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

Profi 2014 F2A first run

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Old 04-18-2017, 03:19 PM
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MJD
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Default Profi 2014 F2A first run

Just a teaser run in the evening on the deck, since I had just finished getting it attached to the test stand.. I had to use the speed pan and some fasteners but finally got it figured out. Put a pressure tap on the pipe seam.

5% fuel, 25% total oil, Profi 10% head (not FAI) and Nelson HD plug. ZZprop .15 bench prop.. 5.75" dia by some rudimentary diamond airfoil blade with maybe 2" pitch. The Uctkam runs about 30.5k on it.

Second bump with the starter it took off immediately (cantankerous speed engines..) into a rich 19,500-20,000 exactly as the pre-stage rpm on the c/l F2A's sounds. I let everything warm up and stabilize then started cranking in - I had the NV cranked wide open and was using the Jett remote NV behind the engine. Very predictable just like the Picco .40.. it hopped up to a bit over 31k, but it was still coughing smoke and acting like it was coiling a spring.

I remember Bill Hughes saying "you'll be surprised when it stages the first time..". I said cool, but I was used to running the OPS .65 and this and that. He just said "you're still gonna be surprised".

Next thing I knew wham!.. 35,36,37,37.2,37.3k.. I jumped

A couple of seconds of that then I cranked the needle open and pulled the line. Oh.... it was so swee-e-e-e-t! It is a monster.. still rich it topped t he Uctkam by 6.4k.
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Old 04-19-2017, 01:43 PM
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I think you need an FAI Speed plane for it. I am surprised it is only 6,000 rpm better than the Uctkam. It is about ten times the money.
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Old 04-19-2017, 04:00 PM
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Well, I think I've read that the hp to turn a given prop within nominal conditions increases as the cube of the rpm? Not sure but if the lift goes up with V^2 it is at least that. 37/31^3 is 70% more, 37/31^2 is 42% more.

But assumptions and arithmetic aside, the bench prop is a very light drag load and I think it essentially lets the engine easily get on resonance. So the rpm certainly represents a major hp increase, but I don't know whether it represents the actual ratio between peak hp, or the engines/pipe "governed" out at those rpm due to tuning lengths and all that and there is more to it than that. Now we're getting to my fuzzy areas (in my brain, thank you).
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Old 04-19-2017, 04:02 PM
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BTW the engine is destined for an Avionik D06, with the from of the speed pan grafted into the nose, inverted, with cowl:


Or if I never do that, I'll electrify this and build something else. Anyway, it is going to fly RC.
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Old 04-21-2017, 05:41 AM
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I think RC is faster than control line anyway because of line drag. RC is really not accurately timed though, from anything I have seen. Keep the plane small for max effect. Hope the wing doesn't fold up @ 350KPH?
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Old 04-21-2017, 06:49 AM
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I maintain that the potential top speed for any engine is higher for an RC model than C/L - indeed, the lines are massive drag. The F3 speedcup results speak to that.

The D06 is built for wrenching around pylon turns - it is a world class competition model with very, very stiff and strong wing. The all up weight will be minimal. 217 square inches. I ain't gonna fold it. Now as to stuffing it into the ground, that could be a different story.

Biggest challenge - apart from the work to mount and cowl it - is fuel delivery. I'll have to use remote mixture control on pipe or pump pressure, likely will go Perry pump to remote needle. Alternative is bladder to Iron Bay regulator and remote needle but I'd prefer pressure. The venturi is more like a crater than an orifice and positive mixture control seems appealing.
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Old 04-21-2017, 07:08 AM
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Have fun adjusting the needle when flying real fast. You will have your hands full. I think there used to be an FAI speed class with no line size, as long as you did the pull test. Years ago, there were line groupers that really let the speeds go up. Of course they were outlawed the next year. The US events always raise the line size and length whenever the record goes over 200 MPH. With the line sizes from the 1960s I am sure there would be some great speeds with the modern engines. Any motor over a .29 is not allowed a pipe now, that slows things a lot. I have not flown speed for maybe 20 years because of no good paved circle. Maybe I found one in Flint Mi? I'll have to see how that goes. $13 to cross the border, deal with the Gestoppo, 2 hr. drive... The guys in the club seem pretty cool.
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Old 04-21-2017, 08:23 AM
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Left hand on the NV, right hand trying to stay in control - sounds like good fun to me. With needle on the throttle stick it is kind of intuitive. Lean - forward, Rich - back, Kill - all the way back. I have this on the .65 delta at >300kph and it worked out okay. Not saying this is like setting up and flying a trainer, far from it. It will be a challenge, but I like challenges. So do my buddies when things don't go as planned and the entertainment value goes up.
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Old 04-21-2017, 08:36 PM
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The weekend is here and so I'll get someone to hold the camera and film my feeble attempts to run this thing and keep it under control. Maybe I'll jump again when it gets up on step..

I found out that the engine's needle valve vibrated out once I got to top RPM. That explains why I had control of the mixture up until then, but once it got to full boogie I couldn't back the remote needle out enough to drop the RPM, so I quickly yanked the fuel line. I had opened it up wide, but apparently did not crank the jam not down tightly enough. Lesson number.. um.. lost track.

The amazing part, is that I got out of my hands and knees on the deck and crawled around in the sunflower seed husks and the firewood and other crud on the deck , and miraculously found it in about 15 seconds. Luck yes, but I plotted a tracectory backwards from the test stand to the woodpile, and got down to look. Phew.. $10 needle valve, but I have to get it from far far away…
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Old Yesterday, 03:59 AM
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Quote:
Originally Posted by aspeed View Post
Have fun adjusting the needle when flying real fast. You will have your hands full. I think there used to be an FAI speed class with no line size, as long as you did the pull test. Years ago, there were line groupers that really let the speeds go up. Of course they were outlawed the next year. The US events always raise the line size and length whenever the record goes over 200 MPH. With the line sizes from the 1960s I am sure there would be some great speeds with the modern engines. Any motor over a .29 is not allowed a pipe now, that slows things a lot. I have not flown speed for maybe 20 years because of no good paved circle. Maybe I found one in Flint Mi? I'll have to see how that goes. $13 to cross the border, deal with the Gestoppo, 2 hr. drive... The guys in the club seem pretty cool.
I'd pay $13 for a 200mph speed fix anyday of the week - just to fly speed is a rush
Back in my CL days 3 strand & 7 strand wires were available , the 7 was too much drag thru the air , the 3 was light but held up ......a bit dicey, but that's what made things interesting back then, too much politics & liabilities nowdays
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Old Yesterday, 09:31 AM
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Same politics, more liabilities for sure. The lines have to be solids now, and pretty thick, and thankfully longer in some cases. At the Nats, there are only about four people that can even fly. All the guys are older than me pretty much, and 60 will be coming up in a while. I got a couple pics of a needle valve lock nut tightening tool that was given to me in the 1970s. You can tighten the lock nut with the cowl on.
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Old Yesterday, 10:23 PM
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The Profi has a tiny stub of a nv with a screwdriver slot cut. On the RC bird I'll either lock the NV rich or plug the opening, and will use the remote only
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