5/16" and 11/32"

[Blinkybill]

Hi all!
I was just wandering how much of a difference there would be in arrow velocity between a 5/16" shaft and an 11/32" shaft of the same weight and spine? And how much of a difference would there be in strength and durability?
Thanks,

Ben

[Stickbow Hunter]

I couldn't say what the difference in arra speed would be but here is a couple of observations for you to consider. If the two different diameter shafts were of the same spine most often the thinner shaft would be heavier than (or at least as heavy as) the thicker one as it is denser with its extra stiffness for its diameter. I think the thiner shaft would be at least as strong as the thicker one. If you were going to be hunting I would use the thinner shaft as it can aid in penetration.

Jeff

[buzz]

Hi all!
I was just wandering how much of a difference there would be in arrow velocity between a 5/16" shaft and an 11/32" shaft of the same weight and spine? And how much of a difference would there be in strength and durability?
Thanks,

Ben

It should be negligible.
Given the same weight and initial velocity (ie bow poundage) the diameter becomes irrelevant.

There have been observations made in extreme cases of the arrow wood being damaged by use and thus the spine-ing going out the window - but I cant think whether the tighter grain on the smaller shaft of the same weight would be a benefit over the more open grain of the larger diameter shaft of the same weight.

Jeff's point about diameter is very valid - for hunting purposes when comparing two shafts of differing diameter with the same velocity, all other things being equal the smaller shaft *should* penetrate better because the all the force is pushing against a smaller area than with a larger shaft.

[jape]

I think there are too many variables to be sure. But Grahame A will tell ya!

I know many manage to bare-tune matching sets and get regular performance and flight but I have bare-tuned sets of matching spine and weight and still got erratic flight as far as grouping goes, and penetration. And I have tested a lot this year, I'm not talking about just one or two shots. Others say that spining is unnecessary and weight matching does it. I am sure that allowing for my errors and lack of skill, that individual arrow have something else in the mix!

I have in front of me right now two very different arrows our of a dozen odds-n-sods left over from a lot of different sets and tests over the last year.

These two are:
POC 5/16 spined 35/40, 29", 125gn broadhead, 3x4" shield feather straight, weight 442 gn
Hardwood 11/32 spined 45/50, 28", 125 gn field tip, 3x3" low round cut, weight 560gn

I take my 'left over' dozen out everyday and shoot them all randomly at ranges of 15/25/40/45 meters with 45# bow.
Allowing for the odd form errors, these two always fly consistently the same and penetrate the same within a six-inch margin of hit (good for me) and an inch of penetration either way out of 12 to 14 inches into a straw bale.

The others, from 300 to 600 gn and fletched from 2.5 to 5", 28 to 31 inch, 5/16,11/32 and 1/2, varying spines 35 to 50 and a bamboo - are all usually far more likely to go off at angles. BUT at those ranges they ALL penetrate within an inch or so of each other unless they hit at an angle!

By coincidence, these best two have red feathers, the rest have yellow, maybe that is why ...

[GrahameA]

Morning Roland

I think there are too many variables to be sure. But Grahame A will tell ya!

"Yes" and "No".

As Buzz said, the mass/velocity/columnar loading question is simple physics. Even taking hysteresis into account they will exit the bow with essentially the same velocity.

Different diameter means different surface areas and thus different drag and thus a different velocity downrange. However it may be relatively small.

The "Strength/Durability" question requires a Wood Technologist - Kevin will know the answer.

[Blinkybill]

Thanks for the replies Guys!
So does this mean that theres not really any advantage with choosing 11/32" diameter arrows to 5/16"?
Thanks,

Ben

[SlowBowInMO]

I will always opt for the smallest diameter shaft that provides the spine I need.

In theory an 11/32" should be slightly stronger than a 5/16" of the same spine, due to the greater diameter, but probably not enough as you'll ever notice it much in real life practice.

[Blinkybill]

Ok, Thanks SlowBowinMO.
I suppose I'll just stick to 5/16" then until I have to go up in spine.
Thanks,

Ben

[doc]

to achieve the right spine for your bow, the diameter may vary according to the wood type in the arrow shaft. Different woods have diff characteristics of course. Indeed different of same timber from differnt trees, diff growing conditions etc will not spine up the same. the is the beauty & art of trad over compound archery. chronograph = best way of assessing velocity of each arrow from your bow. Lenght , weights , fletching, bow, environmental & archer factors must all be considered.

speed of shot isnt as important as accuracy , and the ultimate power of the arrow's thump...momentum imvolves both mass & velocity. Heavy arrows are better for hunting. Target & club shoots dont require this so much.


KISS...keep it simple, keep having fun, & keep asking questions..the learning never stops! (says a rookie)

cheers, Doc

[Blinkybill]

Thanks for that Doc. I hadnt thought of that.
I agree accuracy is more important but I was just curious, thats all.

Ben