I am trying to measure flex characteristics of my masts.
I have built the rig and taken the measurements at 1/4, 1/2 and 3/4 of the 'test' length. The test length being 100mm shorter than the mast length. I believe this is the correct way to do it.
So when calculating the IMCS using the formula

IMCS = OVERALL LENGTH CUBED DIVIDED BY MID POINT DEFLECTION X 460 SQUARED

Is the length in this equation the 'test' length or the actual length of the mast.
Also should the reference mast length be 460 or 465?