Compund Radius And Bridge Radius

[Grand Weepers]

I'm looking at ordering a neck from USACG's and thinking about going with the 7.25" to 9.5" compound radius. My question is where are these measurements taken from and how does that effect the radius of the bridge? Of course the radius at the first fret is 7.25" but where does it reach 9.5"? At the 12th fret? End of the fretboard? And how does this impact the choice of bridge radius. If it's 9.5" at the 12th fret then it should probably be about 12" at the bridge?

Whats the deal?

Thanks,

Chad

[MescaBug]

Compound radius means, in your case, 7.25" at the nut, and reaches 9.5" at the heel (end of the board).

About the bridge; it depends on the bridge itself. Bridges are usually between 10" and 14". I usually try to match the radius with the nut and the bridge for a low action. Example;

10"-14" compound radius on a Floyd Rose guitar; 10" matches the locking nut radius and 14" matches the Floyd Rose tremolo radius.

Is there a reason why you want a compound radius? Because you don't seem to know what it means... I'm just curious.

[soapbarstrat]

Assuming we're dealing with typical neck widths, I'm pretty sure you're going to want the bridge radius set at about an 11" radius. I'm not looking at actual numbers, just going off the top of my head, because I do full set-ups on conical radius neck guitars often enough and the 11" seems familiar for a neck with those radii.

To simplify what's going on, just imagine if the fret-board just continued right up to the bridge, with the same tapering of the radius.

[erikbojerik]

If you use a TOM-style bridge, you'll probably end up having to tweek the slot depths on the saddles. Any kind of bridge with individually adjustable saddle heights should get you there no problem.

[Grand Weepers]

Is there a reason why you want a compound radius? Because you don't seem to know what it means... I'm just curious.

I understand what a compound radius is, and I see the advantages of it.

What I'm saying is that a compound radius would mean that the strings are conical in shape instead of cylindrical. So, if the radius is 9.5" at the neck heel then the radius at the bridge would have to be even flatter than that. Soapbarstrat seems to get what I'm saying.

Matching the radius at the neck heel to the bridge radius is a good way to ensure that you won't be able to have the best possible action. But, not being a calculus whiz I can't come up with a good way to calculate what the bridge radius should be to maximize the conical effect and keep the action as low as possible.

I'm not sure that I'm going to go with a compound radius, but it would make bridge choices a bit easier since it opens up some TOM's if my guess is correct.

Edited April 15, 2008 by Grand Weepers

[DivebombInc]

Actually if you have a compound radius of 7.25" to 9.5" at the heal then your bridge is going to be even flatter then that. If your strings are following the radius of the neck as they should then the radius at your bridge is going to be more like 10.5" to 10.75". I'd have to CAD it to really see how it works out. Your strings continue on a flattening path past the heal so you have to calculate for that. I do a lot of 12" to 16" compounds and they work very well with Floyd Rose tremolos.

[soapbarstrat]

The 7.25 will be at the nut and the 9.5 will be at the 21st or 22nd fret. And you don't have to buy a new neck to get a compound radius like that. Take just about any 7.25 strat neck and it's not a whole lot of work to turn it into a 7.25 to 9.5 compound radius.

[j. pierce]

The stew mac fretting book has the formulas for figuring this out - I'd have to dig out my copy to figure it out - I believe you can figure it all out with the Pythagorean theorem, but I'm not certain...