Arrow Spine for Longer Draws

[bubbles]

I built a bow for my friend, who is a rather large guy 6"+   and has a long draw - 30". 
My draw is only 27 - so I'm having trouble consistently shooting the bow to find the Ideal spine of arrow for it.  It's a 45# bendy handle easter woodland flatbow - 1 1/4" wide in the handle, so, 5/8" off center shot. 
I'm thinking 32 inch arrows with 125gr point  - what spine would you recommend?  I looked at the 3 rivers spine chart - it's saying around 50-55lb spine - is that a good ballpark?  What would you guys with long draws use?

[RBLusthaus]

general rule of thumb to find starting spine -- subtract 5 # of spine for each inch over 28.  So, for a 45 lb draw, start with a 55 pound shaft, which is like 45# at 30 inches - - and tweak from there.  The tweaking is not only more important, but will be hard for you since you cant draw the bow far enough for a decent test.   

Suggestion - - grow longer arms :-)   

Russ

[adb]

For every inch your arrow is longer than 28", go up in spine 5# (ie stiffer shaft). If you're shooting a 50# recurve with centershot, start with 50-55# spine arrows. For longbows which are not centershot, I go down in spine by 5# (ie softer arrow shaft). You can also stiffen spine by using a lighter head, and vice versa. If your arrows are consistently grouping left of your point of aim, they're too stiff, and if they're grouping to the right, they're too soft.

In your case, with a 45# recurve and a 30" draw, I'd start with 50-55# spined shafts, start shooting, and tweak with point weight. With recurves it's not as crtical getting perfect spine. With longbows which are not centershot, it's way more important, and often takes more effort. But, once you sort it out, you're done, and your bow shoots wonderful.

[Pat B]

With store bought wood shafts I start out with 10# under draw weight for selfbows.  Store bought wood shafts are spined for 28" arrow with a 125gr. point. For each inch over 28" subtract 5# as Russ suggested. And if you use heavier heads subtract 5# for 25 grains over 125gr. The reverse it true for both the arrow and point. If you can get longer arrows go with a 32" shaft spined for 65# with a 125 gr point. I like longer arrows. I draw 26" but cut my shafts to 30". I think the extra length helps the arrow get around the bow better plus I like the extra physical weight.
 
 

[adb]

The first thing an arrow does when you release it is bend sideways (ie flex) rather than move forward. The Archer's Paradox. Objects at rest want to stay at rest, and to move, they must overcome their own inertia (I think inertia is the right word?). There are excellent slow motion vids on you tube about the Archer's Paradox. The amount the shaft actually bends is amazing.

The longer the arrow is and the lower the spine, the more it will flex. This amount of flex is standardised by placing an arrow shaft on 26" centers, hanging a 2# weight in the middle, and measuring deflection. The AMO divides arrows up into approximate 'spine' values to roughly match the arrow to the draw weight. To manipulate the spine for deviations from this standard is the goal. To match the spine to the bow, if your draw is longer than the standard, you have to pick a stiffer shaft for it to match the bow, and vice versa. In other words, a longer shaft must be stiffer to maintain the standard spine value.

You can shoot almost any arrow out of most bows, but to shoot accurately, your equipment needs to be tuned and matched. If your draw is longer, go with a stiffer shaft, if shorter, go with a softer shaft.

[bubbles]

Sorry, I am aware of the basics of Archers Paradox and shaft spine, and I have my own spine tester.  I was just looking for a good starting point, as it's hard for me to get a good release/shot so far past my regular draw length.  And I'm looking to have some reasonably matched arrows to this bow - so -

  45#  minus 5-10# for non center shot selfbow = 35-40#
     Plus 2x5#  for 30" draw = 45-50# - that is the spine I should be looking for for a 30" arrow
31" arrow = 50-55#
32" arrow - 55-60#
all with 125 gr points. 
Does that look right to you guys? 

[bubbles]

Those numbers are exactly what the 3 rivers chart says as well.  I guess I just thought it seemed little high.  I'm so used to shooting arrows that spine under the draw weight of the bow.  Thanks for all you help!

[bubbles]

Whipped up a pine tester arrow spined at 52# and cut it to 32"  - Shot with a draw marker at 30".   It bareshafted slightly light in spine - exactly what I would expect.  The only problem is that I can't aim with the arrow pulled back behind my ear, so I ended up hitting the wood slats compressing the cardboard on my target.  :0  Pine arrow held up fine.  I was trying out the Pine arrows that Sasquatch posted the other day.
I'll cut her down to 31 and start work on another 5.   
Thanks again for all the advice. 

[adb]

Sorry, I am aware of the basics of Archers Paradox and shaft spine, and I have my own spine tester.  I was just looking for a good starting point, as it's hard for me to get a good release/shot so far past my regular draw length.  And I'm looking to have some reasonably matched arrows to this bow - so -

  45#  minus 5-10# for non center shot selfbow = 35-40#
     Plus 2x5#  for 30" draw = 45-50# - that is the spine I should be looking for for a 30" arrow
31" arrow = 50-55#
32" arrow - 55-60#
all with 125 gr points. 
Does that look right to you guys?

Sounds reasonable to me. Just remember, these numbers are just a ball park starting point. You'll have to do a bit of fine tuning. It is going to be harder to match arrows which are too long for you to draw, but you're on the right track.

[burchett.donald]

bubbles,
             All the advice here is good but the biggest problem I see is that you may indeed be able to find an arrow that shoots off that bow for you perfectly but when the recipient shoots it? There are so many variables I can't name them all but very seldom do 2 people have the same shooting styles, grip or exact draw length which will definitely affect the deflection of any given shaft. He or she will probably have to tune or adjust spine for their self. JMHO

[bubbles]

Yes, and I'm dealing with a beginner that doesnt have a solid anchor yet. I just wanted something in the right ballpark. Obviously he's not going to notice the difference until he gets more experience, but at least these arrows will get halfway decent flight. Good enough so that he won't think there is something wrong with the bow.