Think 4700W is going to be enough?

[Ededge2002]

Some of you might not know me but I'm sort of famous for sheepishly underpowereing models. The instructions call for 200w I usually aim at 450 or so just to be sure.
My goal with this project was 5kW and I'll admit I missed the mark. It's only 4700w on 1600g(55oz). The wing span is a massive 1450mm (57") and the prop just 17.5x21.8

[Ededge2002]

http://youtu.be/goV5RKgkla8

[Frank v B]

Ed,

That's 1366 watts per pound!!  It really dates your signature line "Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better? "

You've come a long way in 4 years.  To quote Jack of A&J that hotliner power systems are now essentially "a controlled short".

We are eagerly looking forward to your explanation of the dagger-like prop blades (see photo) with grip handle moulded in.

Frank

[Andy Hoffer]

https://www.google.ca/search?q=scalloped+whale+fins&biw=928&bih=587&tbm=isch&imgil=Hb27_NS6hLz3RM%253A%253BWaPB-m3lO0XP-M%253Bhttps%25253A%25252F%25252Fstudent.societyforscience.org%25252Farticle%25252Fare-propellers-fin-ished&source=iu&pf=m&fir=Hb27_NS6hLz3RM%253A%252CWaPB-m3lO0XP-M%252C_&usg=__0ibQ-QL6whpWSJKPARGn4AM9PNs%3D&dpr=0.95&ved=0ahUKEwjiws_jtL_MAhWMloMKHdMSAPMQyjcIMA&ei=oGMpV-LyLoytjgTTpYCYDw#imgrc=Hb27_NS6hLz3RM%3A

Very nice touch Ed!

Andy

[Ededge2002]

As Andy has pointed out with his massive link the prop design IS indeed inspired by the flukes of whales!!

For those that dont know the motor is run on a switch on these models having only off and 100% throttle.  The high pitch 21.8" in this case causes the prop to cavitate and waste energy.  The "teeth" cause the airflow to stay attached to the prop airfoil at the high angle of attack allowing the prop to start getting grip faster.  This model accelerates from about 160kph to 305kph(100mph to 190mph) in sub 2 seconds......  (Frank didn't do the calculation that 746w=1hp so that is 1.8hp per pound)

The flight in the video uses just 40 seconds of motor run time in bursts