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Plantraco micro-racer with flaps

Old 09-05-2008, 04:41 AM
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Default Plantraco micro-racer with flaps

Hi All,

This is my first RC sub-ounce airplane, a Plantraco Micro-Racer Invader P-51, and it's a lot of fun to fly. Here are the specs:

Motor: originally a 7mm 3.3Ohm, but upgraded to a 7mm 1.7Ohm

Prop: tri-turbofan

Battery: Full River 3.7V 90 mAh 15Cxx Bahoma

AUW: 15.4 g (0.543 oz) without flaps; 15.7 g (0.554 oz) with flaps


The main modification that I made on this plane is to tape 1/4" strips of Depron to the trailing edges of the wings. I just used the scrap Depron that was left after the plane was removed from the carrier sheet. To decrease the stall speed even more, I would sometime also tape 1/4" strips of Depron to the leading edges of the wings using bright orange tape, which really helped the plane's visibility inside a gym. The wing extensions were parallel to the wing surface, i.e., not tipped up nor down. These modications are easily reversed and greatly increases the range of speeds (and size of areas) at which the plane can be flown. I had a really hard time flying this plane inside a gym, but with the wing extension modifications, flying in a gym is no problem. Most of the videos that I've seen of this plane were shot outdoors; perhaps there's a reason for this!? Carbon rod was added along the length of the fuselage, which really helped keep the plane together after crashes on hard gym floors. I replaced the tape elevator and rudder hinges with 1mm wide strips cut from an old floppy disk, which were epoxied into place. This allowed the the rudder and elevator to hinge from their central axes more smoothly.

I also soldered a connector to the 900 Tx that allows me to connect a rechargeable 5 cell 2200 mAh NiMH battery. The manual specifically mentions the importance of using 4 AA Alkaline batteries, so I didn't want to take any chance using the 4.8V that would come from 4 rechargeable batteries. The manual also states that a minimum of 4.4V is needed to recharge the lipos, so the the 4.8V from rechargeable batteries may quickly drop below this after some flying and a few lipo charges. So I bought a 5 cell 2200 mAh NiMH battery and soldered a wire with a servo conncetor receptacle to the positive and negative battery terminals inside the Tx. I glued the receptacle to the inside of the battery compartment. The battery is velcroed to the outside of the Tx. I only wish that I could find a smaller 5-cell NiMH that would fit in the battery compartment. This modification still allows 4 alkaline batteries to be used instead of the 5-cell NiMH.

I glued some magnets at the top of the Tx so that I could store extra lipos on the Tx.

I made a carrying case for the plane, Tx, and accesories out of a plastic hardware storage/organizer box. I just cut some of the partitions so that the palne and Tx would fit. I had to place the 5-cell battery at the front of the Tx instead of underneath it so that it would fit in the box.

Flight Report:

With the more powerful motor and without flaps, the plane flies great outdoors. Can loop from level flight and handle wind (~10 mph) reasonably well as long as there's room to maneuver. The 1.7Ohm motor made a big difference in the performance (the plane could barely loop with the 3.3Ohm motor), but the new motor gets pretty hot after several flights. Fortunately, the lipos stay cool. The elevator is crucial to making this an outdoor airplane that can fight wind. Without flaps the plane flies a bit fast for me in a double basketball court gym.

With wing extension flaps, the plane slows down quite a bit and flies more like Plantraco's Classroom Fighters (except that it has the advantage of having an elevator!). If a ~0.25 strip of depron is added to the front of the wing, the plane flies very slowly and can be flown in half a basketball court. The main disadvantage of the front and back wing extensions is that the plane tends to porpoise (too much lift?). Perhaps this can be fixed by moving the CG back a bit or using more down elevator? The wing extensions make flying outside more challenging.


This is a great plane and I've really enjoyed flying it both indoors and outdoors. I'm sure a better pilot would be able to fly it stock in a gym, but for me, adding the wing extensions was critical to making this an indoor flier. Although I often fly in colder weather (and we do occasionally get some snow/cooler weather in Buffalo, so I've had the chance to take electrics on skis in 15 degree F) I was disappointed the the receiver didn't work if the temperature was below 60 F. Perhaps this is more of a problem with the lipo voltage/current dropping at low temperature? When I first built the plane in January '08, I wasn't even able to get the receiver and transmitter to link in my basement because it was too cold. At the time I didn't know that this was the problem and spent a lot time scratching my head to troubleshoot it. It would have helped if the manual said something about this.

In the first photo, note the white depron strips at trailing edges of wings. The second photo shows the 5 cell NiMH battery at top of the Tx connected to +- terminals on Tx board through a servo connector. The third photo shows the travel case that I made for the plane and Tx while the fourth photo shows the depron strips at trailing (white) and leading (held by orange tape) edges of wings for extra slow flight.
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jcerne is offline  
Old 09-05-2008, 04:11 PM
highdesert flyer
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Join Date: Aug 2008
Location: Alamogordo, NM
Posts: 53

cool looking plane. It looks pretty fast.
ekdenton is offline  
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