>Following up on the thread of a few days ago, I offered up the Stratus
>Subaru and Able VW as options. Doing a little more research along the VW
>lines I spoke with Great Planes, who have 17 years of VW conversion
>experience - and everything to gain from recommending a conversion.
>
>In addition to wondering why Europas use 3 blade less efficient (than two
>blade wood) carbon fibre props, he offered the best advice yet (which has
>been rattling in the back of my mind) on engine selection: The Europa is
>an expensive aircraft (from his VW aircraft perspective) and installing
>anything other than the factory recommended engine will severely
>deteriorate the resale value of the aircraft.
>
>Cleve
>A198 Mono XS
>Detroit, MI
I believe that a 3 blade composite prop will always be better than 2 blade
wood on an efficient airplane like the Europa. The intrinsic yaw vibration
cause by any 2 blade prop will damage the laminar flow over the wings and
result in a drag increase. Apart from that ideal airfoil sections for props
are much too thin for wood to be efficient at the speeds required.
Most Long EZs use wood props because wood absorbs vibration better than
aluminum so is less likely to fail (in a pusher environment) however the
favourite these days is 3 blades not 2. The reason is vibration. I wish
someone would develop a multi blade composite for the EZ.
Graham
|