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From: "Rumburg, William" <wrumburg@cdicorp.com>
To: "'Sky2high@aol.com'" <Sky2high@aol.com>, "'lancair.list@olsusa.com'"
	 <lancair.list@olsusa.com>
Subject: RE: Prop Spinner
Date: Mon, 26 Jul 1999 07:06:56 -0400
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>>
	 Scott -
	   I originally sent this last Thursday, but our email server was
screwed up. It appeared to have transmitted, but did not.... 

> I have aluminum backplate with doublers installed and the outside squeezed
> 
> rivets on the doublers have all popped their little heads off.  Bucked
> rivets 
> have held up so far.
> 
> When did the carbon backplate become available?
> 
> Anyone else with backplate problems?
> 
	Scott -
	   I'm installing a new aluminum spinner backplate because I'm
installing a new three blade 63 x 84 propeller (to replace a 62 x 82) and
the new propeller blades were off by a couple of degrees from the old
propeller. The spinner was otherwise in excellent shape.
	   I used twenty four 3/32" stainless pop rivets (MSC-32 in the ACS
catalog) to fasten the twelve nutplates. The carbon fiber spinner that
Lancair sells is "light as a feather" and fits the backplate perfectly, with
almost no trimming necessary at the aft end. I use a camera tripod to align
the spinner. Just remove the sparkplugs, temporarily clamp the spinner in
place with small "C" clamps. Then, slowly rotate the engine with the tripod
almost touching to establish spinner concentricity. Then, drill and check,
drill and check, etc. With care, you should be able to establish perfect
spinner concentricity using this technique. With a good technique
(templates) and careful cutting, you should also be able to establish a
near-perfect 1/8" clearance all around the blades, however, it's necessary
to have 3/16" at the front of the blades, because the spinner will bulge
outward slightly at high rpm's and air loads will then press it rearward
into the propeller blades. 
	   Because this spinner is so light, I don't see the need for a
forward bulkhead. In my humble opinion, a forward bulkhead would be a
difficult installation and alignment (to say the least), probably throwing
off the balance and adding little, if anything, to the spinner's mechanical
integrity.
	   What are the "doublers" you've mentioned? Maybe they're peculiar
to a constant speed propeller?
	At any rate, my installation, with only an aluminum spinner
backplate and Lancair's carbon spinner (fastened with only stainless pop
rivets and nutplates) has functioned well, with no problems whatsoever.

	              Bill Rumburg
	              N403WR  (Sonic bOOm)
	   
	        
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