High neck angle on an acoustic guitar

[CarlosHS]

Following the general rule that a straight ruler should just kiss the top edge of my bridge or a more detailed recommendation from William R. Cumpiano and Jonathan D. Natelson book on Guitarmaking called “Tradition And Technology” to determine the bridge to its position and put a long ruler on top of the attached neck. The airspace between ruler and top of the bridge (without saddle) should be in the range of 1/64" to 1/16" (0.4mm to 1.6mm). So that after stringing up, in theory, the guitar this will result in a medium action.

I have 3 guitars that have the resulting straight edge at 1/4” or 6mm where it normally should just kiss the bridge. The guitars came with “very” high saddles. To fix this issue, why can’t I just make a taller bridge?

I have a custom OM guitar I purchase years back with a very high bridge to make up for this extra space. The bridge is quite narrow, compared to a normal bridge. It has never failed. The guitar plays great. The string action is perfect. I would say it has more volume than your average guitar. On guitars with a high angle, why solve the problem with a neck reset to lower the angle, which over the next 20-50 years will go down anyway? To replace the bridge with a higher one is significantly less effort than a neck reset. Is there a real reason why the fix cannot be taller bridge?

[Nahil.R]

Why not just reduce the saddle height to your desired specs.

Removing and replacing a bridge is no small feat.

[Talldad]

The saddle acts as a lever on the soundboard, the taller the saddle, the bigger the pull on bridge and the soundboard when brought up to the correct notes. pleasingly the higher the bridge the louder the guitar becomes.

Imagine if the saddle were 4" high, bringing the guitar to tune would lever like crazy and belly up the soundboard just before the bridge got ripped off or the saddle broke.

Ultimately there's happy spot where the soundboard, bridge and saddle are safe from distortion and the guitar still plays at a good volume. The strings should make contact with the saddle at around 1/2", 12mm-13mm above the soundboard.

[charles Tauber]

Originally Posted by CarlosHS

On guitars with a high angle, why solve the problem with a neck reset to lower the angle, which over the next 20-50 years will go down anyway? To replace the bridge with a higher one is significantly less effort than a neck reset. Is there a real reason why the fix cannot be taller bridge?

I'm not generally aware of people "fixing" guitars with a high neck angle. Usually, they are what they are and aren't "fixed". The primary issue is with neck angles that are too low causing playability issues.

The distance from the guitar top to the bottom of the strings at the bridge is a design target established by whomever made the guitar. The larger the distance, the greater the torque (moment) on the bridge and top. The Martin target is 1/2". Tops can be thicknessed and braced for the amount of torque expected.

Similarly, there is a design target of how much saddle should project from the bridge for the desired string height. The lower end of the range of design target is determined by having sufficient break angle of the strings over the saddle. The upper end of the range is determined by limiting the torque that the saddle places on the front face of the saddle slot, ensuring that the torque is not sufficient to split the bridge at the sound hole-edge of the saddle slot.

What is left between the two design targets - the vertical distance from the guitar top to the bottom of the strings and the desired saddle projection - is the thickness of the bridge. Given that the bridge is the largest brace on the guitar top, the weight and stiffness of the bridge can be important parameters. Again, if one makes design choices that results in a thick bridge, one can accomodate that in the overall design parameters to choose a lighter bridge material, different bridge size and/or shape, accommodation by top thickness and bracing and so on.


Unless one is concerned that the torque of a saddle that projects greatly from a bridge will cause the bridge to split, an overly high neck angle isn't usually a problem or one that is "fixed". If there is concern that the saddle projection will split the bridge, one can install a thicker bridge, thereby reducing the projection of the saddle. One could alter the size and/or shape of the bridge, as well as chose a less heavy material, in order to not increase the mass and stiffness of a thicker bridge. Redesigning, making and installing a new bridge does involve substantial effort though possibly less than a neck reset. Again, if an instrument plays well, is structurally stable and sounds good there is little reason to adjust the neck angle or change the bridge unless one believes an overly high saddle is likely to split the bridge.

[CarlosHS]

Nahil. Reducing the saddle height on these 3 guitars leaves the string action so low it hits the frets. The cheaper / easier fix is increase the bridge high a bit and leave a normal size saddle (which can be done by anyone / add to the bridge and change the saddle). Alternative the luthier fix would be a neck reset to lower the high guitar angle.

Talldad. I agree. That is my concern. I have a custom guitar made by TrueAx in Canada with 3/4” bridge height. It is called “First Light” and it never had an issue with the high bridge. The bridge is very narrow too (1.0”). That setup, in theory should be putting lots of torque and pressure on the top and ripping out the bridge / top. But it is holding well for years now. Sound is loud and clear.

Charles. Your explanation is much in line with the William R. Cumpiano and Jonathan D. Natelson book on Guitarmaking called “Tradition And Technology”. I am going to go for the neck reset. I have new tools I want to try. For the neck pocket removal:

Jhua Hot Knife Foam Cutter Electric Styrofoam Cutting Tool 36W Hot Wire Foam Cutter Electric Foam Cutting Machine Pen Hot Pen 15CM Styrofoam Cutter Cutting Tool Kit

For the fret extension: The Hangar 9 Sealing Iron, HAN101 and or the 2" X 5" 51 X 127mm 40W Guitar Fingerboard Fretboard Extention Repair Heater Plug which I purchase on ebay. To heat up my knives I purchased a used Everhard Burnt In Oven on Ebay. I also just received my StewMac neck removal Jig. I wish I could post pictures. Maybe I’ll put a video on Youtube on it.

[RonMay]

There is a point of diminished return where what was a good idea if carried to the extreme it stops being a good idea and goes bad.

There's probably a good reason bridges are of a certain median size.
I don't know what that reason is, so maybe a luthier can answer this.

Ron