RC Gliders, Sailplanes and Slope Soaring Discuss rc gliders,rc sailplanes and slope soaring in this forum. Thermaling techniques, airfoils, tips, etc

Run time

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Old 09-22-2016, 06:04 PM
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JGalt
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Hi, I am an old fuel R/Cer getting back into the hobby with an electric glider. The R/C glider ESC & battery powers the motor and radio receiver/servos. The instructions say full power should provide about 6 or so minutes of motor time but my question is will there still be some battery power to land the plane? If so, how will I determine how much flight time I still have?
Many thanks in advance for advice and assistance.
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Old 09-23-2016, 04:45 AM
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da Rock
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It's interesting the glider instructions say something about 6 minutes of full power. Most gliders only use full power for intermittent climbs. anyway...

Get a meter and read out your battery capacity after flights. If you're messing around with LiPos/ESCs/motors nowadays, you REALLY need to have one. You'll probably ruin batteries and good chance motors and ESCs otherwise. With one, you'll be able to figure out how much power on time is safe for the model/motor/esc/battery that you fly. You'll also have the means to insure you store your LiPos at a safe storage charge. (haven't heard about ruining them storing at the wrong charge level?).

This is the one I've been using lately. It will also balance batteries by itself, which has helped me reclaim more than one expensive battery or two. http://www3.towerhobbies.com/cgi-bin...?&I=LXBWUD&P=7
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Old 09-23-2016, 04:59 AM
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So how do you use it?

To judge power on time in flight, use it to insure the flight starts with a full charge. It tells percentage of charge in the battery. Then fly the plane the way you usually do, but limit the flight to less than that recommended 6 minutes. When you land, hook up the meter and read out the capacity remaining. Say you flew for 5 minutes and have 50% capacity left. Figure from there what you want to land with next flight on that battery. Of course, we seldom fly sailplanes with throttle most flights so.....................

When I'm flying my sailplanes, the power is only on for the climbs. So I figure out how many climbs there are in a battery. Looking at the usual 97-98% start charge, and say 5 climbs, the charge remaining tells me how many climbs are remaining. And I don't have a single battery that won't do way more than 10 climbs. And the last few months of flying, I can't remember any flight that had more than 7-8 climbs in it. The last few months, none has had more than 3-4.

The meter mentioned above is called a wattmeter, and that's an excellent and valuable function. It's worth the money just doing that. We can easily and safely fly glow fuel engines without having a tachometer, but there is no way to fly electric without risking motors/ESCs/batteries if you don't have a wattmeter and battery tester.
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Old 09-23-2016, 05:14 AM
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If your transmitter can do it, set it up to show two times: total elapsed time and power on time. I setup my Spektrum to show elapsed time and total time of throttle over 5%. Just before I launch, the elapsed time has been running but the throttle hasn't. Which is worthless info. So I hit the clear button to start the flight. Timer one starts counting again, and as soon as I push the throttle timer two starts. At the top of climb when I pull the throttle off, timer two pauses and timer one keeps on ticking. If I need power again, timer two keeps up with it, adding up all the time under power. When I land I will know how much time the flight was and how much time was spent with the throttle above a couple of clicks.

Truth is, when flying my gliders all I care about are how many climbs. I seldom use power except when climbing from about head high to about 300-400'. All climbs are pretty much the same so count is good enough info. But when I'm flying my Thunderbolt with it's Rimfire80/5S-5000mAh Lipo, the throttle time matters. I figured out what that shouldn't exceed back in the models first outing.

Have fun with electric. However, if you don't want to ruin components, get a meter.
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Old 09-23-2016, 11:56 AM
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Most models these days will climb to thermal country in about a minute or less. To ensure you have some battery to run the on board gear it's likely wise to limit yourself to 4 climbs up of around a minute each. That will ensure you have power to run the radio and servos and enough to fight back to your location from downwind if you find yourself not watching where you're flying or miss the thermal you were trying to snag.

From there learn to fly smoothly and with minimal inputs so you don't drag the model down. And then learn to find and ride thermals.

The point of flying a glider is to learn to soar after all. Once you get to that point you'll likely find that you only ever need to use one or at most two climbs per pack anyway. After that it's stealing altitude from thermals and flying until your neck is sore which pushes you into landing.
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Old 09-26-2016, 06:19 PM
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Thanks so much to all of you for your help!
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