Arrow Spysics and Selection

Where's Bruce?

Where's Bruce?

WKR
Joined
Sep 22, 2013
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Arrow Physics and Selection

I admit I am still learning everything about hunting and archery and though am comfortable with my progress thus far, recognize I will be long dead and buried before I know 1/10th what most of you know. With that in mind, I'd like to better understand the physics of arrows. I read about spine selection, flex, understand the differences in stiffness, how diameters and fletching and heads influence the flight but what I have not found is a formula for creating the ideal arrow and am wondering if there is one. Now I am shooting 29 1/4" long Axis N-fused 10.3gpi shafts with 2" blazers and a 150gr broadhead. My DL is 27 1/2" and DW is 68lbs. I am not shooting for speed but momentum as i typically am shooting at critters bigger than deer. I just don't quite understand how to combine all the data to maximize the flight and penetration characteristics of my arrows. Is there research that defines the optimum arrow design or is it like everything else in archery...which seem to me to be personal preference? Are my arrows too stiff?
 
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Where's Bruce? said:
Are my arrows too stiff?
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I don't know, but they're awfully LONG. You're shooting an arrow almost 2" longer than your draw length. I'm shooting an arrow more than 2" shorter than my draw length. Now.......they may be fine for your setup at that length, but you have a huge amount of room there for experimenting with length, which directly affects the stiffness of the arrow. I would think you could shoot 400's 3-4 inches shorter, even with your 150gr heads and still not be too weak. There are software programs such as Ontarget 2 that will let you play around to find your ideal arrow setup. But from my experience that program always recommends a pretty stiff arrow. Other's think that it's right on par.
 
What spine are they now? With that length, even at .300 they wouldnt be too stiff. You may be too weak if anything less than .300.
 
In that case cut them back as much as you can or go up to .300. You definitely are not too stiff, you are weak with that length and point weight. I shoot a very similar set up with 145 gr of head and insert weight, plus the insert. I shoot 28.5" .300s and they tune and shoot beautifully. You are better off too stiff than even a little weak.
 
No disrespect but this is bad advice on the arrow length. I agree 100% on the length will change spine and performance. Look at Easton's tuning guide, They state 1" beyond the farthest point of the bow with broad heads . You are not gaining much of anything by cutting an arrow an inch or 2 shorter. Can you cut them shorter, yes 100%. Can you cut them 1/4" beyond your rest, yes 100% but why? You are shooting a broad head and you want the clearance. Longer arrows tend to be more consistent and accurate. Look aT long range target shooters...they do NOT cut their arrows SHORT AS THEY CAN. They leave them very long. why? They want the length for accuracy. IMHO, Just my 25 years of experience

5MilesBack said:
I don't know, but they're awfully LONG. You're shooting an arrow almost 2" longer than your draw length. I'm shooting an arrow more than 2" shorter than my draw length. Now.......they may be fine for your setup at that length, but you have a huge amount of room there for experimenting with length, which directly affects the stiffness of the arrow. I would think you could shoot 400's 3-4 inches shorter, even with your 150gr heads and still not be too weak. There are software programs such as Ontarget 2 that will let you play around to find your ideal arrow setup. But from my experience that program always recommends a pretty stiff arrow. Other's think that it's right on par.
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Then shoot whatever floats your boat. 90% of my shooting is at 40+.......the further the better as far as I'm concerned. Perhaps I should try a 36" arrow. Of course my short arrows already are longer than your long ones.

And too weak at 27 1/2" draw at 68lbs with 340's.........seriously? I highly doubt that.
 
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when it comes to accuracy, proper arrow spine trounces all! that includes weight and length. So, if you want to shoot those broadheads you need to either cut your existing arrow back to 27.5 - 28", or buy new .300 spine arrows if you want to keep them long.
 
I'm with 5miles...my sticks are 2+" shorter than my AMO/ATA draw length. There's a number of reasons for cutting them short, and I also agree that the correct spine for the arrows trumps length for accuracy. The other funny thing is that my sticks are still longer than most of those target guys' arrows are, and I'm guessing that 5miles are too. Most of those target guys have slightly shorter DLs, and the ones that have longer DLs, more similar to 5miles and mine...well, they're cutting their arrows 'shorter' than their DLs too.
 
Back to the topic...I don't think there is ONE perfect arrow. I think there are perfect arrows for the particular application at hand. What amounts to perfect, depends a lot on what the individual wants in that particular situation.
 
SDHNTR said:
when it comes to accuracy, proper arrow spine trounces all! that includes weight and length. So, if you want to shoot those broadheads you need to either cut your existing arrow back to 27.5 - 28", or buy new .300 spine arrows if you want to keep them long.
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I'm going to disagree with you here. Arrow spine is not an end all be all to good accuracy or tunability. I've tuned plenty of bows with improperly spined arrows that have shot lights out, even with broadheads. Case in point is Cam Hanes set up. Good spine is just one part of the equation.
 
Choosing an arrow is a combination of spine, and weight. I pick a weight I want to shoot, 450-480 ish grains. I find an arrow that will fit into that range with proper spine and adjust length accordingly. Spine is important, but too stiff and too weak can be tuned just fine.
 
OR Archer said:
I'm going to disagree with you here. Arrow spine is not an end all be all to good accuracy or tunability. I've tuned plenty of bows with improperly spined arrows that have shot lights out, even with broadheads. Case in point is Cam Hanes set up. Good spine is just one part of the equation.
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Other then shooting a lighter GPI and getting a little more FPS. Are there any advantages to shooting an under spinned arrow?

I just don't understand if someone is buying new arrows why someone would purposely shoot a weak arrow. If I got a new bow and had a bunch of arrows from and old bow that are weak spinned for the new bow I see trying to make them work.
 
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You guys are giving me a headache...or maybe that's my heart. Hard to tell. How's my spine look? As for application, I am looking for an arrow in the 450-475gr range capable of sailing out to 50 yards and pass thru an elk. If the BH is too heavy, what would be more appropriate? Thanks.
 
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