Draw weight and sight settings

[Harley]

I haven't thought this through, yet, but I was surprised at the following:

Previously, with a draw weight of 60# I sighted my Mathews Z7 in at 20, 30, 40, 50 and 60 yards, marking the different ranges on the slider sight. The muzzle velocity is 291 fps.

Pulling 60# is painful, due to injured shoulders.

Yesterday, I reduced the draw weight to 50# in hopes that I could practice over the summer, then run it back up to 60# for hunting season. The muzzle velocity is 270 fps.

Here's the surprise: at 20, 30 and 40 yards (the only distances I've shot since reducing the pull weight) I'm dead on at the same sight settings I established for 60#. The arrow takes longer to get there, but hits in the same spot; I'd expected it to hit lower.

Why doesn't it drop? Is it simply because, at 270 fps it's still shooting flat out to 40 yards? I'm certain it will eventually drop below the 60# settings at longer distances.

Harley

[deadon]

Harley, that is exactly what it sounds like to me. I did basically the same thing for the very same reasons, bad shoulders. gone back to my 243 for the same reason. at 50 and 60 yrds you should see a different impact point. By the way Ted Nugent shoots 90 arrows a day and has killed more animals than I have seen in the wild and he hunts with a 50lb pull and always has.He says if you can't pull your bow back slow and smooth without taking you eye of your intended target at any position you may draw at from a stand then you are pulling too much weight. I know guys the have to hold their bow over their heads and pull down to draw it until it breaks to the lighter weight. Its Crazy IMHO

[Harley]

Thanks, Deadon, for the confirmation; now I've got to see if the bow will group tightly at this "looser" setting.

Back in the days when I shot an 80# Oregon bow, I had to start my pull with the arrow pointing up about 45*. I've still got that bow, but I'll never draw it, again.

BTW, not to argue your point about Ted Nugent, but I've seen enough of his shooting/hunting, including Africa, to think that he takes shots so close to his stand that the draw weight wouldn't make any difference.

Harley

[dougedwards]

An interesting article

archeryreport.com/2010/03/arrow-flight-fact-fiction-pin-40-yards/

[Harley]

Doug, I just read your referenced article and find nothing to argue with; it seems a no-brainer to me.

The article is not relevant to setups using multiple pins, slider pins or pendulums, though. In a drawer, somewhere, I have my previously used pendulum sight, one that allowed me to hold dead on up to 30 yards when shooting my old bow at 265 fps; I wonder if that same sight would stretch to 40 yards with my 291 fps bow. Probably, but I've spent so much time setting everything up that I hate to take it all apart. I might, though.

Harley

[deadeye]

doug,thx for sharing that article,now if i can find that tap program! just yesterday i proved to an old friend archer who use to run my pro-shop that his 340gn @327fps was not flatter @ 75yds vs. my 491gn @ 272fps. it was very interesting when he couldnt play out there @ 95yds without a major setup change. harley- i dont know your arrow wt but you will probably be fine out to 60yds with that lower 50# drawweight. dont kill your self over 10lbs of drawweight ;D

[Harley]

Deadeye, when I note the deep target penetration of the 50# bow at extended ranges it makes me think you are right that I don't need a heavier draw weight, but I wish I could find a way to compute arrow velocity at a given distance other than MV; eg., 50 or 60 yards. That would allow a calculation of Momentum at those distances, which in turn would yield expectations of penetration.

Doesn't ANYBODY know how to do this?

Harley

[dougedwards]

May 30, 2010 10:44:33 GMT -5 Harley said:

Deadeye, when I note the deep target penetration of the 50# bow at extended ranges it makes me think you are right that I don't need a heavier draw weight, but I wish I could find a way to compute arrow velocity at a given distance other than MV; eg., 50 or 60 yards. That would allow a calculation of Momentum at those distances, which in turn would yield expectations of penetration.

Doesn't ANYBODY know how to do this?

Harley

I think TAP has a seperate program called "Two Speeds" in which you enter the MV speed as well as speed at 20 yards. It will then calculate speeds at different yardages if I am not mistaken. Below is a free download to a demo.

www.thearcheryprogram.com/index.php?option=com_docman&task=cat_view&gid=26&Itemid=92

Here is a link to a review of the TAP program.

archeryreport.com/2010/03/review-tap-archery-program-software/

[Harley]

Doug, I just downloaded the demo; this is a great program, but at first glance I was overwhelmed by it. At second glance I began to understand it, but now think the Anchor Sight makes calculations impossible because the program wants distances from the peep, and I don't have a peep. It needs the peep reference in order to compute geometrical distances.

I'll spend more time with it, later; thanks for the reference.

BTW, I actually joined a "physics" forum, today, and asked if any of their members could compute varying velocities, given only MV and grain weight of an arrow. I expect they will think this too elementary for their consideration.

Harley

[russkull]

Hello, Harley,

Even without your peep, you could calculate the distance to where the peep would be located.?.? Curious to see what your physics forum comes up with. I spent some time locating formulas for you. I did find a few specific to archery. Seems one person did his physics thesis on the various physics of archery.

[deadeye]

im just not sure distance to the peep would have anything to do with downrange velocity/probably trajectory, i would think arrow weight & mz/fps & degree of helical/&or vanes could affect this,but im not an engineer/ im interested for curiousity purposes also,find something let us know!

[Harley]

Here's what the physics forum came up with; as I posted elsewhere, it's been a lifetime since I was familiar with trigonometric functions. I think I'll go back to the TAPS program.

en.wikipedia.org/wiki/Projectile_motion

BTW, Russkull, that's a good point re: calculate from where the peep used to be.

[sw]

Jun 2, 2010 10:39:46 GMT -5 Harley said:

Here's what the physics forum came up with; as I posted elsewhere, it's been a lifetime since I was familiar with trigonometric functions. I think I'll go back to the TAPS program.

en.wikipedia.org/wiki/Projectile_motion

BTW, Russkull, that's a good point re: calculate from where the peep used to be.

Lloyd,
I used to go to such formulas but got frustrated that NEVER could I find a formula that allowed a compensation for air friction. We don't shoot in space. I'd think in a vacuum that the arrow would slowly accelerate by the vector caused by the acceleration of gravity x time squared. My answer, protect your chronograph well and shoot thru the window at various ranges. The Excalibre(Excalibur ?) web site has an arrow chart that might be interesting. 50# modern compound with a good broadhead won't be lacking in the energy dept. I know a world record recurve shooter(twice national champion - and only entered twice, back to back years) who shoots antelope out to over 100 yds with his 48# recurve. Pass-thrus. A modern 50# compound certainly has more energy than even the most efficient recurves(Palmer .

[Harley]

Steve, the reference to the physics forum (my reply #11, above) does account for friction as well as every other variable subsumed under Projectile Motion, but I couldn't begin to understand it.

I am indebted to DougEdwards for the following link:

www.pinwheelsoftware.com/sfa.aspx

This program does it all and doesn't require shooting through (or destroying) a chrony.

Harley