I'm hoping to shoot cedar arrows from my 50 @ 28 Pittsley Predator recurve. I draw 28". I want to end up with a 125-150gr broadhead and a 30" bop arrow. I tried the spine calculator but was unsure how to enter the correct wood arrow selections. I came up with 70-75? Does that sound right? Thanks in advance.
50@28 +5 (recurve) +5 (center-cut) +10 (2" pass 28") Yes 70-75 sounds good.
Wood arrows can be funny things - they can be sensitive to your rest and release style. I'm drawing 30" on a recurve marked 52#@28" (so, figure 56# or so at full draw) and it prefers cedars of 60-65# with a 125gr head. It's cut a little past center but I build it up with a furniture rug pad sliced thinner with a single-edge razor.
I also have a bow marked 55#@28" and that one prefers 65-70# shafts (same 30" draw w/30-1/2" BOP shafts with 125 gr heads). And a bow marked 48#@28" that prefers those same 65-70# shafts.
One spine range will shoot where you are looking and give smooth flight. That's the one to use regardless of what a table says.
Some insurance company has a table that says you'll live to be XX years old. It's based on historical averages. Your results may vary.
It usually works with a deep-cut shelf to err on the side of heavier - but not always.