A question for bow pro's

[dla]

Discovered something interesting. I was Chrono'ing some different weight arrows through my new Diamond Stud.

Results from my Chrony Alpha-Master with a range of arrow weights
ICS Hunter(1) Carbonhawk(2) ICS CamoHunter(3) ICS Hunter(4)
60lb 253fps 251fps 242fps
70lb 283fps 280fps 272fps 282fps **

1. Beman ICS Hunter, 300 spine, 445gr finished weight
2. Beman Carbonhawk 16/64, 75/85 spine,460gr finished weight
3. Beman ICS CamoHunter, 300 spine, 490gr finished weight
4. Beman ICS Hunter, 340 spine, 422gr finished weight

I expected the lightest arrow (422gr) to shoot the fastest. But it didn't. And I ran a dozen arrows over the Chrony to make sure it wasn't funky lighting, etc.


Couple of questions:

1. Why did the heavier 300 spine arrow shoot faster than the lighter 340 spine arrow?
2. Since all compound bows are shoot through, i.e the string is in line with the arrow rest and line of sight, why don't we all shoot the absolute stiffest arrow made? What benefit is selecting the arrow flexation?

[Catch 22]

Your fastest arrows were your lightest in physical weight. Which makes sense. Spine weight affects arrow flight in the accuracy department.
Someone who knows how to explain this, please feel free to correct me or add to this.

[Browning308]

I’m no bow pro by any means; in fact last year was my first year bow hunting. This is my

As an arrow leaves the bow it does not fly perfectly straight, it bends and flexes, which gives it accuracy and speed.

The spine is how stiff the arrow is and how resistant it is to bending and flexing. The heavier your draw weight the stiffer you want your spine to be otherwise the force the string/bow exerts on the arrow can cause to much flex leading to inaccurate shots and even breaking the arrow.
Bows with lower draw weights will require a lower spine arrow.

So your arrow should have an appropriate stiffness for your bow and draw weight. Different spine arrows will perform different from different bows.

I guess an answer to your question could be that the heavier grain lighter spine arrow in your experiment is the right fit for your bow, bends and flexes better, receives the optimal amount of force out of the others tested. Looks like a win win situation, more mass greater speed.

I am assuming you only shot through the chronograph a few yards away. It would be interesting to see how the arrows preformed at 20, 40, and 60 yards

[3fletch]

As others have mentioned, arrow spline is a very big part of your speed. A week spined arrow will bend under the force and will tend to be a bit slower than the same weight but stiffer spined arrow. I believe one should also check the spine or deflection of an arrow when choosing one for hunting. Another thing one can do is to reduce your tip weight, this will help reduce the bending or deflection of the arrow and should speed it up a bit..

Good information and good luck...


Fletch!

[dla]

Originally Posted by Catch 22

Your fastest arrows were your lightest in physical weight. Which makes sense. Spine weight affects arrow flight in the accuracy department.
Someone who knows how to explain this, please feel free to correct me or add to this.

This BBS doesn't allow me to post a table, which is the original format, so my data gets kindof busy. The 445gr 300 spine was consistantly faster than the 422gr 340 spine.

[Chesapeake]

The bow wasted some of its energy flexing the weaker spined arrow. If you tried to shoot a wet noodle it wouldnt go anywhere, it would just fold up.

I would say with a shoot through bow you should shoot the stiffest arrow that flies well. The loss of energy to flexing will be the same at the other end as the arrow tries to penetrate. A stiffer arrow would be better in my mind.

I would think that with a shoot through bow and mechanical release you could get good flight with a pretty stiff arrow.

[jnicholson]

Wow,
Talk about dialing it in! These guys are right on track on their explanation.
I remember the year I won my first bow fishing contest and my partner and I ordered Onieda Screaming Eagles with the proceeds because it was advertized that it was the first production bow to shoot 300 fps. We figured we'd be shooting whitetails at 100 yards.
Then we chrono'd them when they arrived and while they were much faster and sounded like a .22 going off ... we couldn't get 280 out of them. We called the factory and they said lighter arrows, blah blah blah.
So we did that and went through all the spine problems you're experiencing. we finally got up to about 290 with field points. We called again and they said over draw ....
What? We're hunting with them what the heck is an overdraw.... so we ordered an overdraw (no one had them at the time) and tried again. We finally got the bows to shoot 300 fps with field points and pulling 90lbs. There was no way a broad head was going to go that fast and the bows sounded like they were going to explode any minute because we were told to take the silencers off too to increase speed.

In retro spect, we were young and excited and while it was fun getting there we should have spent more time building tree stands.

Ask yourself why and what's the result and really the need before you spend too much more of your life with this.

John

[dla]

Thanks for the replies folks!

I'm not looking to hit 300fps with a hunting arrow - 280fps is plenty. I know that manufacturers hype the velocities somewhat. This Diamond Stud will be a sweet shooter once the arrow rest problem is solved.

I really like the "wet noodle" explanation