How Much Will Your Arrow Drop At 30 yards?

[Hashiba]

Ragnarok, THANK YOU for bringing up those points.  I was getting feverish reading through & thinking up how I was going to phrase them.

A projectile has to be launched at an upward angle in order to strike a target of the same height at any range.  It will cross line of sight twice.  Once on the way up at very short range, and again on "zero".  If an arrow is launched from 5' from the ground at a target that is also 5' from the ground, it most certainly rises above the line of sight.  The location of the line of sight also changes the apparent drop of a projectile at a given range.  In rifles this is the distance between the center-lines of both your scope and bore.  Here I suppose it would be from your eye to the arrow.

To further confuse the matter:  Ragnarok, do we instinctive shooters always "zero" our trajectory at our currently chosen target?  We subconsciously apply the elevation correction to our given distance, so there is no "drop" from line of sight, only from apogee.

[Looper]

I think you'd be shocked at how much an arrow drops in relation to where it's actually pointed.  One way to tell is to take one of the laser pointers used to sight in a rifle and insert it into a shaft with no insert in it.  Draw the arrow back and aim like you normally would for any given distance. The laser will indicate where the arrow is actually pointed.  Just don't shoot it!  I'll try it later.

OK So I am hunting on a gentle slope I have my favorite bow that puts a 525 grain arrow, with five inch left wing parabolic feathers and a 160 grain point up front, out at 184fps.  the buck is working around towards me and is not at all aware of me.  I standup  to shoot this time.  The buck turns at about 25 yards and is looking away.  As I raise my bow I notice a large branch that is 7 of maybe 7.5 feet high 18 yards out. Do I shoot?  This is of course not considering tree reach, the ability of trees to stick a pencil sized branch in front a moving arrow with no notice.

[Looper]

Ok, I just went out and tried the laser pointer in the shaft trick.  At 30 yards, it looks like the arrow is actually pointing about 4-5 feet above my intended target.  I aimed at the handle of my garage door, and the dot was a little above the top edge of the door.

[Looper]

One of my favorite things to do while stump shooting is to hit a target while shooting through a gap in limbs and brush.  You really need to know what your arrow trajectory is to be successful at it. I've gotten pretty good at it and the practice really pays off.  On a shot at a cottontail this past winter, I had to thread my arrow through a softball-sized opening about 5 yards from the rabbit.  It was a perfect shot and I nearly decapitated him with my broadhead.

[Looper]

Pavan, unless you're throwing the arrow, I think you're safe from hitting that branch.

[SlowBowke]

Probably already listed by someone else but didnt read them all.

"The formula for earth's acceleration of gravity for someone who isn't familiar is 32fps x etc etc"

32ft/sec per sec squared is the correct rate of **ACCELERATION of gravity.**

AKA......how much the drop INCREASES IN SPEED per second.......not HOW MUCH it drops.

and.....calucations for gravity are generally taught to be accurate "within a vaccuum" and dont include the many things.........and there are many (most not consistant, day to day) that effect drop in flight.

Atmospheric pressure is but one of these, as you mentioned.

This is why simple calulations of drop dont exist. Each second of projectile flight is not equal in RATE of drop due to gravatational pull, the arrow is also slowing down, and other outside forces take effect as well.

Also consider that the acceleration of speed of drop due to gravity doesnt magically CHANGE in speed of drop AT each second. (no second-third gear, lol)  32fps per second is an "average" used calculating, again, in a vacuum.

The rate of gravitation pull is slowly, throughout flight, increasing in rate of drop AND the FPS of the arrow also changes every micro second. (slowing down lol)

A quick and understandable comparison is that a ball dropped off a building is dropping FASTER EACH second than the second previous to it. (actualy micro second). It is constantly increasing in speed till max gravitational pull is reached. No, I dont recall what that is.

Too difficult for me to even consider calculating.

Just some reading for you of high tech thoughts. lol

 http://www.lightandmatter.com/html_books/lm/ch03/ch03.html  

but again, I do feel, personally, such calculations reduce the simple beauty of trad archery.

As nicely as I can put this...."who cares?"


Just me, sorry. No offense.

God bless

[Eugene Slagle]

My arrows drop like a rock...    

I can agree with that assesment that the arrow would drop nar to the mark that you have quoted.

[Rob DiStefano]

all this science/physics stuff only goes to prove that the most successful trad bowhunters fling arrows like pitchers throw baseballs - pure "instinct", and both require a LOT of practice and neither are thinking about projectile trajectories.    :D

[Swamp Yankee]

Originally posted by Rob DiStefano:
all this science/physics stuff only goes to prove that the most successful trad bowhunters fling arrows like pitchers throw baseballs - pure "instinct", and both require a LOT of practice and neither are thinking about projectile trajectories.     :D  

Amen!

[SlowBowke]

LOL......how true.

If you wanted to get messed up but good......think of such a trajectory discussion on a basketball (dropping IN a hoop at unknown distances?...uhh) or a GOLF forum.

Less tech information I need to know = more fun for me!!!

 

[Javi]

Even though I have a solid foundation in ballistics, I never think of any of it when I'm shooting a longbow... I look at my target and shoot; trusting my experience and my brain to guide my arrow to its mark. But it's still fun to discuss it occasionally..

[2fletch]

We are speaking different languages here. What we need is someone who is bilingual. Forge, I don't doubt the accuracy of your info, it just doesn't answer the question. I'll try again.

First of all, imagine a target at 40 yards and the bullseye at a height of about 5ft which is the same height as the shooter. The range is level so the arrow and the target are on the same level. Now assume that we are on earth and the gravitatioal pull is 32-32.2 fps. Assume (for our purpose) that there is no atmosphere to affect speed or rate of acceleration. Also, there is a backstop wall at the target that is 40 feet tall and marked clearly in 1 inch increments to show the height. Now the question is, "At what height on the wall will the arrow (not sights) be pointed for a bow shooting 170fps to hit the bullseye? The distance from where the arrow is pointed to where it impacts is the total drop. The reason it never reaches that height is because gravity starts working immediately to bring it down.

I looked at some of the trajectory info sites for archery but they seem to be looking at it from the standpoint of where the arrow would impact using one sight pin for the various distances. That's not the same thing.



Get up and Gety up!  

[ishoot4thrills]

           

[Javi]

I think the confusion comes from the word "DROP" most folks equate drop to flight path... When in this instance we are talking about one leg of the aiming triangle...  | or how high is the aiming point at the prescribed distance which for the original post of 170fps at 40 yards would be approximately 9 ¼ feet... this is what is described as drop in this situation.. the arrow never gets that high because of drag and gravity but you have to aim that high to get there...  The arc of the arrow is another thing altogether and as I said earlier the apogee is 27.79 inches above line of sight at 21 yards..

BTW Line of sight is eyeball to target.... not aiming point..

Ay 20 yards you would aim approximately 2 1/8 feet above the target yet the arrow will reach apogee at 12 yards at a height of 4.8" above line of sight.

[LimBender]

Interesting, but now I gotta shut all this out for shootin!   How am I gonna shoot at 30 yards with thoughts in my head like my arrow is gonna drop 9 feet?   :D  

Pull to anchor, focus on spot and let her fly!  

[Hashiba]

Javi says it well.  The "drop" as its being talked about is irrelevant.  Apogee is much more a concern for archers, as that is the factor that will determine if your arrow will strike an object such as a branch or fence wire on its path to the target.

[2fletch]

Redneck Engineer said it first D = 32.2 x time squared x 1/2, but I didn't get it. Just a few minutes ago I was sitting in the recliner when it occured to me that the formula I was using was for the acceleration of gravity and only gave the speed the arrow was dropping at the end of the 40 yards, not the distance. Dividing by two would give the average speed which would be the approximate  distance of the drop.

This all got started because of a guy by the name of Harry who argued that he was only pointing the arrow a few inches over the target that he was shooting at 40 yards. This begain a debate that eventually spilled over to this site. If any of you became confused, dizzy, or disoriented because of the fuzzy numbers, blame Harry it's his fault. Ha! He'll be over here in about 5 hours if you'd like me to pass it on.

Thanks for the fun and knowledge. Now I want to get back on the instinctive side as Rob recommended.

Giddy up and let's get out of town!      

[Ragnarok Forge]

This is why I shoot instinctive.  I enjoy the math but I don't bother with it when shooting

[Bjorn]

Time to put away the calculator and eraser. If I didn't miss by 4 feet obviously it did not drop 4 feet!