dynamic spine- point weight vs shaft length.

[ozy clint]

been doing alot of tuning in the last year or so, setting up a few different arrow setups for my border recurve, (see signature)

i'm using axis arrows. i've found that the dynamic spine is much more sensitive to changes in shaft length than changes in point weight. i may have to shed 100-200gr of point weight to see a stiffening effect. i've been confirming the need for shaft trimming by using lighter points till flight is good.

now i don't fuss about bh's not being exactly the same weight. they have to be different by alot to matter.

what's your findings? how much shaft length trimming/gr's of point weight?

[katman]

Don't have an exact length/gr # but yes carbons are more sensitive to length changes. Also the axis being a skinny shaft and the border cut past center the makes it less sensitive to slight changes. About 50 grains gives me a dynamic spine change I can repeat with bare shaft if I am close but if way off on spine not so much. Very good thing to confirm weak with lighter points before cutting.

[Orion]

I shoot Easton Axis shifts out of my ACS longbows.  I don't know what the inch fractions vs grain weight ratios to dynamic spine might be. I don't use shortening to tune the arrows to the bow.  I cut them to the length I want ( 1 inch beyond the riser at full draw) and tune with point/insert and adaptor weight, and sometimes side plate and brace height adjustment.  

That being said, I can take two axis shafts, each with the same amount of up front weight, about 275 grains, one an inch shorter than the other, and they both shoot the same to the naked eye.  Granted, these are fletched, not bare shaft.  

I've also found that I can vary the point weight by at least 50 grains on the same length shafts, all other things being equal, with no noticeable difference in flight. Also with fletched shafts.

They shoot like lasers in both cases. And I'm not a rookie in judging arrow flight.  Been at this for nearly 60 years.

What I'm finding, in short, is that these shafts are very adaptable and forgiving with high performance bows cut past center, as long as you have enough spine to begin with, or more precisely, as long as you're overspined quite a bit.

[LostNation_Larry]

I have noticed the same with other carbons.  My guess would be 50-75 grains equal 1" length difference, but I don't have any good testing to verify.  Great question.

[Steve O]

I keep my carbons full length. I found them VERY stiff when I was cutting to tune. I've also found point weight makes a much bigger difference than nock weight.

[Ray Hammond]

me too, Steve O. I buy the stiffest ones they make, and I just keep stacking weight up front until they fly right...no need to shorten them.

[damascusdave]

I tune until I get a combination that works...I have no idea about any equivalency between change in point weight and change in length...I pay absolutely no attention to such things

DDave

[Tedd]

Me too. But I have a long draw. I can't see how people are shooting .400 and .500. I use .300 and my AD trade are something like .275.
The need to make all carbon shafts 1" longer!!!!!

Tedd

[Pivo]

I shoot a CE 350 heritage old style which are .320 spine at 32" bop and 250gr w a reg insert with only 60 lbs. I tried to bareahaft tune 250's and they got too short w the same weight. I bet a 350 at 28" with the same weight would be good past 70lbs.  Length makes a huge difference in carbon w a lot amount of weight up front my opinion.

[ozy clint]

interesting observations guys.

lost nation's 50-75gr per inch of trimming is somewhere close to what i've been experiencing.

i've had full length shafts fly good with 125gr points and i've had to cut 4-5" off to get them to work with 300gr points

[Orion]

Ozy:  If your draw length is such that you can shorten the arrows that much to get good arrow flight, no problem.  On the other hand, you could also just move up one spine range.

[ozy clint]

i have have a 26" draw so i'm able to trim down to about 27".