Offset hole - brace question

[ken cierp]

Here's my "SWAG" assesment --- scientific wild ass guess"

The one on the left, with only two "A" frame braces positioned at/under the outer wings of the bridge which I would make 6.5" or longer.
The ladder under the bridge is good but I'd add something similar in location to the standard shoulder brace. I'd also place some very thin finger braces in logical places to prevent splits along the grain. I predict it will be on the bassy side.

[Dave Bagwill]

Thanks Ken,

I wonder if the ladder brace and the UTB would benefit from the flying buttress treatment?
Do you think that stopping the 'A' braces short of the kerfing would allow that area to vibrate more easily and still retain structural integrity?
Why the 6.5" or greater bridge?

[Dave Bagwill]

That is where I got the basic idea, John. I chose to come up with a different body shape but yep, his plans were an inspiration.
His A-frame bracing just looked a little too minimal, is why I started this thread. I was, and am, tempted to try Lowden's 'dolphin' system but will save that for a normally - placed soundhole instrument and go with Mottola's A-frame, only I'm going to try the 4 brace A. Very very light braces and as Ken suggested, some small finger braces and an UTB.

[John Parchem]

I agree I would like to see a UTB under the fretboard. Or maybe with a 2-3 mm spruce patch under the fretboard with the As notched over them.
When I saw your 4 brace A, I was wonder what the 2 braces outside of the bridge area would do. I would rather make the 2 As just a bit taller if I was nervous about the structure. Stiffness increases by the cube of the height but only proportionately to the width. For any brace height making the 2 inside braces 1.3X taller would give you the same stiffness as 4 braces. I am just not so sure the outside ones would give support much support against string tension. I guess if they were thin enough they can act like non-structural fan braces.

[Dave Bagwill]

Thanks John. I appreciate your input.
Looking at Mottola's plans some time ago, I was a little puzzled . I understood the A-frame concept, which Tacoma used successfully, and which does simplify construction and provide excellent support for the bridge against the pull of the strings.
But I did not understand the lack of 'tone bars' or their equivalent, or some protection against cracking via finger braces.
So the outside A is not intended to be structural, but will be more along the lines of fan braces, which I can use for tonal purposes as well as crack protection.
I'm really not trying to revolutionize anything - but I do love to experiment and from what I've seen the past few years, if a fella is paying attention, he can make a bracing scheme work if he follows a few basics.

I'd love to hear more ideas about this A4 scheme before I actually do it!

[John Parchem]

Dave, This makes sense to me. It will be interesting to know how it turns out if you decide to make one.

[Dave Bagwill]

I'll start next week, as a matter of fact. I'm going to spend a couple of days with Brian Burns (lessonsinlutherie.com) and when I get back, join up some redwood for the top and eir for the back and get 'er going. Thank goodness it's getting cooler.