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

DD Questions

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Old 11-30-2004, 12:50 PM
  #1  
robert92679
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I've been flying the Diamond Dust for nearly two months now and have it pretty well dialed in. I settled on the APC 9x8.5 and did some tuning on the pipe. I get into the high 15k RPMs on the YS-45. I have a couple questions I'd like to toss out to the group:

First, would there be any benefit to trying the the APC 'narrow' props? (By the way, benefit = faster!) These are the props at a similar size, but designated N or NN.

Second, in a screaming power dive the plane wants to roll to the right and I have to counter with a fair amount of left aileron. At our field we 'generally' fly a clock-wise pattern. I climb a bit on the downwind leg, then roll in out of a power dive on the base leg for a low pass down the center line. It is otherwise trimmed in level flight. Is this just engine torque causing the roll, or is there some other problem?

Lastly, there is this great 'whooshing' sound that can be heard even when the plane is flying straight and level (albeit at WOT). It isn't flutter, and it isn't the covering resonating. It's fairly noticeable, even at a distance over the engine sound. Any guess what is causing it? Unless there is a problem, I don't want to stop the noise (it adds a fairly cool effect). I'm just curious what is causing it.

Thanks,

Robert
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Old 11-30-2004, 02:34 PM
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Default RE: DD Questions

If the rolling were a torque issue, it would roll to the left... not to the right. Check if your plane it straight... it's easy enough to correct. If your plane isn't straight, and you trim that out with the elevons flying straight and level, that a change in speed (like a power dive) will change the trim.

The APC "pylon" props are better suited for high rpm operation... the narrower blade helps in getting the rpm up... they may be worth looking into, although the "sport" props are fine too, for sport flying.
Your YS could probably do with another 1000 rpm... try a prop from the 8.8" series, and reset the pipe.

The "whooshing" sound can be a number of things... probably just drag amplified by the airframe...
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Old 11-30-2004, 03:11 PM
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Carl.E
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Did you use MonoKote to cover your Dust by any chance? My 2nd Dust is covered with MonoKote and it also wooshed...retightening the covering stopped it somewhat. It's caused by the 130MPH+ wind vibrating the covering. It does sound really cool though, doesn't it? It's probably slowing the plane down a little, but I think the sound more than makes up for it. [8D]

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Old 11-30-2004, 06:22 PM
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Mike Connor
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Default RE: DD Questions

Robert,

My first Dust started rolling to the right after reaching high speeds when the airframe had about 90 flights on it. By that time there had been a few repairs to the airframe from mishaps. Twice I pulled the covering off (MonoKote) to check and reinforce possible flex points. I never did figure out the problem and the plane went in about 30 flights later. My second Dust has not started doing it yet but does not have that many flights on it. It seems like I remember Carl.E and one other with a similar problem on a Dust. I believe the newer Dust kits have a modification to help stop airframe flexing.

I have heard several people talk about the Dust "whooshing" sound but neither of my Dust's made that noise. I suspect that what ever is causing the noise is also causing drag.
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Old 11-30-2004, 08:03 PM
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FlooredCOBRA
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Default RE: DD Questions

Oh dont forget to inspect your prop before flights. I usually always check mine but one time I didnt I threw a prop.

When the prop threw you can imagine how out of balance it was with one blade. Well the vibration was so bad one of my pushrods came off the servo horn. Well since it is a Delta I was out of luck trying to land it safely. It just rolled into the ground. I just watched it slow roll as it went in. Not good[>:]
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Old 12-01-2004, 09:10 AM
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evan-RCU
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Default RE: DD Questions

The trim issue is easy. You are trimming the plane to fly straight when at less than full throttle. This is when the motor torque is causing left roll and since the airflow over the airplane is low it allows the airplane to roll and you are correcting it with right trim. Then when you are at full throttle the apparent engine torque disapears and you still have right trim in and it goes to the right. Prop.... well books have been written about props, the best thing to do as long as you have money is to try as many as you can. What's working for one airplane/ engine/ fuel/ weather combo won't work for another. Slightest things make a difference and the only way to find out is to try it yourself. Airframe noise.... EVERY fast DD that I know of makes this noise, seems to happen with Monokote at about 145mph, sometimes less, sometimes more dependent on weather more than anything. I have the leading edges sheeted on my current version of the Dust and it still does it, seems to come from the large open area towards the rear near the vertical stabs, could be disrupted air coming around the engine???
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