From: keltro@att.net
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: engine mount geometry
Date: Sat, 22 May 2004 06:02:23 +0000
Message-Id: <052220040602.13356.40AEECEF000B51530000342C2160466648FF908D8B939A@att.net>

  Kevin,

    Ditto the advise from Marv! The Dyke Delta has its offset

  at the firewall end of the engine keeping the prop flange

  on the A/C centerline. FWIW

  Kelly Troyer

--
Dyke Delta/13B/RD1C/EC2 
		
			
> "kevin lane" <n3773@comcast.net> wrote:
>   > > > 
> I am fabricating the bed mount plate for my 20B in an rv-8.  my
> understanding, from Tracy's advice, is to offset the engine about 1 1/2
> degrees to the right if I use his 2.85 drive.  as I see it there is a
> centerline of the fuselage and a centerline of the engine/redrive.  if I
> mount them such that they are 1 1/2 degrees out of parallel, then those
> centerlines will intersect.  my question is where? ...snip...   < < < 
> 
> 
> I'm not an RV builder, but I did have the same decision to make when I was 
> fabricating the mount for the 13B in my Lancair LNC2.  I temporarily installed 
> the cowling to the fuselage and found that in its normal position the 
> centerline of the fuselage aligned perfectly with the centerline of the cowl. 
>  I also noticed that there was a tilt to the flat face that would mate up with 
> the spinner, so I assumed that the c/l of the prop should match the c/l of the 
> fuselage, consequently when I built the mount all the offset was at the rear 
> of the engine.  The center of the prop hub is aligned with the c/l of the 
> fuselage.  From an aerodynamic standpoint, I don't know that it makes much 
> difference where the offset comes from, except that if you keep the firewall 
> end of the engine centered on the firewall, the c/l of the prop will be offset 
> to the left or right, as required.  This would impact how the cowling fits up 
> to the fuselage and give you a convex surface on one side and a concave 
> surface on the other where the cowling meets the fuse (when viewed from above 
> or below).  Personally, I'd prefer to keep the lines of the fuselage nice and 
> smooth and symmetrical so aligned the prop hub's and fuselage's c/l's.  What 
> happens under the cowling has little impact on the final external appearance, 
> ergo, I build in the offset back where it would be invisible.  Just my 2c.
> 
>   <Marv>
> 
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