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RE: Compound bow - set up question
ORIGINAL: GMMAT Then how do you explain setting one up with a level and a square? If it's perpendicular/plumb to the string......it's Perpendicular/plumb to the ground. Ifyou're using a bubble level to set your arrow......what's it "level" to? |
RE: Compound bow - set up question
Then how do you explain setting one up with a level and a square? If it's perpendicular/plumb to the string......it's Perpendicular/plumb to the ground. If you're using a bubble level to set your arrow......what's it "level" to? Think about this Jeff, when you shoot 40 yards, do you not raise your bow? If you were to shoot 60 yards, do you not raise your bow higher? If you put your bow in a shooting machine, plumbed and leveled it so the arrow is level and shot it, it would not make the spot on the 20 yard target. It would not arch up, it would come straight out of the bow and start to drop immediately. When your shooting 20 yards, your not holding the arrow level, your bow is level side to side not front to back. |
RE: Compound bow - set up question
ORIGINAL: GMMAT Jeff, if your at full draw and aiming at a 20 yard target your arrow will not be level to earth, it will be point high/nock low. Your arrow does not leave the bow level when shooting at targets down range, remember the arch, ORIGINAL: GMMAT Also......This has nothing to do with the original question......but wouldn't the location of the target at 20 yds determine whther or not your arrow was "level" with the 20yd spot? Or....are you saying that ther eis nowhere you could put your target and have your arrow be "level"? |
RE: Compound bow - set up question
The arrows elevation on the bow at rest is set in readings that are 90 degrees to the string. The string however would not be perpendicular to the ground if you were shooting at a target 20 yards out shoulder high. The arrow would also not be parellel to the ground. Rob said.... The bow/arrow is set up at level/plumb/center in a vice, not when your holding it. That is designed for the arrow to come out of the bow as straight as possible. Then you pick up the bow, and your raising it to shoot down range. And this.... Think about this Jeff, when you shoot 40 yards, do you not raise your bow? If you were to shoot 60 yards, do you not raise your bow higher? If you put your bow in a shooting machine, plumbed and leveled it so the arrow is level and shot it, it would not make the spot on the 20 yard target. It would not arch up, it would come straight out of the bow and start to drop immediately. I'm not sure it "rises", though......unless someone can explain to me why it has to be set up UNlevel. When your shooting 20 yards, your not holding the arrow level, your bow is level side to side not front to back. What if your arrow was perfectly level.......on a parallel line with a line coming from your 20yd target. Now....."I" think your arrow line would be above your 20yd target line.....and the fact that you're looking down from your sight line would make this compensation. Heck I'm gonna draw it.....I know this is confusing...:D |
RE: Compound bow - set up question
WHY DOES THIS MATTER SO MUCH?
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RE: Compound bow - set up question
Why do you care, Ryan? I want to know why things are the way they are.
"It just is" don't do it, for me....and I'm betting there's a lot of folks who thought they knew a little more than they did about this stuff. Am I wrong? If this isn't interesting to you..........move along. No hard feelings.;) |
RE: Compound bow - set up question
You know what's funny. You askedthequestion and here you are telling everyone how wrong they are........AGAIN...... This is pretty basic stuff. Now let's talk about hunting....
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RE: Compound bow - set up question
No, its not that, it just seems like it was explained enough already to figure it out and understand. And if not, was the little bit of info gained, REALLY worth the enormous effort to obtain it?
I would think a physics book, and a chapter on projectile motion should clear things up in a hurry. As opposed to relying on 15 "mr wizards" who slept in a holiday inn last night :) |
RE: Compound bow - set up question
ORIGINAL: GMMAT Is there nowhere that target could be that would find your arrow level (parallel) to the gorund? ORIGINAL: GMMAT Tell that to the bubbles on your level;) They won't read plumb/level if the bowstring/arrow isn't/aren't. ORIGINAL: GMMAT WHY can't the sight line line (from eye to target) and the arrow line intersect and then reconnect at 20 yds. ORIGINAL: GMMAT I'm not sure it "rises", though......unless someone can explain to me why it has to be set up UNlevel. |
RE: Compound bow - set up question
But for S's and G's.......why couldn't your arrow be level .....shooting at a 20yd target? Is there nowhere that target could be that would find your arrow level (parallel) to the gorund? The string however would not be perpendicular to the ground if you were shooting at a target 20 yards out shoulder high. |
RE: Compound bow - set up question
I would think a physics book, and a chapter on projectile motion should clear things up in a hurry. As opposed to relying on 15 "mr wizards" who slept in a holiday inn last night :) There is one spot, but it is below the straight line you draw from nock to tip. The only level I am familiar with is the one on my sight, and it only reads plumb/level in one plane...a different plane than the arrow flight travels on. Do you have a level for each of the 3 planes involved? WHY can't the sight line line (from eye to target) and the arrow line intersect and then reconnect at 20 yds. They do...always. If the target is below that one magical spot that I mentionedfirst in this post, then the arrow will not rise. Ifthe targetis anywhere above that spot, then the arrow will rise. |
RE: Compound bow - set up question
ORIGINAL: GMMAT The arrows elevation on the bow at rest is set in readings that are 90 degrees to the string. The string however would not be perpendicular to the ground if you were shooting at a target 20 yards out shoulder high. The arrow would also not be parellel to the ground. Rob said.... The bow/arrow is set up at level/plumb/center in a vice, not when your holding it. That is designed for the arrow to come out of the bow as straight as possible. Then you pick up the bow, and your raising it to shoot down range. And this.... Think about this Jeff, when you shoot 40 yards, do you not raise your bow? If you were to shoot 60 yards, do you not raise your bow higher? If you put your bow in a shooting machine, plumbed and leveled it so the arrow is level and shot it, it would not make the spot on the 20 yard target. It would not arch up, it would come straight out of the bow and start to drop immediately. I'm not sure it "rises", though......unless someone can explain to me why it has to be set up UNlevel. When your shooting 20 yards, your not holding the arrow level, your bow is level side to side not front to back. What if your arrow was perfectly level.......on a parallel line with a line coming from your 20yd target. Now....."I" think your arrow line would be above your 20yd target line.....and the fact that you're looking down from your sight line would make this compensation. Heck I'm gonna draw it.....I know this is confusing...:D I was explaining as if both shooter and target are on the same level ground at the same elevation. |
RE: Compound bow - set up question
I was explaining as if both shooter and target are on the same level ground at the same elevation. |
RE: Compound bow - set up question
Is there anything wrong with this sketch?
No deductions for drawing skills (or lack, thereof) please.;)  |
RE: Compound bow - set up question
Where are the anchor points for the shooter? From the looks of that the anchor points need to be around the shooter's waist.
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RE: Compound bow - set up question
I can alter the sketch......to show the lines closer together.....but the end result will be the same (in my mind and on paper). It'll just look "different".
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RE: Compound bow - set up question
But the peep sight would have to be at a 45degree angle to the bow sight on full draw and that is not realistic.
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RE: Compound bow - set up question
If all thisREALLY matters to you, there is areally good book by Robert Rinker called "Understanding Firearms Ballistics." It is one of the most definitive works on projectile ballistics I have seen. And while it was wriiten about firearms, the principiles are the same as what you are describing here.
The arrow, as it leaves the bow, does NOT travel a straight line. It travels in a parabolic curve, whose rate of fall increases as range increases. This is due to the fact that acceleration due to gravity is not a linear function, but a squared function (acceleration due to gravity = 32 feet per second SQUARED). The arrow starts falling the instant it comes out of the bow, so we must aim the bow upwards (via our sights/line of sight/which IS a straight line) to make this curve that the arrow is traveling intersect with the staight line that our sight follows. The projectile will cross the line of sight twice in any normal setup. It might be possible to set a bow up where you could have the line of sight just barely kiss the tangent of the curve of the parabolic flight of the arrow, but i think it would be too unwieldy to use. And you can launch an arrow perfectly parallel to surface of the earth, it just depends where your target is. |
RE: Compound bow - set up question
I don't see anything wrong with your sketch.
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RE: Compound bow - set up question
ORIGINAL: brucelanthier But the peep sight would have to be at a 45degree angle to the bow sight on full draw and that is not realistic. |
RE: Compound bow - set up question
But the peep sight would have to be at a 45degree angle to the bow sight on full draw and that is not realistic. For my illustration (wheter it's right or wrong....I don't know) what difference does it make......as long as it shows the line of the arrow and the line of the sight line crossing at some point in front of the shooter....and reconnecting at the intended target? I could make the sight line much less of a grade. But.....for the purposes of what I'm looking for....I don't see the point. If you can explain to me why that's important.....I'm all ears. It's not to scale, either. And while it was wriiten about firearms, the principiles are the same as what you are describing here. The arrow, as it leaves the bow, does NOT travel a straight line. It travels in a parabolic curve, whose rate of fall increases as range increases. The arrow starts falling the instant it comes out of the bow, so we must aim the bow upwards (via our sights/line of sight/which IS a straight line) to make this curve that the arrow is traveling intersect with the staight line that our sight follows. Is that what you're depicting? And you can launch an arrow perfectly parallel to surface of the earth, it just depends where your target is. |
RE: Compound bow - set up question
I'd saythe stetch is correct mainly because of the height of the target. Something that has been mentioned.
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RE: Compound bow - set up question
OK.....I'm not disagreeing with you....I just want to know why it's traveling on this curve? And....how does it do this (law?) if we've set up our bow with the arrow level? I'd like to understand this. We set our bow up to ensure that the arrow is perpendicular to the string, the only way to accurately do that is to use bubble levels. Thats it. When we shoot at things far away we have to aim slightly up to conteract gravity. So I think you've got it. We set up level, aim at a target 20 yrds away which makes the arrow at a3 degree angle of relative to level (for illustrative purposes), because we raise the arrow rest up w/ the sight to aim, and the nock stays in the same place. Then we release the arrow travels up and passes through the sight line because when it leaves the bow it has some forces from the bow pushing it up. When gravity overtakes the forces fromthe bow the arrow begins to fall. And we hope it intersects the line of sight at the target. Think of throwing a ball straight up, its going to come down, eventually all the force we put in the ball is overtaken by gravitational forces. |
RE: Compound bow - set up question
Bob...I didn't set out to draw something "incorrect":D. I hope it makes sense.
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RE: Compound bow - set up question
Okay Jeff, most of your last post was spot on. We are saying pretty much the same thing, just in different ways.;)
The reason the arrow does not travel a straight line is because as soon as it leaves the bow, gravity begins to accelerate the arrow towards the earth at 32 fps squared. The farther the arrow falls, the faster it falls... Acceleration due to gravity is not a linear function (it will not plot as a straight line on a graph), it is a squared function, which means it's rate of fall gets faster the further it falls. It will plot as a curve on a graph. If it fell at a steady rate all of your sight pins would be the same distance apart, but we know this is not true. The further the distance the further apart the pins get. This is due to two factors, one, the force of gravity keeps accelerating the arrow towards earth faster and faster, and it is compounded by the fact that the arrow is slowing down horizontally because of airresistance, allowinggravity more time to work on the arrow. You see, this is really a problem ruled by time... Once there is nothing left holding the arrow up in the air,resticting it's fall, the effects of gravity take over. In theory, in a vaccuum, disregarding the curvature of the earth;), you could shoot an arrow perfectly parallel to the earths surface at the exact same instant that you dropped a second arrow, and they would both hit the ground at the same time. This fact really takes folks aback the first time they hear it, but it is true. Both arrows are accelerated towards the earth at the same speed due to gravity, it is acting on both arrows equally. One just travels a much farther horizontal distance before it impacts the earth. The law? I think it had to do with that Newton guy and the apple.:D:D:D Sorry, don't know the number of that law, but I'm sure it's in the top five laws of physics. As far as your picture dipictions, I saw nothing wrong on them that needed to be corrected. Sorry if you took my post that way. |
RE: Compound bow - set up question
Jeff, your sketch is correct. Did it provide any information to you? To me, I see that if you move the target up/down, and/or the bow up/down, the arrow CANNOT be parallel to the ground any more as indicated in your sketch. (I better list my obvious assumption since you seem very interested in picking nits today: you dont move 'each' the same distance one direction)
It is still parallel to the string when you let down (obviously) even if no longer parallel to the ground when you, say, move bow down 2 feet. What questions are you still struggling with? To me, by your sketch, you have a grasp of everything you have 'discussed' |
RE: Compound bow - set up question
ORIGINAL: Critr-Gitr Okay Jeff, most of your last post was spot on. We are saying pretty much the same thing, just in different ways.;) The reason the arrow does not travel a straight line is because as soon as it leaves the bow, gravity begins to accelerate the arrow towards the earth at 32 fps squared. The farther the arrow falls, the faster it falls... Acceleration due to gravity is not a linear function (it will not plot as a straight line on a graph), it is a squared function, which means it's rate of fall gets faster the further it falls. It will plot as a curve on a graph. If it fell at a steady rate all of your sight pins would be the same distance apart, but we know this is not true. The further the distance the further apart the pins get. This is due to two factors, one, the force of gravity keeps accelerating the arrow towards earth faster and faster, and it is compounded by the fact that the arrow is slowing down horizontally because of airresistance, allowinggravity more time to work on the arrow. You see, this is really a problem ruled by time... Once there is nothing left holding the arrow up in the air,resticting it's fall, the effects of gravity take over. In theory, in a vaccuum, disregarding the curvature of the earth;), you could shoot an arrow perfectly parallel to the earths surface at the exact same instant that you dropped a second arrow, and they would both hit the ground at the same time. This fact really takes folks aback the first time they hear it, but it is true. Both arrows are accelerated towards the earth at the same speed due to gravity, it is acting on both arrows equally. One just travels a much farther horizontal distance before it impacts the earth. The law? I think it had to do with that Newton guy and the apple.:D:D:D Sorry, don't know the number of that law, but I'm sure it's in the top five laws of physics. As far as your picture dipictions, I saw nothing wrong on them that needed to be corrected. Sorry if you took my post that way. |
RE: Compound bow - set up question
WOW, way TMI but still a good read.
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RE: Compound bow - set up question
Jeff, your sketch is correct. Did it provide any information to you? To me, I see that if you move the target up/down, and/or the bow up/down, the arrow CANNOT be parallel to the ground any more as indicated in your sketch. (I better list my obvious assumption since you seem very interested in picking nits today: you dont move 'each' the same distance one direction) OK.....so that being what "is"...... What happens on the straight down shot?.....since gravity becomes a non-factor? I may have just proved MYSELF wrong in a previous post......which was what I was after.;) Assuming the shooter/hunter was 20yds up in the tree (for this exercise).......it would seem the lines would NOT meet back at 20yds (even though they WOULD still meet at 'per Matt/PA' 8yds)......and the shooter would shoot HIGH if he utilized his 20yd pin. Is THIS incorrect/correct logic? |
RE: Compound bow - set up question
That absolutely can be done through a shooter machine, not human. The machine would need set up at full draw with the arrow parallel/level to ground and the bow shot. The target then would need to be moved up or down depending on where the drop of the arrow hits the target. Then and only then could you sight in your pin to the target.
:D OR, The target remain stationary and the shooting machine raised or lowered until the arrow impact/drops hits the target and then and only then could the pin be moved into position. :D |
RE: Compound bow - set up question
ORIGINAL: GMMAT Jeff, your sketch is correct. Did it provide any information to you? To me, I see that if you move the target up/down, and/or the bow up/down, the arrow CANNOT be parallel to the ground any more as indicated in your sketch. (I better list my obvious assumption since you seem very interested in picking nits today: you dont move 'each' the same distance one direction) OK.....so that being what "is"...... What happens on the straight down shot?.....since gravity becomes a non-factor? I may have just proved MYSELF wrong in a previous post......which was what I was after.;) Assuming the shooter/hunter was 20yds up in the tree (for this exercise).......it would seem the lines would NOT meet back at 20yds (even though they WOULD still meet at 'per Matt/PA' 8yds)......and the shooter would shoot HIGH if he utilized his 20yd pin. Is THIS incorrect/correct logic? The arrow is no longer traveling perpendicular to gravity, the the affect is lessed... |
RE: Compound bow - set up question
ORIGINAL: GMMAT Assuming the shooter/hunter was 20yds up in the tree (for this exercise).......it would seem the lines would NOT meet back at 20yds (even though they WOULD still meet at 'per Matt/PA' 8yds)......and the shooter would shoot HIGH if he utilized his 20yd pin. Is THIS incorrect/correct logic? |
RE: Compound bow - set up question
I haven't shot this shot in a couple years, now.....and it's clear I didn't understand it whenI was shooting it (for practice, only). I'm really trying to learn something with all this.....if you'll bear with me.;)
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RE: Compound bow - set up question
Jeff, here a is a pic of trajectory, note, the different angles are angles of launch. I.E. the angle the arrow is relative to horizontal when it leaves the bow.
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RE: Compound bow - set up question
So technically if you could shoot "straight" down, the flight of your arrow would no longer be a parabolic curve, and would once again be very nearly a straight line. Your sights would be setup to compensate for the curve of the mystical flight of the arrow, which would no longer exist... Now the arrows path IS a straight line (which we said didn't happen, my my crow tastes good:D). Now you should shoot high because your sights are compensating for dro that isn't there.
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RE: Compound bow - set up question
ORIGINAL: GMMAT I haven't shot this shot in a couple years, now.....and it's clear I didn't understand it whenI was shooting it (for practice, only). I'm really trying to learn something with all this.....if you'll bear with me.;) I have never taken the shot tho would be interesting to find somewhere to practice 20 yards straid down. |
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