Ashby and velocity?

[Biathlonman]

So I've read most of the Ashby studies and I don't recall velocity ever being mentioned.  Surely velocity has to have something to do with it.  Now I'm not a big velocity guy, but I just borrowed a cronograph to play with it.  Curious what the numbers mean.

[straitera]

mass x velocity = energy (expressed in Newtons I believe?) Convert to ft/lbs for relationship to kinetic energy which itself is a misnomer for bowhunt purposes yet does offer reasonable estimate of force through any given animal. Ashby's research was aimed towards "penetration" mostly of big game.

Like you, heavy arrow speed is important to a point. I'd not give up my Hills to shoot Turkish horse bows which are the fastest trad bow I know of.

[JimB]

I've noticed that too.I can't remember if he explained that anywhere.If you know the momentum formula,you can take his momentum figure and sort of work backwards and also using the arrow weight,find the exact velocity.

Keep in mind,I believe he chronographs the speed at the target,not directly in front of the bow.

Here is an example,if you really want to know the speed.One of Doc's last setups,listed:ACS-CX 54#,Impact force .474 slug feet,655 gr arrow.

.474 X 225218=106753.332 divided by 655 (arrow weight)=162.98 fps.That is his arrow speed at the target.

You did ask.

[Doc Nock]

And that would be, JimB, if and only if (this is a question, honest), if the arrow was perfectly tuned to the bow?  So many places for an arrow in flight to LOOSE energy due to oscillations beyond normal paradox, etc, etc, etc before it GOT to the target, thus affecting REAL Speed on target, yes?

If a shooter's chrono #'s are consistent, and he's got a well tuned set up, the chronie tells him he's got a decent and consistent release, eh?

Beyond that...on-impact damage and penetration is a lot of factors...broad head design, sharpeness, tissue impacted...etc.

Bottom line, tune em and shoot what you like that flies well and have fun doing it!

[elkbreath]

http://www.tradgang.com/ashby/Momentum%20Kinetic%20Energy%20and%20Arrow%20Penetration.htm

He discusses velocity thoughts in this quick synopsis.  Again, he was primarily concerned with penetration.

[khardrunner]

The velocity difference at the target vs. at the bow is negligible for an aerodynamic projectile.

[pdk25]

Originally posted by khardrunner:
The velocity difference at the target vs. at the bow is negligible for an aerodynamic projectile.

Fletching isn't aerodynamic, my friend.

[khardrunner]

It is aerodynamic enough.

Watch mythbusters "walking on water" episode. They chrono an arrow out of a light bow there at several distances with only a small, nearly negligible change in velocity. It proves that arrows behave like other aerodynamic projectiles, especially at short distances.

At the distances we shoot, horizontally speaking the velocity is almost constant. Vertically of course is a different matter.

[Chain2]

I am having issues with this also. I picked up another bow 55lbs at 32" and I chronoed my arrow at 166 fps but it is less than thew 650 gr arrow weight Dr. Ashby favors in his reports. I also have an arrow combo I want to try that is 594 gr with over 20 % FOC but an torn between a reasonable trajectory and weight/momentum. Thank you

[Hoyt]

Does the dynamic spine work out on the EFOC arrows?

[JimB]

Originally posted by Chain2:
I am having issues with this also. I picked up another bow 55lbs at 32" and I chronoed my arrow at 166 fps but it is less than thew 650 gr arrow weight Dr. Ashby favors in his reports. I also have an arrow combo I want to try that is 594 gr with over 20 % FOC but an torn between a reasonable trajectory and weight/momentum. Thank you

Chain2,I don't think you can go wrong with either.Both are good hunting weight arrows for your setup.I personally can't see the trajectory difference that 50 grs makes on my arrows at my normal shooting differences.You should try that for yourself though,pick the one you like and tune it well.

[Chain2]

Thank you. My concern is my first hunt with this bow will be for elk this fall. It will be my first archery elk hunt, a bit different than my 300 mag.

[JimB]

I'm sure you will be just fine if your arrows are tuned well and you can put them where they need to go.A lot of elk have been efficiently harvested with less.It is brought up a lot that Fred Eichler took most of his North American big game with a bow 54# at his draw length and arrows a little lighter than yours.

Good luck on that elk hunt.That time will pass before you know it.

[elkbreath]

whats the point of impact differeance at say... 20 yards.. with 50 added grains up front?  I know for me I wouldn't be able to tell the difference much.   If the EFOC flies well, I'd say use it!  Sure cant hurt.  Confidence goes along way out there.  With both being adequate arrows, one having a slightly flatter trajectory, the other penetrating better, which one will give you more confidence in your setup?  

Since for me, the POI wouldn't change much, I'd use the one with even slightly higher ability to penetrate.  Good luck and enjoy it either way!

[**DONOTDELETE**]

a 50 pound bow shooting 500 grains will kill any big game animal you choose to hunt if you do your part..... period.

 Ashby's findings proved heavier arrows in lighter poundage bows had better penetration..... but...When you start measuring how far the arrow is sticking into the dirt after its passed through the animal it'd moot point i think.

i like a good balance of flat trajectory and arrow weight myself. 10-11 gpp will typically give that to you.

Btw....If you hit the shoulder bone on an elk, it don't matter if you are using a high powered rifle, it isn't going down and staying there....

[Biathlonman]

So my 650gr. Arrow with 25% foc at only 150 should be ok to tackle deer and black bear?

[ChuckC]

It should be fine,  but you can likely get a bit more speed (if you wish) and still stay with a fairly heavy arrow.  There are LOTS of options available to us.  Deer and bear are not especially hard to penetrate.
ChuckC

[JimB]

Originally posted by Biathlonman:
So my 650gr. Arrow with 25% foc at only 150 should be ok to tackle deer and black bear?

As long as you don't mind your broadhead burying itself in the dirt on the other side.It is an excellent setup and should be good for elk.Forget what you have been told about speed and find out for yourself.

[Doc Nock]

Sharpeness of the pointy thing and placement trumps speed every time!!!

[Breeze430]

Velocity has to be in the equation gentleman.. it's physics . Mass x Velocity. It does effect penetration. Is it the most important thing no. Simple analogy. Do you want to shoot a home invader with a .22 or a .45? Big object moving  slow, but fast for it's size, or small object moving fast?