View Full Version : calculate my arrow speed?

03-21-2011, 11:44 AM
I tried to use the calculator on the Backcountry site,but my phone doesn't support Adobe flash. If someone could punch the numbers for,that would be great.

Cams- single Mpro on Cheetah(315-320 ibo) Binary cams on Athens Accomplice 34(330+ ibo,7"BH,80% LO)
Arrow-Harvest Time Archery HT-2 @ 7.6gpi
Arrow length-28"
dipped w 3-2" Blazer vains(20gr total approx.?)
String-D loop,slanted kisser,G5 hunter peep

I calculated my total arrow weight as follows:
7.6gpi x 28" + 20gr(vanes/dipped) + 100gr head = 332.8gr
".............................................." + 125gr head = 357.8gr

if I've missed anything let me know.

03-21-2011, 12:18 PM
Add nock and insert to the arrow weight. Approx. 25 grains. And whatever you have on the string such as peep, loop, kisser button, string silencers.

Arrow Splitter
03-21-2011, 12:26 PM
281 fps

273 fps

03-21-2011, 12:31 PM
Had a brief minute waiting for a download, so ran it thru the Software for Archers program. http://www.pinwheelsoftware.com/sfa.aspx

Harvest Time Archery HT-2 340 arrow
100gr: 347gr 12.51% F.O.C.
125gr: 372gr 14.96% F.O.C.

Athens Accomplice34
100gr: 289 fps
125gr: 281 fps

Martin Cheetah
100gr: 267 fps
125gr: 260 fps

All numbers posted here are for are reference only, based on info provided, mfr info in database and mfr claimed IBO in database
(actual individual results may vary :) )

03-21-2011, 12:42 PM
thanks guys. I just wanted an idea. Not particular on speed. Both of my bows are great shooters. There are more important things than speed,IMO

03-21-2011, 01:06 PM
Oh......just an FYI, but appears the spine is good with boths bows also.
Shows a bit stiff with the 100gr point on the Cheetah, but that's not an issue

03-21-2011, 03:14 PM
it should be good either way. They're actually 400 spine HT-2's. I can't wait to shoot them. They look to be of very good quality at a great price.

03-21-2011, 03:42 PM
Then disregard what I said about spine.......and I guess the rest of it too for that matter.
I made a mistake and "assumed" 350 (not 340) based on the grs/in mentioned, which the 350 showed 7.3 in the database, and 6.7 for the 400.
Not being familar with Harvest Archery, I just looked up the arrows.....website shows a bit heavier than the program database.

The 400 is probably fine for the Cheetah, but have some doubts it's stiff enough for the Athens, especially with a 125gr head, but only shooting it will tell for sure.

03-22-2011, 06:33 AM
I'm a bit confused. With both bows at the same draw length and weight, why would they be ok for one but not the other? Also, if I went w 27" instead of 28", will that 1" diff change the spine? I've got a couple easton flatline 400 @ 7.4gpi that fly great out of both bows. I'd like to set the arrows up to shoot effectively from both bows so I can just grab one bow or the other and shoot. I've got a decent selection of arrows to use. Gold tip 5575, Blackhawk Vapor 4000, carbon express predator 4560(came w the Cheetah),carbon express 2216 aluminum...think that's it

03-22-2011, 07:25 AM
All bows are not created equal. Different bows have different cams, with different efficiencies, creating different affects and/or requirement for the proper arrow.
There is a reason the 2008 Cheetah is IBO rated 310 and the Athens is rated 330
It's sort of like the old apple to oranges comparison.

Same goes for arrows. Different manufactures may claim the same 400 range spine, but they are not all necessarily exactly .400 spine. Not considering manufacturing variables, you still have differences in inserts and/or nocks used, each of which cause balance changes and varied stresses on the spine of the arrow.

Now chances are if you get an arrow stiff enough and flying well out of the highest performance bow, even technically being too stiff for the lower performing bow it will still fly well.
But the other way around using an arrow that is too weak in the higher performing bow may cause more erratic arrow flight problems

Download that demo program on the link, input your info and you can see how each of those arrows perform (in theory)

03-22-2011, 10:59 AM
makes perfect sense. I appreciate the detailed, no BS explainations people get in response to questions. It makes learning fun. Thank you