I'm in the middle of getting my Hartzell 2 blade prop overhauled for my Lancair
360.  I got a new hub at 50% discount from Hartzell to eliminate the recurring
eddy current inspection. The prop shop doing the overhaul has issues with the
blades and they will not issue the formal 8131 (I think) paperwork for the
overhaul.  The problem is the blade length.

I bought the airplane 3 years ago and it had an overhauled "0" time prop when
the airplane was built in 2002. The blades are 70" long according to the prop
shop.  They also say that the Hartzell recommends a 72" blade. But Hartzell
also allows a 68" blade for the Lyc 360.  They do not however, recommend a 70"
blade.

The question is, since I've had no problems or vibration issues with my 70"
blades - should I be concerned? I guess Hartzell's recommendation is based on
some harmonic resonance or some other vibration related things (which are
outside my knowledge).  Does my 70" blade length provide cruise or climb
capabilities that are greater or lesser than a 68" prop.

I'm planning to have the 70" blades reinstalled on the new hub, and the log
entry will just say the standard overhaul stuff (except the IAW stuff), and it
will specify "experimental A/C usage only."

Any thoughts?

Thanks,
Matt McManus
lnc2 360
408 hours total time airplane.