Targeted Bow Design Brace Ht

[Friend]

Take  two different performance bows with nearly identical specs - the same poundage, same shelf , same string, same limb material,  same speed with same arrow and the difference being in the design which accounts for a targeted brace ht on one at 7” and the other is designed for 8 ¼”.

The bow with the 8 ¼” brace ht., even with a ½” brace ht. reduction, shoots the arrow extremely weak. The bow with the shorter 7” BH shot the same arrow slightly stiff.  Adding six twists to the string was all that was required for great arrow flight.

The above finding may be an anomaly or is it. Yes, shorten or lengthen the brace height will definitely impact the spine. Should the initial designed targeted brace height for a particular bow be a significant factor in specking out an arrow?

[Shaun]

Brace height will change the length of the power stroke and also the paradox angle. Degree of "cut to center" or even past center will have even more effect.

[Orion]

Yes.  What Shaun said.

[Friend]

Typically we speck out an arrow to match the dynamic spine with the arrow dynamic spine required for the bow.
We consider the following factors:

   Arrow Type (spine, dia,)
   Arrow Length
   Point Wt
   Insert Wt
   Footing
   Nock Wt
   Fletch Type
   Wraps
   Total Arrow Wt
   GPP
   FOC

   Bow Type
   Rated poundage @ 28”
   Actual Draw Length
   Shelf with respect to center
   String type

Once we find a match in reality, we may adjust Brace Ht to fine tune.

No where have I seen that the initial brace ht recommendation for a particular bow design as being considered in specking out an arrow.
May be I am totally wrong, however I am of the opinion that bow designs with intended brace ht’s that are significantly different will
notably effect the dynamic spine requirement. To ignore this, is the same as saying that every bows target brace ht no matter where it is, are equal.