arrow spine and wood grain

[Vanya Goud]

So what is the correct orientation of wood grain when spine testing an arrow shaft? If you place a shaft on a spine tester and rotate it you get a selection of deflections....which one is the correct spine?

Interestingly, a friend of mine put a selection of shafts in a sash clamp to see which way each one bent in relation to the grain. Each one was different. So given that under pressure a shaft will always bend to its' weakest direction first, how do you make sure it bends away from the bow. I know the general rule is that the nock is orientated so that the string will be perpendicular to the grain, but is this always right?

Any thoughts?

[geoffretired]

Originally Posted by Vanya Goud

Each one was different. So given that under pressure a shaft will always bend to its' weakest direction first,

I'm not sure that the above is strictly correct, when applied to archery.
If you hold your arrow and bend it by hand, it bends according to which way it is held and in which direction you apply your bending force. Hold it gently and you can sometimes feel it tending to turn so it bends in its weakest direction.
An arrow on a string is bent by the pressure from the power stroke but the direction is applied by the geometry/mechanics(if they are the right terms) of the release, causing it to bend towards the bow first. The arrow will be unable to turn as the nock is located on the string.
I have a feeling the grain direction is more to do with safety. Get it wrong, and if the arrow breaks, the sharp end is directed to the bowarm /bowhand.
I can never remember which is the safe way however.
Someone will let us know soon. I am keen to find out, too.

[English Bowman]

Originally Posted by geoffretired

Someone will let us know soon. I am keen to find out, too.

Since you insist....try this wooden arrow making guide

Am working on a new version so should be updated soon, but any comments are welcome

Thanks

Daniel

[geoffretired]

Hi EB,
Thanks for the link.
I've read it and it all makes good sense to me.
Just out of curiosity, you say the spine varies according to the direction in which it is measured. Do the stiffer spines, round the shaft, tend to be the ones that are also the right way for the grain in the finished arrow?Or put another way, does the finished arrow have its stiffest spine horizontal?

[Vanya Goud]

Originally Posted by geoffretired

Hi EB,
Thanks for the link.
I've read it and it all makes good sense to me.
Just out of curiosity, you say the spine varies according to the direction in which it is measured. Do the stiffer spines, round the shaft, tend to be the ones that are also the right way for the grain in the finished arrow?Or put another way, does the finished arrow have its stiffest spine horizontal?

No, the way it was described to me is that the spine was variable and not always related to the grain direction.

However, the direction of force applied by a sash clamp and a shot release will be different, but whether this over-rides any variation in orientation of the weakest spine direction I don't know.

[geoffretired]

Hi Vanya Goud,
Thanks for the update. So the stiffest spine measurement could be in any direction? It depends on each piece of wood then, rather than grain direction.That's good to know.
Having read English Bowman's article, the over riding aspect of the grain direction is for safety. And spine is measured in the direction of the grain as that is the way the arrow will bend on release.

[SVL]

Sounds like we could do with some high speed video footage of longbow shooting. Perhaps the same arrow but with different nock orrientation for each shot.

[geoffretired]

Agree with that SVL. Wouldn't it be good to see what different set ups create; and then a video of your own shooting to see what that shows up.

[Macbow]

Daniel pretty much sums it all up perfectly.
If you look at a shaft there will be two sides where the edge grain is clearly visible. Check it on a spine tester and it will be stiffer when the edge grain is running vertically. That is the side you usually want against your riser.
Static spine as measured on a spine tester can only measure the stiffness of a particular shaft. It is a helpful indicator that a collection of shafts are reasonably close regarding stiffness but no more than that.
The acid test of an arrow is how it flies from a particular bow. A truly matched set of arrows is when they all group together irrespective of spine stiffness.
As far as actual grain direction goes my spine tester cannot differentiate whether a shaft is placed on the tester with the direction with or against the grain.
I prefer that the grain feathers towards the nock end - easier to taper when you are going with the grain - and should a shaft break on release possibly less chance of a shard of pine penetrating my bow hand.It also somehow seems more aerodynamic going with the grain.

[geoffretired]

Macbow, can I just clarify something. You say you prefer the grain feathers towards the back, and mention the breaking issue in reference to that. I take it you are looking at the underneath surface of the arrow, underneath when on the string that is. When looking at the upper surface, while on the string, the feathering will be towards the front, yes? Or are you talking about barrelled arrows?