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Thanks to Fred for the detailed fabrication instructions on the smooth spinner. Fred's inspiration came from a propeller and spinner I designed and built for the 97 Great Cross Country Race that Fred and I flew in my IV-P.
After flying this prop for about 150 hours I moved to an 2200' airstrip and decided to install a reversing MT for the extra stopping power. When I removed the smooth spinner / prop I noted that three had been a noticeable amount of rubbing between the forward bulkhead and the hub. This despite the fact I had made a form fitting cup over the end of the hub that was bonded to the spinner's forward bulkhead (see attached).
I too did not have the facility to dynamically balance the spinner so there was undoubtedly an off balance dynamic moment that would cause the spinner to nutate (wobble). It is therefore very important that there is a close fit between the hub and forward bulkhead to prevent an increasing out of balance condition with RPM. Carbon or E-glass will grind through aluminum in a hurry.
Also, an "on engine" dynamic propeller balance is a very good idea and well worth the fee. Having balanced the components, performing an overall dynamic balance will reduce vibrations and the associated fatigue failures.
Wishing all a Merry Christmas!
Regards
Brent Regan
Prop2.JPG
Prop6.JPG
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