> > > I am 90% done with the airframe of my dragon
fly I
> >
> > am intending to
> >
> > > power it
> > > with a 13b. Any comments? (snip)

The top speed is proportional to the cube root of the HP. The rest
of the time you can throttle back and not use the HP.

Paul Lamar ...No rotor no motor.


Folks, I've been lurking for a month or so, gathering info for an article
I'm preparing on aero-rotary power. I may be of some use in this particular
discussion.

VW engines, all-up, weigh between 165 and 185, depending on who made them
and what size accessories (particularly starter and alternator) and ignition
(magneto? 2 mags? All-electronic?) are installed. Count on no more than 80
real hp from any direct-drive VW up to 2180cc, and about 60 from a perfect
1835. Though some have indeed had success with belt drives, the extra weight
vs hp gains generally put that configuration at a disadvantage.

You make many good points about range vs speed vs weight. Think about what
kind of flying you'll be doing. The big consideration isn't so much weight
(extra weight just dogs your range and payload) as CG, which is, obviously,
determined in large part by weight and its distribution. A PSRU way out
front is more of a concern than the same amount of weight at the firewall.

As for the gear, the Dragonfly used two different main arrangements, and it
looks like the subject airplane has the later (narrower) gear.

If you're looking in the 230+ pound range, you can easily accommodate any of
the old hand-prop Continental fours (C-65 through C-90), and, for a little
more (still within the weight range of a 13B conversion), even an IO-240F.
If the -240 sounds like too much engine for a Dragonfly (and IMHO, it is,
not mentioning the expense), then so is a 13B.

As for "reliability issues" and "50-hour valve jobs" on VWs, I respectfully
submit that either you don't know what you're talking about, or you're the
worst mechanic in North America.

Also, somebody wrote, "There are no new O-200's. Also the rotary is now far
far cheaper to overhaul." As for overhaul costs, you're probably right; but
TCM introduced its latest-model O-200 (with induction on top, for instance)
at Oshkosh '06. Furthermore, though production numbers have been small, the
O-200 has not been out of production since its production started.

Tim Kern
Former CEO, Mosler Motors (built over 400 "VW aero conversions" and worked
with Rex Taylor, whose HAPI Engines (Eloy, AZ) did the development work, and
who (Rex), by the way, built a very good --160+ -- HAPI-powered Dragonfly
and ran the company and its successor, Viking, for well over a decade.)


Tim Kern

How much money for a new O-200?

Paul Lamar

Low $20K range, I believe.
Tim

In other words the p-port all aluminum 13B rotary is 2.5 times
the power of a O-200 with about the same weight for half the price.
Paul Lamar

Tim for a chap who is prepared to put pen to paper, you had better include
for comparison the single rotor and the aluminum housings or your
credibility might well be shot to pieces, when considering C of G, weight,
power and reliability comparisons.
George (down under)


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