Continental O200 or Rotax 912 S

[Andrew G]

I'm waiting for the Kitfox 8 with RG, a RR-300 turbine and deluxe cupholder.

Here is wishing Happy holidays to a great group

[jtpitkin06]

The other piece of the performance puzzle is prop specs. My understanding is a long 2 blade prop is more efficient than a tri blade. Anyone have details around this?

Chargerbill,

Prop manufacturers spend millions on R&D. I’m just a guy that tinkers with small aircraft. So take the following with a grain of salt.

The best advice I can give you is to use the prop others have proven works well. There’s a reason most Rotax flyers use a 3 blade. It works. Likewise, many Rotec Radial engine installations use a 2 blade… because it works. Using the engine/prop combination that others use will save you lots of cash in the long run.

With that in mind we can try to answer your other question: Why use one over the other? A 3 blade prop is often installed on an engine/airframe to obtain greater ground clearance or to lower the tip speeds at max RPM. The 3 blade often has a lower perceived noise and vibration levels.

There is no guaranty that a 3 blade will always work better. For example: The Cessna Cardinal RG climbs and cruises faster with a 2 blade prop. The thinking is the 3 blade prop has more drag with the extra blade and it sucks up too much power. There may be something to that.

It’s a subject that can fill volumes.

Then, there is the most important reason for choosing one design over another; because it looks good.

John Pitkin
Greenville, Texas

[HighWing]

With most of us that spend a lot of time thinking of alternatives, most of our discussion is theoretical at best. The published or even calculated engine weights don't really have a lot of practical value, in my opinion. As you suggest, there is a great deal of difficulty getting accurate information on weights. An example, Grove, the gear folks list their Model IV gear as weighing 24.3 lbs. This turns out to be without axles, mounting brackets and hardware. The actual mounted weight is almost 32 lbs. - from a question I asked a Grove rep - total installed weight including nuts bolts and washers. They actually put me on hold as they got the parts together and put them all on a scale - for the first time, maybe?. Maybe apples and oranges, but it illustrates the marketing pressures that lead the producers to do a bit of slight of hand with numbers. There are numerous factors that combine to add to engine choice weights - engine mount, accessories, etc. This discussion was passionate and furious when the factory supported the NSI Subaru conversion. With the pro guys insisting, including the NSI factory, that the forward package was only 35 lbs heavier than the R-912.

Then the discussion drifted to how to mount a 26 lb. battery in the tail for W/ballance compliance. I never could get the answer as to why a 26 lb. battery was necessary at eleven ft. aft of the datum to balance a 35 lb. weight three ft. forward of the datum. The ultimate proof of the discussion was and will be the actual empty weights of the various engined airplanes. There is a lot of data in the history, but most of it is not easy to find as human nature prevents most of us that experimented to come clean with the final data if it tends to embarrass.

I have talked to guys that maintain that all the old data is just that, old, and their installation will be different. Personally it is of no particular interest to me what a guy wants to put in his airplane, but for the guy that is truly interested in data, check the classifieds and see what is out there and what the prices are and the total flight hours. I think this latter is very revealing as well configured Kitfox is fun to fly - not so much if performance and payload is lacking. Ask the guys that are running the various engines what their numbers are - on the scales, climb, cruise and Hobbs.

[chargerbill]

HighWing,
How much coolant does your 912 require? I'm very curious!

[cap01]

the amount of coolant will depend a little on the plumbing of the engine . when i filled my 912 the first time i used the waterless stuff and still had some left in a 1 gallon jug . not sure how much i had left since its been awhile

[Av8r3400]

This has been a really good discussion.

I have been (and still am) a heavy proponent of the 912 Rotax motors. I do not have any first hand knowledge of weights, only what is published. I do know from first hand comparisons that they perform much better than the Subaru installations. I always attributed this to weight.

I'm about to remove my 912UL off my IV-1200 project. I would like to weigh the engine with mount and FWF items mounted to see what it really weighs. Adding in the radiator, plumbing and coolant would be the only additions.

I will post here (hopefully with photos) when I have some hard data.

[HighWing]

That is a good question. And again all you can get from me is an opinion or recollection. My first Model IV is in a salvage yard and I have oil, coolant and panel systems to go to get my new IV flying. I do recall, however, that I would mix the coolant 70/30 and have part of the mixed gallon left after filling the system. My guess would be three quarts.

[DesertFox4]

I'm waiting for the Kitfox 8 with RG, a RR-300 turbine

Andrew- hope the Kitfox model 8 has a mid-air refueling probe. That turbine is thirsty at 26 to 34 gal. per hour burn rate.

[DanB]

that 300 turbine should be just right for the Kitfox 10 which should be a four passenger bush plane with a large baggage area.

[Andrew G]

Ok ok... you make sense re the gas mileage, but I would gladly give up a baggage compartment for Cessna RG style legs.



Sorry I moved this otherwise excellent discussion off track.