Spine Queston

[Boswell]

How are arrows spined, I got some 45-50 spruse, but I shoot 200 grain tips on a 27 inch arrow. my queston is how is the spine messured, tip weight? Length? bow weight?

[McDave]

Arrow spine is measured on a spine tester, which you can see examples of for sale at 3 Rivers and other places.  A weight is suspended in the middle of the shaft and the amount the shaft is deflected is measured.  It is supposed to give you an indication of what bow weight to use with that arrow, but it is only a place to start.  I believe the measured spine is based on a 125 grain point on a 28" arrow.  Your 200 grain tip would decrease the effective spine, while your 27" arrow would increase the effective spine.  If your bow is not cut to centershot, you would use a weaker spine, but if your bow is a more efficient bow than the standard, you would use a stiffer spine.  Your bow probably is a more efficient bow, because the standards for spining arrows were set many years ago.

Where this leaves you, is that in order to get good arrow flight, you need to shoot a bare shaft and adjust accordingly. The real use of the marked spine is that spines don't change, so once you know what you need, you can order it again.

[SHOOTO8S]

Spine is actually a static measurement, which amounts to supporting the shafts between two center's,(26'' or 28'') hanging weight on the shaft( 2# or 1.94#) and measuring how much the shaft gives under the weight, which is called deflection.

What static spine will be correct for your bow, shooting a 200gr point and 27'' arrow is a whole different question,as spine requirements can be influenced by such things as shooter form, degree of centershot you bow is cut to, among many.

[SHOOTO8S]

Sorry McDave, we must have been posting at the same time.  :D