Prop centering

[Kai]

I have been using a Sensenich wood/glass prop on my Jab powered Sonex in combination with the standard massive Sonex supplied spinner since it took to the air in 2005. The only thing that centers the prop on the engine prop flange, are the Jab supplied prop drive lugs, originally with a very snug fit in the prop boss. Every time the prop goes on after the annual, maintenance- whatever, the holes in the prop boss for the drive lugs are getting just a small fraction larger. Finally, after 13 seasons in the air, the hole diameter has increased to such an extent that the prop has become almost impossible to center properly. The result is a peculiar resonance in the airframe, starting around 2800rpm.

Has anybody else experienced this? Is there a cure for it? Comments?

Thanks
Kai
Sonex #0525 DS-TD

[peter anson]

Hi Kai, I think it's time to have a chat with Sensenich. The simple solution is a new prop but they may be able to do a repair. An out of balance caused by your prop not being centred is not going to do your engine any good. For those drive holes to wear there must be a problem with either bolt torque or creep in the propeller hub. You could also check that the Jabiru drive bushes have not worn.

Peter

[Kai]

Peter,

Yes- more or less my thoughts as well: I already did contact Sensenich. So far they have been silent.


Thanks
Kai

[meglin]

I'm sure that's a bad way to center it. The most reliable way is to make an axial insert with a precise fit.