Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

First flight of the Magnum... Wow!

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Old 12-27-2002, 03:05 PM
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flybike
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Default First flight of the Magnum... Wow!

Thanks to everyone who helped me get my magnum going. I had the first flight yesterday- total success! Lake Superior has 18 inches of ice on it. It was actually quite warm, about 26 degrees F. No wind, and not a cloud in the sky. The person launching it only had to let it go. It flew straight as an arrow, no trim needed. This thing is fast! I had to keep turning to keep it in sight. After a few minutes, the plane landed perfectly on the smooth ice. Right now I am using an APC 9x9. Is this too much prop? Thanks, Hans
BTW, the ice fishermen said it was going 250 mph... Of course they are mistaken, but this thing certainly looks fast.
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Old 12-27-2002, 05:08 PM
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Default First flight of the Magnum... Wow!

what kind of engine are you using?
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Old 12-27-2002, 06:19 PM
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Default 9x9...

Are you using an APC 9x9, with the West engine?
What rpm are you getting with that prop?
Does it come (and stay) on the pipe flying level?
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Old 12-27-2002, 10:14 PM
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Default First flight of the Magnum... Wow!

Just got in from another flight. The people in windsleds on the ice really liked it. I have not put a tach on it yet, will do tomorrow. The engine is the one that comes with it, West 50. I have a bunch of different props, will try them. Right now it is plenty fast. It seems to all of a sudden pick up a bunch of rpms towards the end of a dive, is this what you call on the pipe? Hans
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Old 12-27-2002, 10:52 PM
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Default First flight of the Magnum... Wow!

Originally posted by flybike
It seems to all of a sudden pick up a bunch of rpms towards the end of a dive, is this what you call on the pipe? Hans
Yeah..you might be a little short for the prop and need to dive to get the R's up enough to get it on. I hope it's not speeding up because the clunk is sucking air..this will speed up not just the engine, but also the deterioration of the engine.

Next time back the pipe out a tad, like 1/4" or slap a 9X8 on it and I bet it will run on the pipe just fine. You might shorten the 9X9 a little to get the R's up to where it gets on the pipe easier.

I bet the sedate ice fishermen are freaking out.
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Old 12-27-2002, 11:28 PM
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Default First flight of the Magnum... Wow!

I have a bunch of props, 8x8, 8x9, 8x10, 9x7,9x8, 9x9, and some pylon props, so I have some experimenting to do. How do you know if the clunk is in air? The ice fishermen like it, it gives them something to do! What should I see for rpms on this engine? Also, is there an idle adjustment on this engine? It likes to quit at low rpms. Thanks, Hans
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Old 12-28-2002, 12:48 AM
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Default Clunk coming out...

I was almost kinda sorta joking about the clunk. Anytime you point a plane down, and there is not a full tank of fuel, and your tank is plumbed for the stopper at the front and the clunk at the back, the clunk can be exposed by the fuel tubing holding it out of the avaiable fuel when the fuel gravitates towards the front of the tank. How's that for a run on sentence?

I bet this isn't what you are experiencing...

Just put a prop on there that runs a little faster, or lengthen the pipe a little....then see how that works for you. Personally I'd lengthen the pipe, it should make it easier to set the needle and if you get the 9X9 on the pipe it'll be pretty fast.
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Old 12-28-2002, 03:37 PM
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Default First flight of the Magnum... Wow!

the standard idle is very high for this engine, you can make it richer and get it to normal engines idles with smooth pick up, we've shortened the pipe 1" for 8x9 APCs and 5-10% ProSynth
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Old 12-29-2002, 01:51 AM
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Default hmmm

Doesn't the centrifugal force hold the fuel in the back of the tank in a dive?

Kinda like the roller coaster theory...

james
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Old 12-29-2002, 02:11 AM
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Default First flight of the Magnum... Wow!

Centrifugal force only applies to loops and stuff. Well to everything where a change of direction is involved really...

In a dive (90 down aka straight down ) however, fuel only stays in the back of the tank if you accelerate faster than 9.81 m/s. As our planes don't have unlimited speed, eventually gravity will catch up, and the fuel will drop to the front of the tank... Test this with a slow plane: put in a stiff clunck line so the clunck doesn't drop forward when you hold the plane nose down. Now fuel her up and take her for a spin. Get up there really high. Now throttle back to idle and take her straight down...Prepare for a dead stick landing!
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Old 12-29-2002, 05:00 AM
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Default Clunks..

I don't know the scientific explanation, but I know in a prolonged power dive I've experienced sucking air. Usually won't die if you throttle back, but in planes like the Duellist where I really don't want to lose an engine I try to keep the power dives toward the first half of the tank.
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Old 12-29-2002, 06:03 AM
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Default First flight of the Magnum... Wow!

Nothing scientific about it, the only thing that happens when you throttle back is that your engines draw much less fuel, so the fuel lines don't fill up with air so quickly. At WOT things happen fast. If you level out, and apply full power again, those few bubbles mostly don't stop your engines.
I always make sure the clunck is capable of going anywhere it wants to, because that's usually where the fuel is. That's why I turn my own cluncks, and make 'em about 3 times as heavy as the ones usually supplied with tanks. Plus I use a very thinwalled clunck line...
In a 2 oz tank, things get complicated of course...
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