your half way there.

Brock, are you saying that you add more saddle height to your standard bridge thickness or that you slim down your bridge thickness so that you can have more saddle height? Just wondering if what you're seeing in the power of the insturment could also be a result of a thinner bridge or if you're not using a thinner bridge, do you think using a thicker bridge with with no extra saddle height above the bridge would give the same effect?

Interesting stuff guys. I made a rough design out in CAD using a dead flat top, but I think I need to go through it another time to make sure I got everything correct and to account for a radiused top, because with a dead flat top and around a .345-.375 thick bridge I was only seeing about a 1/2 degree angle. It was only until I made the bridge around .625 that I got anywhere near a 1 and 1/2 degree neck angle. I'm sure adding a radiused top to the design will yield a more believable neck angle.

I also do mine as Tony says and don't use any specific angle. I zero the dial indicator of the neck angle jig onto the top. I then take the fingerboard thickness, fret height and bridge height into account and adjust the indicator accordingly. I've only done 3 this way, but it's been dead on, However, I am seeing that on my second guitar the fingerboard plane has changed to just below the bridge surface after being under string tension for several months. But that's a whole other thread.

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Thanks,
Blain

http://www.ullrichguitar.com

"89.67% of all statistics are made up on the spot."

Neck angle as Alan points out is a vague term. If you are using stock necks ala Martin , they have a 1 1/2 degree angle designed into them. I have seen neck angles from various suppliers range from dead square to 2 1/2 degrees. I plot my geometry on the guitars I build with the neck that I am using.
What I aim for is a 1/2" height at the bridge. If you do the math for the resultant force you can see if your top and bracing will take the load. Also there is a point where you get too much rotational force and a point where you loose energy . This will influence the head room of the instrument along with the voice of the guitar . It isn't all about break angle . While break angle is important , I can create the same break angle on any bridge by manipulating the slot and ramping the bridge but you cannot manipulate the total string height without it affecting the action.
This is where the neck angle comes into play. If you know where the most efficient load is to be for exchange of energy from the string to the top , this is your target. I have found for my guitars that .500 to .565 is my target . If I go higher , the rotational force will cause issues and below .500 will not allow the top to have access to all the string energy.
This is why as a guitar changes shape and you get into the reset area , the guitars sounds better after the reset because you get the energy back into the top.
So back to the neck angle , once you know where your target is and you know what the angle of the neck you are using , you can set this so your fretboard extension will come on to the top in a straight line. Some builders will establish this in the sides before the top is glued or others will sand this angle into the top itself . For those that don't think or plan for this , it can often be seen in how the fretboard extension drops off or rises at it comes on the top.
Alan , what is your feeling to what I have stated?

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it