|Sep 03, 2012, 08:28 PM|
I just finished building a big MDA Agri-Duck. It was meant for glow but of course i electrified it. It's made of poster board and balsa wood, I bought it with most of the pieces already cut out, which saved a lot of time in building. Took about two weeks to finish, maiden hopfully this week. I also added a working hopper that will dispense powder to simulate a crop dusting run and the pilot's head moves back and forth with the rudder I have not put her on a watt meter yet but calculated watts with this set up is just over 1000. I'll see how it flies and will switch to a larger prop for more power if need but this plane was build to fly slow and has tons of lift (and drag). Video to follow once maiden in complete.
WS - 110"
Weight - Just under 15 lbs
Radio system - Spektrum DX-8
Servo - 6 (2 ail, rud, elev, powder drop, pilot head), tailwheel is free caster.
Motor - Hyperion Z4035 12T
ECS - 70a No BEC (2000 4.8v NIMH rx batt)
Prop - APC 17x10E
Battery - 6s 5000 40c Lipo
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|Sep 04, 2012, 08:08 PM|
Beautiful job Kyle!
Love those big balloon tires and hypnotic hubs.
Got the 80" Mud Duck short kit a few years ago but haven't built her yet - maybe this will motivate me.
Good luck to you and the Count on the maiden and subsequent crop-dusting jobs.
|Sep 05, 2012, 02:24 PM|
Great job! I've been looking for plans for this plane since last October. Not much activity on the forums until yours just appeared. Keep posting
|Sep 07, 2012, 04:54 PM|
OK first flight complete, but she was underpowered. I had full throttle the entire time and was barely able to get it back around without stalling and crashing in the field. Right aileron seemed to be almost useless without rudder, left hand turns could be accomplished without rudder but is easier with it. The video is of the 1st flight.
2nd flight was this afternoon with a bigger prop, 19x10E, Watt meter says i get 900w at 42amps on the bench, compared to the 800w and 39amp i got out of the 17x10E prop that i used on the 1st flight. Performance was a bit better but i still needed to carry almost full power the entire flight to keep it up in the air. ESC overheated and died while in flight (not sure why, it was a 70A ESC that could handle up to 8s), hard landing in the weeds took out the landing gear and broke the prop, no other damage.
So she is grounded until i fix the gear and upgrade to a more powerful motor/ESC. If anyone has any suggestions on a motor/ESC combo that will give me about 1300w on a 6s 5000 mah 25c lipo please let me know. Thanks
|Sep 07, 2012, 07:29 PM|
Way to hang in there and bring her back home safely. Agree on your requirement for more power so you do not have to carry full power for cruising.
I had a 15 pound Cub-like plane a few years back that used about 1,000 watts in and I found that it required more pitch speed to cruise at less than full power. I eventually upped the power to 1,200 watts but made sure I still had enough pitch speed. I used an Astroflight 60 and then a 90 with a belt drive so it is hard to equate that to modern outrunners. In the end when she worked well she turned a 23.5x16 prop at about 3,400 rpms - giving about 50mph pitch speed and 8-10 pounds thrust.
The AgriDuck may have more drag than my old Cub-like plane, so she'll likely need a bit more thrust than you currently have and the same or more pitch speed.
It may also be a characteristic of the AgriDuck that she requires both rudder and aileron to be used together to make turns. Maybe folks on RCUniverse have some flying reports from which you could get some data. Lack of turning authority could also mean she's a tad tailheavy.
Have fun experimenting and best of luck with her - she's a great plane.
|Sep 07, 2012, 10:19 PM|
Thanks guys, it was slow but still scary...lol Not like my old Combat Models F-16N that was a rocket but i managed to get back on deck safely as well. Anyways, i'm still looking for a power system setup, so keep the good ideas/suggestions coming. Thanks again.
And yes, it does require both aileron and rudder for sharp turns.
|Sep 07, 2012, 11:38 PM|
Joined Oct 2006
The reason your agriduck turns easier to the left is due to the 4 left turning tendencies that affect propeller driven aircraft.
To setup your ailerons to work better you want to program some differential in them so the aileron that is moving up moves farther than the aileron that is moving down. This will help counteract some of the adverse yaw due to downward moving wing having more drag than the outboard/upward moving wing.
If you're using a computer tx this is very easily done with the differential setting and the ailerons servos will have to be plugged into different channels. If you have them plugged into the same channel or your tx doesn't have this function you can just offset the servo arms.
Furthermore if your tx has an aileron/rudder mixing function you can program a little bit of this in and it will make it turn easier.
Also use a little up elevator on takeoff in the grass to help keep it from nosing over. You might what to think about making that tailwheel steerable, when you get a little wind it's going to weather vane into it really bad. A steerable tailwheel won't totally correct this but it will help quite a bit.
If you ever have the engine quit again just point the nose straight at the ground and flare at the last minute as these things don't glide.
|Sep 08, 2012, 03:33 AM|
Joined Dec 2004
Motor should be fine, it can handle a lot more power.
I would suggest a 20x14 prop, and an ample speedcontroller.
If you happen to have 4S packs around, you could use your 17x10 prop and 2 packs in series for 8S, which would work nicely too.
You need a bit more pitch speed for more thrust at flying speed, hence the higher pitch on the prop. For a speed controller a Castle ICE 100A would be a good choice, with the budget option being the Hobbycity Kforce 150A (for 6S, for 8S you'd need a HV controller live an ICE2 HV or Sentilion )
Did you check the voltage under laod of your lipo's? I'm under the impression that they might be slightly low on voltage. (What lipo's are you using, how old are they)
And what speed-controller were you using?
|Sep 08, 2012, 08:54 AM|
I agree the motor should be able to achieve the desired watts, i just need to get there using the equipment i have, i.e my battery (2 6s 5000s). The battery is Zippy 6s 5000 25c: http://www.hobbyking.com/hobbyking/s...idProduct=8586 They've only been used a few times and are in good condition. My ESC is a Grayson hobby 70A: http://www.graysonhobby.com/catalog/...bec-p-254.html
Its a cheap one, thought it could handle it but i guess you get what you pay for I'm deciding between the CC PHX Ice 100 or a Turnigy 120A-HV-OPTO ESC. May just get both and go from there I didn't get the voltage under load, but will as soon as all the new stuff arrives. What other props would you or anyone else suggest? I'll buy a few when i order them.
I'll try to stick with this motor and see what i can get out of her before trying to upgrade. Thanks
D, thanks the advice, i'll put in some ail-rud mixing. Unfortunately i only have a 6 ch rx and they are all taken right now (ail, elev, rud, throt, hopper, rx battery) so i'll have to mechanically put in the aileron differential. Its been a while since i've flown a tail dragger and i wasn't expecting the tail to rise up so fast, i got better on the second attempt The tail wheel is pretty much just for looks, taxis fine without it being steerable and the plans call for just a stick there anyways...lol
Thanks for all the advice guys, keep it coming.
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