spine confused

[Ladams]

I just finished building a spine tester,
and was checking it with some arrows of known spine.
all woodies fell into the proper range, but when i tested carbon and alum. it seemed to be way off.
cx150 tested around 70# cx250 tested around 75#.
2018 whitch is clearly marked 55-60 tested around
70#.
My question is,  are carbon and alum. spined by a different method or am i doing something wrong.
I dont intend on trying to test carbons and alum. but i was just trying it to see if it was accurate.
LA    

[LAR43]

Sounds like your shaft supports are set @ 26 inches. Move them out to 28 & see what the carbons & aluminums spine out at.

Larry

[Ladams]

Plans said 26", will moving them not give a false reading?
LA

[JRY309]

Wood arrows are spined at 26" centers and wood and aluminum are spined on 28" centers.I have used a spine tester not to check what pound spine an arrow is but to match them closer together.Then I tune my arrows to the bow.

[Ladams]

that could explain part of the problem. Are carbons the same as alum.
LA