Spine testing different kinds of wood?

[frank4570]

It seems to me that the amount of force required to bend an arrow might not correlate to how much spring that particular wood might have. A piece if wood might be stiff but still sluggish.
 I have a whole bunch of dry sticks here. Some wild Rose, some hazelnut, probably some hickory and dogwood, and a hand full of really nice river cane.
 Will spine testing be almost useless? Or am I just over thinking this?   :confused:

Thanks!

[ChuckC]

Ultimately, if the arrow shoots well out of a bow, it works, tested or not.  

Spine testing just helps choose the ones that are most likely to work ( once you know what that takes...).

[Shadowhnter]

Spine is spine no matter wood type. Spine testing would eliminate those too far from where you need to be, as already stated, if you have a target spine in mind.

[Orion]

Spine testing will put you in the ball park, but your observation that some materials recover faster than others is also true.  Carbon recovers faster than wood, for example.  

I've also found that I needed to increase spine by 5# to 10# when I moved from a mid weight softwood like Sitka spruce or POC to a much physically heavier birch or hickory shaft, in part because the hardwoods don't recover as fast (out of the same bow, all other things being equal).

[BAK]

No, spine is not spine.  If that were true there would be no difference in performance between POC and carbon, and we all no there is a great difference.

It is not just about the arrows stiffness, but also about how rapidly it recovers after being bent.

[SC Bowhunter]

Spine is not the arrows recovery rate after being bent.
It is the arrows stiffness.
Hence, you can have 50# spined arrows in carbon, aluminum, POC, Douglas Fir, etc.
They are all spined at 50# but each has a different recovery rate and flight characteristics.

[ChuckC]

IS this gonna be like paradox ?

[BAK]

When someone says that spine is spine I interpret that to mean an arrow made out of wood and one made out of carbon, both spined at.500 will react the same.  

Of course they don't.   So I guess to me  spine refers to the dynamic performance, not the static measurement.

[Shadowhnter]

Originally posted by BAK:
When someone says that spine is spine I interpret that to mean an arrow made out of wood and one made out of carbon, both spined at.500 will react the same.  

Of course they don't.   So I guess to me  spine refers to the dynamic performance, not the static measurement.

Someone did NOT say spine is spine....SOMEONE said spine is spine no matter what kind of WOOD. SOMEONE never mentioned carbons or aluminums, as I think the OP was talking about wood wasnt he?

[BAK]

It also varies between wood species as far as dynamic performance is concerned.

[Shadowhnter]

Originally posted by SC Bowhunter:
Spine is not the arrows recovery rate after being bent.
It is the arrows stiffness.
Hence, you can have 50# spined arrows in carbon, aluminum, POC, Douglas Fir, etc.
They are all spined at 50# but each has a different recovery rate and flight characteristics.

This ^^^^    

[AkDan]

Well spine on a spine tester as the op posted is just that static spine nothing more nothing less.  

Where the confusion started was the op's post on recovery.   Without directly saying it.  Referencing dynamic spine

Static spine is a measurement .500 is .500 regardless if its rebar or a spahgetti noodle.   A measurement of deflection. That allows you to batch similar spined shafts.  


Dynamic is not  a measurement as much as it is a action (or in our case reaction) to being shot.    Change a variable.   To keep it simple, adding weight to the point or nock end will change the DS.    The static spine stays the same.  

They are not inter changeable.   sp vs dp.    This thread seems to be attempting to, or confusing with the idea it can and or is.

[frank4570]

Ah, I get it now. Spine is one component and is a rough predictor of what dynamic spine is likely to be. But it does not exactly correlate to arrow recovery. Right??


   And I need to get up to speed on the terminology.

[SC Bowhunter]

Shadowhnter,
I don't get your problem with my post.
I may not have stated it as clearly as AkDan did, but my point was the same.
Dynamic spine and static spine are two different things and can not be interchanged.

[Orion]

You got it frank 4570. Very nice and accurate summary.

[kenneth butler]

Orion beat me to it. Frank4570 nailed it. Make your arrows close in spine to what flies well out of your bow. Then adjust length and or point weight as needed. My observations are that wood usually requires a little stiffer spine. It recovers a little slower.    Ken

[Shadowhnter]

Originally posted by SC Bowhunter:
Shadowhnter,
I don't get your problem with my post.
I may not have stated it as clearly as AkDan did, but my point was the same.
Dynamic spine and static spine are two different things and can not be interchanged.

Lol! You dont get it, because there is no problem with your post! I used your post to answer a prior post again. I was agreeing with your post. The head banging wasnt directed at your post, but the discouragement involved around prior post.

[Stumpkiller]

I'm going with Shadowhunter and stiffness being = to spine regardless of material.  "Spine" is defined as deflection from a 2# weight between 28" centers.  Pretty straight forward no matter what material you are measuring.  Other factors do come into play beyond that (ye olde dynamic spine - or leprechaun influence, etc. ).  Recovery may be quicker with carbon - but so too is tapering a wood shaft for the last 12".  

The way it shoots for you is the determinate no matter the material.

[Prairie Drifter]

AMO spine is measured on 26" centers with a 2# weight

ASTM is 1.94# on 28" centers

[tecum-tha]

1.)
Spine in # is not the stiffness of an arrow.
2.)
Spine in # is a correlation between a static deflection in inches using a standardized method of testing and the poundage of a corresponding bow out of which a shaft having that deflection is supposed to shoot well out of (= matching dynamic behavior).

The testing method of wood arrows is:
26" on centers "roller supports", 2# load in center, deflection measured in inches at center.
Shaft is placed with grain orientation parallel to the direction of loading.

Testing method for aluminum and carbons is:
28" on centers "roller supports", 1.94# load at center, deflection in inches at center.

Test method for aluminum and carbon can be well converted by using the following formula:
(26/ (deflection of carbon/aluminum shaft))x1.2115= equivalent wood spine in #.

The wood spine charts was developed in the late 1930ies. Bows were wooden or wood laminated reflex longbows with limited shelf cut outs. Essentially Hill Style Longbows. The charts are most accurate in the range of 30-50#, the predominant weight at the time. For these bows the correlation works almost perfect as is.
For spine deflections above 55-60#, the difference between the # spine numbers gets smaller and smaller, thus the inaccuracy mounts.
This can be prevented by using 3# and adjusting the scale accordingly.

For modern bows(Recurve/hybrids/wheelies) and modern string materials the old wood shaft correlation is generally adjusted, as these bows require stiffer spined shafts.

Another problem of spine is center cut of bow and arrow diameter.
Existing correlations work well with diameters equaling the wooden shaft diameters. Ultra slim shafts will require less bending to clear the bow and will align closer to the plane of the string. To shoot well, these will need to be stiffer.
The same is true for cut to center or slightly cut past center bows.