Lift-off/Launch Speed, LiPo battery use

[Sooner51]

Two Questions:

1. I have never flown a model airplane. However, I am a pilot and I have flown the simulated models on the computer. Therefore, I believe I can fly, and land, the model once I get it in the air. I have attempted to launch my Decathlon by hand tossing it with the motor at full speed. The result was a nose dive to the right. The plane is balanced at the proper fulcrum location. Concluding that the air speed was inadequate, I made a rig for my bicycle that would allow the plane to lift when I had achieved the proper speed. I peak out at 15 mph. The plane appeared to be on the verge of lifting at that speed. My exhaustion prevented full verification of this. A hard surface runway is not available. Question: Does one need a stiff headwind to hand launch, and how much gusto is required in the toss?

2. Assuming I ever get the airplane flying, the ratio of flight time to battery recharge time seems to be pretty dismal for the NiMH batteries. It looks like one can improve this significantly by using a LiPo battery pack. However, the voltage would about 11.1 V instead of the 9.6 for the NiMH's. Does anyone have knowledge as to whether the system would stand the extra voltage?

Thanks.

[ronin4740]

I'm by no means an expert but I have hand launched a model airplane once or twice :) My method is to give the plane a good, hard, straight throw at about 10 degrees above the horizon. No twist in the wrist when releasing the airplane. Depending on the amount of thrust I usually set the throttle between 2/3rs and full.

Watching the video of the Decathlon from HL's website I would think it would produce enough thrust for this to work as it becomes airborn from the ground very quickly.

Perhaps the motor you received is bad or perhaps the propeller has been installed backwards causing the prop to produce less thrust than is required for the plane to maintain airspeed?

As to your second question a typical brushed motor designed for 9.6V will tend to have it's life span shortened if you use an 11.1V lipo battery. The good news is that new brushed motors are relatively cheap so if you burn one up it won't be a big expense to replace it. Increasing the voltage will also increase the RPM of the motor which should produce more thrust and make it easier for you to get the plane in the air. Finally it'll weigh less so once you recheck your center of gravity the plane should fly longer and be faster.

I don't own this plane but hope that my reply is helpful in a general sense. I imagine one of the Hobby Lobby forum reps will pop in and offer more specific advice shortly. If not I'd give them a call and see if you can't work out the bugs.

[Sooner51]

Ronin,

A reversed prop may have been part of my failure-to-launch problem. Following your clue, I reversed the prop, and believe I sense somewhat more thrust. I will see if that will do the trick at the next opportunity.

I suspect that the motor can handle the increased voltage of the nearest LiPo pack. It is the receiver and servos that I am concerned about.

Thanks for the response.

[ronin4740]

There's no need to be concerned about the receiver/servo's if you use a 11.1V lipo. The ESC (speed controller) takes care of stepping down the voltage to the receiver which in turn supplies the servos with voltage.

I should have mentioned it but on all of the props I use there's nuumbers and lettering. The numbers represent the size and the lettering often indicates the manufacturer. On every prop I've ever used the numbers and letters face the intended direction of travel. So, on a tractor prop model the numbers/letters face ahead of the model.

Finally you might want to post in the Electric Plane Talk or Beginners forums if you need more specific information about your plane. Doubtless one or more of the forum members here have flown this plane and can offer feedback, advice or impressions for you.

http://www.rcgroups.com/electric-plane-talk-7/

and

http://www.rcgroups.com/beginner-training-area-electric-8/

are the links to those sections of this board.

Hope this helps.