The problem with used Rotax 912 80 hp engines is they usually get overhauled to make the Rotax 914 turbo 115hp engine for 1/2 the cost of a new rotax 914. Check with Bob Robertson of Light Engine Services for a used engine or new. He can at least connect you with someone in Sweden or area who might be able to help you out. Check the local flying schools that fly the older model Katanas.. powered by Rotax 912 engines. They may have an timed out engine...still good but "expired" for commercial use. Check with your local Rotax 912 dealer??? There are more Rotax 912 engines flying in Europe than in North America.
Rather than build the HDS wings which require more power and have a much higher stol speed (reduced climb rate)...the airspeed increase is not really there either. Install a better engine, a Rotax 912 80 hp will climb your HD 800 - 1200 fpm (dual/solo). The Rotax is a far more reliable engine. You should be able to pick up a used Katana motor in the $2500 - $3500 range.
The problem you mentioned about sonex are common. It seems they say one thing to get a sale out the door and when you have trouble you are on your own. I am a memeber of the Sonex forum, I have been doing research on the possibility of building a Sonex or waiex and the one thing have noticed is the Monnetts don't say to much until they get some negative responses or someone mentions something that keeps out of the food chain. There was a heated discussion sometime ago about baffling, soemone said there baffling was junk and that got real upset, then a few months later a NEW and IMPROVED baffling design came out even though the other one was supposed to be great.
You must be like me, plans building in two years is quite an accomplishment. I really enjoyed building so I'm looking for a new project but I just don't know how to get my wife to go along with it and not wind up in divorce court!
Like you I wish I had never went with the vw, but the cost made it very attractive. I did not have the money for a Rotax and I have always been a vw nut so it just made sense for me to use it. Had I gone with rotax I would have always wondered how the Vw would have done so I guess the education is or was worth something.
I plans built my entire plane in 23 months. I bought the redrive and a few parts from Great Plains Aircraft Supply and built the rest of the engine from parts obtained locally at a hot Vw shop where I have always done business and had good service. Until now. they did not machine the case properly so I had to take it all the way down to the crank to fix it.
I also had cooling issues that took me a year and a set of heads and then the case problem came up so I started over and did the fat fin mod. Without question this is the way to go, we need to get someone casting these heads with huge fins. I have documented it well on my Zenith Aero page, Air_Vw and Aeroconversions on Yahoo Groups. "Fat Fin Head" thread.
My plane is extremely heavy empty 742 lbs. or 336.57 kg. If my math is correct. The climb suffers but I see 600 to 900 fpm ( 182 to 275 meters per minut ???) at 1075 lbs or 487 kg. depending on the outdoor temp. Take off is pretty spectacular. I see about 87 mph in cruise and 3800 rpm. Fuel burn is abour 6 gallons per hour ( 22 litres per hour)
Aero vee does not have a great reputation over here. They sure tend to inflate figures. There are opinions of them, those that will fight you for them and those that will fight you because of them !
Hey be sure to stay in touch.
Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, power distribution panel, Approach Fast Stack harnesses, Dynon and Garmin avionics, and more.