Shaft spiner?

[Bow Bandit]

i guesse i have to make a trip to my archery shop then i only have shafts ive made and shafts ive been givin ...have no clue to the spine of any of them...

Thanks Brandon

[mnewcomb59]

on that site it says the distance between them is 26 inches and you guys say you measure spine at 28 ?

im confused

Brandon

Well the standard length for shafts is 28 inches, so most commercial spine testers are set up at 28 inches. If you shoot a 31 inch arrow though, your spine you  get on your spine tester will actually be 15 pounds heavy because of the extra flexibility the longer shaft gives you. (5 pounds an inch) If you shoot 31 inch shafts then I would set it up at 31 inches. If you are making shorter shafts then I would set it up at the actual length so you can get the most accurate spine reading that you can. This is just me though, other people may like to stick to the standard 28.

Matt

[Justin Snyder]

I have been contemplating this since I saw that site with the 26" spine tester.  I think I would change it to 28 if its not to much work.  Even a 26 inch draw would have a 28 inch arrow because you dont want to draw a broadhead to the back of the bow.  Its probably not a huge deal on parallel shafting but if you get into tapered or barrel shafts the center will be stronger than the end. So the more shaft you get between the posts the better.  Justin

[Bow Bandit]

how would i convert the spine tester to the 28 inch ...because there is a whole chart i would have to do so would i switch the 26 to 28 (or what ever length) in the equation to get the proper delfection for the right spine???

Brandon

[Pat B]

A spine tester is set up for 28". If your arrow is 31" it will still spine the same but when you shoot the arrow it will shoot like an arrow with 15# lighter spine. the extra length( 3") will reduce the arrow spine by 5# per inch over 28". At 31", it in still spineing between the 2 post set at 28" apart.
   Now, I'll bet you are really confused!!!  LOL    Pat

[Bow Bandit]

OHHHH so just move my posts 1 inch farther on either side and it will spine lower but more acurastely????lol i think thats what i have to do...this is the one i have built... http://www.jamesmhill.com/Spine_Tester.html

Thanks Brandon

[DCM]

I'm a very practical person.  I just hang a crescent wrench from one end of a shaft suspended in the center on a nail, and held at the other end similarly.  Calibrate using shafting of known deflection.  I used aluminum shafting, being careful to place the center consistenty.  I haven't found bows to be so sensitive to spine that a couple of pounds one way or the other made any difference.

[Justin Snyder]

Actually your chart might be off by 2# if you switch to  28". You would need a new chart I think. Probably should leave it alone unless you are going to use tapered or barrel shafts. Spine according to Jim is length/deflection. 26/.565=46# subtract 10# for 2 additional inches=36#     28/.777=36# according to the chart .777 deflection =33-34#  OR I could be all screwed up... Justin

[mnewcomb59]

Well Pat you didn't confuse me... I know what you mean. If you are going to shoot a 31 inch shaft just make your arrows spine 15 pounds higher... The deflection will still be the same even if the posts are farther apart. If it pulls down .565 then it will still be 50#, the length of the shaft doesn't matter.

[Bow Bandit]

oh i finally get it lol ...ill just make it to 28 considering it will be the same also i will put a piece of dowel on top of the dial indicator to make it so the shaft doesnt need to be PERFECTLY straight...thanks for the help guys...

Brandon

[Justin Snyder]

The deflection will still be the same even if the posts are farther apart. If it pulls down .565 then it will still be 50#, the length of the shaft doesn't matter.

  No the deflection will be farther.  It will be around .72 which will be 36  #.  The 26 deflection was .565 which was 46# but when you compensate for the two inches of extra arrow outside the posts you subtract 10# which makes the true spine 36#. I shoot 31 inch arrows spined at 28 inches so with three extra inches over 28 I have to subtract 15#. Justin

[mnewcomb59]

No what I mean is if you put the posts further apart... If your posts are set at 30 inches and it pulls down .565 then it is a 46# spine. Sorry bout the confusion.

[Justin Snyder]

No the deflection will not be the same. the deflection will be slightly more for posts 28" apart.  If your posts are 30 inches apart and it pulls down .565 then you divide 30 by .565,  30/.565=53.09  so the spine is 53-54.  If you spine the same arrow with the posts 26 apart the deflection will be around .278,  26/.278=93.5 so 93-94#. But this arrow has 4 more inches so we subtract 40# ending with the same 53-54# as when the posts were 30". The formula is  Space between posts divided by deflection.  Then you must compensate for other factors such as longer arrows or heavier tips.    I'm sorry I confused you.  It really is in your best intrest to just use the chart Jim Hill provided and build with the posts 26" apart, unless you are using tapered shafts. Maybe even then the difference will be minimal. Justin

[Bow Bandit]

well heres a chart i made up last night for the 28" posts ... i hope its right...



Brandon

[Justin Snyder]

"PERFECT" Good job That is just what you needed for a 28 inch space between posts. You can see there is only a couple pounds difference but thats the whole point to spining.  Justin