Electric Glider based UAV flight times?

[vector_vortex]

Hi,
I am thinking about building a UAV based on an electric glider airframe. I would like it primarily for long endurance flights. I am looking at a sub 2 meter wingspan, geared brushless motor and LiPo power.

Does anyone have experience flying glider based airframes as UAV's? what capacity batteries are used and what is the average flight times, without thermalling etc.

The various solar powered projects seem really interesting. Has anyone done a flying wing designed one to maximise wing surface area and hence solar collection area?

What other issues need to be looked at for these aircraft?

Thanks

Joel
Australia

[iflytrikes]

well lots more work to do ...but if i could be of help ...i'll do my best.
please remeber i have eyeballed the whole thing ...used benchmarks ...this is my first project ...see my blog
Neville

[treehog]

Sunset to sundown electric model competitions are probably the best source of info

I dont have any links but a search should come back with results

A study of the atlantic UAV aircrafts that succeeded to those long flights using glow fuel are also worth looking at as endurace in glow with huge fuel tanks would be similar to problems to electric endurance


planes will generally have no excess weight U/C or fancy shapes probably high aspect ratio wings similar to gliders

pusher props tend to be chosen as this gives some ten to twenty % improvements

There was attempt by one UAV project toharness Thermals and this method could result in dramatic increase in flighttimes

UAV flight times of two hours with lipos should be possible with
2 metre f5b craft based on non UAV types get one hour plus with Nicads

Sunset to sundown competions have succeed to get 4 hour engine run times with NiMH which often give 5 to 8 hour flights from thermal assistance

Figure properly made properly figured out madel craft of 3 metres with unlimited budjets could exceed 8 hour motor run time in level flight with 50MPH plus speeds

2 metre more budjet project project with lipos should get in excesss of 2 hours motor run time level flight at 50mph

probably best to identify the min flight time min distance min stall speed min cruise flight speed max budget and max wing span requirements you want to do as roughly the bigger the wing the better
also brushless motors tend not to be very effecient at low speeds so might require use of brushed motors or high speed engine runs with glide combo rather than continious motor runs

Ralf

[jbeanelliott]

I don't know if you can believe it, but the MicroPilot website claims
55 minute duration for their MP-VISION electric demonstrator UAV based
on the Electra Pro glider sold by Northeast Sailplanes. See

http://micropilot.com/prod_mpvisione.htm

excerpt:
In order to bring you a UAV for only $6,999 USD, MicroPilot uses a sturdy, mass-produced model airplane strengthened for use as a UAV as the basic platform. We add our MP2028g autonomous flight control system and an RC transmitter (customer supplied) for takeoff and landing.
Length = 4 feet
Wing span = 8 feet
Weight = 6 lbs
Engine (electric) = Axi Brushless
Flying Time = 55 minutes
Surfaces = Rudder, elevator and ailerons
Control = MicroPilot's MP2028g autopilot with HORIZONmp Ground Control Software with RC option
Average Speed = 60 km/h
Maximum Winds = 30 km/h
Payload Capability = 5 ounces to 1 pound

[brianhomer]

Since glider can flying without power. If the weather condition and the control is good. this is possible (assumed the Electric glider is using ESC with break, the motor can be stopped during gliding and the batteries can be long lasting)

[builder]

The results for the micropilot UAV are max duration at 400 feet under moderate wind conditions. The figure of 55 minutes was taken from an actual flight started on a full charge until the speed controller cut off power to the motor when the 9V voltage limit for the 3 cell packs was reached.
The packs were 4X -3cell 2100 MA Thunder power pro-lites, and an Axi 2028-10 with a Schulze 46 BE speed contoller.

Greater flight times than this are possible; a clean airframe, light wingloading and high capacity batteries help a lot in reaching this goal.

[elossam]

The packs were 4X -3cell 2100 MA Thunder power pro-lites

Your talking about a 3s4p configuration with 8400 mah total capacity?

[builder]

That is correct, 8400 MA total. The packs are seperate and not bundled in one brick so that they will fit in the fuselage. Of course this is very easy on the packs, they will only see about 11 amps max draw each.

[dogbert]

Vector Vortex (Joel), Im looking at building something along similar lines -
I'll be using a EPP foam flying wing - 2.4mt span, elevon system and maybe adding rudder controls to the tiplets.
I was going to use the above batteries but only 2 for starters, then seeing how it goes with 4.
I will have a LOT of other stuff though - digital video recorder, video overlay, plus the usual GPS and autopilot (Still looking at Autopilot choices until brain hurts every night), video transmitter, + more on board.
I'm after the same thing - to stay in the air for as long as possible.