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To:  lml@lancaironline.net
Date: Thu, 18 Dec 2008 20:10:09 -0500
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From: "Bill Edwards" <wpedwards@hilgardhouse.com>
References: <list-3372223@logan.com>
In-Reply-To: <list-3372223@logan.com>
Subject: RE: [LML] Re: Slick Spinner  reversing MT
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A reversing MT?  Would you mind taking the time to elaborate?  I have an
IVP, and one of the strips I fly into is short (not as short as 2200 feet,
but close).  It's led to some hair raising landings and warped rotors on the
mains. A reversing prop sounds like the ticket and I'd appreciate your
guidance.   Merry Christmas to all.  Bill Edwards

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Brent
Regan
Sent: 12/18/2008 1:44 PM
To: lml@lancaironline.net
Subject: [LML] Re: Slick Spinner - no visible screws

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