RCU Forums

RCU Forums (https://www.rcuniverse.com/forum/)
-   RC Gliders, Sailplanes and Slope Soaring (https://www.rcuniverse.com/forum/rc-gliders-sailplanes-slope-soaring-112/)
-   -   Elictric motor size for Airtronics Olympic sail plane (https://www.rcuniverse.com/forum/rc-gliders-sailplanes-slope-soaring-112/11684843-elictric-motor-size-airtronics-olympic-sail-plane.html)

Calmo2 11-16-2020 05:57 PM

Elictric motor size for Airtronics Olympic sail plane
Hello; A friend of mine gave me an old Airtronics Olympic650 sailplane kit. I have been looking on the internet for some information about this sailplane and I have seen where a few people have used 400 size motors in theirs. I have a Rimefire 400 motor and was wondering if this would be a big enough motor for this sailplane. To me it looks rather small for this size sailplane. Any help or recommendation for a motor for this sailplane would be appreciated. PS. I have never built or flown a sailplane!!!

speedracerntrixie 11-16-2020 09:24 PM

That motor will have plenty of power. Expect to move things around s bit. I'm thinking the servos will have to go under the wing and maybe the RX. Under the canopy will be the battery and ESC. Select a 3 cell battery that is the smallest that will give you a CG of 40% behind the LE at the root. Not having had a sailplane before, that will seem a bit far back. Mount the motor with no thrust offsets but you will need to mix in some down elevator with throttle. Trim the airplane to fly hands off with the power off. Best of luck.

Calmo2 11-17-2020 06:10 PM

Thanks Speedracerntrixie; That helps out a lot. Thanks for all the setup advice. The CG does seem a little far back alright but you have a lot more experience with sailplanes then I do for sure. All I have ever built and flown were planes!!! Thanks again for you advice. I looks like it is going to be a fun build.

speedracerntrixie 11-17-2020 07:46 PM

You're welcome. Best of luck, you will hopefully find that using the motor to get some height an then finding that first bubble of lift that takes you up beyond your comfort level is quite addicting.

BMatthews 11-17-2020 10:32 PM

Calmo you can get pretty decent casual climbing performance by setting up your model with around 60 to 70 watts per lb of model. This will give it around a 45 to 50 climb at a decent but not racy speed. A model the size of the Oly650 should also be at or under around 32'ish ounces. And ideally end up in the mid to high 20's. The Rimfire 400, after looking around for information, handles up to 160 watts maximum in steady running. So your motor will EASILY fly your 650. At 60 to 70 watts/lb you will only need to run it at a lazy 120 watts. On a 3S pack that's only about 10.5 amps. Watts being amps x volts after all. Or you can push it to closer to the 160 watts max and have your model climb at more like 70

You can check for the CG as it's shown on the PLAN AT OUTERZONE. It shows as being on the spar. Start there but as you get comfy with flying the model play with moving it back a touch at a time until you find that the model is becoming sketchy for pitch stability. The closer you get to neutral stability the better the model will signal lift to you by kicking the nose up or down. But when it's too close to neutral most find that they don't like the constant balancing act on the elevator stick. Find your own happy place and you'll really like the model. And best of luck on your first few thermals and that ever so happy first half hour flight from only 20 seconds of climbing power.

Calmo2 11-18-2020 07:52 PM

Thanks BMatthews: The info you found on the Rimfire 400 sure put my worries to bed. I live in Fernie BC right in the middle of the Rocky mountains so I should be able to find some thermals. I have a couple of fiends and they have the E-Flite Radian glider and the have gone for 20 to 25 minutes without ever using the throttle!! Thanks again.
PS. I notice your picture of a motorcycle. Do you ride? I have 2 bikes. A Harley Nighttrain and a Honda CRF 250 L dual sport. Just another vice.LOL

da Rock 12-24-2020 10:07 AM

got a finished Oly II to show off

will look up the details tonight when I have time.

BTW, there is an exhaust pipe back of the wing saddle in the picture above. It was added to enhance cooling for the heat generated from climbing. The powerplant was chosen to give very strong climb performance. I didn't want to see smoke trails now did I.

da Rock 12-24-2020 10:19 AM

I've retrofitted a number of my sailplanes from the past. I flew thermal with the Minnesota RC Soaring Society back before electric made the scene. A couple of the those birds have been moved all over the US and were on hand a few years back when I got the itch to electrify. A scratch built "own design" was the first to go under the knife. A 2-meter Sagitta might get the treatment next. The Oly II needs the spoilers updated and that'll precede the Sagitta. The Sagitta fuselage doesn't have much room for airflow through the center so it'll be awhile. The Oly has shown it's old form even carrying lots more weight but has no trouble with temps.


da Rock 12-24-2020 10:25 AM

Oh yeah, you might also notice the rubber bands that mysteriously appear from the fuse. hehehehe Been doing that since the 60s. They work great and don't cause as much drag as the usual setup does.

All times are GMT -8. The time now is 10:58 PM.

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.