I'm trying to improve my set up, aren't we all. So what I have is a 1970/80'S 55# Bear Grizzly. My draw is 29" and I am looking for alluminum shafts to fit it. I have been putting numbers in Stu's calculator and coming up a couple of options. One is 2213 30"bop, 3*5 fletching b50 string, 125gr point and cut to center. Tells me I'll get 204fps but only 7.7gpi. I always see 10gpi as a magic number and 23% less than that seems a lot.
I have tried wood and can't seem to get them to fly well and can't afford carbons. Aluminums have flown well in the past including 2114 and 2016.
Any thoughts or suggestions would be appreciated.
I can't help you because I don't know a lot of technical specs but what is your setup doing now? Just a little more info might help determine whats wrong. :)
I have a mixed bag of arrows, mainly woodies, that I have been flinging around. They are close but not close enough for hunting. I want to get a set that are consistent and stick with them. Current stuff is not good enough for comparrison unfortunately.
Do you mean accuracy wise? Porpoising fish tailing?
The first 2 numbers in the aluminum designation indicates shaft diameter and the second two are wall thickness.I much prefer narrower shafts,for penetration and thicker walls for strength.I think a 2016 would be a good choice or maybe a 2018,with a slightly heavier point.
You say your bow is cut to center which is zero (0) on Stu's calculator, but you didn't state how thick in inches your strike plate is. If the strike plate thickness is not subtracted from the cut to center number (0), then the 2213 is most likely going to be the wrong arrow since the number should be a positive (+) number such as (+1/16) which is +0.0625 or (+1/8) which is (+0.125).
When using Stu's calculator, the strike plate thickness has to been figured in for the correct Center Cut/Strike Plate Position number.
Bow is cut to center, so when working the numbers on the calc I have been playing with the shelf number. I increase it to weaken the needed spine of the arrow. It is good for getting closer to the 2# number that is recomended between bow and arrow..
What I am looking for is a good match to then fine tune. The arrows I am shooting now I can group out to about 10yrd but after that they are all over the place. Want the consistency of the aluminum shafts to then fine tune. Am concerned about the gpi for down range power.
Latest numbers I've run are;
2117, 30"bop, 145gr head, 25gr insert, 3*5 fletch total of 65.3 dynamic spine.
55# grizzly, b50 string, 29" draw, center cut for a dynamic spine of 65.6.
Total weight of 549gr, 9.4 gpi, 13.9 foc, 184 fps and 41.3 ft/lbs of energy
Seems like better numbers to me than some of the other mixes. Now have to get the components put together and see how they fly.
How does it sound to you guys.
ttt
I'll give you my example using Stu's calculator for both of my recurves.
A Blacktail recurve's shelf is cut 3/16" past center. That's (-3/16) or it's numeric equivalent of (-0.1875).
I'm using a velcro strike plate which is 1/8" thick (2/16") and on the calculator that number is (+0.125).
I have to subtract my strike plate's thickness from the cut past center distance. So, (-0.1875) minus (+0.125) gives me a negative number of (-0.0625).
This number (-0.0625) is -1/16 and this is the correct number for the Center Cut/Strike Plate Position for my Blacktails.
thanks NW, I have a good appreciation of the calculator and shelf width. What I am looking for is a confirmation on gpi for differnt set ups and any suggestions for combinations.
I have a similar setup and draw length and have always shot 31" 2117 with 125 gr. head and they work very well.
John
Razor,
It's not GPI. That stands for "grains per inch". The number you mean is GPP which stands for "grains per pound". You can see that in my signature.
GPP is determined by taking the overall grain weight of the arrow divided by the poundage you shoot.
Find an aluminum that spines around 70#s, cut to 30"s and shoot 125 grain point weight, bet it is on the money. Shawn
Thanks for simplifying it Shawn. :)
Arrows by Kelly used to have the best chart I have ever seen on picking a spine to shoot for woodies and aluminum. If Kelly Petersen is still around it would be awesome for him to post it. I used it for woodies for a couple years and he was always dead on! Shawn