Primitive Archer
Main Discussion Area => Arrows => Topic started by: billmac on March 22, 2007, 11:25:37 pm
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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?
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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.
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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
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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?
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billmac, that's correct.
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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
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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
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...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
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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# ;D
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justin where do you get yer shafts??
Dana
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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
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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.
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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.
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Thats right Marius. Further searching should find more from Art(atrcher1,ArtB)about hardwood shoot arrows and arrows in general. Pat
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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
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Thanks for the explanation Art,you make it sound real simple.Did you get those feathers I sent you awhile back?It's also good to see you on hear.
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Thanks for the reply, Art. I knew you were lurking out there. Hope things are good with you. Pat
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I took a 45-50# store bought sikta spuce shaft 31" checked its spine on my homemade gadget it spined at 45-50#, I put a nock on cut it to finished length of 28"
glued a 125 grain point on and it still spined at 45-50# Does this seem right?
DanaM
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Some good info up above, my spine meter is 26" long. However I start adjust my lengths at 28". For me a 55# bow with 29" arrows and 125 grain tips, shooting 1/2" off center shot. My spines are adjust from 52# to 55# measured at 26". They would likley measure 10# less if I were to measure at 28". There are some real good arrow tuning sights out there, look under O.L. Adcock. He has one of the best sights for tunning arrows. Steve
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dana, in both cases you measured the static spine. the dynamic spine would have changed, had you left the arrow longer than 28" or shortened it to less than 28". let's say you would have left the arrow 29" long, it would still spine out at 45-50, but behave (in flight) like a 40-45 spined arrow. also, had you used a different point weight, it would have behaved differently, (with the heavier point making it behave like a softer shaft).
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Thanks but I'm getting more confused LOL, dynamic spine vs static spine so spine in motion vs spine at rest. So what use is a spine meter other than a ballpark
estimate. Also wouldn't the shorter arrow have more dynamic spine(stiffer) than the longer shaft? I'm probably overcomplicating this just can't seem to wrap my brain around it.
DanaM
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Also wouldn't the shorter arrow have more dynamic spine(stiffer) than the longer shaft?
DanaM
yes. see, you got it. ;D
edit: this statement "let's say you would have left the arrow 29" long, it would still spine out at 45-50, but behave (in flight) like a 40-45 spined arrow" was related to your 28" arrow still spining out at 45-50.
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Thanks Dustybaer yer a true gentleman.
DanaM
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my pleasure, sir
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Thanks again for the feathers Eddie. Going to have to make you up some nice cane arrows to repay you. Course, going to have to talk Pat out of some more of his shoots first. He grows the best you know! ;D
Pat, let's just say I'm doing somewhat OK. Thanks for asking.
Unless someone is going to building a spine tester it's best to forget about that number 26". That number is just for the end spacing on these testers and only makes things more confussing when discussing arrow spine. Perhaps the reasoning behind the 28" concept was to allow for extra paradox of the arrow for these around-the-handle bows. Anybody know for sure? Anyhow, starting your adjustment at 28" seems to work out just fine for these types of bow. -ART B
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Art, I didn't make it to the coast for Bambusa at Christmas as I wanted but maybe this summer. You are on the top of my list! Pat
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Art,Really glad to see you posting.I've found some bamboo I'm going to cut in a few days.The nodes are really far apart.I,m going to cut the tops out again like I did the arrow boo,they are about 25' high.The good thing is it's my neighbors and growing over my shop roof.I've also found two more places to get more arrow boo.Take care
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If you cannot understand the way length changes spine, try this. Take a new pencil and grab the ends and break it. Now take one of the pieces and grab the ends and break it. Now take one of those pieces and grab the ends and try to break it. It is still the same pencil diameter. Still just as tough/weak as it was when it was full length. But because it is shorter it SEEMS tougher. The arrow is the same way. You cut it shorter and it reacts different even though it is the same arrow. Justin
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I use a spine tester on factory made arrow but not on switch cane arrows. With cane arrows I found a problem getting a good read due to the location of the dynamic spine not being in the center of the shaft.I now size the base of the shaft for a general idea of its spine. I then shoot the shafts to get a bit closer to my desired spine for a given bow.
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You have any idea of their species Eddie. I tried the Japanese boo that Chris sent me but don't really care for them. Sasa boo is OK but their nodes are rather pronounced but shoot surprisingly well. Cane and bambusa I got from Pat are my favorites. Tonkin is excellent also. Anyhow, let me know if you think they'll make arrows and we'll work something out.
Gave my last set of Bambusa arrows away last year Pat. Can't keep cane arrows, everybody wants those. Found a few of each that I didn't know I had so that'll hold me for awhile. Going to hide these when I get 'em finished. Thanks again Pat.
Here's how I handle the problem of weight forward on cane/boo shafts Matte. I allow 10# for the shaft's natural taper and start a couple inches longer (for spine adjustment) then needed to begin with. I then find the center of the shaft and mark that. Next I balance the shaft on a pencil to find it's balance point. I then measure the distance between the two marks and then adjust the spine 5# for each 1/2" of difference. Example: If the marks show 1" difference between them then that additional 10# pounds I first added compensates for the difference and no additional spine would be needed (this is where that extra 2" of shafts length we started with would be used for spine adjustment if needed). That's seems to work really well as far as getting a good spine match in a set.-ART B
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You are right Art. You can change the value of your tester and get a close reading. One thing that I have found out about cane is the base diameter is a good indicator to measure spine.It is far from exact but close enough that I don't have to use a tester.Cane seems to be less sensitive than other materials when shot.I suppose this is due to its natural taper?
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On the cane and some of the other boo you certainly can gauge your spine pretty close to each other by diameter alone once you have a good idea of where to start. Tonkin it seems, is the worst offender for this method though.
Cane/boo's natural taper does two thing Matte. It moves more weight forward for better arrow recovery in flight but also lessens paradox. Simply put, it uses it's natural taper to reduce paradox by giving you a sight picture of a larger diameter arrow at full draw but leaves the bow as a smaller diameter arrow. -ART B
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Well said! I have felt that the taper was the reason I have no trouble getting the arrows to work. I wasn't sure exactly what all was taking place but your statement was in line with my thiking.
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Matte, have you noticed that you'll get that same effect off the shelf /hand from these tapered shafts? Got to elevate my shot a little higher myself when shooting full tapered vs just rear tapered arrows. Perhaps a slight string nock adjustment downward would eliminate that "down hill" effect. -ART B
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I have noticed that it makes little difference how your arrows rest.Most of my bows are shot off the fist and they shoots well. I also bare shaft my arrows when tuning in a new bow. I have been doing it this way since the eighties.When I do this I generally move the nocking point down slightly,this eliminates most of the nock high readings one normally gets.When the arrow is fletched I move the nock back up to a good shootng position. You mentioned having to elevate your shot? This leads me to think you shoot instinctive? If this be the case try useing the gap method just to add to the picture. The reason being if your nock is high,not extremely high, a gap shooters arrow will hit a bit higher,just the opposite of what an instinctive shooter experiences.This is what I am getting but this is still only theory on my part.
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Good read Matte, yeah, I'm pretty much an instinctive shooter. Or was. Due to ever changing physical requirements I've gone to gap shooting here of late. But I shoot both styles equally bad anymore :'(.
What I was referring to, the same benefit you get from tapered arrows around the handle, is not beneficial over the hand/shelf in itself. Going from large point end to small nock end creates that down hill effect that I previously mentioned. But if the bow is tuned for this then it doesn't matter. Which none of mine are because I mostly shoot parallel rear tapered arrows. A very noticable difference when both types of arrows are shot together though. I just aim a little higher when shooting natural or full tapered of arrows instead of adjusting my string nock.-ART B
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YooooHooo!,Glad you're posting Art.Everytime you do I learn something about arrows.If nothing else,how to cut boo.
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Hey, is there some primitive method to measure spine? :D I mean, how was it done before invention of testers?
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Shoot the arra and see what happens I guess ;D
DanaM
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What you are doing with a spine tester is measuring the deflection of the arrow. If you have arrows of differant spine weights you can stick 2 nails in the wall 26" apart, place the arrow on the nails and hang a weight at the center. Mark the deflection of each arrow so you will have a referance.
You can test the spine by feel also. After you do it a bit you will feel the differance between differant arrows. Pat
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