Hello All!
More, undoubtedly oft-times repeated, newbie questions.
I didn't know there was such a thing as "spine" before today. I found a thread in one of the other forums (very slow day at work) about an spine measuring doovalackie and how an arrows spine had to match the poundage of the bow it was to be shot from. There seems to be a correlation between the diameter of the shaft and "spine" as well which is to be expected.
Is there a table anywhere as to what diameter of what timber falls between what ranges of "spine"?
How would you estimate the possible "spine" of prospective ash shoots before you cut them if you wanted to try making arrows from shoots as per Jay Massey's article in TBB 1? Has anybody else out there tried making arrows from shoots?
Andrea
Arrows & Spine
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Andrea Willett
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Stickbow Hunter
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Not really. Shafts of a set diameter can vary greatly in spine weight even when they are all made from the same species of timber. Each piece of wood can, and very often does, vary in stiffness.Is there a table anywhere as to what diameter of what timber falls between what ranges of "spine"?
I don't believe there is anyway of knowing what the spine will be of arra shafts made from shoots before they are dried.
Jeff
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Mick Smith
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- Location: Surf Coast Victoria
Hi Andrea
The spine of a shaft is the "stiffness" of the shaft. It would be possible to have a shaft with a diameter of 5/16 inch with a stiffer spine than a shaft with the larger 11/32 inch diameter, even when they are made of the same type of timber. There is normally some correlation between the diameter of shafts and the spine, ie 5/16 inch Port Orford cedar shafts are generally lighter spined than 23/64 inch cedar shafts, but the diameter is usually fairly irrelevant.
Say, you were looking for a lightweight shaft spined to suit a 50 pound bow, you may well try to buy some 5/16 inch cedar shafts because they would be physically lighter in weight than shafts with the same spine in a larger diameter.
When you buy shafts you usually specify the spine your require as well as the diameter you want. Some heavier spines may not be available in smaller diameter shafts. Some timbers are heavier and have a stiffer spine than other timbers even when the diameters are the same, as you would expect.
Have arrows that are spined correctly can be very important, particularly if you are shooting a bow, where the arrow is held some distance from the longitudinal centre of the bow, ie, a bow made without an arrow shelf, where the arrow must shoot around the bow in order to hit where it is aimed. With this type of bow, you need a shaft that will bend just the right amount when released. It needs to bend enough to clear the bow without contact, yet not that much that it flys erratically afterwards. Most modern recurves are designed to be "centre shot", which means the arrow rest allows the arrow to sit in a direct line with the string. The flexing of the arrow has less influence on where the arrow flies with this sort of bow, that is unless the arrow is too flexible and bends to extreme upon release. So, you can see, the design of the bow comes into the equation too.
To complicate matters even more, your draw length also comes into the equation because the shorter the arrow, the stiffer it becomes over it's entire length. When you buy shafts at the archery shop, the spines are rated at the standard 28 inch draw length, so say you wanted to make some arrows to suit a 50# bow, but your particular draw length was only 27 inches, you would have to buy arrows spined for a 45# bow (45# at your reduced draw length, that is), otherwise they would be too stiff and they may not shoot well. Conversely, if you have a longer draw length, you must buy arrows with a stiffer spine to compensate for the extra arrow length.
It can get even more involved if you decide to use points that are heavier or lighter than the standard 100 grain or 125 grain points (depending on spine). If you opt to use say, 190 grain points, you will need to compensate and buy shafts with a heavier spine because the heavier points will tend to make the shafts flex more than the standard 125 grain points.
Spine is very important. It can be very frustrating to actually find the correct spine for any archer/bow combination. In the end, after all the theories have been applied, it all comes down to the practical results when you start the actual shooting. It is literally, a trial and error process until you manage to get it right. It is crucial however, if you are looking for good consistent performance from your bow.
I hope I haven't made this too complicated or difficult to understand.
It is rather simple, but it's difficult to explain.
Mick
The spine of a shaft is the "stiffness" of the shaft. It would be possible to have a shaft with a diameter of 5/16 inch with a stiffer spine than a shaft with the larger 11/32 inch diameter, even when they are made of the same type of timber. There is normally some correlation between the diameter of shafts and the spine, ie 5/16 inch Port Orford cedar shafts are generally lighter spined than 23/64 inch cedar shafts, but the diameter is usually fairly irrelevant.
Say, you were looking for a lightweight shaft spined to suit a 50 pound bow, you may well try to buy some 5/16 inch cedar shafts because they would be physically lighter in weight than shafts with the same spine in a larger diameter.
When you buy shafts you usually specify the spine your require as well as the diameter you want. Some heavier spines may not be available in smaller diameter shafts. Some timbers are heavier and have a stiffer spine than other timbers even when the diameters are the same, as you would expect.
Have arrows that are spined correctly can be very important, particularly if you are shooting a bow, where the arrow is held some distance from the longitudinal centre of the bow, ie, a bow made without an arrow shelf, where the arrow must shoot around the bow in order to hit where it is aimed. With this type of bow, you need a shaft that will bend just the right amount when released. It needs to bend enough to clear the bow without contact, yet not that much that it flys erratically afterwards. Most modern recurves are designed to be "centre shot", which means the arrow rest allows the arrow to sit in a direct line with the string. The flexing of the arrow has less influence on where the arrow flies with this sort of bow, that is unless the arrow is too flexible and bends to extreme upon release. So, you can see, the design of the bow comes into the equation too.
To complicate matters even more, your draw length also comes into the equation because the shorter the arrow, the stiffer it becomes over it's entire length. When you buy shafts at the archery shop, the spines are rated at the standard 28 inch draw length, so say you wanted to make some arrows to suit a 50# bow, but your particular draw length was only 27 inches, you would have to buy arrows spined for a 45# bow (45# at your reduced draw length, that is), otherwise they would be too stiff and they may not shoot well. Conversely, if you have a longer draw length, you must buy arrows with a stiffer spine to compensate for the extra arrow length.
It can get even more involved if you decide to use points that are heavier or lighter than the standard 100 grain or 125 grain points (depending on spine). If you opt to use say, 190 grain points, you will need to compensate and buy shafts with a heavier spine because the heavier points will tend to make the shafts flex more than the standard 125 grain points.
Spine is very important. It can be very frustrating to actually find the correct spine for any archer/bow combination. In the end, after all the theories have been applied, it all comes down to the practical results when you start the actual shooting. It is literally, a trial and error process until you manage to get it right. It is crucial however, if you are looking for good consistent performance from your bow.
I hope I haven't made this too complicated or difficult to understand.
It is rather simple, but it's difficult to explain.Mick
There is no use focusing on aiming if you don't execute the shot well enough to hit what your are aiming at.
Hi Andrea
As Jeff suggests there is no way to correlate diameter to spine in a useful way .
Spine is a little more complicated than that as it is a measure of how the arrow deflects and recovers as a result of acceleration.
This is necessary when shooting a trad bow to overcome the fact that the arrow needs to bend around the bow when fired then straighten up again.
( this is because the bow is not cut away enough to make it centre shot like modern bows )
If you intend to cut shoots for arrows you will have to just cut a lot and when dry check them. This is the way everyone does it no matter what the natural material is.
Having said all that, although it is not of much use the spine does increase with diameter as more material ( of the same type ) obviously makes an arrow stiffer but not in a predictable enough way to be of any use.
Hope this helps
Graeme
As Jeff suggests there is no way to correlate diameter to spine in a useful way .
Spine is a little more complicated than that as it is a measure of how the arrow deflects and recovers as a result of acceleration.
This is necessary when shooting a trad bow to overcome the fact that the arrow needs to bend around the bow when fired then straighten up again.
( this is because the bow is not cut away enough to make it centre shot like modern bows )
If you intend to cut shoots for arrows you will have to just cut a lot and when dry check them. This is the way everyone does it no matter what the natural material is.
Having said all that, although it is not of much use the spine does increase with diameter as more material ( of the same type ) obviously makes an arrow stiffer but not in a predictable enough way to be of any use.
Hope this helps
Graeme
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Andrea Willett
- Posts: 27
- Joined: Sun Jan 29, 2006 10:42 am
- Location: Geelong, Victoria, Australia
Hi Andrea
If you are keen there a number of tutorials on the web that show you how to make your own. ( Google it )
Essentially it is just a jig that supports the arrow with a set weight hanging on it and then a way of accurately measureing the amount of bend.
To my mind it is easier to just buy one as the things that measure accurately enough cost more than a simple spine tester. To this end I would suggest you contact John Mc Donald at AMSO128 ( see link on front page or details in "Materials" -- phone 02 98753032 ) he will be able to to give you a price.
Graema
If you are keen there a number of tutorials on the web that show you how to make your own. ( Google it )
Essentially it is just a jig that supports the arrow with a set weight hanging on it and then a way of accurately measureing the amount of bend.
To my mind it is easier to just buy one as the things that measure accurately enough cost more than a simple spine tester. To this end I would suggest you contact John Mc Donald at AMSO128 ( see link on front page or details in "Materials" -- phone 02 98753032 ) he will be able to to give you a price.
Graema
Hi Andrea
Archery - an accessory sport first a simple bow and arrow, then a tab.. bracer.. quiver.. bow stand.. binoculars.. spotting sope.. fletching jig.. more fletches .. another bow.. serving tool..
The bow and arrow is cheap - it is the accessories that send you to the poorhouse.
Some of the best advice ever given - keep an eye out for old publications concernong archery because they have lots of plans for making things yourself.
Keith sells Spining Jigs:
http://www.ozbow.net/phpbb2/viewtopic.php?t=4231
and I think his are as low priced as they get.
The other alternative is to make one and there are lot of plans available on the net. Or you could design your own.
Now that you have a spining jig you will need to consider that that you need your arrows around the smae weight - so somwhere down the line you will probably buyt a grain scale - or you can weigh them on your kitchen scale as a mate of mine does. He reckons it is close enough.
Archery - an accessory sport first a simple bow and arrow, then a tab.. bracer.. quiver.. bow stand.. binoculars.. spotting sope.. fletching jig.. more fletches .. another bow.. serving tool..
The bow and arrow is cheap - it is the accessories that send you to the poorhouse.
Some of the best advice ever given - keep an eye out for old publications concernong archery because they have lots of plans for making things yourself.
Keith sells Spining Jigs:
http://www.ozbow.net/phpbb2/viewtopic.php?t=4231
and I think his are as low priced as they get.
The other alternative is to make one and there are lot of plans available on the net. Or you could design your own.
Now that you have a spining jig you will need to consider that that you need your arrows around the smae weight - so somwhere down the line you will probably buyt a grain scale - or you can weigh them on your kitchen scale as a mate of mine does. He reckons it is close enough.
Grahame.
Shoot a Selfbow, embrace Wood Arrows, discover Vintage, be a Trendsetter.
"Unfortunately, the equating of simplicity with truth doesn't often work in real life. It doesn't often work in science, either." Dr Len Fisher.
Shoot a Selfbow, embrace Wood Arrows, discover Vintage, be a Trendsetter.
"Unfortunately, the equating of simplicity with truth doesn't often work in real life. It doesn't often work in science, either." Dr Len Fisher.