Arrow weight to spine ratio

[agd68]

Has anyone that makes shoot shafts or planed shafts noticed if there is a coralation between the weight of a shaft and it's spine. Todays rule of thumb on arrow weight is approx 10grs per pound of draw weight. I'm curious if anyone can confirm this. Eg, 600gr shafts of varing woods - are they all around the same spine ? Diameter may be differnt due to differnt wood densities. This may be why medevil fletchers did not factor spine,they had no way to measure it.They may have been accounting for  it by using the back door instead, by using arrow weight instead. Does this seem plausible or am I off base ?

[Stefan]

Medival fletchers were propably able to determine spine to some extend, probably by flexing the arrows. I find it unlikely they weight shafts..probably just trial and error and experience

Just as with bows they always have a similair weight (bowyers bible). But if you make arrows to kill people is spine really important, a heavy arrow (and according to your statement a higher spined arrow) penetrates better.

greetings stefan

[markinengland]

I weighed and spined a couple of thousand Bamboo shafts a while back. There was some correlation between weight and stiffness but some heavy shafts were relatively weak, some light shafts unexpectedly stiff. I think that generally density is a good indication but is not 100% reliable.



This is the bar graph I made from my results.  In this picture diameter is shown compared to spine but weight/spine showed  similar spread. I would expect that wooden shafts may be similar but haven't done a similar weight/spine comparison.

[agd68]

Mark in England, agreed no system is ever 100 % reliable. I wonder however, if bamboo being hollow may not adhere to this theory as well as a solid wooden shaft.

[markinengland]

Why would being hollow make a difference?
if you drilled a hole down the middle of a machined wooden shaft or shoot shaft, would the density/weight issue be materially changed?

[Slackbunny]

I don't think weight would be a consistent measurement of spine. There is just too much variation among wood from even the same species. The spine is definitely related to weight, but there are just too many other factors for weight to be a singular measure of it. I mean you have weight, diameter, orientation of grain, quality of wood, wood species, etc.

If you combined two or three of those factors together you could probably come up with a good model, but it would be awful hard to quantify the orientation of the grain or the quality of the wood.

[crooketarrow]

  I have'nt weighted nor spined a arrow for 15 years.
 Shoot arrow have a wide spine of about 10 #'s meaning arrow that shoots out of say a 45 # bow will also shoot out of around a 55 # bow.
  The closer the bows to center shot the spline ratio gets bigger.
  I'VE BEEN SHOOTING DOG WOOD ARROWS FOR SO LONG I CAN LOOK AT IT AND JUST TELL IF IT WILL SHOOT OUT OF THAT POUNDAGE BOW.
 If it don't I just save it I build lots of bows sooner or later I'll have a bow it will shoot from. I give them with the arrow with the bow I've just made for someone. But I'm uselly close when building a arrow.