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CarlosII
02-23-2011, 04:08 AM
I'm not too good at the science of archery so I thought I'd pose the question to those who understand such things.
Assuming an foc of 10% with a point weight of 75 grains in an arrow weighing 275 grains, how will a Bohning X vane shield cut 1.5 inches affect the flight of the arrow compared to the same vane 2.25 inches.

I hope that's clear and I hope someone can provide some insight.

RLW
02-23-2011, 05:26 AM
I'm not too good at the science of archery so I thought I'd pose the question to those who understand such things.
Assuming an foc of 10% with a point weight of 75 grains in an arrow weighing 275 grains, how will a Bohning X vane shield cut 1.5 inches affect the flight of the arrow compared to the same vane 2.25 inches.

I hope that's clear and I hope someone can provide some insight.

Sound like a P.I.A. math problem I would have had 30yrs ago.......

By switching vanes all the other variables change. The 1.5 vane is claimed to be 3.0grs, the 2.25 vane says 5.5 grs.
You've just added 7.5grs to the rear of the arrow, effectively lowering your 10% FOC. To what? I don't know without the arrow/length, but maybe lost 1% or more, and the extra weight has also dropped initial arrow speed maybe 2-3 fps.
But even if you forget all that and assume every else stayed equal, going from 1.5 vane to the 2.25 vane will create more drag. Larger vane may stabilize the arrow better but will slow it faster and drop faster, and that is affected more or less by how much, if any, offset the vanes have to..........bottomline, getting progressively worse the farther it goes, you maybe ended up loosing 5-6fps and arrow hit 2-3" lower way out at 60yds

Other than the lower than I personally like FOC, really not that much practical difference

elkslayer4x5
02-23-2011, 09:58 AM
As I read it, he's going the other way From 2.5's to 1.5's, so he's loosing 7.5 off the back end and increased his foc % ( sorry Sonny ! ) by some small amount. :D

RLW
02-23-2011, 10:13 AM
Ok, then if going from a 2.25" to 1.5" ....would be the bass ackwards version of what I typed.

CarlosII
02-23-2011, 11:08 AM
Actually, I was inclined toward going with the longer, heavier vane. Since my shooting is mostly 3D out to 40 yards max, I'm really looking for more down-range stability. I guess I was trying to determine if the drop in FOC would off-set the increased stability.

Does that make any sense?

Thanks for the responses.

RLW
02-23-2011, 11:18 AM
what arrow, and length?

Larger vane should stabilize better, but for 3D with target/field points out to 40yds, I doubt it makes much difference. Might try a couple both ways if you can and go with whichever shoots best groups for you.

SonnyThomas
02-23-2011, 02:10 PM
I thought I posted this once or is within some link I posted. Of course FOC and personal perference doesn't always match up.

Here's a link. Search down, find auto calc. you desire. http://www.backcountrybowhunting.com/articles/tools.php

Common F.O.C.s for each style of archery.
FITA 11-16%
3-D Archery 6-12%
Field Archery 10-15%
Hunting 10-15%