All about spine.

[billmac]

Is there a good resource for learning all about arrow spine for do-it-yourselfers?  I've read a bunch of stuff in various places but it's all a little confusing.  Do you spine test your shafts before tipping and nocking?  How do you reduce spine?  I read one fellow's advice to sand a bit in the middle of the shaft to reduce spine and taper sand the ends to reduce weight.  What does arrow length have to do with spine?  Do you match the spine exactly to the draw weight of the bow?

[Justin Snyder]

For recurves and high performance longbows add 5-10# bow weight. For selfbows, subtract 5-10# bow weight. For high performance recurves add 10-15# bow weight. For 160 grain points add 5# bow weight. For 190 grain points ad 10# bow weight.  You heard right about reducing or increasing spine. Length affects spine by leverage. For every inch of arrow length (string grove to back of point) over 28" you need 5# more spine, for every inch under 28" you need 5# less spine.

[Pat B]

Spine weight reflects the deflection the arrow shaft makes when shot. With most selfbows, lighter spine weight is needed to get the arrow around the handle.  With self bows I like 10# to 15# less spine weight than bow weight but that depends on the bow and arrows. The standard spine weight is measured on a 28" arrow. I believe that it includes a 125 gr point. For every inch over 28" you can decrease spine weight by 5# and for every inch under 28' you can increase spine weight by 5#. You can also reduce spine weight by sanding the center of the shaft, thus making it bend easier. Or you can reduce the arrow's physical weight by tapering the front and back of the arrow but leave the center thick. The arrow bends in the center so by leaving the center thick the spine remains high but the physical weight of the arrow is reduced. An arrow with a single full length taper, like a hardwood shoot arrow or a tapered arrow, the spine weight is reduced by the simple fact of the taper. The arrow doesn't have to bend as much to get the back end(the thinnest) of the arrow around the bow.    Pat   

[billmac]

28 inch arrow shafts are tested on 26 inch jigs are they not?  Are the measurements buillt into most jigs assuming a 28 inch shaft?

[scattershot]

billmac, that's correct.

[DanaM]

If ya order shafts aren't they 32" and they are spined at 45-50# then you cut them to 29" Does this make them 60-65# now???
Subtract 5#/inch right. Arra's are tougher than bows I think. Lets say I have a 50# @ 28"self bow, average performance somewhere around 140-150 fps, bow is within 1/8-1/4" of being centershot, 125 gr point and I want a finished arra of 30". what spine weight do I order? Assuming store bought shafts are 32"
So Selfbow minus 10-15# and 2" longer than 28" add 10#,  45-50# spine right???

It would be nice if ya could order one arra shaft at time, sucks that ya have to order 12 at a time, makes getting the spine weight right kinda important at the price. Or at least it would be nice if ya could get a test kit of wooden shafts only ones I've seen are carbon shafts.

DanaM

[Pat B]

I believe that when you order arrows, even if they come 32" long, are spined at for a 28" arrow. Anything over or under 28" should be adjusted at approx 5# per inch either up or down. This spine weight includes a 125 gr point. For self bows subtract 10# to 15# of spine weight to get the arrow around the non-center cut bow. If you are dealing with tapered shafts, either artificial tapers as in store bought tapered shafts(either barreled or full taper), or natural tapers as in hardwood shoots(maybe even some softwoods) and canes, you can subtract 10# to 15# just for the taper because the arrow doesn't have to bend as far to get around the bow.
   I hope Art Butner see this. Art knows arrows, inside and out and has done an excellant job of explaining it to me. For me to process that info and try to explain it to you is a totally differant matter.     Pat

[Pat B]

...one more thing...the weight of the arrow head effects the spine also. The more weight above the 125gr will decrease the spine weight, and vice versa.     Pat

[Justin Snyder]

Dana,  Like Pat said, they are all spined for 28".  It is one of those AMO standardizing things. 
For a 50# self bow shooting 140-150 with 1/8-1/4" offset I would say,
50# - 10# = 40# for selfbow, (being almost center shot it would reduce the archers paridox)
40# +10# = 50# for 2 inches over 28
I would go with the 45-50# like you said because it seems to forgive a weaker arrow a little more than a stiff.

Some of the shaft retailers sell a 12 arrow kit with 3 arrow in each weight. 3@45 3@50 3@55 3@60.  My suppler doesn't offer it, but I called and asked them if they would put one together for me.  I got 2 dozzen, so I have 3 in each weight from 40#-75# 

[DanaM]

justin where do you get yer shafts??

Dana

[Justin Snyder]

The guy I used to get them from sold the business.  I have purchased from the new owner, but I don't know if I will again.  The quality of the shaft matching has gone down. I even got a couple that were 15# off.  Justin

[Evil Dog]

I have found it a very good idea to check the spine on each and every shaft no matter who they come from.  It is amazing the variance encountered.

[Dustybaer]

   I hope Art Butner see this. Art knows arrows, inside and out and has done an excellant job of explaining it to me. For me to process that info and try to explain it to you is a totally differant matter.     Pat

in fact, you can learn a lot by reading art's posts on arrows in the archives.  just follow the discussions on the cane and boo shafts and you'll learn just about everything there is to know about spine.  i think he went by artb and archer1.  pat, please correct me if i'm wrong.

[Pat B]

Thats right Marius. Further searching should find more from Art(atrcher1,ArtB)about hardwood shoot arrows and arrows in general.    Pat

[artcher1]

Hey guys, just to confirm what Pat and others said about measuring the spine of wood arrows. If you're ordering shafts the spine is set at 28" but come in longer lengths.  So, no matter their length you have to start your adjustment at 28" using the 125gr point. That seems to be the common standard and works very well. Everybody's needs and spine requirements differ somewhat but having a starting point really helps. As was mentioned, making your arrows shorter then 28" will increase their spine by 5# but making them longer then 28" will decrease their spine. Example: if you order shafts at 45-50# and leave them long, say 32" using a 125 gr point, then you have in effect some 25-30# spined arrows. Point weight is an issue also. Going from a 125 gr point to a 145gr add 5#. But if replacing a 125gr point with a 145gr point subtract 5#.  For 160gr, 175gr, 190gr ect add or subtract one spine range for each weight change.

For my purposes I prefer using as stiff an arrow as I can possibly shoot. And then reducing dynamic spine in other ways like point weight and tapering.  Arrows for me will recover much quicker from paradox for better flight. Not to mention that they're tougher and will take more abuse then a lighter spined arrow. And the older I get the more abused they get. -ART B