FOC and trajectory
07-28-2008, 06:47 PM
#2
Nontypical Buck
Join Date: Aug 2006
Location: Southern MD
Posts: 2,520
RE: FOC and trajectory
If the arrows weighed the same and had the same fletching you probably woudn't see a difference. A difference in total arrow weight will give you a different trajectory though.
I have a 533 grain arrow that is 12.63 inches high (above line of sight/aim) at 22 yards on a 40 yard shot and I have another 605 grain arrow that is 14 inches high at 22 yards on a 40 yard shot. They do have a different FOCbut the total arrow weight gives me the different trajectorys.
It is also possible that a four feather fletch with a severe helical and offset would give you a different trajectory than one with 3 blazers at a slight offset but that would be because the arrow speed is affected, more drag with the feather configuration, so the feathered arrow would have a higher trajectory.
I have a 533 grain arrow that is 12.63 inches high (above line of sight/aim) at 22 yards on a 40 yard shot and I have another 605 grain arrow that is 14 inches high at 22 yards on a 40 yard shot. They do have a different FOCbut the total arrow weight gives me the different trajectorys.
It is also possible that a four feather fletch with a severe helical and offset would give you a different trajectory than one with 3 blazers at a slight offset but that would be because the arrow speed is affected, more drag with the feather configuration, so the feathered arrow would have a higher trajectory.
07-28-2008, 07:23 PM
#4
Giant Nontypical
Join Date: Feb 2003
Location: Burleson TX USA
Posts: 6,455
RE: FOC and trajectory
Wouldn't a higher FOC cause the tip of the arrow to want to nosedive a little more, resulting in a lower hit?
With higher FOC arrows the extra weight on the front end actualy pulls the arrow through the air. Lower FOC arrows with light tips, the actual shaft has to push the tip loosing more speed and impacting lower on longer shots. Which is why high FOC arrows maintain more momentium down range.
07-29-2008, 05:46 AM
#5
Giant Nontypical
Join Date: Dec 2004
Location: Ohio
Posts: 7,876
RE: FOC and trajectory
Do it. Depends on a lot of things. Then ask yourself, what's the point?
The Olyimpic Javelin used to have no foc, it wouldn't stick in the ground. They gave it some and now it does. You need some, how much depends on other things but if all things are equal, 10-14 should be great.
The Olyimpic Javelin used to have no foc, it wouldn't stick in the ground. They gave it some and now it does. You need some, how much depends on other things but if all things are equal, 10-14 should be great.
07-29-2008, 06:10 AM
#6
Giant Nontypical
Join Date: Jun 2007
Location:
Posts: 7,367
RE: FOC and trajectory
ORIGINAL: Kanga
No.
With higher FOC arrows the extra weight on the front end actualy pulls the arrow through the air. Lower FOC arrows with light tips, the actual shaft has to push the tip loosing more speed and impacting lower on longer shots. Which is why high FOC arrows maintain more momentium down range.
Wouldn't a higher FOC cause the tip of the arrow to want to nosedive a little more, resulting in a lower hit?
With higher FOC arrows the extra weight on the front end actualy pulls the arrow through the air. Lower FOC arrows with light tips, the actual shaft has to push the tip loosing more speed and impacting lower on longer shots. Which is why high FOC arrows maintain more momentium down range.
All my arrows aren't Super high FOC, but I believe the minimum for broadheads should be 12%. I have one set of FMJ's that are over 20%.
Awesome flight and excellent penetration!
Dan
07-29-2008, 06:19 AM
#7
Dominant Buck
Join Date: Feb 2003
Location: Blossvale, New York
Posts: 21,199
RE: FOC and trajectory
All you ever wanted to know about FOC and more.
http://www.ubbc.ca/resources/documents/archive/understanding_and_applying_foc.pdf
http://www.ubbc.ca/resources/documents/archive/understanding_and_applying_foc.pdf
07-29-2008, 06:35 AM
#8
Giant Nontypical
Join Date: Feb 2003
Location:
Posts: 7,571
RE: FOC and trajectory
ORIGINAL: gzg38b
How much does FOC really affect arrow trajectory?
With all else equal, how much more drop would I have at 30 yards with a 20% FOC versus 10% FOC?
How much does FOC really affect arrow trajectory?
With all else equal, how much more drop would I have at 30 yards with a 20% FOC versus 10% FOC?
07-29-2008, 06:22 PM
#9
Nontypical Buck
Thread Starter
Join Date: Oct 2005
Location: Flushing Michigan
Posts: 2,355
RE: FOC and trajectory
Randy Ulmer says that FOC DOES affect trajectory.
This from Randy Ulmer:
"Your arrow’s balance point will affect its trajectory – at least slightly. For example, an arrow that is “tip light” will remain a little more level in flight and will actually plane or sail along a flatter trajectory than one of the same weight but with a heavier nose. But, tip light arrows don’t correct quite as fast when they come out of the bow. The closer the center of gravity gets to the physical center of the arrow the less stable the arrow will be in flight. A slashing arrow pivots around its center of mass (balance point). The farther the balance point is from the fletchings the more leverage they have and the quicker they can bring the arrow back on line.
The experts at Easton feel that an FOC value that is between 10 and 15 percent will produce the best compromise between stability and a flat trajectory for most hunting situations. The American Society for Testing and Materials have published a procedure for measuring balance point, and in it they state that a value of 9% is typical. But, they also add that the range can be as wide as 7% to 18% while still producing good arrow flight. 3-D shooters seeking a flatter trajectory often go a little lighter on the nose with many shooting arrows having FOC balance points closer to 6 percent. "
http://www.randyulmer.com/archive/2007/02/07/arrow-stability/
This from Randy Ulmer:
"Your arrow’s balance point will affect its trajectory – at least slightly. For example, an arrow that is “tip light” will remain a little more level in flight and will actually plane or sail along a flatter trajectory than one of the same weight but with a heavier nose. But, tip light arrows don’t correct quite as fast when they come out of the bow. The closer the center of gravity gets to the physical center of the arrow the less stable the arrow will be in flight. A slashing arrow pivots around its center of mass (balance point). The farther the balance point is from the fletchings the more leverage they have and the quicker they can bring the arrow back on line.
The experts at Easton feel that an FOC value that is between 10 and 15 percent will produce the best compromise between stability and a flat trajectory for most hunting situations. The American Society for Testing and Materials have published a procedure for measuring balance point, and in it they state that a value of 9% is typical. But, they also add that the range can be as wide as 7% to 18% while still producing good arrow flight. 3-D shooters seeking a flatter trajectory often go a little lighter on the nose with many shooting arrows having FOC balance points closer to 6 percent. "
http://www.randyulmer.com/archive/2007/02/07/arrow-stability/
07-29-2008, 06:43 PM
#10
Giant Nontypical
Join Date: Jun 2007
Location:
Posts: 7,367
RE: FOC and trajectory
Lots of things in Archery are not Black & White, 2+2=4, or the Gospel[8D]
Too many variables in shooters, and setups.
For every expert you find that says one thing on a subject you can find another that says different.
Shoot your arrows, do your testing on whatever thesubject is,and make your own mind up.
My main hunting arrows will be about 12% FOC, but I do have a set of FMJ's I will use out of one rig that has over 20% and they fly, group, and penetrate outstanding. Trajectory is more arched but they weigh over 100 grains more than my other arrows.
If they would fly flatter with less FOC? Personally I don't care I have seen the advantage of extreme FOC and those arrows will only be used short range anyway (approx. 35 yards or less)
Dan
Too many variables in shooters, and setups.
For every expert you find that says one thing on a subject you can find another that says different.
Shoot your arrows, do your testing on whatever thesubject is,and make your own mind up.
My main hunting arrows will be about 12% FOC, but I do have a set of FMJ's I will use out of one rig that has over 20% and they fly, group, and penetrate outstanding. Trajectory is more arched but they weigh over 100 grains more than my other arrows.
If they would fly flatter with less FOC? Personally I don't care I have seen the advantage of extreme FOC and those arrows will only be used short range anyway (approx. 35 yards or less)
Dan