Fastest Funjet Ultra 184MPH (296km/h)

[MrJimneutron]

awse effort mate I have the orignal funjet and clocked it with a gps at 297km/h on 6 cells but at those speeds it locksout and has no control.. now that its bounced off the ground planing too beef up the servos and control surfaces and try more cells 320 any one????

[francoishaha]

the doppler theory is great, im using the wave specktrum to calculate the speed, and the result is the same as your radar gun, 184mph at 20 degre celcius.

[panther3002]

@francoishaha Hey how do you do this exactly? I'm very curious. Do you have some special software, or are you just calculating the speed using the doppler effect it by hand somehow?

[francoishaha]

@panther3002 youtube.com/watch?v=DZZWtT32ym­Y

[cluzeauu]

coz am a bit congused here due to all comments... what's the full setup of the ACTUAL funjet flying in this video mate? thanks..

[psionic001]

@panther3002, ps, be sure to check the rated top speed for your prop. I calculated somewhere about 27000rpm for the APC.

[psionic001]

@panther3002, all good info. All sounds approximately what I came up with within 5-10%. I think I came up with 30% loss in pitch speed vs actual speed and I use this to calculate my estimates. My next build should top about 205mph at best if it's built well.

[panther3002]

Some more nerdy info I've been curious about on your setup: A propeller is extremely inefficient if the tip speed reaches or exceeds the speed of sound (Mach 1). So, I calculated your tip speed (plane at rest) to be 551.0 mph. At sea level on a Standard Day, (speed of sound = 761.2 mph) this is a tip speed of Mach 0.72. However, at with a forward velocity of 180 mph, the total tip speed is 579.66 mph, or Mach 0.76. So you still have a little room to go until the prop no longer works right. =]

[panther3002]

Using the pitch calculation& solving for pitch, I calculate a needed pitch of 7.5, on a 7 in long prop.ie: a 7x7.5 prop.However, this assumes that this prop will still produce26460 rpm, which is wrong, since it should produce more with a smaller prop, & it assumes that drag increases linearly with airspeed, which is also wrong, since it's more of an exponential increase, so anyway, enough of that crap, I'll just try it until it works. Now we know u have a pitch speed of 225.5mph.Good enough! =]

[panther3002]

Note: pitch_speed(mph) = RPM x pitch(in) / 12(in/ft) / 5280(ft/mile) x 60(min/hr).

So, based on your specs of a 7x9 prop, and 26,460RPM, that means that your pitch speed is 26460 x 9 / 12 / 5280 x 60, or 225.5 mph! With a top speed of 180 mph (averaged each direction to remove wind effects), this means that a pitch speed must be ~25.3% higher than the desired airspeed of this aircraft, due to the effects of drag. So, if I want a 150 mph setup, I should need a 188mph pitch speed...(see next post)

[masonkim7]

everytime I see this plane... I'm telling you... some terrorist might use it for something.

[illuminatorix]

Hiiiiii!!! I have made the same setup in my ultra and it rocks! the only difference is that I used APC 7x6 prop with a 200Amps ESC (140 static for my plane) and was DAMN FAST! Everyone in my fly field when the plane made the fast passes they stayed with their mouth open! xaxaxaxa

[psionic001]

@illuminatorix - Good work. Now get a 7x9 for better speed.

[EDF6399]

How can the 100amp esc handle the 154a draw?

[psionic001]

@EDF6399 - It's a 200A CC Esc.

But some 100A ESCs will burst to 150 too.

[panther3002]

@psionic001 Very cool video psionic. I am planning on building a setup similar to this sometime, except I don't want a speed record, I just want a fast yet reliable plane. Therefore, I'm planning on getting a 1600W setup in a Funjet Ultra to cruise around at a measly :) 150 mph or so, inspired by Frank from rcfoamfighters. For all you nerds out there though, I've been wondering for quite some time now about what kind of pitch speed one would need to go this fast. (see my next post)

[maynardr6]

Did you have to mix roll with throttle? Also, just flying around, does it do unpredictable things with throttle transitions. I had a 3648 turnigy in mine with a 7x6, and i just couldn't control it. Every time I gave it some stick, it would roll. Just wasn't fun to fly, so I went back to a lowered powered setup. So, what's the trick?

[psionic001]

@maynardr6 - No, I haven't mixed roll to throttle, but I intend to.

[1ArtisticSoul]

I'm sure you had to compensate for torque roll with that size prop at those RPM's. The last time I used a prop that size running those RPMs on my funjet I lost control of it and crashed. I actually think it ripped one of the ailerons off and I lost control of it. It happened so fast I couldn't tell, but I would have to have one aileron at least half way up to keep the plane level at wide open throttle. I don't run any bigger than 6X4 now. Enjoyed the video~

[psionic001]

@1ArtisticSoul - I trimmed for no roll at about 150MPH. When it got to 180+ I was fighting it.

I've since been 202MPH but when I cam off the throttle it rolled severely (due to trim), plus the servos were straining, and I crashed.

New build hopefully coming soon.

[panther3002]

@psionic001 Try putting a gyro on each of the elevons for roll stability. It will self-correct for torque roll. go to mycoolrc(dot)com and click on "How to use a Gyro to stabilize a control surface on an airplane" for installation guidance.

[mooncoinphoto]

@psionic001 Brilliant. Did you ever go for twin motors rotating opposite to get rid of torque effects?

[psionic001]

@SCJohnson77  - Next one will be over 4KW.

[pixeldixelshizel]

Intend to power mine with an ARC 28-58-1 with a 6x4, 4s battery and a CC 100 esc. Must be mighty difficult to launch with a 7x9 with the torque roll?

[psionic001]

@pixeldixelshizel

ARC 2858 is too small for speed, you must go for the 36mm can.

CC100 is too small too

7x9 gives massive torque roll. Mine takes off vertically and rolls at least 6-8 times before I have any control!!!

[pixeldixelshizel]

Awesome run mate! Any reinforcements done on the airframe? What servos were you using?

[psionic001]

@pixeldixelshizel No special reinforcements mate, but when I had a minor crash the fuselage snapped so I used 3M bidirectional glass tape to hold it together. I believe this would also serve to reinforce the whole fuselage.

[FLAMEBMWZ4]

Did you make any changes to your setup after shooting this video?

What size 6S pack are you using

[psionic001]

@FLAMEBMWZ4 I don't understand your question. Set-up is posted above.

[serververde]

Where did you buy these prop?

[psionic001]

@serververde it's an APC 7x9 prop. Just standard.

[farrkenbeauty]

That is nuts LOL, I bet that guy walking shat himself LOL

[EvvyThomas]

Wow.

[mattyboy47]

Geez-Amazing. Can't believe haw that stays in one piece at those insane speeds! Great stuff.

[kwahyttam]

nice job!

[ExtremeRadioControl]

Now you gotta be happy with that! :) 154 amps? how was the motor after the speed runs? bloody awesome! :)