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About arrow points - necessity or useless?
willie:
nice performance :)
it is my understanding that weight forward of center might let you get by with smaller/less fletching, and the fletching is only there to create drag, your enemy when shooting for distance.
I have experimenting mostly with atlatl darts though, and do not know if some recommendations can be extrapolated to arrows.
10 to 15 percent FOC seems to be enough, although some archers seem to go to extremes
having the FOC created by a distributed mass in the front half of the projectile seems to work better than just adding weight to the tip. I think this has something to do with where the dynamic flexing happens (slightly off topic).
JNystrom:
It is true that arrows with FOC let you use smaller fletchings, but they also make the arrow drop shorter. There's no gliding effect of back balanced arrow. I wish i got to see Monus arrows with some information and dimensions...
The 10-15% FOC is way too much in flight arrows, in my opinion. The most i would do is 5%. If you look at the turkish arrows, all of them are more than -5% FOC, so quite the opposite.
Distributed mass in front is worth trying. Many of those museum arrows from the record guys are footed with hardwood.
willie:
My experience with atlatl darts has been a pleasant way to see how aerodynamics effect dart design changes. Short ranges and low velocities make for easy observations, and I do not expect the 10% FOC for darts should be applicable to flight arrows.
Actually, FOC calculations should be replaced with an examination of Cp, (center of pressure) when looking at flight characteristics over varying velocities, as the Cp of an arrow changes with velocity, while FOC is an arbitrary approximation based on the length of the projectile, but does not consider the shape of the projectile.
Hardwood footings would seem to allow a smaller diameter profile for a more centrally balanced shaft.
Have you been able to examine the taper or barrel profiles of some turkish flight arrows?
A simple explanation of Cp, can be found here
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avcase:
I agree with Willie's comment about the center of pressure. The center of balance doesn't mean much without knowing the center of pressure of an arrow. A negative FOC arrow will still fly stable with little or no fletching as long as the center of pressure remains rearward of the center of balance.
It is also interesting how the center of pressure moves depending on the speed of an arrow. A marginally stable arrow might fly just fine right out of the bow, but suddenly turn and fall from the sky as soon as it slows down enough that the center of pressure has moved ahead of the CG.
Back to the original question, I always put a light point on my arrows made of metal, bone, or horn just to protect the arrow from impact. It isn't necessary for much else that I know of.
Alan
Selfbowman:
Guys I just came from the flats. My broadhead arrows were 27-29 inches in length. I put a 20" tapper on the arrows. My balance point was between 11-13" from my broadhead points. My fletchings was way too big . I managed 200 yds out of arrows weighing 450-500 grains from 50 pound selfbow. 20 short of record. I will be working on points and fletchings on that set of arrows and moving mass around in other arrows for more distance. Maybe y'all can do the math on what I just gave ya. I can't I will tell ya. Arvin
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