Choosing wood arrow spine

[jerseyboy]

Currently I'm shooting three different longbows two zippers and one A&H.  All of them are 42 to 45 lb. I draw 28 in and I'm using a 160 grn tip.  I know I need to go heavier on wood then I would on carbon or aluminum so I ordered 50 to 55 lb. I ended up cutting them down to 28 1/2 in with a 160 grain tip and they all showed very weak on all three of my longbows... I cannot get over the fact that I need to go heavier than 50/55. Is there a formula for figuring all this out?  Any help would appreciated

[snag]

I believe 3Rivers Archery has a spine calculator on their website. Anything over 125 gr for point weight weakens the spine and makes be considered.  I would put some 125 gr points on them and see if you could use them. But ultimately you will need stiffer shafts to shoot those 160’s.

[Orion]

The formula for determining spine at 28 inches was developed back in the day of all wood bows.  You have four additional features on your set up that require additional spine.  As noted, 160 grain points require about 5# more spine than 125 grain heads.  Add another 5# for high performance bows, another 5# for low stretch strings, and probably another 5# for the shelf cut to or past center.  Long story short, you need spines in the 60-65# range (and maybe even higher) for your set ups.

[Maclean]

I agree with Orion on those easy calcs to get you in the correct zone for spine. Once you have that figured I would highly recommend getting a spine test kit (3 Rivers and Surewood Shafts have them) and see which spine flys best from your bows with your shooting nuances. It's the only way to know for sure, and the results might surprise you. It sure surprised me.

[trad_bowhunter1965]

The formula for determining spine at 28 inches was developed back in the day of all wood bows.  You have four additional features on your set up that require additional spine.  As noted, 160 grain points require about 5# more spine than 125 grain heads.  Add another 5# for high performance bows, another 5# for low stretch strings, and probably another 5# for the shelf cut to or past center.  Long story short, you need spines in the 60-65# range (and maybe even higher) for your set ups.

Ditto
I shoot a very similar setup [email protected] with a 29” 60/65 160gr point shoots lights out bare shaft tune out to 20 yards.

[Longcruise]

How about playing with strike plate distance from center?

[trad_bowhunter1965]

I use tin goat leather it is tough what are you using?

[Tim Finley]

I shoot a 50# @ 28" I draw 27 1/2 I spine all my arrow  58 t0 61 lbs I order them that spine and I pay more for then to be spined lilke that but it is worth it they all fly like lasers . I would say you need about a 50 t0 55lb. Ive messed with arrow spine on wood arrows for 50 years and it can be frustrating to get perfect flight ,spine is important.

[Orion]

Longcruise.  Could certainly build out the side plate.  I'm not familiar with where the side plate is cut on Zippers, but they're 3/16 inches past center on A&Hs.  That's a lot.  When i owned them, I built out the side plate a lot. 

[MnFn]

I have a 68” 45# Liberty English. I draw a little over 28”.
I got a set of three spines from elite arrows (Paul Jalong).
I could shoot 55/60 or 60/65. I shooter them all through paper with 160 grain and 29” arrows.

[GCook]

I run that spine for the same weight bows and have to run 125s for some and 100s on others.  Bow performance makes some difference.   160s I'm sure you need to add quite a bit of spine.

[sagebrush]

I also shoot an A&H. I build out my strike plate a lot also. I only shoot wood. It took me a while to figure out what was going on. They are cut way past center.

[Wudstix]

With my heavier bows I usually start with bow weight then add 5# for over 28" arrow, 5# for D/R style longbow or high performance recurve, 5# for broadhead over 160 grains.  Then round up.  So, 66# bow would be 81#, so 80-84#.  This works for me with tapered and footed wood arrows.  I've found that I can get away with a tad heavier spine with tapered arrows.  YMMV
 

[Bobby Sikes]

If I recall, it was Stew's calculator, or something like that.

[Rob DiStefano]

Woodies, both raw shafts and completed arrows, are sized at 26" with a 2lb weight.  28" is for non-woodies; carbon and alums, and require a 1.94lb weight to be used.

As to what spine woodie for what bow type/weight/draw, that will take some 'sperimenting to figure out.  I'd get a Doug fir shaft selection package from Surewood as a good starter, and different point weights.

[Ben Maher]

For woods on cut to centre [ not past ] plus side plate and with 160 heads I tend to find bow weight at my draw plus 5# works pretty good , even with 160 heads and 1.5" clearance in length.
Mind you I tend to shoot "weak" spine compared to many with alloys and carbons as well

A Poison Dart for me shoots just dandy with 5# extra and 1.5 length clearance . 50# @ 29" flies dandy with 55/60 with 160gn head at 30.5". This bow is cut just shy of centre
A Widow PLX shoots same specs but likes a 60/65 at 30.5 as it cut to centre .

Past centre , its recurve specs for me .... and lest face it , past centre its a recurve anyway with straight  limbs