My FOC and what it means...
04-24-2006 | 12:57 PM
#1
Thread Starter
Fork Horn
Joined: Nov 2004
Posts: 204
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From: Maine
My FOC and what it means...
I just calculated my FOC and it came out negative...is it supposed to be an absolute value or is there something terribly wrong??
I followed the instructions to a T...
balance point = 17 7/16
Total Length = 30 1/16
30 1/16 / 2 = 15 1/32
15 1/32 - 17 7/16 = -2 13/16
-2 13/16 / 30 1/16 = -8%
I am shooting aluminum XX78's (2317)
Shooting 68-70 lbs
100 grain FP's and BH's
Any help would be great!
I followed the instructions to a T...
balance point = 17 7/16
Total Length = 30 1/16
30 1/16 / 2 = 15 1/32
15 1/32 - 17 7/16 = -2 13/16
-2 13/16 / 30 1/16 = -8%
I am shooting aluminum XX78's (2317)
Shooting 68-70 lbs
100 grain FP's and BH's
Any help would be great!
04-24-2006 | 01:05 PM
#2
Giant Nontypical
Joined: Feb 2003
Posts: 6,455
Likes: 0
From: Burleson TX USA
04-24-2006 | 01:16 PM
#3
Joined: Feb 2006
Posts: 2,877
Likes: 0
From: Kodiak, AK
RE: My FOC and what it means...
I suspect that you measured your balance point from the wrong end of the arrow. Unless you've got some seriously heavy cresting wraps and large vanes that FOC should actually be +8%.
04-24-2006 | 01:23 PM
#5
Giant Nontypical
Joined: Feb 2003
Posts: 8,318
Likes: 4
RE: My FOC and what it means...
I think you got your two figures backwards....
17 7/16 (17.4375 decimal) - 15 1/32 (15.0312 decimal)= 2.4063
2.4063 * "100" = 204.63
204.63 / 30 1/16 (30.0625 decimal) = 6.8068191....
17 7/16 (17.4375 decimal) - 15 1/32 (15.0312 decimal)= 2.4063
2.4063 * "100" = 204.63
204.63 / 30 1/16 (30.0625 decimal) = 6.8068191....
04-24-2006 | 02:00 PM
#6
Thread Starter
Fork Horn
Joined: Nov 2004
Posts: 204
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From: Maine
RE: My FOC and what it means...
Determine FOC:
To find the FOC (which is always expressed as a percentage) divide the overall length by two. This should produce the physical center of the shaft. Now subtract this number from the balance point and divide by the overall length. Multiply by 100 to express the fractional value as a percentage.
Most expert archers agree that an FOC value that is between 7 and 10 percent will produce the best compromise between stability and a flat trajectory. The American Society for Testing and Materials, in their specification for measuring balance point, state that a value of 9% is typical. But, they also state that the range can be as wide as 7% to 18% while still producing good arrow flight characteristics.
To find the FOC (which is always expressed as a percentage) divide the overall length by two. This should produce the physical center of the shaft. Now subtract this number from the balance point and divide by the overall length. Multiply by 100 to express the fractional value as a percentage.
Most expert archers agree that an FOC value that is between 7 and 10 percent will produce the best compromise between stability and a flat trajectory. The American Society for Testing and Materials, in their specification for measuring balance point, state that a value of 9% is typical. But, they also state that the range can be as wide as 7% to 18% while still producing good arrow flight characteristics.
Does anyone know off hand...
GPI of XX78's
weight of 4" duravanes
nock weight of uni-nock's
04-24-2006 | 04:28 PM
#9
Giant Nontypical
Joined: Dec 2004
Posts: 7,876
Likes: 0
From: Ohio
RE: My FOC and what it means...
17.4375/30.0625=0.58004... Anything over .5 is the foc yours is 8004... Percent. I don't go from the crotch though. The end of the nock doesn't drop off every time why not count it.
04-24-2006 | 04:36 PM
#10
Thread Starter
Fork Horn
Joined: Nov 2004
Posts: 204
Likes: 0
From: Maine
RE: My FOC and what it means...
7.5 to 8% is what I calculated too...thanks for the help guys...
I was reading in the bowhunting folder that people were finding 10-12% to work better for them...do you think it would be advantageous to try and go with a heavier head to raise my FOC to that range?
I was reading in the bowhunting folder that people were finding 10-12% to work better for them...do you think it would be advantageous to try and go with a heavier head to raise my FOC to that range?