Verner radial vs. Rotec radial

[mickey]

Reliability with the Verner is certainly a concern, since it'll be my narrow behind up there.

Another slightly less "out there" idea:

http://www.experimentalfuelinjection.com/

How about a Rotax 914 turbo with electronic fuel injection and ignition? Fully redundant computers are an option. He uses an oil-to-water cooler, so you only need to worry about a radiator in the airstream.

As you can see, I'm not somebody who is content with the status quo. But I've got good life insurance.

Edit: If the Verner engine fits inside the standard "bubble cowl" then drag and frontal area won't be an issue. That's a big "if", though, since I can't find any info on the diameter of the engine.

[RandyL]

Mickey,

"Radial engine" and "fast" don't normally go in the same sentence. Of course that huge frontal area and all those fins are enormously draggy. Since good high DA operation is your goal I'd look really hard at a 914, possibly with tweaks and improvements as you've mentioned.

I don't know if you've built any airplanes before but I can tell you that as soon as you deviate from any of the well-engineered kits you are taking construction time up by a factor of at least ten. Kitfox offers a standard FWF installation kit for the Rotax and everything is completely thought out for you and proven to work. All needed parts are provided. With any of these other installations you're on your own for everything. First there's designing the systems, then there's finding and fabricating all the parts, then there's testing to see if each system works, then there's the inevitable revision iterations. Not trying to discourage you, just point this out. Still, this is experimental aviation and we're all free to try different things, and that's good so long as you're up for the challenge, and that's how we advance the state-of-the-art.

Personally, given your objectives of speed and good high-DA performance, the 914 seems ideal, and there should be plenty of room for experimentation to keep you happy. I know I like to tweak things myself and am seldom happy just following the plans without some attempt at *improvement*. Heck, I'm barely into my Kitfox project and I've already got a "Mods" page on my project web site. Who knows what will end up there by the time I finish.

FWIW,

[mickey]

Killjoy.

Well, I DO still own plans for a Hatz Bantam. And I intend to build it someday. That one will have a radial for sure. I think you're right about the value of a turbo engine for my intended purpose.

I'd REALLY like an excuse to use a turbodiesel........

[paulc]

Mickey,

"Radial engine" and "fast" don't normally go in the same sentence. Of course that huge frontal area and all those fins are enormously draggy. "
FWIW,

Nonsense.

Radial powered Focke-wolf 190 was faster than the Inline powered Spitfire and P51.

Race planes such as the Gee Bee's were unbeatable, Even now days Rare Bear at the Reno races is the fastest of the lot. All radial powered.

Air cooled engines need to be cooled, if they be round, flat or inline, makes no difference. Cooling equals drag period.

[jonbakerok]

Nonsense.

Radial powered Focke-wolf 190 was faster than the Inline powered Spitfire and P51.

Race planes such as the Gee Bee's were unbeatable, Even now days Rare Bear at the Reno races is the fastest of the lot. All radial powered.

Air cooled engines need to be cooled, if they be round, flat or inline, makes no difference. Cooling equals drag period.

I think your logic only applies to golden age aircraft when the cowl is a carefully designed NACA cowl, as in your examples. Until the invention of the NACA cowl, water-cooled designs were generally faster.

The concept of the NACA cowl is to create enough jet boost from the cowl exits to overcome the radial's frontal area. It squeezes the cooling air to increase its velocity after heating, much like a jet does. The combination of the jet boost plus the radial's lighter weight gives better performance, which is why radials ruled for most of the golden age despite their frontal area.

The Kitfox bumpy cowl is definately not a NACA cowl, and I doubt that a 125 HP radial would fit inside it anyway. But if it did, it would be an interesting question, since in that case both alternatives would be suffering the same frontal area penalty. Maybe the radial would be faster, since it has more power and can swing a bigger prop. Or that gain could be offset by the weight penalty, which would cause the angle of attack to increase. It would be an interesting experiment.

[paulc]

I think your logic only applies to golden age aircraft when the cowl is a carefully designed NACA cowl, as in your examples. Until the invention of the NACA cowl, water-cooled designs were generally faster.

Hmmm not sure about that. I don’t think Rare Bear or the Fw190 were "golden era" the golden era was 1920-1930's.

In fact as far as piston powered aircraft are concerned these were the high water mark, before the kero burners came to be in the 1940-50's

Would the Germans have had NACA technology at their disposal during the peak of WWII? Oh and let's not forget Japan's Zero, Russia's I 16 Polikarpov's all as fast as bullets. Definitely not slow!

NACA cowl or not, it’s a complete fallacy to associate radials only with slow speed. The OX5 was an inline V8 and powered the Jenny Bi-plane was just about the slowest thing around. So do we say that V8's are slow or that Jenny's are slow?

[jonbakerok]

Hmmm not sure about that. I don’t think Rare Bear or the Fw190 were "golden era" the golden era was 1920-1930's.

In fact as far as piston powered aircraft are concerned these were the high water mark, before the kero burners came to be in the 1940-50's

Would the Germans have had NACA technology at their disposal during the peak of WWII? Oh and let's not forget Japan's Zero, Russia's I 16 Polikarpov's all as fast as bullets. Definitely not slow!

NACA cowl or not, it’s a complete fallacy to associate radials only with slow speed. The OX5 was an inline V8 and powered the Jenny Bi-plane was just about the slowest thing around. So do we say that V8's are slow or that Jenny's are slow?

We're getting a little off-topic here, but since the board traffic has been a little slow lately, I'll bite...

Sorry about my sloppy use of the term "golden age", but my point is still valid. You need a NACA cowl to make a radial go as fast as an equivalent inline engine. That's how the Focke-Wolf, Zero, and Gee-Bee did it. NACA developed the cowl in 1927 (just checked Wiki). The design was in wide usage throughout the 30's.

The OX5 in your "Jenny" was a 400 pound V8 that barely made 90 horsepower. Not a reasonable comparison. Consider the Spad 13's Hispano-Suisa or Fokker D7's Mercedes, both of which were must faster than the equivilent poorly cowled rotories of the same period

Rare Bear is a special case. That's a huge, dual-row radial with twice the horsepower of the Mustangs it races against. It goes fast by sheer brute strength, but it's still as likely to lose any given race as it is to win.

Frontal area has more to do with how fast a plane flies than horsepower. Without a special cowl to overcome the radial's larger frontal area, the smaller profile of an inline water cooled engine will win every time. The two may have the same theoretical cooling drag, but the cooling efficiency of cast fins hanging perpendicular to the breeze is much less than water transferring the heat to the closely-spaced thin aluminum fins in a radiator behind a duct.

No need for theory, though. We've got proof. Several Kitfoxes are flying with that beautiful Rotec on the front. None of them are as fast as a 100 hp Rotax. Speed is not why you put a radial on a Kitfox.

Please don't think that I don't like radials just because I'm aware of the limitations. I'd give up a few knots for that look any day.

[paulc]

No need for theory, though. We've got proof. Several Kitfoxes are flying with that beautiful Rotec on the front. None of them are as fast as a 100 hp Rotax. Speed is not why you put a radial on a Kitfox.

Not sure about that. Here are the actual accounts of one Radial powered Kitfox owner. I’d be surprised if any Rotax (even at 6,000rpm) could match these numbers. No cowl fitted NACA or otherwise!

Due to landing gear length, I know some Rotec/Kitfox owners have compromised performance by running smaller props on there Rotec which is designed to run larger props via its superior torque. 76" diameter is the optimum.

Kitfox Classic IV: Brian Henneman
Engine R2800 MkI
Prop: 76"D x 50"P then to 76”D x 55”P.
Burn: 6 gal/hr
Max RPM: 3600 (via 3:2 gear box)
Cruise RPM: 3000 = 2000 at prop.

Comment (26th June 2002): I did a static thrust test this past weekend and it will pull 480 lbs. Very impressive. More later.
Comment (11th June 2002): Just wanted to let you know I received my new prop a 76"dia. X 55" pitch and the performance really increased. The climb is still about 1500'/min. and the top speed is 130 mph. I can still exceed the red line up to about 3700 rpm. I have been cruising it at 3400 rpm and I am indication 110 -115 mph. I could use about another 5" of pitch to have a really good cruise prop but I will keep this one for demos.
Comment (28th April 2002 “I got in a couple of hour flying this weekend so far and I took Steve up in it with me. With the prop I have on it, it is really a climbing machine. I can peg the VSI at 2000' / min. and that is really going up for a little airplane”

[Joe Meyeres]

This is in response to John Baker on his comment of the Rotec 2800 vs Rotax 912. I have a Classic IV with the Rotec on the nose swinging a wooden 70" Climb Pitched Sterba Prop. At full power straight and level I am seeing 127 MPH, 75% power is 105 to 110 MPH and 65% yeilds around 90 to 95 MPH. I don't know what the Rotax will give you, but if you are looking for speed out of an airplane, the Kitfox is not the greatest choice. It's got alot of drag and the tube and fabric construction some would consider not as durable. However, I would not give up the aesthetic value achieved by putting the Rotec on the nose. It is "robust" and you can not match the sound it delivers. As for the speed... it's a Kitfox, but it sure not the slowest one to the party! I get alot of comments that it looks somewhat like a Beaver or Monocoupe. In my way of thinking, that's not bad company to be in!!! Pictures and videos are available on the Rotec Website at www.rotecradialengines.com