Arrow diameter and tuning?

[Biathlonman]

I know that there are no hard and fast rules, but I was wondering what the hard and fast rules say about diameter as it relates to tuning.     If I was shooting 11/32" arrows and switch to 23/64 will I need more or less point weight?  Or the other way, I've been shooting 5/16" carbon and just picked up some slimmer carbons, more or less point weight?

[RedStag5728]

23/64th shafts are stiffer than 11/32, it's not only spine which is affected but also total mass. As far as tuning goes, I would get a test kit of multiple grain weight field points and bare shaft tune your arrow. Start off at 10 yards and shoot one shaft and see how it flies.

If it strikes the target nock left, the spine is stiff which means you need to add more weight, nock right it is weak and you should lower tip weight. Keep adjusting weight until they fly decent at 10 yards, then step back to 15 or 20 yards and fine tune it. This is how I do it and I am sure I am not the only one        

[damascusdave]

Those are factors that are taken into account in Stu Miller's Dynamic Spine calculator...that will point you in the right direction...I do shoot arrows from 17/64 to 23/64 in diameter and it is just too confusing to commit that sort of information to memory

DDave

[Gordon Jabben]

I have always grouped 11/32" and 23/64" together as long as they were the same spine and weight and they seemed to fly and group the same.

[RedStag5728]

I personally take stu's calculator with a grain of salt, it can get you close but I personally think bareshaft tuning is the way to go.

True that everyone has their own way, this is just what I do and my 2 cents    

[Biathlonman]

I know how to tune, that's not what I'm asking.  Diameter, center shot relation, etc.  That's what I'm looking for.

[BAK]

It stands to reason, if building the strike plate out compensates for weak spine, larger diameter arrows(spined the same) will do the same thing.  Just use the same logic.

[Biathlonman]

So a larger diameter should, in theory, act a little stiffer as it's further from center?

[Orion]

[Orion]

Larger diameter places the center of the arrow further from the center of the bow.  Thus it must flex more to achieve the same arrow flight.  To flex more, it's dynamic spine needs to be softened with additional point weight.  Conversely, a skinnier arrow is closer to the center of the bow so it does not need to flex as much, and to increase dynamic spine and reduce flex, you would lighten the point weight.

So, going from 5/16 to 9/32, you would lighten point weight a little.  That's if the spine to start is identical in both instances, which it probably isn't. With that small of an arrow diameter change, quite likely you can stay with the same point weight.  You're more likely to run into a problem of the spines being quite a bit different, which might require a change in point weight.

[gonefishing600]

I hate when I'm wrong!

[gonefishing600]

I stand corrected!

[Orion]

gone fishing.  We're close, but not quite in agreement.  Building out the side plate is done to accommodate a shaft that's too weak.  it doesn't make the shaft weaker.  If the shaft is too stiff and the side plate is built out, it will shoot stiffer yet, i.e., shoot further to the left for a right handed shooter.

Likewise, a skinnier shaft won't give a stiffer reading (remember, we're supposedly starting with shafts that are identically spined), but because it is closer to the center of the bow, a stiffer shaft is needed. The only way to impart more spine to that skinny shaft  is to lessen point weight or shorten the arrow. Well, adding weight to the nock end also stiffens spine.

[gonefishing600]

Is this the same thing as static spine and dynamic spine?

[Orion]

Static spine is measured on a spine tester.  It doesn't change for a given arrow.  However, we can change how the arrow acts under the forces of the shot, i.e., it's dynamic spine.  

We can make the arrow behave weaker (bend more) by adding point weight, , i.e., we decrease its dynamic spine.  Or we can make it behave more stiffly by shortening it, reducing point weight or adding weight to the nock end. That increases the dynamic spine.

Can't change an arrow's diameter, but arrows of the same static spine, but different diameters, will behave differently when shot, i.e., they will have different dynamic spines.

[gonefishing600]

Well Orion, this has connected several unconnected dots for me.

Thanks

[Orion]

And this is supposed to be a simple sport     Hope I helped out.