'Radius" Bridge

[papawhisky]

I have come to really prefer a radiused fingerboard. It makes me wonder why the bridge is not shaped in a way that conforms to the fingerboard. Is there a reason why the bridges are the same for flat fingerboards and radiused fingerboards?

[foldedpath]

The fretboard radius is for left hand comfort, and by the time you get down to the bridge it's all about picking efficiency. A flat bridge saddle means you can focus on moving the tip of the pick laterally through the strings, instead of having to also move the pick a tiny bit up and down as you move across the four string courses on a curved saddle.

It's interesting to contrast this with fiddle technique. Fiddles have a strongly radiused fingerboard, and Classical and many other "Folk" traditions use a curved bridge to match. The fiddle bow only touches the top of the strings, not having to move through the strings to make a sound. The radius bridge allows a fiddler to only touch one string at a time with the bow. We don't have that problem on a mandolin using a flatpick. A curved saddle would just be more work for the right hand.

That's my theory anyway, and I'm sticking to it.

[Marty Jacobson]

I use a radiused bridge. It's pretty pronounced (14"), and sets up perfectly on the compound radius fretboards I make. I've never had anyone comment that they noticed a difference in the way it felt.

[illinoisfiddler]

The Kentucky KM-1500 that I have has a radiused fretboard AND bridge.

[Cobalt]

I wasn't aware of the use of a flat bridge with a radiused fretboard. In my view, such a combination would wreak havoc on the set-up, making it difficult to set the height of the strings above the fretboard in any consistent way. I had thought that the radiused bridge was a natural consequence, and a requirement of a radiused fretboard.

[illinoisfiddler]

It seems to be.

[dang]

I wasn't aware of the use of a flat bridge with a radiused fretboard. In my view, such a combination would wreak havoc on the set-up, making it difficult to set the height of the strings above the fretboard in any consistent way. I had thought that the radiused bridge was a natural consequence, and a requirement of a radiused fretboard.

I think many do a compound radius, more pronounced at the fretboard, flatter at the bridge

Or at least Collings does a compound radius...

[Cobalt]

I think many do a compound radius, more pronounced at the fretboard, flatter at the bridge

Or at least Collings does a compound radius...

I suppose a conical profile would achieve that, string-heights could be maintained consistently, and the curvature towards the nut would be tighter, as one heads towards the apex of the hypothetical cone.

[multidon]

Keep in mind that the bridge saddle may appear flat, but there could be an “induced” radius by slight variation of the string groove depths.

[Hendrik Ahrend]

I wasn't aware of the use of a flat bridge with a radiused fretboard. In my view, such a combination would wreak havoc on the set-up, making it difficult to set the height of the strings above the fretboard in any consistent way. I had thought that the radiused bridge was a natural consequence, and a requirement of a radiused fretboard.

I agree. But those bridges sag.

[Phil Goodson]

I agree. But those bridges sag.

Pretty broad sweeping statement.

[amowry]

I would always radius a bridge if the fretboard is radiused.

[Marty Jacobson]

I agree. But those bridges sag.

Not mine!

[O. Apitius]

I've been offering radiused fretboards as standard for over 40 years and the vast majority of my customers much prefer them. Not everyone of course and for those I offer a flat board at no charge. Recently though, I have moved to a conical fretboard with a tapered radius that matches the fret board's tapered width. This way each of the strings are presented with a straight surface beneath them. In an unchanging radius, the fretboard surface increasingly drops away from the strings. This results in an action that is higher than it need be as you go further down the string. Because the width of the fingerboard tapers by only a 1.3 degrees, the effect is minimal, but it is real. For my particular fingerboards, I start with a radius of 7 1/4" at the nut and end up with a radius of 12" at the bridge.

The images below help to visualize how this works. Fig. 1 shows how a straight line (string) placed at an angle to the axis of a cylinder becomes higher off the surface as we move along it's length.



Fig. 2 shows how a properly tapered or conical radius maintains a straight line contact along the entire length of a straight edge.



I actually wrote about this in my last blog of 2018 on my website.

[Old Growth]

I haven't had the pleasure of playing instruments from several of the builders commenting in this thread(hoping to one day) but, I can say the O. Apitius I am familiar with is a joy to play up and down the neck. Ease of play is outstanding.

[Hendrik Ahrend]

Not mine!

Okay, I admit, not all of them sag.

[papawhisky]

I really appreciate the comments. I’ve learned a lot. The Apitius radius makes a lot of sense. And I own a Mowry OM with radiused fingerboard so I ran over to check the bridge—sure enough it too is radiused.Thanks Andrew! I recently acquired an MT2-V. It is this mandolin that made me wonder about the bridge. It seemed flat to my untrained eye. I also feel like the E strings are harder to fret as I get past the 10th fret. I agree I may have no business up there, but still, there I was and I noticed resistance. I thought that perhaps this was caused by a flat bridge but now I understand it could also be caused by the type of radius.

I looked at Cumberland just now to see if they offered a radiused bridge, and they do. A 10 in and a 12in. I then placed a straight edge on my Collings bridge and it does seem to have a radius. Live and learn.