Arriving at the flying field I eyed the windsock nearly straight out from the pole.  The only control line person at the field with many radio flyers I convinced myself wind is my friend and put the plane on the circle.
All went well with 5.26 second lap time, taken over 10 laps at 52.6 seconds, and I pulled into the reverse wing-over.  Recovering on the other side was one of those special moments when it is great to participate in this sport of ours and all is well with the world. These moments of peace are even more intense when you are over 70.

Around and up the second leg of the reverse wing-over, oh what a great feeling; then about 2/3 up the prop and the plane parted company  .

The friendly wind blew it over the top and tightened the lines the other side. The KR Timer shut the motor down and with motor and battery intact the planes' balance was not affected resulting in a good landing a lap later. I managed to see where the prop went and found it further along the tarmac, one blade broken from the impact.  It was a Dennis Adamisin 13x4 ½ F2B before I reworked it to a 12 x 5, shame it used to work so well. The whole prop attachment assembly, one of those that is a taper sleeve and the more you tighten the prop the more secure it is, pulled off the motor shaft.  I thought it was tight and it stayed on for 27 previous flights maybe I should check the prop nut more often.
 
The photo shows the Centurion after the landing without a prop.  It is powered by a MVVS 8/680 motor 9,600 revs (handheld tach) using TP G8 25C batteries at 5,200 feet above sea level.

Hello Dennis.  There was no warning in terms of vibration or sound.  Not even when the prop came off.  It simply just disappeared straight up into the sky. Checking the shaft  there is no evidence of twisting off marks.  On the last flight coming into the wind and going out of it there was a motor sound change but I still think that was the timer kicking in and out to keep the revs steady.

Percy,

Good narrative.  Did you miss your calling?

Linheart

Crist you may of course be right but the point is the prop did not come off by itself the prop adaptor came off the motor shaft.  I repitched the prop at the hub (from 4 1/2" to 5") and the prop broke 2/3rds to-wards  the tip. That part of the prop lay close to the rest of the prop, the prop adaptor and spinner (which stayed together as an assembly) on the tarmac, it seemed to me the tip broke when it hit the tar.  Maybe the prop broke and the vibration helped the adaptor to separate from the motor shaft but there was no vibration.
Thank you to be concerned enough to take the time to write and warn about it, I appreciate it and take note of your experience and concerns.

Linheart thank you for your comment.

Hello Percy,
One thing not mentioned frequently enough is that a tapered collet prop drive should have its inner bore and the motor shaft carefully cleaned with alchohol or acetone to assure that there is no oil or bearing lube on these surfaces.
At 3000 watts (RC Pattern-ish) no amount of prop tightening is sufficient unless these surfaces are squeaky clean.

Regards
  Dean P.