Peroxide

Hey, what's the fastest plane/engine combo that you have ever seen? I guess I'm probably asking for it, but no BS.
-Ian

Rudeboy

The fastest planes I have ever seen are F3D pylon racing planes... I know there are faster things on this planet... but these are already plenty fast...

These things do an average of close to 200 mph on the 10 lap course... and that includes take off and accelerating for about one lap on that tiny prop...
On a straight line they must be capable of well over 200 mph...

sydclement

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Peroxide:
Rudeboy is right on about the F3D racers but they are expensive.
A Mini DD with a Jett 50 will do 200MPH most any time If you have good eyes
and thumbs to keep up with it.
Just fly it on clear sunny days around noon time for best results.

Syd

OLD_SLOW and in the WAY

There "WAS" a diamond dust powered by a 1 inch ducted fan engine that "was" ballistic it "was" flown by a very capable young lad that could barely keep up with it. i dont know the speed but it would have put a F1 pylon plane to shame. then on that fateful day...... an instant of dumb thumb created a 100 yd long balsa yard sale.

Razor-RCU

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If jets count- there are many that hit 250+ (Harley Condra's BVM Bobcat for eg.)

For prop-driven F3D I would think...

wilkigmc

I had a go with a pylon racer (F3D I think) against a Mini DD with Jett 50. Left the Diamond Dust standing. Don't know how fast it went, but flying the DD afterwards was almost boring.

Rudeboy

Razor... jets don't count... this is the extreme speed PROP planes forum...
Any properly set up pure speed jet will outrun a prop plane... why do you think every air force in the world converted to jets shortly after WW2? Because of the cool sound or the wow factor...? NO, because of the sheer power and speed...
There are RC speed jets on this world today that will do 300 mph EASILY if you keep the throttle where it should be and providing you can keep up with them...

As for prop driven planes... the giant scale racing planes are hard to beat... but they are also horribly expensive...

If you want to go fast cheaper than giant scale... design yourself a good plane around an OS 91 VRDF engine, mould yourself a good prop and go to the doctor for some valium...

Razor-RCU

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I was making a funny- ( He did say "plane engine combo")

Aren't you still flying prop jobbers in the Belgium military? [X(]

Rudeboy

Indeed... but I don't consider the belgian military to be a real army anyway... it's more like an expensive hobby club or something like that... too bad I'm not in the club, but still have to pay membership fees...

AirGar

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Team Extra (Futaba) regularly practices where we fly, and them planes cruise the skies at 220+ MPH! Impressive, to say the least!

Gary

Alexspeed

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Hmm,

I guess that there are different ways in defining "fast". There is the absolute speed, there is the scale speed, there is the speed for a concrete racing class... There is the emotional factor and the scientific factor. Which is faster: A pylon .15 plane at 150Mph or a .90DF at 220Mph? Is a Top Fuel Dragster faster than a Formula 1 car? Who is faster when and where? I think it´s open to everybodie´s taste. But if we need to think in absolute terms, we just need to equippe a full scale F-104-F Starfighter with RC-equippment.

Peroxide

How are these engines able to spin so fast? I seem to remember most OSs in the 40-60 range being rated for only 18k or so. Isn't the power peak somewhere around 17k on the .50sx for example? Has anyone tried gearing an engine to spin a prop faster, but keep the engine in it's power band? How about 3 or 4 bladed props? I know there would be landing issues, but by keeping the prop tips subsonic, there would be definite efficiency gains.
OK, just one engineer's rambling imagination.
Thanks,
Ian

Alexspeed

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Ian,

My MVVS tuned .15 Diesel makes 24.000 rpm with a 6.5x6.5 APC

My Rossi .21 makes 32.500 with a 7x6W APC

There´s a difference between big engines and fast engines...

ALEX

Rudeboy

Gearing a prop UP is crazy... why would you want to do that?

Fast two strokes aren't fast because a fast spinning prop makes a plane go faster, they are fast because you can get more power out of them by running them faster...

If your standard .50 angine puts out 1.80 hp... gearing it up would only do one thing: it would cost you power (gearbox efficiency)...

daven

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The Nelson engines that I use for Racing Q500 routinely turn a 9 pitch prop approximately 19,500.

The Nelson engines that I use for Racing Q40 routinely turn a 8 1/4 pitch prop approximately 24,000.

Couldn't tell you why or how, but thats what they do.

As to the original question, The FAI planes are fast, but they are also pretty big. I think the Q40 planes appear to be going just as fast because of their smaller size (and smaller race course).

On of the faster appearing planes I have ever seen was a 15 sized scale combat Japanese plane with a Nelson .15. I don't think it was as fast as a Q40, but it sure looked it due to its small size.

Peroxide

Thanks for the data points guys. However, I am a little bit confused as to why a gearbox wouldn't be such a good idea. I know big 4-stroke car engines (spec the 5.8L 351 Fords) and maybe that's my problem, but I thought that all engines had a power peak at a certain RPM, and running an engine faster would drop your power LOWER. Are the stock specified RPM numbers on the box simply WAY below the power peak on rc engines? Anyway, just curious.
Thanks again,
Ian

Rudeboy

True, if you run a given engine at a higher rpm than where its power peak is, output power will start to drop off.

But fast engines are built to run fast... While a sport .40 engine may reach it's maximum power at say 16000 rpm, some .40 racing engines make their power at 30000 rpm or even more... and it will put out close to rwice the amount of power of the sport engine... but if you run that racing engine at 16000 rpm it will not fare too well...

You mentioned big four stroke car engines... well then look at Formula 1 engines... F1 engineers are constantly working to get the rpms up on those engines... they are currently running them V10 engines at close to 20000 rpm...

The specified power numbers on the box of your model engine are mostly exaggerated, not understated.

A gearbox in our planes is not useful because we can still run a prop at 20000 rpm without the prop going supersonic, so we don't have to gear anything.

Peroxide

OK, that makes sense. Thanks rudeboy. So, on to the next question. How do I distinguish between the sport and racing engines? I've seen some names like West, MVVS, and Rossi thrown around here; who makes these and where can I find them?
Thanks,
Ian

AWDEVO8

There is a reason why two engines of the same displacement can have such drastic rpm differences. Its called piston speed and it has a direct link to the lengh of the stroke of any given engine. A shorter stroke equals a lower piston speed but higher rpm's. A long stroke means lower rpms for a given piston speed. Get it?

FlooredCOBRA

here is a link to some engines

http://morrishobbies.com/default.php...7da6f12f7267d1

I am running a MVVS GRRT FAI in my DD and love it.

Gravityisnotmyfriend

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I came across this link. I think it has been posted on RCU before. http://213.84.42.244:8087/paulraaf/f3d_training.mpg
I had a hard time believing any prop planes were this fast.

FlooredCOBRA

You can hear a noticeable difference in engine sound. That would be a high end racing engine in video and compare how it sounds to say an OS.46 or something. Huge difference in the sound and a big gap between rpm ranges.

One thing is I couldn't fly with venturi only... I would be a nervous wreck. I had to pull mine off and put a carb on it...

I used to have a Scat Cat a while back and used to think it was fast with a piped OS.46. To bad I didn't have my GRRT then, that little thing would of really hauled!

Rudeboy

Gravity,

You really should go to a race some time if you can... You can't really capture the essence of these planes on video...
When you are on the starting line, and three or four of these babies are standing there screaming ready for take off... it's just awesome... the noise goes through your spine... without hearing protection you will hear a dull undertone in your ears, besides the sound of the engines: that's your eardrums getting damaged ... They just can't keep up with all that noise (sounds a bit like a subwoofer that is overpowered)
Then when they take off and make the first turn coming back at you, the first thing you think is: these thing are coming for me...

Check this video out... it's on the same site: [link=http://213.84.42.244:8087/paulraaf/FAI_pylon.avi]3 plane F3d heat[/link]

Cobra,
I don't think the scat cat would do too well on a GRRT... these engines just need props that are too small for a Quickie... Quickies need 9" props to pull that draggy airframe through the air... FAI engines turn 7.5" to 7.8" props... that's too small... you'd just be making a lot of noise (which is cool too )

Gravityisnotmyfriend

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Man! that is insane. I'd love to hear a whole flock of those things take off the line in person. I gotta say I have alot of respect for those pilots. It seems like it would be very easy to lose track of your plane or - worse yet- mistake it for one of the others that are racing.

Rudeboy

For the pilots, not really... when flying you are so concentrated and fixed on your plane that everything else is a blur...

But the race officials have a hard time... I am "official" very often at pylon races, and it is very hard sometimes to keep track of the planes... especially when they have the same colours, are racing really tight and are going around the pylon which is the farthest away from you...
And you cannot make mistakes as an official... if you screw up just as one of these guys has made the perfect flight he will eat you alive...