sight marks
Question:
Should sight marks be equally spaced? Or should they get closer together as the range increases ? Why?
Response:
: Should sight marks be equally spaced? : Or should they get closer together as the range increases ? : Why? ‘tother way – has to do with gravity and 128 fps/s; standard balistics. Larry Diehr
Response:
> Should sight marks be equally spaced? > Or should they get closer together as the range increases ? > Why?
As you increase in range your pin gaps will increase but the increase in pin gaps will be less the further out you go. For example, if your 20 to 40 yard pin gap = 0.25" your 40 to 60 yard pin gap may be = 0.35". Your 60 to 80 yard pin gap will be greater than your 40 to 60 yard pin gap but the increase will be smaller than the 0.1" increase observed above (for example 0.42"). You should never see the pin gaps for longer ranges less than that observed for shorter ranges. I have never tried to noodle out why this is but in calculating sight marks from 180 fps up to 310 fps I have never seen an exception to the rule above. I have in fact, used this method to help archers identify bad pins/sight marks and it has always worked. Good Shooting! Perry
Response:
> Should sight marks be equally spaced? > Or should they get closer together as the range increases ? > Why?
This is a somewhat subtle question; for any range over about 10 yards, sight marks will get further apart as the range increases; for instance, on my bow, the different in sight marks between 30 and 50 meters is 0.95 inches, between 50 and 70 meters is 1.00 inches, and between 70 and 90 meters is 1.05 meters. You get the idea. The range drops off more and more quickly as you point the bow into the sky; the maximum range for my kit is about 270-300 meters. The "Why" of it is that the sight mark is closely related to the inverse sine (arcsin) of the angle of launch above horizontal; the sine function is very nearly linear for small angles, so that your sight settings are approximately linear as long as the range isn’t too great (large launch angles). The "subtlety" is that if you try to get sight marks for very close ranges, (less than 10 yards) the difference in height between your eye and the back of the arrow (usually at chin-level?) starts to affect the sight marks in a bizarre way; if you try this, you’ll find that the sight mark for, say 2.5 meters is actually lower on the sight than the mark for 5 meters… Good shooting, Lev
Response:
Howdy Lev, > for instance, on my bow, the different in sight marks between > 30 and 50 meters is 0.95 inches, between 50 and 70 meters is > 1.00 inches, and between 70 and 90 meters is 1.05 meters.
1.05 meters???? wow.. you must have a really long sight bar!!! :> :> > You get the idea. The range drops off more and more quickly as > you point the bow into the sky; the maximum range for my kit > is about 270-300 meters.
I have always been curious as to what mines is… I guess I could do the math considering I know apx. my arrows velocity… to much effort though… Lazy spell. :> Jonathan
Response:
> Should sight marks be equally spaced? > Or should they get closer together as the range increases ? > Why?
They should get farther apart if anything. As the arrow flies farther and farther it loses velocity. This gives gravity more time to pull the arrow down while covering the same distance. The arrow is traveling faster at 20 yards than at 50 yards so therefore it will drop more while covering the same distance. Find a technical physics book and look at the projectile motion sections. This is a classic problem with a twist. The twist being that most of the problems cover constant velocity of the projectile. The basis here is that the arrow is falling at a constant rate but moving forward at another. The arrow is accelerating(speeding up) in the -y direction (down) at the constant gravitational acceleration rate and deccelerating (slowing down) in the +x direction (away from you). This is also why a faster bow will have the pins closer together than a slower bow, and also why speed give you a better margin for distance estimation error. The trajectory is simple flatter. Mike — * | Archery * * Michael P. Sullivan | O * * Digital Technology Research Lab. | <|-| >–> * * Motorola Inc. | | / * * | Copyright 1995 MPS *
Response:
In my experience (and according to various coaching papers I have read), sight marks are equally spaced over most of the distances used in target shooting (ie between 30-70m). On my bow they must up the bar and then down again when moving in closer from about 30m to 5m – I expect this will hold for most other bows. Moving back from 70m the spacing is no longer equal but I can’t recall offhand how it changes, anyway I have to move the extension bar in at 90m. Why? Don’t know for sure but if you know/remember 1st year university physics (or even earlier college physics) you could see if a simple parabolic trajectory scales the bow’s elevation angle (ie the angle the arrow is above the horizontal) to give even spacing on the sight bar. Might try the maths myself if I get some free time. PS this is for recurves, I don’t have any experience with compound or crossbow. >Should sight marks be equally spaced? >Or should they get closer together as the range increases ? >Why?
Response:
>Should sight marks be equally spaced? >Or should they get closer together as the range increases ? >Why?
Your sight marks should actually get further apart as the range increases. The basic reason is that when something falls, it falls faster and faster because of the acceleration applied by the gravitional force. This means that for each metre out from the bow your arrow travels (and the arrow is falling from the moment it leaves the bow), the greater distance it drops while covering that meter. So, the 10 metres between 40-50 metres require a bigger sight adjustment than the 10 metres between 20-30 metres, because the arrow falls further while covering that distance (i.e. 40-50 metres) The actual rate of increase for your sight marks is determined by a number of things, but the two most important are your arrow speed, and the air friction for your arrow in relation to its mass. I vaguely remember an elastic sight marking strip, put out by a sight manufacturer, which only required you to sight in your bow at a short range and a long range. Stretching the strip between those marks gave intermediate sight settings correctly positioned. Maybe someone can give a bit more information about it (Check-It sights ?). Cheers… Chris Brennan
Response:
PSE used to publish a chart from which you could create your own sight marks for all yardages from 15-80. The marks are based on a balistic curve (parabolic projection), and expand linearly based on the speed of the bow. This same principal has been applied by several well known archers to make stick on "sight tapes" so that once the yardage is known, just set the sight to that marker. The old PSE tapes were designed around a recurve and have some problems when applied to modern high speed bows. There have been corrections made by some of the manufacturers, and those tapes work pretty well. I maintain the masters for a local archery shop to create custom tapes for the target and 3D crouds (very short to very long tapes). Larry Diehr
Response:
|> Why? Don’t know for sure but if you know/remember 1st year university physics |> (or even earlier college physics) you could see if a simple parabolic trajectory |> scales the bow’s elevation angle (ie the angle the arrow is above the |> horizontal) to give even spacing on the sight bar. Might try the maths myself if |> I get some free time. this might be true if you were shooting in a vacuum. But the flight of an arrow is in no way a simple parabolic arc. If you follow the vertical component only, it may go up and down the same, but if you look at the horizontal part, the arrow is constantly slowing down. This distorts the shape of the parabola, and should make your sight marks be farther apart at longer distances. Greg Wong
Response:
The pins will remain equal distances apart from 30 to 80 yards. – Hide quoted text — Show quoted text -> Should sight marks be equally spaced? > Or should they get closer together as the range increases ? > Why? >They should get farther apart if anything. As the arrow flies >farther and farther it loses velocity. This gives gravity more >time to pull the arrow down while covering the same distance. >The arrow is traveling faster at 20 yards than at 50 yards so >therefore it will drop more while covering the same distance. >Find a technical physics book and look at the projectile motion >sections. This is a classic problem with a twist. The twist >being that most of the problems cover constant velocity of the >projectile. The basis here is that the arrow is falling at a >constant rate but moving forward at another. The arrow is >accelerating(speeding up) in the -y direction (down) at the constant >gravitational acceleration rate and deccelerating (slowing down) >in the +x direction (away from you). This is also why a faster bow >will have the pins closer together than a slower bow, and also >why speed give you a better margin for distance estimation error. >The trajectory is simple flatter. >Mike >– >* | Archery * >* Michael P. Sullivan | O * >* Digital Technology Research Lab. | <|-| >–> * >* Motorola Inc. | | / * >* | Copyright 1995 MPS *
Response:
>The pins will remain equal distances apart from 30 to 80 yards.
And what kind of bow is this? What arrows? How many lb. pull? It seems to me that you have figured out a way to overcome gravity and air resistance. I want $5 worth of what he’s having!!:-) John
Response:
(JohnLGrove) writes: >The pins will remain equal distances apart from 30 to 80 yards. >And what kind of bow is this? What arrows? How many lb. pull? It seems to >me that you have figured out a way to overcome gravity and air resistance. >I want $5 worth of what he’s having!!:-) >John
At what yardage does the "booster" kick in? Woody Williams If you’re too busy to hunt, you’re too busy
Response:
> The pins will remain equal distances apart from 30 to 80 yards.
You must study only art at the U of L ? Pick up a classical physics book. Maybe one by Halliday and Resnick. If that doesn’t help, how about talking to Newton, he must be rolling over in his grave. — * | Archery * * Michael P. Sullivan | O * * Digital Technology Research Lab. | <|-| >–> * * Motorola Inc. | | / * * | Copyright 1995 MPS *
