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

How fast is fast?

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Old 06-20-2007, 10:26 AM
  #51
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Default RE: How fast is fast?

You think the fan tips in turbines are subsonic? Believe me it will happen. What are you running in your Vector and what speeds have you recorded? Prop, fuel, motor, no pipe? RPM's?
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Old 06-20-2007, 10:48 AM
  #52
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I have the Nelson F1 motor on the Vector. I recored 177mph in a dive, turning 21,000rpm on the ground using APC 8x7. I haven't use 60% nitro yet.

Now on my Evo, from bigbruceracing.com, I use MB Profi, Bruce's prop combo and new tune pipe, I get 29,500rpm on the ground. its 210mph in level flight and 235mph in a dive with no wind.[>:]
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Old 06-20-2007, 11:01 AM
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Default RE: How fast is fast?

I don't know what size blades they use in those EDF's. But just for giggles....A 5" fan turning 500,000RPM is
7,437.5MPH tip speed.....Depending on altitude and temp....That's about Mach 9.5.....Sorry, I don't think so.
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Old 06-20-2007, 11:23 AM
  #54
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Quote:
ORIGINAL: SSGSPEEDMAN

I have the Nelson F1 motor on the Vector. I recored 177mph in a dive, turning 21,000rpm on the ground using APC 8x7. I haven't use 60% nitro yet.

Now on my Evo, from bigbruceracing.com, I use MB Profi, Bruce's prop combo and new tune pipe, I get 29,500rpm on the ground. its 210mph in level flight and 235mph in a dive with no wind.[>:]
I'm happy for you, what's the Vector do level and how are you checking speed? [>:][>:][>:]
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Old 06-20-2007, 11:23 AM
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Default RE: How fast is fast?

I also don't think a ducted fan (electric or glo) will beat out a turbine simply due to tip speeds of the fan. A 5" prop or fan will start hitting mach 1.0 at around 55,000RPM. There are other complicated factors like 3-dimensional flow I won't attempt. I'm no powerplant engineer, but I think the advantages of compression and exit velocities go to turbines for speed. A ducted fan is a ducted prop and the fastest full size prop planes hit the wall around mach 1.0. The Republic XF-84H, aka the Thunderscreech, was the fastest prop plane and it isn't even considered fast compared to a modern day jet fighter (unless you fly A-10's). It produced noise like no other aircraft. If you are a South Park fan, it was claimed to produce the 'Brown Note' which made some people sick to their stomachs.
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Old 06-20-2007, 11:31 AM
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Quote:
ORIGINAL: Destiny-RCU

I don't know what size blades they use in those EDF's. But just for giggles....A 5" fan turning 500,000RPM is
7,437.5MPH tip speed.....Depending on altitude and temp....That's about Mach 9.5.....Sorry, I don't think so.
You don't think so... now or in the future or ever? I'm talking future here... Do you think a 5" fan can have 740mph tip speeds? I know that's just below Mach 1... What do you think the limits will be?
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Old 06-20-2007, 12:40 PM
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Quote:
ORIGINAL: Destiny-RCU

....A 5" fan turning 500,000RPM is
7,437.5MPH tip speed.....
Not taking sides here but that isn't too far off the tip speed of todays full size turbins I believe.
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Old 06-20-2007, 12:42 PM
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Default RE: How fast is fast?

There's no sides Mike... we're just having a discussion...
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Old 06-20-2007, 12:56 PM
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Default RE: How fast is fast?

I read too much Pop Sci so I always take 'future' talk with a grain of salt. It's sort of like local news, "New discovery, chocolate makes you lose weight and stops heart attacks! More at 11..."

At that last German Speed Cup there were a bunch of 'E' power guys throwing thousands of watts into F5D airframes and getting some good passes in the 230-240 range. I just read about some local guy here who was DS'ing (dynamic soaring) the same airframes and getting consistent 230-240mph... Kinda funny IMO.
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Old 06-20-2007, 03:57 PM
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Quote:
ORIGINAL: evan-RCU


Quote:
ORIGINAL: SSGSPEEDMAN

I have the Nelson F1 motor on the Vector. I recored 177mph in a dive, turning 21,000rpm on the ground using APC 8x7. I haven't use 60% nitro yet.

Now on my Evo, from bigbruceracing.com, I use MB Profi, Bruce's prop combo and new tune pipe, I get 29,500rpm on the ground. its 210mph in level flight and 235mph in a dive with no wind.[>:]
I'm happy for you, what's the Vector do level and how are you checking speed? [>:][>:][>:]
I'm using the Eagle Tree flight data recorder.

In level flight its 163mph.
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Old 06-20-2007, 06:38 PM
  #61
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Default RE: How fast is fast?

Pretty lame to compare electric to glow. We are a long way from achieving the energy density of liquid fuel with batteries. However electric does offer some huge advantages. I personally havn't seen or heard any glow motors turning over 35,000 RPM in anything remotely close to .40 size. A more realistic limit is about 31-32,000. This is "just getting warmed up" rpm for an electric motor. Tips going supersonic is not the end of the world either. Effeciency goes down at supersonic tip speeds however the prop does not suddenly stop warking. You can cram an incredibly powerful motor in a very slick slim fusalage with electrics allowing for a very aerodynamic powerplant that also offers an extreemly powerful setup in a compact space. You also don't have to worry about any weird airflow issues into the carb at ultra high speeds or weird tunning changes of the engine that happens when it unloads. I guess the biggest adavntage is at such performance levels you have a dead reliable platform that is incredibly consistant. What is even better is you have a variable throttle not on/off operation like you do with a highly tweaked 2 stroke. How many Q40/Q500 races have you seen where someone is dominating because he is 10mph faster through the straights and pulling out harder from the corners because he has a motor that is running "super sweet" while everyone else is not unloading quite as well and is playing catchup even when this guy turns somewhat sloppy. The last Q40 event I had my radar gun out and I was surprised to see how much faster some planes were then others. Some where going 185 in the straights and others were strugling to break 170. All running the identical Nelson motor. I think the thing everyone loves about electrics is the set it up and forget it aspect of the powerplant. As long as you take good care of your batteries the only drop off you'll ever see is a results of your cells aging. Those high nitro mix fuels are not exactly cheap either and the fuel effeciency of 2 strokes at this power level is not exactly great either. TheTick's setup is a perfect example of this. His nemesis is going an honost 195mph dead flat in the straights and it is this fast everytime he flys it. His power system cost him about $550 but he also won't need to replace the batteries for at the very least 100 flights but with proper care he could easily stretch this to at least 200. A similar power compact glow motor would eat up at least 2 ounce per minute of 20% nitro. 100 flights x 4 minutes = 400 minutes x 2 ounces = 800 ounces of 20% nitro fuel. The cheapest I have seen this stuff is about $30 a gallon. 100 flights would be about 6 gallons of the stuff or $180. If he went with a glow motor he would have more drag as a result of the muffler/head and requiring cowing which increases frontal area. He doesn't need quite as much power as an FAI Nelson to got this fast but I'm not sure what is available that can provide the power and rpms with a rear exit tuned pipe and how much a motor like this would cost. Clearly there are some huge advantages here before going into the whole dealing with chemicals, starting, burnt glow plugs, wasted fuel in flooded engines that refuse to start and other typical stuff. Electric is the future make no mistake. I'm not saying they are ever going to offer performance that will exceed a turbine in power/weight/speed but its not exactly difficult to beat a 2 stroke piston in this game. Fan powered jets that are powered by glow are pretty much by the way side now because big electric systems are way more reliable, more consistant power, and much lower maintanance and easier to operate.
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Old 06-21-2007, 12:36 PM
  #62
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Default RE: How fast is fast?

Well do you have way to reduce the heavy weight thats going to be on that aircraft for speed?

How much power would there be to hit a constant 200mph. If you convert the F3D Evo to E-powered?


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Old 06-21-2007, 12:57 PM
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Default RE: How fast is fast?

What are the interior dimensions where you can fit batteries? Remember the fuel tank area won't be used and the electric motor is lighter than the internal combustion motor. remember you can have a sleeker airframe because you won't need an exhaust pipe, though the pipe I have to think is pretty well hidden aerodynamically in your application. What is the airframe weigh with out your fuel tank, fuel, and motor with mount? Approximate...
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Old 06-21-2007, 01:33 PM
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The fuse would weigh 2.5 lbs..... You could put some long batteries in the fuse....

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Old 06-21-2007, 01:35 PM
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Default RE: How fast is fast?

Quote:
ORIGINAL: SSGSPEEDMAN

Well do you have way to reduce the heavy weight thats going to be on that aircraft for speed?

How much power would there be to hit a constant 200mph. If you convert the F3D Evo to E-powered?


Kevin
Weight is still a slight issue but it's disappearing quickly. Before you had to stack up 2 to 3 sets of equal voltage lipo cells in parallel to be able to draw the amps needed to produce the end wattage which brought the pack weight up. Now they have cells that have the capacity and low resistance to use just one cell capable of 100-150amps or bursts of over 200 amps. That's SERIOUS amperage!! I'd have to calculate it out, but I think you'd be able to do a Q40 plane with the latest cells and come in close to the flying weight and have the same power. Mark F.'s F3D plane is around 7lbs but it also has more power (4500+ watts/6HP) than an MB motor (said Rob Metkemeijer) and the wing has extra surface area to keep the surface loading reasonable. It's a bonafide 200+mph plane. Big Bruce was suppose to be shoehorning an electric system into an Evo to see what it could do but I haven't head from him in a while.

I'd assume a Q40 airframe RTF minus motor would be about 3lbs, add 12oz for the motor??
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Old 06-21-2007, 01:48 PM
  #66
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Default RE: How fast is fast?

how much would that setup cost?
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Old 06-21-2007, 02:04 PM
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Default RE: How fast is fast?

Approximately $300 for the motor $500 for the speed controller, and $400 for each battery pack. You might or might not want more than one pack. I can imagine that you would be waiting an hour or two between runs...
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Old 06-21-2007, 02:09 PM
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Default RE: How fast is fast?

Quote:
ORIGINAL: Troy-RCU

I'd assume a Q40 airframe RTF minus motor would be about 4lbs, 4oz and then add 12oz for the motor to get 5lbs??
Actually, my Q40 Polecat RTF minus the 6oz of fuel is 3lbs 15oz which is pretty standard no matter who's Q40 you buy..
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Old 06-21-2007, 02:14 PM
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Default RE: How fast is fast?

Thanks, I just saw the min. weight was 4lbs, max 6lbs.

$260-330 for the motor (Neu 1515 or 1521 series)
$170 for the speed control (Castle 125)
$300-400 for the batts. 6S-7S lipo...
These are all just quick retail prices.

From the last contest I read on F5D, guys were running one Lipo pack for the weekend and just recharging after each flight so really you don't need a whole stack of batts.

I did a quick calculation and to get about 2000 watts of power the power system (motor-batt-esc) it'll be about 37oz or 2.4lbs. That's running a 1515-3D Neu motor, 6S-4300 Lipo (6 4300 mAh lipos in series), and Castle Creations speed control. You could bump up to a 6S-4900 pack but it'll add about 3oz and tack on $60.
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Old 06-21-2007, 04:16 PM
  #70
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Default RE: How fast is fast?

A decent charger will charge 8s at 6 amps, so shouldn't take more than a half hour to charge most packs. Even less if you don't complety deplete the pack. It should be interesting to see what people do with the new 60C lipo's. We should start seeing light 200mph planes soon.

It's cool that you can now have a 200mph electric f3d plane that you can taxi to the runway and have full throttle control in flight. With some throttle management, they should be able to stay in the air for a decent amount of time.
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Old 09-11-2007, 03:06 PM
  #71
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Default RE: How fast is fast?

Ive got a west combat .25 motor with tuned pipe any sugestions on what airframe. im looking for something around 150mph if posible.
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