Arrow spine chart

[GOLDGT]

Sorry if this is a repost but thought I would put this diagram up for everyone. Not saying it is perfect but a good rough guide.

[matt_d]

Thanks Hamish.. That is probably the most realistic arrow spine guide I've seen yet. Arrows should be selected based on centreshot and bow speed.. Poundage is not a very good guide!
Matt

[stringnstik]

erm can you explain that chart a little .Im not sure I understand what its telling me.

[Stephen Georgiou]

What it says is that if your bow is centre cut the standard spine chart from arrow manufacturers can be as stated but when your bow is not centre cut you must add or subtract poundage as stated on this chart.
For example. The typical internature or samick long bow is 1/8" from centre cut so by this chart if you are using a 50lb bow the arrows chould be correct if your bow is 3/16" from centre cut the arrow spine should be weaker by 5lb to accomodate a larger bend during the archers paradox (which is the nature of the arrow to bend and clear the shelf during release)
It also indicates in the test that If the arrow is shorter it is stiffer so you must also allow for this in your spine calculation.
Hope this help, Mark.
SG

[stringnstik]

Thanks Steve,
I pretty much understood this b4.
Centre cut, the further you go out the more the arrow has to bend and thus it requires flexibility.
Shorter draw, shorter arrow its stiffer so again add flexability ie lessen spine.

However the chart shows +5 @ centre cut? I would expect 0 but then I dont understand why it goes up either. ie +10 @ -1/16. Thats the bit I didnt really understand. Why stiffer when its erm "over cut".

Id also gotten confused by the length of the green lines. Thinking they meant something but I take it, its just the way they marked the numbers.

I think I was trying to read allot more into it than was there :lol

[Stephen Georgiou]

I suppose that the reason for the stiffer spine is that most of the bows are normally set up with1/8" off centre. even the target dudes do this. typically the arrow is set up so that the right hand side of the arrow lines up to the left hand side of the string for the target recurve set up and maybe they call this normal?
So as I understand, the arrow shooting under cut must be stirffer as the initial force applied to the arrow would already start the arrow travelling sideways even with out the archers paradox.
From my experience ( which isn't much, just enough to know it's not my caper) I found that the bow shot like a dog when I had put the arrow at centre or undercut so I suppose they had to put something on the chart!
Don't know when you would use undercut anyway. Maybe someone else can enlighten us.

[matt_d]

G'day Mark, the poundage system for arrow spine (As Steve suggested) is formulated for an American flatbow with a dacron string and shelf cut 1/8" from centre. So for that combination, you would be inclined to stick to that guideline. Personally I wish they would just use deflection in thousanths of an inch as it would make things much easier. So, a longbow with shelf cut to centre would require a stiffer than recommended arrow because it is still using the outdated wood arrow spine system.

Steve, a bow which is cut to centre will still have the arrow pointing left of the string centre line due to the diameter of the arrow shaft. I have a recurve cut 3/16" past centre and with 17/64" shafts the centreline of the arrow lines up nicely with the outside edge of the string. (So in reality it would be 5/64" plus the thickness of the strikeplate material outside the centreline of the bow) This is also the setup I use with my target recurve and I find it shoots very well.

Cheers,
Matt

[stringnstik]

ahh yes of course the thickness of the arrow itself
interesting

[SlowBowInMO]

A very good chart, and it empahsizes a component of arrow selection that is often overlooked. I find the depth of your shelf is nearly as important as the actual draw weight when trying to determine proper arrow spine.

For example, I have two bows that are 1# different in draw weight and perform near identically. Yet the bow cut 3/16" past center needs 65/70's and the other cut well shy of center needs 45/50's. That's how much difference it makes. Good chart!

[GrahameA]

Morning Matt

G'day Mark, the poundage system for arrow spine (As Steve suggested) is formulated for an American flatbow with a dacron string and shelf cut 1/8" from centre. So for that combination, you would be inclined to stick to that guideline.

Spot on and that is the start to understanding the charts.

[ed]

the arrow spine adjustments for length is confusing.
If you take an arrow spined for 28" and need to draw 29" then it is effectively weaker than the stated spine. With every inch of draw beyond 28" yo uneed an arrow of approximately 5# heavier spine for a center cut bow. Less so the more off center you are.

Personally I find such charts not so useful anyway as the performance of your bow may change the spine you need by up to 20# of spine. Does it have a lot of early power, or late power. Early power seems to require a stiffer bow and is not at all related to the draw weight at that length.
For example a bow that is stacking, has a lot of weight but not much force for recovery as the amount of movement at the tips is not translating as effectively to movement at the string (i.e they are travelling as much vertically as forward).

Personally I still prefer to bare shaft my arrows and start from long and weak arrows and shorten until the spine is right.

[GOLDGT]

the arrow spine adjustments for length is confusing.
If you take an arrow spined for 28" and need to draw 29" then it is effectively weaker than the stated spine. With every inch of draw beyond 28" yo uneed an arrow of approximately 5# heavier spine for a center cut bow. Less so the more off center you are.

Personally I find such charts not so useful anyway as the performance of your bow may change the spine you need by up to 20# of spine. Does it have a lot of early power, or late power. Early power seems to require a stiffer bow and is not at all related to the draw weight at that length.
For example a bow that is stacking, has a lot of weight but not much force for recovery as the amount of movement at the tips is not translating as effectively to movement at the string (i.e they are travelling as much vertically as forward).

Personally I still prefer to bare shaft my arrows and start from long and weak arrows and shorten until the spine is right.

I see your point Ed, I am the same as you, I never get any shafts pre cut, But I just thought it gives you a good ball park figure to work with if you have'nt got a clue. Like me most of the time

[Stephen Georgiou]

Buying your shafts full length is also a great idea.
What I do when I get a new bow is buy some arrows either side of the one that the charts suggest and check that it is right.
Nothing worse than buying a dozen arrows and find they are the wrong spine.
I have been guilty of this in the past and have made gifts of my bad choices.
What I do is look for someone with a bow that suits the errant arrows and make a gift of them.
You could sell them I know, but they do say the gift is in the giving. win win I see it as.

[GOLDGT]

Buying your shafts full length is also a great idea.
What I do when I get a new bow is buy some arrows either side of the one that the charts suggest and check that it is right.
Nothing worse than buying a dozen arrows and find they are the wrong spine.
I have been guilty of this in the past and have made gifts of my bad choices.
What I do is look for someone with a bow that suits the errant arrows and make a gift of them.
You could sell them I know, but they do say the gift is in the giving. win win I see it as.

Im sure you have good karma Stephen with that attitude .

[Stephen Georgiou]

GOLDGT, thanks for the arrow shafts. I have started making them up for Shahan.
Shahan was the young bloke who brought a longbow selfbow from some chap and has a great deal of trouble getting the bow. When he didi get it, it fractured the first time he used it. Sent it back and the bowyer replaced it but sent it to the wrong address. When shahan found the bow some bright sparke has brike it in two. He asked to have another one sent down but had trouble with that process as well. SO, Timbo gave him a longbow. He still shoots this bow every time he gets a chance but because of the process he went through was short of cash. No good having a bow without arrows so some of us have given him the gear he needs to kepp going and this set of arrow you have sent down will be prefect for him. So again I thank you on behalf of Shahan.

For those of you who are reading this post. If you have got some gear that you are not using, ask around and find someone who might get some use out of it who can't afford "at the time." It is far better to share the stuff around than letting it sit under the bed of in the garage.

Many of us have big ideas about Traditional Archers and what seperates us from the run of the mill mob. GOLDGT has proven this once again with his generosity.