[Roskoe]

We were messing around with this in elk camp as well. Except we live at 5,000 feet in elevation. My bow was still right on, but my buddies bow was hitting at least 4" high. Never did get it resolved. I know bullets have a higher ballistic coefficient at high altitude. Makes sense that arrow would be affected, at least to some degree, as well.

 

[outdoorsguy48]

We were messing around with this in elk camp as well. Except we live at 5,000 feet in elevation. My bow was still right on, but my buddies bow was hitting at least 4" high. Never did get it resolved. I know bullets have a higher ballistic coefficient at high altitude. Makes sense that arrow would be affected, at least to some degree, as well.

Thanks Roskoe - that's sort of what I was thinking. I've got to believe someone has done a study on this. Seems that this would be important, especially to serious target shooters.

 

[wis_archer]

Yes. The higher up elevation wise the weaker the pull of gravity, and hence less drop.

 

[Huaco]

Yes. The higher up elevation wise the weaker the pull of gravity, and hence less drop.

Sorry... I don't think it has much to do with gravity.
It has a LOT to do with air density. The air is MUCH thinner at 9,500 ft. Any private pilot know about this... they have to tune up their fuel mixtures and if equipped, feather the props.
If gravity was the case... the space missions would never make it back to earth.

 

[Woody69]

Yes. The higher up elevation wise the weaker the pull of gravity, and hence less drop.

I don't know if it would be because of less gravity, i mean the earth still has enough gravity way out in space to keep the moon in orbit around the planet ???

I think maybe it has more to do with thinner atmosphere at higher altitude creating less drag on the arrow, so it doesn't drop as much ? that's my guess anyway ! :darkbeer:

On a similar subject has anyone noticed that different atmospheric conditions at the same altitude can have different effects, ie, shooting at sea level on a bright sunny clear day, and shooting at sea level on a cloudy overcast day, or different barometric pressure ???

Woody

 

[bowhuntermitch]

Yes, the thinner air but not less gravity, but four inches like mentioned seems like alot

 

[flintcreek6412]

Could be a result of both less gravity and atmosphere. I didn't know this but thanks to Google I did find that gravity does decrease the farther from the center of the earth(elevation) you get.

http://galitzin.mines.edu/INTROGP/n...n.html&page=Gravity: Notes: Elevation Effects

 

[KSU Turkey Nut]

Yes it will too some degree. Just like it does a golf ball.
Best thing for your ego is to hit a good drive at altitued

 

[wis_archer]

Gravity will make a difference. Example. The acceleration of gravity is 9.8 meters per second per second at sea level. At about 400 feet above, it is about 9.81 meters per second per second.

At that altitude I would imagine (I am to lazy to spend the time doing the math) that the difference would be significant - air resistance is minimal however, and I would imagine would have little affect on the arrow.

If you are inclined to find the exact gravitational acceleration for your altitude, this is the equation.

g = 9.780 327 (1 + A sin2 L - B sin2 2L) - 3.086 × 10-6 H m·s-2

 

[Stormbringer]

Just watch how far a field goal can be kicked, and, scored here in the Mile High Stadium, or, what the Top Fuel crew has to do to get John Force down the Bandimere Speedway drag strip on Thunder Mountain....something about this Mile High Air!

 

[outdoorsguy48]

Thanks all. Glad to hear it wasn't just my imagination but probably a combination of thinner air and lower gravity.

 

[a3dhunter]

I shot high on a mule deer buck, just enough to catch a limb 5 yards in front of my deer before the arrow dropped back down. A couple inches can mean the difference between a filed tag and an unfilled tag. This left the arrow in two pieces at the feet of the buck I wanted, he didn't like that....



I took the shot at about 10,000 feet, I sight in at 3600 feet.

To me it just feels like shots sail a little bit more when hunting above 10,000feet. I shoot a lot at home and get used to the arc of my arrow, up in the mountains it just seems to shoot flatter.

 

[Big Shot]

That doesn't work

The acceleration of gravity is 9.8 meters per second per second at sea level. At about 400 feet above, it is about 9.81 meters per second per second.

The higher the gravity --> the higher the force applied to an object by gravity --> the higher the acceleration due to gravity. That means if gravity goes down as elevation goes up.... Acceleration due to gravity will go DOWN as elevation goes up.

 

[stixshooter]

Yep I live a 600 ft and my cabin is at 4,500 ... We shoot about 2-3" high at 40 and more the further out you go. We sight in for the elevation before the season

 

[Huaco]

I'm stickin' to my guns on the not gravity, but thinner air theory... The Earth's gravity pulls that big block-o-cheese around the earth EVERY month... I don't think a 400 grain arrow is going to be appreciably affected by a few thousand feet change in altitude... especially when it is what...8,000 MILES to the center of the earth's gravitational force!

 

[outdoorsguy48]

Thanks to everyone for the input.

At least now I know what we experienced was real, and we'll need to account for it again next fall.

 

[wis_archer]

I'm stickin' to my guns on the not gravity, but thinner air theory... The Earth's gravity pulls that big block-o-cheese around the earth EVERY month... I don't think a 400 grain arrow is going to be appreciably affected by a few thousand feet change in altitude... especially when it is what...8,000 MILES to the center of the earth's gravitational force!

Minus air resistance, a 1000# ball of lead and a 1# ball of lead, fall at the same rate.

I found out today that the gravitational acceleration is 9.792679308 meters per second per second at 8,000 ft. above sea level. So the gravity causes about 2 cm less drop at 8,000 than at sea level @ 100 yards, with a 300 fps arrow.

Air resistance is the other part of the drop. Air resistance counts for the majority of less drop at your higher elevation.

I think you misunderstand what gravity is. I have a gravitational attraction, as do you, as does the pen next to you. The reason the earth has such a high gravitational pull is because of the extremely large amount of mass it has. Example - Drop a pencil...the earth also moved in the direction the pencil was dropped.....just not very much.

All mass has an attraction to other mass. In other words, masses attract.

There is a center of the overall gravatational force yes, but did you know that at the moon there is still 70 some percent of the earths gravity? Even at the moon's distance, if the moon wasn't there and you were, you'd weigh about 3/4 of what you do here.

 

[rkboz]

I'm gonna have to go with temprature. colder shrinks the strings and hotter vice versa. An arrow doesn't have enough wind resistance to be affected as much as you say. Move your peep (string shrink) just a hair and you get big shot movement......................

 

[chrstphr]

When i shoot in Las Vegas (2023 above sea level) my marks are set. Then i go shoot in cali at el Dorado Park (at sea level) and my sight marks always have to go higher ( more air to shoot thru). When i go to Nationals in Colorado Springs (6035 above sea level) my sight marks drop to lower than in Vegas ( less air to shoot thru). Its all from air density. The less air to shoot thru, the less drag, the more air to shoot thru, the more drag. More drag and your arrow is slower, less drag and your arrow is faster.

you always set your marks at the altitude you will be shooting. IMHO.


Chris