Hi all,

I was wondering if anyone has had experience with the Great Planes Basic Light Trainer? I built it as per the instructions, kept it in the 9-13 oz range (11oz.) and used the recommended battery pack and motor. The motor package is as follows:

T280 ferrite motor w/2-pin female plug
T280 4.1:1 ratio gear box
11 tooth pinion gear
ElectriFly C-10 micro speed control
APC 10x4.7 slo-fly propeller

The battery is a Great Planes 6-Cell 650AAA NiMH Panasonic

In the instructions it states that I can cut the motor from 3/4 to 1/2 and it should maintain altitude. After many attempts at trim/cg modifications (starting with the recommended CG point and working slightly aft before returning to the recommended point) I've come to the conclusion that this thing must be slightly underpowered as built. I have increased the wing incidence slightly by placing a 1/16 piece of balsa under the leading edge of the wing. While this reduced the up trim necessary to fly level at speed, as soon as I cut the power by even a fraction, the plane begins to slowly descend. Has anyone built this plane and modified it or found it to be slightly underpowered? I'm still relatively new to R/C, although I've been building balsa planes since I was a kid, so any suggestions would be great. I did a search and found a couple of ideas, but I'm wondering if there's anything I can do with the plane as-is to improve its performance.

Thanks in advance!!

you could try a smaller prop...the 9x7 e-prop should give you more thurst...

john

All I'm finding are 9 X 6 E props and 9 X 6 slow flyer props. No 9 X 7's except wood. Would the 9 X 6's work? And where can I find the difference between the E props and the slow flyer props?

Thanks!!

The "E-props" and slow flyer props are similar... The 10X4.7 is intended for a very slow flying model, making good static thrust but not provinding must top speed to the airraft. The 9X6 e prop would reduce static thrust, but might help you maintain airspeed at the lower throttle setting.

Electric props are not as strong or as heavy as those intended for glow power as the electric motor does not have the power pulsing of the glow engine. A glow engine would snap a wood "electric" rated prop.

You should find some difference in the 9X6 E and the 9X6 slow flyer prop too... again it will be in the weight and strength of the prop. The slow flyer prop will be lighter and more fragile, getting closer to looking like a rubber power prop with a large shaft hole. The "E" propis made for a stronger, higher speed motor, the slow flyer prop is made for the litttle 280 and smaller motors and may be expecting a gear reduction to keep the prop within its designed tip speed limits.

You can stick a "E" prop where a slow flyer prop is recommended. the only real penalty doing this is a small amount of weght.

You can not stick a slow flyer porp on where a E prop is recommended.

Go ahead and try the 9X6 E rated prop. It can't hurt. You may find that clmb rate suffers... You may find that all areas of performance are so much better that you stomp on the 10X4.7...

Thanks for the info. I'll try both types of props on the little bugger. I tried it again tonight after moving the COG back a little more. After the initial climb, I still have to keep it at full throttle to maintain altitude. Not really looking for speed, just would like to hold the altitude for a few minutes. My next idea is to reduce the recommended down thrust to see if that improves the situation, if the new props don't change anything. I've read both positive and negative posts about this little airplane and I'm thinking that there must be a key step that I'm missing. I'll post here again after I try the newer props.

Thanks again for the info!!

I think your biggest problem is that battery pack. It's kind of a given with electrics, that if you're using a NiMH pack, add a cell. I would recommend getting a 7 cell NiMH pack at a minimum. 8 cells would allow you to throttle back for half the flight I'm guessing.

Keep in mind, 8 cells would stress the motor a bit, so you would want to throttle back as often as possible. (Constant full throttle would shorten the motor life.)

Another option. but more costly, would be LiPoly cells. The cells and chargers are expensive, but the packs weigh much less which would a;so improve performance. The capacity of a Lipoly pack is much higher and would give longer flights as well.

Good luck,
Dennis-

Well,

I had ordered a 9 X 6 E prop as well as a 9 X 6 Slow flyer prop. The new props arrived today, and tonight I took it out for a quick flight. The wind was blowing a steady 8 mph with gust running up to 15. Well above recommended flying speeds, but I had to check it out. Using the 9 X 6 slow flyer prop, the plane shot out of my hand and power climbed to about 70 feet before leveling off. Even though the wind was howling for the little plane the extra thrust from the new prop allowed me to throttle back and maintain altitude. The extra thrust allowed me to actually manuever into the wind. I couldn't however keep it level with the wind like it was so I brought it down. I was suitably impressed with the improved power. When I get a calmer day I'll post how it responds in more favorable flying conditions. Thanks for the prop suggestions, they helped a lot!!

Last post on this one for me. The suggestion to use a different prop was indeed the best one in this case. The 9 X 6 Slow Flyer prop works great. The wind died off to zero about 5:45 and I was able to fly the plane for about seven minutes. I could maybe have squeaked another minute out of it but the light was fading. Didn't speck it out, but I believe I could have made several hundred feet altitude with it. Throttling back allowed me to maintain altitude just fine. Heck, I even looped it once. Another suggestion was to use a one cell larger battery pack. I think that step will be next once I've gotten all the kinks worked out of it. While I built it within the 9-13 ounce suggested weight range (11 ounces), building it lighter would probably have given me better performance with the recommended motor/battery combination. Now if I could just get one day where the wind is calm in the middle of the day, that'd be nice. I'd have to say that the plane is fun to fly now.