Help Choosing Bracing Pattern

[Walt]

I'm currently building two mandolins: (1) a standard 13.875 scale mandolin for a friend, and (2) an 11" scale mandolin for my three-year-old daughter. These are identical, with the exception that mandolin (2) will be scaled down 80% and will have only 4 strings.

I'm having trouble selecting a bracing pattern. I am more concerned with the standard scale instrument, since the smaller copy will have, by design, very low string tension.

Here are what I think are the relevant specs:
(a) the mandolins will have flat tops. I will try to induce a slight arch (15in radius) with the braces. I'm planning on leaving the top thickness at around 0.125".
(b) the mandolin will only have a single treble sound hole. It's really four individual holes, but I'm treating them as one unit. See pics.
(c) the mandolin will have an elevated fingerboard. For all intents and purposes, it will be an A-5 with a flat top and back. I know this will probably increase the break angle and tension.

Here are the bracing ideas I am considering. The red lines are the braces. The black cross section indicates the location of the bridge.

TONE BARS



X BRACE



MODIFIED X BRACE



H BRACE



X BRACE WITH TRANSVERSE BRACE




Any feedback is greatly appreciated. And I'm very much open to other ideas as well. Thanks!

[pops1]

I think any of these patterns would work well except the X pattern. With the bridge sitting on the center of the X there would be no support for the top for the bridge at the feet, even if it were a full contact or one piece. Since it is a flat top and needs the support I would not use this pattern.

[sunburst]

This is just my opinion, but I'm not crazy about any of them.
I would go with an X, but I would move it toward the neck so that the braces cross toward the neck from the bridge position. I would splay the braces wider toward the neck and tailpiece. It would be much like your "modified X brace" but splayed wider in the fore and aft direction.
I'm trying to find a picture to illustrate, but so far I haven't found one...

[Walt]

This is just my opinion, but I'm not crazy about any of them.
I would go with an X, but I would move it toward the neck so that the braces cross toward the neck from the bridge position. I would splay the braces wider toward the neck and tailpiece. It would be much like your "modified X brace" but splayed wider in the fore and aft direction.
I'm trying to find a picture to illustrate, but so far I haven't found one...

John, something like this? I have everything in Adobe Illustrator, so I can quickly change the layout.

[sunburst]

Yeah, something like that. I think you get better support for the bridge, and (normal) spruce is plenty stiff lengthwise, so it doesn't need as much bracing in that direction as laterally.

[Marty Jacobson]

Your soundhole design is stressing me out... :-)

[pops1]

Your soundhole design is stressing me out... :-)

I don't mind your soundhole design, but I would move it to the bass side so the player can more easily hear it. I had a Woodley with one sound hole on the bass side, liked it a lot.

[Walt]

Your soundhole design is stressing me out... :-)

Hahaha! That's what I'm calling the implied f-hole. I'm a bit stressed out thinking about cutting it out. I'm thinking I might need to reinforce it somehow.

[Walt]

I don't mind your soundhole design, but I would move it to the bass side so the player can more easily hear it. I had a Woodley with one sound hole on the bass side, liked it a lot.

I really like the one sound hole look. I thought hard about putting it on the bass side. I ended up moving it to the treble side, so it can be more easily mic'd, and I'm putting a soundport in the bass side rib.

[Walt]

Assuming an X pattern is used, does anyone have thoughts on where the braces intersect the bridge? E.g., should they intersect the very edge of the bridge, or further inside? For the pics below, the bridge is represented by the green line.

Edit: Also, the bridge will be full contact.

WIDE X



WIDER X



WIDEST X

[Drew Streip]

Somewhat related? Maybe? Interesting shot of the new Northfield flattop bracing... almost akin to the Taylor V-class bracing discussed here recently. Good luck!

[Walt]

Somewhat related? Maybe? Interesting shot of the new Northfield flattop bracing... almost akin to the Taylor V-class bracing discussed here recently. Good luck!

Interesting, thanks for posting. That's very similar to the flat top bracing in Graham McDonald's book. I picked up the digital copy this morning. I was sort of basing the "H Brace" above on that idea, only I couldn't extend the transverse across the face of the entire instrument because of the sound hole placement.

[Marty Jacobson]

You shouldn't need to reinforce the soundhole the way you have it there.
I do think there is a lot you can do to make it look more intentional... I've been designing these things for fifteen years and sound holes take more time than anything else. I like the concept, the "implied f-hole" is genius. I just wasn't getting the point of it without your explanation.
If you're married to it as is, that's fine. But I would be happy to help you refine it (while keeping it entirely your original design) if you're interested.

[Graham McDonald]

I would be inclined to move the bridge position back to somewhere closer to the middle of the soundboard. I think the most important thing in bracing flattop mandolins is to cope with the compression of the tailpiece longitudinally up the body and to offset the sinkage under the bridge. This where I think the H bracing might be a good solution. I would worry about cantilevering the fingerboard and a high bridge. This puts even more downwards force on the soundboard. A 15' radius on the soundboard gives you a couple of degrees back angle on the neck with the fretboard sitting on the soundboard and that will give you around a 1/2" bridge height. Less downwards pressure on the bridge means the bracing can be lighter and the instrument more responsive.

Walt, always happy to discuss stuff in the book by email. Thank you for buying a copy.

Bemused that Northfield seems to have copied my bracing pattern. Mind you it owes a lot to the old Gibson Army/Navy mandolins of a century ago, but perhaps I should suggest a royalty anyway.

Cheers

[Walt]

But I would be happy to help you refine it (while keeping it entirely your original design) if you're interested.

Absolutely, Marty! I'll send you a PM.

[Walt]

Walt, always happy to discuss stuff in the book by email. Thank you for buying a copy.

Thank you, Graham. I will definitely reach out. The body shape and bridge placement was based on the Griffith loar, so it definitely has that forward-positioned bridge thing going on. I have already bent sides, but there's still time to make adjustments to the neck design, I think.

[j. condino]

Having played the Griffith Loar and heavily spec'd it out, I can comfortably say that there is absolutely no reason to mess with the design- the tonebars and forward shifted bridgework great!!!