Arrow woods/Spine and 1970's arrow charts

[Don Stokes]

Frequently there are questions on these forums about how different arrow woods compare to each other. A decade or so ago I wrote an article for "Longbows & Recurves" magazine, and I thought I'd share the table from the article, since the magazine has been out of print for some years and this is probably new information for a lot of the TradGangers. The units for the column headings got scrambled in publication.

     

The far right column is a spine rating number based on specific gravity and bending strength (MOE). Port Orford Cedar has a rating of 4.O, and Osage orange (for illustration) is 1.6. Everything else falls in between. I also included the calculated weight of a 29", 23/64 shaft for each species.

Disclaimer: These numbers are based on averages found in the Wood Handbook, a publication of the USDA Forest Service. The coefficient of variation for some of these data is on the order of 40%, so there can be a lot of overlap between species. A good arrowsmith can pick lighter or heavier sets for any species.

Enjoy!

  ALSO....

Dave Worden submitted these "old time" arrow charts (mostly for stickbows) as a valid comparison against todays modern (compound) arrow charts - much obliged, Dave!
 
The charts below are from the Anderson Archery catalog from about 1973 ...

   

   

[Old York]

Neat!

Any guess as to what
"Spine Rating million psi"
means in laymen's terms?

Thanks

[Don Stokes]

That's what got scrambled. The headings for the columns should read:

Specific gravity
Modulus of Elasticity (MOE) (million psi)
Calculated weight of 29" 23/64 shaft (grains)
Radial toughness (in-lb)
Spine rating (MOE/SG)

Sorry 'bout that.

[Rob DiStefano]

summer '98 l&r ... (sorry, couldn't get the magazine moire off) ...

 

[Broken Arrows]

All that info is great but for the person who wants to go with wooden arrows for the first time, how does the info help them choose the wood arrow that best suits them?

[Don Stokes]

Broken Arrows, if you want to get the flattest shooting shaft, go with a high spine rating number. If you want heavy arrows, go with the lower spine rating numbers. If you want the best of both, choose a higher spine rating number and a higher mass weight from the calculated weight of a shaft. If you want toughness, it's obvious that hardwoods are the way to go. Unfortunately I couldn't find toughness numbers for all of the species. Hickory is almost indestructible, based on the toughness numbers and real-world experience.

For instance, Douglas fir looks really good as a flat-shooting, hard-hitting and relatively tough compromise in the softwood group. I prefer yellow poplar in the hardwoods because cucumber magnolia is almost impossible to find, and my arrows are heavy enough (usually around 600 grains) and tough enough without sacrificing a relatively flat trajectory.

Remember that these are averages, and a good supplier can choose heavier or lighter shafts from any species.

[Old York]

Okay, can anybody out there define "Radial Toughness" and the associated numbers/units as in the chart ?

[UnderControl16]

Could anybody tell me what grain i should be shooting for a 40#? Anyone know what the numbers are for a red ock shaft either?

[Don Stokes]

York, radial toughness is measured in inch-pounds. The test is done by putting a standard sized stick into a machine that breaks it with a swinging ball. The breaking force is measured as inch-pounds. The standard test gives us a method of comparing woods without personal bias.

UnderControl, there are several species of red oak with properties that vary a good bit. Generally, the dry specific gravity is around .65 and the MOE is around 1.9 million psi, which gives a spine rating of around 2.9, similar to ash and maple. That translates as heavy arrows. I shoot 600 grain arrows from my 40# bow, but that's just a matter of preference. The old rule of thumb is 10 grains per pound of draw weight, but many of us like more.

[UnderControl16]

What happens if you shoot under 10 grain per pound? Like what would happen if i shot a poplar shaft on a 40# bow? Also, what type of wood would i shoot then for a 75# pound bow?

[Don Stokes]

I don't change species when I change draw weight. All of my shafts are yellow poplar. You just go up in spine for heavier draw weights. In any given big batch of wood shafts, the weight of individual shafts will vary as much as 100 grains, so if you have enough shafts you can make matched dozens of about any weight you want within that range.

The heavier your arrows, the quieter the bow will be, all else equal. Some bowyers will void the warranty if you shoot arrows that are too light, like under 6 or 8 grains/#. Ultralight shafts are much harder on the bow than heavy ones. It's not likely you will have to worry about that, since most woods will give you heavier arrows than that anyhow.

[UnderControl16]

Ok but how is yellow poplar a hard wood? Do i just ahve a different type of poplar that is a soft wood or what?

[Leo L.]

Where's cypress on that chart?

[Don Stokes]

UnderControl, hardwoods and softwoods are separated technically by vegetative characteristics, like type of leaves, type of seeds, etc. Some hardwoods are "softer" than softwoods, and vice versa. Yellow poplar is a hardwood, but it's lighter than many other hardwoods.

Leo, cypress has a dry specific gravity of .46 and an MOE of 1.44 million psi. That gives it a spine rating of 3.1, which would make for relatively heavy arrows for a softwood species.

[UnderControl16]

Thanks Don!

[Terry Green]

Interesting.....thanks.

[dbscott]

Should you recheck your spine weights if you ordered them according to what you need?  I ordered pre-spined and pre tapered shafts but did not double check them when I recieved them.

[mstk]

Hi all,

Can someone explain and express the units?

I can use these data very well but its not clear enough.

[divecon10]

Really interesting stuff Don, Wish I knew more about our sticks, there r some really hard ones and I wonder if anyone has done a similar comparison.

[Don Stokes]

Divecon, there is some similar information that I've run across in old literature, published under the title "Archery, the Technical Side" if I remember correctly. I have a copy around here somewhere...

I looked hard at a wood from down under that seemed to have excellent properties, but the export to the US was just too much to handle with any economy. Can't remember what it was called, unfortunately. It was something that Dan Quillian came up with. I know there's bound to be some good stuff down there. If you have a government funded department like our USDA Forest Products Laboratory, that would be a good place to look for info.

mstk, it's hard to explain any better than I tried to do earlier in this thread. That's why I developed the spine rating number, to try to simplify the technical jargon.