I am working on maxing out the speed on the X8. The current take off weight is 3.8Kg and we are using a 4S 10Amp lipo with a Scorpion SII-3026 710KV ( http://www.scorpionsystem.com/files/i1,082_data_chart.pdf (http://www.scorpionsystem.com/files/i1,082_data_chart.pdf))
The airframe is re-enforced pretty much everywhere with cf and glassfiber, no wobbles anywhere. I am quite sure we can push it further.
The prop we have now is a 14x6 and in this setup we get around 140km/h. Now with disregard to flight time, what motor and prop combo would you recommend to get more top speed?
Something is wrong here. According to the information you have given, the 3026-710 on 4S with a 14x6 should have a max pitch speed of around 81km/h. You shouldn't be going faster than that in level flight. Also this matches very closely with the data linked in the PDF. At 4S with a 13x6.5 prop the pitch speed is listed as 51mph (82km/h)
So 140km/h must be in a dive? Or the data you have given is wrong somewhere.
You need more than 4S to go faster because:
Increase pitch of propeller : Downside is you need to decrease the diameter of propeller to stay within the watt limit of your motor, this means you have less thrust. If you have too little thrust you can't take off or even get to that speed with a large draggy aircraft.
Increase KV of motor : Downside is that as your KV goes up your torque goes down, so you need to spin smaller props which means you lose thrust and you are back to first point where you don't have enough thrust to take off or even get to that speed.
Increase voltage of battery: Best solution, give your motor more power to turn larger props with higher pitch speed, more thrust and more top end speed.
Need rockets....do eeeet
Hey guys and gals!!
So I am also working on this project.
The Skywalker X8 drive system (Motor Kv? / Prop size? / ESC Amps? / Battery size?) can be a bit tricky to set up, especially if you add lots of FPV gear to the plane making it the Epic platform it is supposed to be.
Typically the AUW is about 45oog (4.5kg)
I have been using eCalc.ch to help me tweek my set up as I want it take off from the ground without throwing it or using a bungee cord/rubber tube.
My AUW is 9188g (9.18Kg)
Here is what I came up with for battery, time, & Power to weight ratio setup for a heavy Skywalker X8.
~Battery, 6S Lipo 10,000mAh-20/30c (x4 packs)
~ESC, Tribunus 06-120 opto
~Motor, HKIII540-530 (530Kv)
~Prop, Aeronaut Cam Carbon (15x10)
-Power-Weight 130w/lb
-Thrust-Weight 1.00:1 Ratio.
-Wing area 80/dm2
-58% throttle @ 6400rpm gives 3282g thrust (3.28kg) for 80.1 minutes.
-Estimated stall speed is 54km/h
-Max current 118.40A
-Efficiency 92.7%
If your AUW is much lower than my X8, just follow the good accurate advice posted above by "dogzilla" and reduce the prop size then increase the pitch to just below prop stall values.
Now your flying as fast as your plane will go with the reinforcing you have done!
The AV-8B Harrier II Jump Jet has a Thrust- Weight Ratio of 1.18:1 If i recall correctly, that's allot of thrust!! for my X8.
Although That's what i am going for, the big climb to a low throttle position.
Sounds like your looking for quite the opposite. (small prop / high pitch / high KV motor.)
Good luck! :sparta:
Not sure why you would want to make a Skywalker X8 into a speed machine..?.
It's not that kind of plane....Its a distance cruiser, first and last.
If you want to go fast and far, try converting one of the high end Gliders, they will glide faster than the X8 under full power.
:vulture: