Not your every day arrow question. For the arrow masters.

[beaver#1]

I am looking into building a spine tester. Every plan I saw calls for centers @ 26 or 28. With a 2 lb load on the shaft. I shoot 31 inch arrows. What would it do if I made my centers for full length(32inch) arrows?  The structure of a spine tester is too simple for me not to make one vs buying one. I just need help on the math.
Thanks
Dustin

[moebow]

Beaver,

Standard spine testers are as follows,  26" centers with a 2# weight OR 28" centers with a 1.94# weight.  The 26" standard is what is historically used for wood shafts and gives a spine for  a 28" arrow!   The 28" standard was developed more recently (nobody really knows why) and again gives the spine for a 28" arrow and more commonly used for aluminum and carbon shafts.

Going to 32" centers for your homemade spine tester might be OK as long as you "stay in house" and don't compare what you get with commercial spine results.

I'd suggest sticking with one standard or the other 26" or 28" with appropriate weights.  For longer arrows, the old 5# rule still works pretty well overall but remember that these results are still a "starting" point to get properly spined arrows.

Arne

[beaver#1]

Thanks moebow

[beaver#1]

So for a spine is measured at55# for a 28" arrow at 32" it would be 35#. Looks like I need to rethink my arrow setups.

[old_goat2]

Long draws are a blessing and a curse!

[beaver#1]

Yep. They are

[reddogge]

A spine tester only measures deflection so you can make your tester any length you want as long as you can figure out what deflection you need at 32" for your 32" arrows.

[beaver#1]

Yes red dodge. I just didn't know how to calculate that

[Dave Worden]

I think you'll find it more useful to make it to the standard.  You already know that you need an xx-spined arrow to shoot well with your set-up.  Creating a unique spine tester will certainly work for you, but you won't be able to directly compare your numbers with those listed on arrows you buy.  If your tester measures just like everyone else's making comparisons will be a lot easier.