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arrow drop question
jag
Member Posts: 484 ✭✭✭
been cruising some of the topics and replies, pretty tough group but here goes...I just bought some pre fletched arrows w/vanes and wraps. they are about 23 grains heavier than the feathers without wraps that i usually shoot. the poi is the same when using my old and new arrows with field points. the new arrows are about 6" lower @ 25 yds than the older feather arrows with broadheads which shoot the same as my field tips. (following this?) why would this be? can the 23 or so grains added to the back of the shaft change spine or foc that much to have such a different point of impact? thanks for any "insight"
Comments
If the change was a spine issue, you would see left or right misses.
You also might be seeing some vane contact with your rest, feathers don't have a problem with contact, they just move out of the way.
shoff-i kinda agree as the only thing that makes any sense is that the feathers-which are also offset more than the vanes-are controlling arrow flight much better. the thing is-wouldn't that just help them group better with less strays? why would the vanes/wraps all group low and not just all over?
Back to the stabilization idea. If your broadheads are planing through the air, the vanes might not be able to make up for it like the feathers would. This could give you high and low misses, at least in my head I can see that happening.
By any chance, do you know if your arrows are porposing? I say this due to the fact that I went back and read through the Easton tuning guide. One of the causes of low broahead flight is from a high nock point.
which arrows do wyu have noe be specific.
I agree with shoff on the porposing that would cause the low hits. but usually you can see the arrow do this on its way to the target.
and if the spine was not correct you can see tail whip. but like shoff sais that would be left to right.
also are your broadheads alligned with the vanes the same as with the feathers//
As the force against which the arrow is rotated is not constant but depends on the airflow angle and the overall air flow speed (arrow linear speed and angular rotation speed) it's a more complicated case then lifting the weight. The more the arrow has rotated the higher the force against which the arrow is moved.
The aim is to minimise the time it takes and minimise the angle through which the arrow rotates for arrow stabilisation as this minimises the change in overall velocity of the arrow resulting from drag (as we'll see in a minute).
Once the arrow has stabilised then you have an arrow with a changed velocity and with the arrow shaft at some angle to the air flow. The behaviour of the arrow is then similar to the displaced pendulum above. The arrow fishtails/porpoises back and forth with an energy oscillation between fletching potential energy and and the arrow rotational kinetic energy. As discussed elsewhere fishtailing/porposing has a minimal effect on the arrow overall flight direction as the drag effects are more or less symmetrical and cancel out. The launch alignment of the arrow itself has no significant effect in changing the overall arrow flight path.
As discussed elsewhere fishtailing/porposing has a minimal effect on the arrow overall flight direction as the drag effects are more or less symmetrical and cancel out.
which direction would that be? left to right or up and down, or subsiquent cosine of those directions. It may not have an effect in one direction, but it will in another. If you were to create an equilibruim diagram of arrow flight, there would be forces in 4 directions.
Shoff I dont think we hace enough info we dont even know what arrows he's shooting are they cut to the same lenth so on and so forth. what do ya think more info needed????[?]
yes and no, The only thing i would like to know if there is a differnce in diameter of the shafts. This would cause the nock point to be wrong compaired to the old shafts. You might not notice until broaheads were put on.
wow thats a lot to decipher! they are the same 8.2 gr an inch. same diameter, same spine, etc. i didn't include all that info, just figured it was a given(my bad). buckey i am a firm believer in broadheads being in alignment with arrow SHAFT not at all concerned with broadhead to vane alignment. i don't believe that has anything to do with anything)though its probably a good argument topic!) shoff, my guess is similiar to yours but....if i was porposing would my broadheads with feathers impact the same spot as field tips? also would the arrows stick into the target nice and parallel like they do? the only reason i bought the vanes was the whole country is sold out of gt's otherwise i would have bought the shafts and fletched them with feathers like i'll probably do to these anyway, although i really like the cresting effect and may spray paint some of the ends(sorry purists, its easy and cheap!) and only adds about 2 grains... also considering trying some quick spin vanes. any thoughts on these? how are they with shoot through rests? thanks again!
Well I can tell you that if I dont line my muzzys up with the vanes they do not shoot nearly as well. also with all that sid the only thing different is the change from feathers to vanes and the wraps so that must be it.
(following this?) why would this be? can the 23 or so grains added to the back of the shaft change spine or foc that much to have such a different point of impact? thanks for any "insight"
I'd stay thats why you are shooting low..the extra weight,foc
surekill, i'd agree the extra weight will cause low shot, but 23 grains= 6" low @ 25 yds? that seems like quite a bit....
What he really needs to be looking for is consistancy in his arrows and I agree 6" @ that distance doesn't seem right.
No problem jag, the physics problem is what I was trying to convey here. Besides I will still disagree with you on the spine issue, i.e. if an arrow is has a designation of say 2117 the outside diameter is the main factor in determining shaft stiffness (spine) and the 21 = 21/64, this is the shaft diameter rounded to the nearest 64th of an inch. The wall thickness code is the second two digits or 17. These represent the wall thickness to the closest one thousandth of an inch so 17 = 0.012. the wall thickness is the main factor in determining shaft weight. So in reality these are a given and never change. But by adding or subtracting weight to various points on a shaft, notice I didn't say tip, it will affect the flex of the spine differently, even though the poundage remains the same. The same thing would apply if you lengthened or shortened your arrows and every thing else remained the same. The arrow will flex differently, you may need more or less spine but not that spine. Yes very confusing, but that's physics. Like I said it effects the way the business end of the arrow accepts the energy transfer and everything in between.
What he really needs to be looking for is consistancy in his arrows and I agree 6" @ that distance doesn't seem right.
HOWEVER, a change in spine or spine issues will give you left/right misses. NOT up and down.
feathers have much better steering charactoristics then vanes do. My guess would be that due to the added turbulence (sp?) of the broadhead with vanes your vanes are not making up the differnce in turbulence with the broadhead. On the other hand, your feathered arrows are capable of making up this difference.
If the change was a spine issue, you would see left or right misses.
You also might be seeing some vane contact with your rest, feathers don't have a problem with contact, they just move out of the way.
Thank Shoff he was right .. hit it on the head first post . nice job shoff. and Also Jag Nice to see your all set[8D]