On Apr 17, 8:41*am, "oilsardine" wrote:
schrieb im ...
.... Seriously, more info would help. *What is you goal? *What kind of
plane?

I have a Revmaster (normal aspirated) in an slightly :-) overweight Sonex..
The plane hasn't flown yet. Some extra HP could help. The Conti would fit
weight-wise, but seems also underpowered for this application. The Conti
turns slower than the Revmaster, but my prop diameter is limited by ground
clearance...

Kinda spected this was where we was headed. Unfortunately I don't
know of a good solution to your problem. The prop diameter limitation
and intended cruise speed (common on lots of VW based designs) means
for all practical purposes you are stuck with a direct drive solution,
and in this power range the options are limited.

The Subaru won't gain much over the VW in direct drive configuration
and adds the complexity of water cooling.

Making some assumptions about your Sonex, a Rotax with a 3 blade prop
might be an improvement? But it too is water cooled.

Some seem to like the Jabiru as a VW substitute.

How much over weight? Would a diet be a better solution?

Too bad there isn't an inexpensive controllable pitch prop available
for this kind of application........................other than the
Ivo?

Editorial comment: 2 place VW powered planes are practical IF BUILT
LIGHT and the true limitations of a VW based engine are kept in mind.
Unfortunately it seems that builders of everything from Cygnets to Qs
and Vari EZs fixate on advertised numbers and we end up with
dissatisfied builders due to less than advertised performance. In
most cases it's not due to "embellished" factory numbers but the fact
that in this weight and Hp range there just isn't any more to give and
a hundred, even 50, pounds more makes a drastic cut in performance.
This is one of the oldest stories in home built aviation, and not
limited to VW designs. It's sad that it keeps getting repeated. If
expectations were more realistic, and thus met, maybe our sport/hobby
would have more active members?
==========================
Leon McAtee