Hi Gordon,

Yes, by single rotor, I mean a shortened 13B engine. This requires a few
custom made pieces, primarily the eccentric shaft, but these are probably
going to become more available as the Sport Pilot class of planes comes
online.

Mazda did make smaller engines, but it was a long time ago. The 10A ended
production in 74 I believe. The 12A was a good engine, and it's "only" been
out of production for 20 years. The 13B is by far the most commonly
available engine today, though it won't be too many years before the Renesis
will take over that honor. Unfortunately, the smaller engines aren't all
that much lighter, since it's the rotor housing and rotor that get narrower.
Also, as the 13B advanced, the rotors got lighter, to the point where a late
model 13B rotor is probably lighter than a 10A rotor. I haven't looked at
the weights, so that's just my estimation. Bottom line is that the 13B, and
Renesis are about the only realistic choices for single rotor conversions at
this time.

What would be better than a single, would be a smaller two rotary. There
are any number of these popping up, but like so many other new engines we
see, they just never seem to materialize, and if they do, they're so
expensive that they lose their appeal. There are some very attractive
rotaries made for UAV/target drone use, but they aren't sold for manned
aircraft, and I haven't been able to figure out what the TBO would be.
Can't imagine the life expectancy of a target drone is very many hours :-)
Getting parts for these odd engines would be a problem as well.

Cheers,
Rusty


I'm intrigued by your twin-wankel idea. I appreciate the elegant
simplicity of the wankel design myself and try to keep abreast of what's
happening in the rotary avaition community.

When you say single-rotor, are you talking about a 13b that has been
shortened? I wonder too about the smaller displacement Mazdas -- you never
hear much about those, but I would assume they should be lighter than the
13b.

Regards,

Gordon.