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Great Planes Tutor power system question!

Old 10-15-2006, 09:08 PM
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joeman11
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Default Great Planes Tutor power system question!

Hi all! I plan on building this little beauty. It says to use the 280 size motor with the 4.1:1. Ok. It says on 7.2 volts, it gets 6.5 oz of thrust. I'm going to use a 2 cell lipo. The plane is going to be around 14-16 oz. This will brobably going to get it off the ground, but will be very underpowered. My slowstick with the 300size motor on c gearing got 13oz of thrust. The slowstick powersystem only weighs .2-.3 ounces more, with twice the output. Now, I now I cannot just put that powersystem on the tutor, because it won't have enough airspeed. Just thrust to get it up to stalling speed(15-18mph) So, I thought I could get a gws 300size motor with a smaller gear ratio. So, instead of 5.33:1(c gearing) I could go to 2.8:1 or 3.22:1. Thus, increasign prop speed, and I'll just need to get smaller props. Possably an 8x6 prop. I want to know if all the stuff I just wrote made any sense, and if I'm going in the right direction. In summary, Instead of putting on an underpowered, greatplanes 280size motor with 4.1:1 gearbox, I'll go with a gws 300 size motor with a 2.8:1 or 3.22:1 gearbox, thus increasing airspeed, and giving me better performance. Thanks for any response. Joe
Old 10-16-2006, 08:14 PM
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Matt Kirsch
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Default RE: Great Planes Tutor power system question!

You're definitely on the right track.
Old 10-17-2006, 04:26 PM
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joeman11
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Default RE: Great Planes Tutor power system question!

After doing some searching, I remebered motocalc, and after about 4 hours, I found the perfect combination: gws 300 motor, with gear ratio: 3.75:1. It should pull 8.1 amps, with the prop:9x4.7--thrust:11.4--topspeed:28.3mph. At 21mph, the battery should last 16:36 minutes. Thanks motocalc!
Old 12-08-2006, 03:50 PM
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Trogdor the Burninator
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Default RE: Great Planes Tutor power system question!

I have this plane and used the original underpowered 280 setup recommended with nimh and lipo battert packs... pretty weak either way but it flew.

Then I got other planes and slapped on a GWS 350 B gear (I think the Formosa stock motor) and used 8 or 9 inch props. 8 inch props were good power and plenty for a beginner - you can do loops and all. 9 inch props were more fun but more load. My old 2 cell 1200-1500 lipos still did fine on these combos though. Modern packs may require smaller props?

You don't need to go too fast.. you just get loads of lift and it loops spontaneously! good thrust is great to get up high and try to glide down as long as possible.

Nice little plane and makes me want to try another kit soon to go with all the ARFs. Maybe a stevens or mountain models plane.

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