Compound FB Radius measurements.

[J E C]

I have had a question about Compound FB Radius measurements that I need answered. Lets take as an example a 10" to 16" Compound Radius. Now obviously the 10" would be the measurement at the nut. The question is.... Were is the 16" measurement at? The 12th fret, the 22nd, the 24th, the bridge or? :scratchch

Thank for the help. John

 

[Zerberus]

Re: Compound FB Radius measurements.

I do not know the answer, but my guess is that the 16" is measured at the 12th fret like you said, and then the radius remains 16" to the end of the fretboard.

This would be a compound radius from the first to 12th fret , and a constant radius from teh 12th up, which would be the most hellish setup nightmare ever concieved.


As a general rule, the measurements are taken at the nut and the 21st /22nd /24th fret. Anything else is adding an unnecessary potential for errors.

 

[jumble jumble]

Re: Compound FB Radius measurements.

They usually say it's at the "heel", which isn't very precise at all really. I usually take this to mean the 21st fret, because the 22nd fret is on an overhang so is actually past the heel.

You can't have compound radius for a while and then constant radius after that, it would be impossible to get the strings to run over the frets properly. It has to constantly change all the way from nut to bridge.

I wrote this a while back, it'll do the maths for you, although it's very basic:

http://www.jumbleguitar.com/neckRadius.html

The values that it defaults to are 10-16 at nut and 21, and then when you hit the calculate button it'll show you what the radius is at certain key points on the guitar, including the bridge. You can see that if you change the 16" measurement from the 21st to 22nd fret, it results in a difference of 0.2" radius at the bridge. In terms of actual string height, a difference from 18.34" to 18.54" radius (roughly a 1% change) is well outside the realms of what you would actually notice when playing.

 

[Lazarus1140]

Re: Compound FB Radius measurements.

You can't have compound radius for a while and then constant radius after that, it would be impossible to get the strings to run over the frets properly. It has to constantly change all the way from nut to bridge.

That is perfectly logical. That's the last time I'll guess instead of thinking at work.

 

[jumble jumble]

Re: Compound FB Radius measurements.

If you really want to get into the maths of it, I wrote this article about it a couple of years ago. A bit nerdy though.

http://www.jumbleguitar.com/2012/04/17/bridge-logic-revisited/

 

[Lazarus1140]

Re: Compound FB Radius measurements.

^ Nice!

 

[J E C]

Re: Compound FB Radius measurements.

Thanks guys I really appreciate all the input. I was pretty sure that the 16" was close to the heal. Just making sure, and I wasn't sure if there was an industry standard that says "The 16" radius is measured at fret X". So it sounds like "Point X" is a generalized position. LOL I had don some rough calculations based on the 16" being at the 22nd or 24th and determined that at the bridge it would be about 18".
I am about to build a machine for radiusing necks. Most of the pre design work is finished and I have most of the materials. It will be adjustable and able to do standard and compound/conical radiuses on guitar and bass necks and FBs using a router. I will keep you all up to date on its progress.
Once again.... Thank you! John

 

[J E C]

Re: Compound FB Radius measurements.

Jumble, just read your post/blog on the calcs you did. WOW excellent! I never had trig or algebra, so you about fried my brain! LOL I went about it a different way. I will do it again and post how I went about it, just for kicks.