Intersting Tuning Discovery

[SteveC]

This may be "old news" for you folks, but I've discovered something while tuning my arrows to a new to me bow. I made a post regarding a tuning question, that the bare shafts show slightly stiff. The fletched arrows and bareshafts have the same point of impact at 20-25 yards. (Didn't check any further).

I just realized that adding weight on the BACK of the arrow adds stiffness the the arrow. This is per Stu Millers and 3 rivers dynamic spine calculators. My arrows spine at 60lbs bareshafted, but per both of the calculators, my arrows spined at 62 lbs, which is 2.2 lbs of what my bow comes up.

So per my observations, not only are the feathers stabilizing the arrow but also causing more stiff arrow. Play around with Stu Millers calculator and you will see.

[Over&Under]

Yup...I always try and bare shaft ever so slightly weak as the feathers and wrap stiffen slightly
👍🏽

[Hermon]

Yep.  Any weight on the rear of the arrow makes it dynamically stiffer.  Weight on the front makes it dynamically weaker.

[lt-m-grow]

Is it the weight making it more dynamically stiffer in the rear or is the fletching stabilizing it faster thus reducing paradox?  The latter result would be very similar to a stiffer dynamic shaft if true.

[Hermon]

With fletching I think it is both.  With a bare shaft if you add weight to the rear you increase total arrow weight and would slow down the limb as they return to brace.  If you move weight from the front to the rear (keeping same total arrow weight), there would be less resistance at the front of the arrow (Newton's third law) so the arrow would act stiffer.  Not a scientist, but my thoughts.

[Friend]

Adding weight to the rear of the arrow stiffens the shaft.

Adding wt to the rear reduces FOC thus the fletching imparts less control due to reduced stabilizing pressures from having a shorter lever arm.

[Wheels2]

You can remove the nock of carbons and aluminum arrows and add a BB or three into the nock.  A drop of super-glue holds them in place.  They weigh 6 grains each

[fujimo]

weight at the front of the arrow resists the imparted energy from the release of the string, forcing the shaft to flex more.- weaker dynamic spine

extra weight at the back of the arrow- resists the imparted energy in the same way- but it does not force the shaft to flex as much- hence a stiffer Dynamic spine