Use this formula it will get you real close to your desired weight.
EXAMPLE:
The bow is 68" long,45 lb.@ 28",you want 55 lb @ 28"
55lb divided by 45 lb = 1.22(1.22%)
Lose the 1 (100%)
0.22 divided by 5 = 0.044
0.044 x 68" = 2.99"
2.99" divided by 2 = 1.495
So take 1.495" (almost 1 1/2") off each end.
To find out what a given reduction in length will produce:
EXAMPLE: The bow is 68" long,45 lb. @ 28",you only want to take of 2" (1"
off each end)
Take off 2" for a 66"bow
Short Way
1" x 2 = 2" 66" = 1.145 x lbs
2" divided by 68" =0.029 64" = 1.295 x lbs
0.029 x 5 = 0.145 (14.5%) 62" = 1.440 x lbs
Add 1 (100%) for 1.145 (114.5%) 60" = 1.590 x lbs
1.145 x 45 lb =51.525 lb (just over 51 1/2 lb)
Take off 4 " for a 64" bow
4" divided by 68" =.059
.059 x 5 = .295
Add 1 for 1.295
1.295 x 45lb = 58.275
Take of 6" for a 62" bow
6" divided by 68" = .088
.088 x 5 = .44
Add 1 for 1.44
1.44 x 45lb = 64.8
Take of 8" for a 60" bow
8" divided by 68" = .118
.118 x 5 = .59
Add 1 for 1.59
1.59 x 45lb = 71.55