Cavelamb did you post the Video on the Cygnet?

canuck_bob wrote:
Thanks Richard,

I really like the layout and thought for a long term project it would
be a little unique and the plane has a solid record for a strong
airframe.

I'm planning an affordable plane, mild steel tubing except for primary
flight load tubes, locally procured wood and building supplies, etc.
I'm a big guy so I feel I would need more than a VW. They are also
much more expensive to procure here in Canada.

I've looked at the Corvair as a possibility and it has some promise.
It needs modification to add a thrust washer at the prop end and a
fifth bearing to take other prop loads. That starts to get pricey
quickly. I am not fond of the 2 stroke Rotax engines, however the
Yamaha 700cc triple snowmobile engine interests me. Piston seizure
caused by shock cooling and heating seems to be real common on air
cooled 2 strokes in planes. The Yamaha is a triple water cooled
engine. Smooth and the best reliability of any sled engine I've
researched. This is my other choice for an alternative engine. As
much as I like 4 stroke the power to weight advantage of tuned 2
strokes is impressive. First choice is always a small Continental but
every potential repair problem is horribly expensive.

Piston seizures and shock cooling seem to be mostly operator error.
At least that's my opinion - from my own experience.

Having said that, may I point out that the Rotax 582 (and 618) are water cooled.