Versatile arching jig

I designed a brace arching jig based on the one used prominently by Jon Sevy in his great tutorial, which he attributes to American Lutherie:

It's also based on The Long Compass. While the curve produced by this method is actually elliptical, at large radii it is a very close approximation. I combined these concepts into a shooting-board-like jig that can be used with a hand plane or modified to work on a table saw or band saw. I chose a hand plane because most bracing material is soft and a hand plane will cut through them like butter.

I drilled 7/64" holes along a line, spaced 1" apart, for use with 3/16" shelf pins. You space the pins for the length brace you need and deflect the brace by the amount for desired radius, then lock the toggle clamp. See the tables below for brace length and deflection distance.

Once clamped in, you plane the outside edge of the brace until it's flat, parallel to the jig. When you release the brace, it springs back into a graceful arch.

The exact dimensions of the block aren't critical, but I made my jig roughly 24" long and 8" wide using a piece of hardboard for the base and two scraps of plywood.

Length represents the length of the brace, or the chord across the arc, really. D is the distance by which you must deflect the brace (inward) in the center to achieve the desired radius.

40-ft radius:

Length	D (inches)	D (16ths)	D (32nds)	D (64ths)
1	0.000	0	0	0
2	0.001	0	0	0
3	0.002	0	0	0
4	0.004	0	0	0
5	0.007	0	0	0
6	0.009	0	0	1
7	0.013	0	0	1
8	0.017	0	1	1
9	0.021	0	1	1
10	0.026	0	1	2
11	0.032	1	1	2
12	0.038	1	1	2
13	0.044	1	1	3
14	0.051	1	2	3
15	0.059	1	2	4
16	0.067	1	2	4
17	0.075	1	2	5
18	0.084	1	3	5
19	0.094	2	3	6
20	0.104	2	3	7
21	0.115	2	4	7
22	0.126	2	4	8
23	0.138	2	4	9
24	0.150	2	5	10

28-ft radius:

Length	D (decimal)	D (16ths)	D (32nds)	D (64ths)
1	0.000	0	0	0
2	0.001	0	0	0
3	0.003	0	0	0
4	0.006	0	0	0
5	0.009	0	0	1
6	0.013	0	0	1
7	0.018	0	1	1
8	0.024	0	1	2
9	0.030	0	1	2
10	0.037	1	1	2
11	0.045	1	1	3
12	0.054	1	2	3
13	0.063	1	2	4
14	0.073	1	2	5
15	0.084	1	3	5
16	0.095	2	3	6
17	0.108	2	3	7
18	0.121	2	4	8
19	0.134	2	4	9
20	0.149	2	5	10
21	0.164	3	5	11
22	0.180	3	6	12
23	0.197	3	6	13
24	0.214	3	7	14
25	0.233	4	7	15
26	0.252	4	8	16
27	0.271	4	9	17
28	0.292	5	9	19
29	0.313	5	10	20
30	0.335	5	11	21