dewilcox

I’m flying a Rotec conversion in Arizona. I have 20+ hours on my 2200 with the liquid cooled heads. I flew today, photo attached. OAT 50f, Water temp 132f, CHT 228f. This is in a Jabiru SP. RPM OAT CHT OT H2O VLTS EGT OP

"Mini Imp" caught my eye. I love the aircraft. Get rid of the retracts and it's pretty simple to build. I can't speak for builds in Oz, but I know of none that are building in the US. I bought the plans for Molt's Mini Imp some time ago. He used a flexidyne (ABB 75D X 1 3/8 FLEXIDYNE DRIVE) the get thru the torsional harmonic problem typical of long driveshafts. The flexidyne is designed to be used on heavily loaded motors to soften the starting load. It has steel shot that drives a "turbine" until the rpm is such that it locks up. From my research, the flexidyne doesn't last more than 100 hours on the Mini Imp. A driveshaft on a propeller is just a bad idea. One of Burt Rutan's first jobs was working for Jim Bede, assigned to figure out how to make it work on the BD5. Interesting to note that Rutan's pusher designs have no drive shaft.

The core element of my radiator is 99 in^2. One example of the Rotax 912 radiator is 70 in^2. I looked at smaller radiators and alternate nacelle locations. But since the space was available behind the engine, why not go with a robust size? There are two electric water pumps, one on the airframe system, the second backup pump is on a rechargeable lithium ion battery. Water temp in cruise at 7500’ with 85df oat is now about 200df. My primary problem was the oil temperature which was up to about 235 in climb, 220 in cruise. It is now a comfortable 195 in cruise after relocating the oil cooler and baffling the engine sump fins. Water temp is about 230 in prolonged wot climb. CHT is about 310 in climb. When I get more time on a stable configuration I’ll finish an article I am writing about the conversion. All of my cooling air inlets are currently crude sheet metal. I’m now finished with the mechanical installation and ready to begin extensive fiberglass work. I bought the plane with a heat damaged engine. All but one of the heads were cracked. It also had a minor accident in the past. A wheel had come off, destroyed the landing gear and had a prop strike. They repaired the gear with with a Grove solid aluminum design, huge wheels and brakes. That system prevented installation of all fairings. I have the correct gear (30 lbs lighter) on it now and am in the process of repairing and installing wing root fairings and wheel pants. The pervious bunch installed a Warp Drive prop. Which is also coming off as soon as the fairing work is done. The cruise IAS is only about 90 mph now. I’m confident the POH performance will return when I get it back to OEM configuration. I was told by JabiruNA that new air cooled heads were not available due to the Camit fiasco. That is the main reason that I decided on the Rotec liquid cooled heads. Rotec customer support is good. The plane does not feel as solid as my Sonex in flight, very sluggish. It is also about 25kts slower, which I’m sure is part of the “feel” problem. I’m confident that 10kts will come back with the right prop and fairings, possibly 15. If I do get 15, I’ll be selling the Sonex. If not, I’ll sell the SP. I currently have 15 flight hours on the Rotec-Jabiru. The Rotec heads seem to be a good product. The CHT is higher than I expected, but beats the heck out of the air cooled heads. I need to recheck the solid lifter valve clearance soon.

A diaphragm fuel pump has a limited life. The likelihood that an impending failure can be reliability detected during periodic maintenance isn’t good. The likelihood that the diaphragm will start leaking and losing pump pressure before its performance affects required engine flow, is good.

I too was surprised to see fuel pressure remain after engine shutdown. My Sonex/Jabiru/Bing does not have an electric pump, although I did leave the engine pump in the system, contrary to the advice of the installation manual. I do not get an increase in pressure, but the 3 psi normal pressure from the pump is always there. I doubted the reading for a long time, so I disconnected the line and the pressure fell. I guess it means that you have a healthy float needle valve in the carburator. The pressure increase may mean there is a little air in the line somewhere.

New to RF. David Wilcox. Payson Arizona, USA. Just finished conversion of a Jabiru 2200 to Rotec liquid cooled heads, on a Jabiru SP experimental. Have 10 hours on it now. Also flying a Sonex with Jabiru 2200.