All about spine.

[mullet]

  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.

[Pat B]

Thanks for the reply, Art. I knew you were lurking out there. Hope things are good with you.    Pat

[DanaM]

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

[Badger]

     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

[Dustybaer]

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).

[DanaM]

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

[Dustybaer]

Also wouldn't the shorter arrow have more dynamic spine(stiffer) than the longer shaft?
DanaM

yes.  see, you got it. 

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.

[DanaM]

Thanks Dustybaer yer a true gentleman.

DanaM

[Dustybaer]

my pleasure, sir

[artcher1]

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!

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

[Pat B]

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

[mullet]

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

[Justin Snyder]

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

[MattE]

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.   

[artcher1]

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