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

Diamond Dust Maiden Flight

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Old 08-20-2004, 12:07 PM
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Kelly W
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Default Diamond Dust Maiden Flight

Hi guys,

I logged the 1st and 2nd flight on my Diamond Dust! This plane has a new OS 46 FX with Maccs tuned pipe kit. The engine is running an APC 9x8 prop and peaks at around 16,000 RPM on the ground.

I set the CG up about 1/4" ahead of the rear-most position, with the 8oz tank empty. My servos are Hitec HS-625's on the elevons, and an HS-81 on the throttle. Control throws were set to 3/8" up and down for both elevator and aileron function. The ailerons seemed a bit twitchy, even with 45% expo, but I sorta like them that way. The elevator seemed about right, although I might increase the expo some more yet on both functions.

Overall its a SUPER fun plane to fly, but I was expecting it to be a little faster than it was. That being said, the engine probably needs a few more runs to get it broken in properly. I'd recommend this kit to anyone looking for a little more adrenaline training... I'm curious what prop combinations you guys are using on this engine/pipe configuration? Eventually I plan to install a Jett FIRE 50 but I'd like to get the most out of this package for now.

Thanks,
Kelly
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Old 08-20-2004, 02:37 PM
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Goinstraightup
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Default RE: Diamond Dust Maiden Flight

Nice Job Kelly!! I have a bud that lets me fly his every once and a while, and it is always a treat. His has an OS 32 SX and the Macs pipe. I know what you are saying about this plane being a blast! His was clocked at 138 into the wind. It is quite a thrill to be allowed to fly his plane. I was doing high speed low passes at about 20 feet from a HUGE dive as fast as I could get it to go. Lets just say that our RC field was going by VERY fast. Anyway, he was standing behind me shouting LOWER LOWER. Heheee, at about 10 feet off the ground I didn't want to push it any more. The 32 SX one floats beautiful on landing and is going very slow for that final skid. I don't know what prop he has on there but we were getting mid to high 17,000's.

Jeff

Here's a pic of the DD.
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Old 08-20-2004, 03:13 PM
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WILDCRASHWILLY
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Default RE: Diamond Dust Maiden Flight

I'm running an APC 9x8.5 pylon prop on a Magnum 46XLS. My plane does great and performs better than I expected it to.
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Old 08-20-2004, 08:32 PM
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Kelly W
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Default RE: Diamond Dust Maiden Flight

I was checking tower today and I think I'm going to order up a bunch of 9x9's and 9x8.5 pylon props. The local shops don't really have much to choose from. I just get the feeling this motor is running a touch under pitched.

Jeff, ya those 32SX motors are amazing. I have one shoe horned into a House of Balsa mustang (the 20-25 size one). I shortened the wing by 1 rib per side, moved in the ailerons, and strengthened the wing spars and center Joint. Otherwise its stock and we measured the speed at 118mph on an APC 9x7 prop.

That's the 2nd modified HOB mustang I've flown. The 1st one had a piped Fox Q40. That was nuts... I stripped the scoop off the bottom, shortened the wing by a rib, cleaned off the canopy, and removed the undercarriage. It was pretty difficult to launch, but if it got airborne and on the pipe, man it was quick too...

Incidentally, we measure speed by Doppler effect. We measure the frequency of the motor coming and going in level flight, and find the velocity based on the differential. A friend has a digital sound recorder that he downloads into a laptop. From there he finds the frequencies and pipes them into a Excel spreadsheet with the environmental conditions, and out comes the speed!

Kelly
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Old 08-22-2004, 02:42 PM
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robc
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Default RE: Diamond Dust Maiden Flight

I just flew my Dust this afternoon. After tuning and finally settling on an APC 8x8 on my K&B 7.5 fan engine with a Mac pipe we got over 200mph on radar! The engine is a bit hard to tune but it gets on the pipe 22000 rpm on the ground. This thing is amazing and scary at the same time. I can't imagine going mush faster. This plane is great.

Rob
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Old 08-22-2004, 04:21 PM
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Default RE: Diamond Dust Maiden Flight


Hi Rob,

I’d suggest to recalibrate your radar gun before the next flight.

Even if your K&B 7.5 fan engine unloads to 26.000 rpms in the air the theoretical speed (in a 'perfect' environment without any parasitic drag from an airframe etc.) produced by an 8" pitched prop is below 200 mph.

Maybe you want to measure speed using the Doppler effect for instance?

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Old 08-22-2004, 06:14 PM
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Carl.E
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Default RE: Diamond Dust Maiden Flight

The real question is if you came through the radar from a big long dive, or was it a level run? Equations are great, but they don't take full-power dives into account. 200mph from a power dive I could see.

Carl
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Old 08-22-2004, 11:30 PM
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Default RE: Diamond Dust Maiden Flight

I maidened my first Dust today... and this thing is not suitable for high speed!
One could get some speed out of it by putting an oversized engine on it, but overall the plane has just too much drag to go fast.
I fly on a 300 foot long field, and I can make a long vertical dive (without engine) at one end of the field, and still put it down at my feet at the other end of the field without stretching things. So the thing is just plain draggy.
If you do this with a clean pylon plane, you're landing 1000 feet out of the field... or you could just do an extra circuit bleeding off some speed and try again...
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Old 08-23-2004, 06:28 AM
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Default RE: Diamond Dust Maiden Flight

ORIGINAL: Carl.E

Equations are great, but they don't take full-power dives into account.
200mph from a power dive I could see.
You're right, equations do mostly not display the real in-flight situation. Each plane/engine/pipe/prop combo gives different results, sometimes much differing from the performance expected.

However, I personally do prefer the trial end error method and lots of practice. But in that particular case i found the theoretical approach being a good argument

Here's an example to achieve good maximum speeds.

http://www.rcuniverse.com/forum/220_...2001757/tm.htm

Post No. 13 of that thread also explains why an airframe like Diamond Dust or Whip is not well suited for ‘high speed’.

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Old 08-23-2004, 09:35 AM
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Default RE: Diamond Dust Maiden Flight

Rudeboy, how fast do you consider to be 'high speed'? I've had 2 Dusts, one with an MVVS FAI GRRT 40 and my current one has a Jett 46. When I built the one with the Jett, I built in pitot tubes and installed a data logger to measure airpseed, and even calibrated it in a wind tunnel. Ready to fly minus fuel, it weighs 2lbs, 14 oz. From level flight, the Jett pulls the Dust over 140 MPH consistently. Long 45 degree dives are over 160. To me, that's not exactly slow. It is a very clean airframe without the engine and muffler hanging in the wind, and still pretty good with. Like any other delta, you get about 1 turn before you lose all of your energy, which makes it a bad choice for pylon racing. I have the side-exhaust version Jett; with the rear pipe from the fan engine, he's got less drag than I do, so I expect he's got faster speeds. Maybe 200 is pushing it, but just because you can't go that fast doesn't mean he didn't just happen to get his needle set just right and had the perfect conditions and got 201 or something.
Also, if you can't glide your Dust more than 300 feet out of a power-off dive, you might want to check your CG and move it back some...mine glides forever.

der_steuermann, I saw that thread, and wouldn't mind one of those planes...now only if I had the $$ for it. [8D]

Until Rob comes back and explains exactly how he got over 200MPH on radar (flight path, where they measured from, etc), there's not much we can do to prove/disprove his claim.

Carl
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