I need help determining motor/gearbox/prop for sailplane - RC Groups
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Apr 29, 2002, 10:17 PM
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I need help determining motor/gearbox/prop for sailplane


I have the following:
E-Flite Odyssey, 87" span, 566sq in, 13-14oz wing loading, 52-55oz flying weight, 6 cell 1500scr and 7 cell 1700scr packs, stock 550 can motor, 30 amp esc, 8x4 folder.

I would like to upgrade the drive system but am having difficulty deciphering Motocalc. I want to (all I can afford) stay with the less expensive car motors, the batteries I have and my esc. If I read Motocalc right it looks like the best setup is a 3.5 gearbox, 13x6, 13x7 or 13x8 prop. I was thinking of the Magnetic Mayhem reverse motor. Do you agree or do you have a better suggestion.

Thanks in advance...

Last edited by Chris K; Apr 29, 2002 at 10:31 PM.
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Apr 30, 2002, 08:34 AM
Registered User
Should work just fine. If it will fit in your glider, the Master Airscrew 3.5:1 gearbox and Magnetic Mayhem would be a good combination. You may want to go a bit bigger on the prop. Prop for about 25 amps, and the MM will be happy.
Apr 30, 2002, 08:49 AM
Registered User
Mike Smart's Avatar
You should be able to swing a larger prop on the 7 cell pack. I have a Thermik Star about the same span/area but 66oz AUW. This uses a 600 and 2.8:1 box and climbs well on a Graupner 14 x 9.5 CFK folder.
On a 550 and 3.5:1 box, you should be able to swing this prop OK.
I use almost the prop size you are quoting on a 400 geared 4.5:1 - 12 x 9 carbon RASA Slomotion prop.

Apr 30, 2002, 10:48 AM
Scott Summersgill
smsgill's Avatar
I'm using the following setup in my Goldberg Electra and performance is awesome. With just a little headwind I can climb at near verticle. It only takes a 20 to 25 second motor run to be at a good thermal hunting altitude and I can get 4 good climbs with the CP1300's. Here is the setup.

Kyosho Endoplasma
MPJet 3.8:1 planetary gearbox
Aeronaut 13.5x7 folder

I've also run this setup of 7x2400's with much more duration but climb performance suffered a little from the extra weight.

Hope this helps,

Oops, just noticed you wanted to stay with your 30 amp ESC. The above setup pulls a little over 40 amps. Oh well. Maybe for an upgrade.
Apr 30, 2002, 03:06 PM
Registered User
Hey Chris,
I have an Odyssey also, I just ordered a speed control from E-flite, and will be flying it soon. I've read some other posts that say it's underpowered, and a handfull to control.
Has anyone had any luck with getting this thing into some thermals. I'll probably try it stock, and then upgrade.
May 01, 2002, 10:29 PM
Registered User

I haven't yet had a chance to fly it. S&E Modeler - May 2002 just did a write-up on the Odyssey. It seems they recommend a 7-cell pack.

Quote: "so I purchased a new Duratrax Piranha 1500-mah from the lhs. The next few flights were all right, but the model was still relatively underpowered. It would climb to about 500 ft in three minutes or so, but would stall and lose altitude several times along the way."

Quote: "Once again, the extra voltage of the 7-cell pack noticeably improved the climb."

There is more to the article and it would probably be a good idea to read it. There are some other tips and tricks the writer used to improve the plane.