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Jan 21, 2021, 09:07 AM
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E-36 freeflight to rc conversion


I finally decided to convert my rarely flown ff models to single channel, rudder only, rc assist to help keep them on the field. First up is the electric powered Super Pearl e-36 model. It will be set up and trimmed to function and fly just like a pure freeflight design, with a constant turn to the right, but will fly straight when servo is activated.

Should get a lot more use out of it. No good ff flying sites available here in Austin.
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Jan 21, 2021, 12:27 PM
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I’ll be watching this one. Could watch vids of free flight all day. There’s just something elegant about a well trimmed flight.
Jan 21, 2021, 02:06 PM
B for Bruce
BMatthews's Avatar
The newer E36's I've seen fly are amazing. Climbs that put all but the strongest 1/2A models to shame and give up nothing in the glide. They really are amazing to see in flight.

The downside to that sort of performance is that they glide pretty slowly. So you will still be limited to flying in lower wind speeds or it will just point into the wing and drift downwind a little more slowly. If that is the goal then great. But if you want to be able to fly in even moderate winds I think you'll need some way to feed in at least a touch of down trim to push into a faster sort of glide speed along with the rudder.

I've thought of such conversions as well. I was plotting along the lines of a spring loaded pull only thread to the rudder and where the stabilizer sat on a fully conventional FF style DT rest I'd put a servo operated cam at the trailing edge which would let me trim from the normal glide to maybe dropping by some amount up to around 3/32". That would give me enough down trim to go into a faster glide or very shallow dive and push back into the wing more effectively.
Jan 21, 2021, 03:43 PM
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I plan on taking out a slight amount of incidence in the stab with the adjustment screw and moving the CG forward a touch. First flights after conversion will be in safe wind conditions so I can get a better idea of what its capable of. The version of the Pearl that I have is supposed to cruise faster than the original so fingers crossed that it will do ok in average central Texas conditions.
Jan 21, 2021, 08:51 PM
B for Bruce
BMatthews's Avatar
Moving the CG and stab trim away from the ideal (and I presume already trimmed FF setting) will adversely affect the hands of power pattern though. I took your thread to be that you were looking for a "way back" after a mostly "free" flight.

Ya know... I can see using a rudder activated down trim. Fly it all normally just like a free flight model normally flies. And when you get as far downwind as you can tolerate a quick blip of rudder held just long enough for the servo to cycle full over and trip a release that snaps in a touch of down trim. You'd set this to give you a fairly speedy but still safe to land glide trim.

And if you find you need little more speed you could use a trick from old world rudder only flyers that would do a series of shallow "S" turns that go maybe 20 to 30 to each side of the return path. The turns will drop the nose and speed up the model a little more. It sounds counter productive to do the S turns but the speed it gives the model more than makes up for it.

What'cha think of this idea?
Jan 21, 2021, 11:30 PM
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It's trimmed well as a freeflight model. I think I can find a happy medium between squeezing a little more glide speed out of it and maintaining a decent power pattern.

As far as setting up some kind of secondary stab trim setting, that's possible, but I'm also dealing with a non-proportional single channel transmitter, my homebrew remote DT. So anything triggered by rudder input is going to be a one shot deal on the first command input.

I will have to experiment with how much control I have once I get it in the air, but my plan is to only be able to straighten out the glide when the radio transmitter is activated. Maybe a slight turn in the opposite direction of the normal glide.

The rebuilt vertical stab and sub-fin/rudder are ready for covering and the return spring is installed, waiting for the pull line to be threaded through the DT line guides for final set up.
Last edited by edfmaniac; Jan 21, 2021 at 11:37 PM.
Jan 22, 2021, 12:33 AM
B for Bruce
BMatthews's Avatar
So... if I understand this correctly you can flip the rudder tab one time only? And then there's no further control inputs possible? Or is it a case of you can blip the button and flip the rudder back and forth repeatedly but only a full travel with the blip and full back when you release?

If it's a one time flip and then it stays there I think you're wiser to stick with using it as an RDT. Wind changes in the air could well end up making the model veer off and then you're sunk. At least RDT makes it come down when you want it to come down.
Jan 22, 2021, 08:14 AM
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Non-proportional. You can activate the servo as many times as you like but it's basically an on/off situation. No dual rates or throw control for triggering a second function.

Now I could use the timer's DT servo output and a second servo to trigger something after a set amount of time, and still have my single channel transmitter for directional control. But I don't want to be tied down to something on a timer in regards to the stab trim.
Jan 22, 2021, 11:10 AM
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Larry Jolly's Avatar
I have to ask, why not use a radio with flight modes, and fly it as a F/F , with the possibility to save the model should things go badly??
Jan 22, 2021, 12:07 PM
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Directional control, as limited as a single non-proportional function can provide, should be enough to keep the model safe, while providing as much joy and relaxed freeflight style entertainment as possible.

Why not use a standard transmitter with modes to switch to proportional capabilities? I just want to use the single channel radio that I built.
Last edited by edfmaniac; Jan 22, 2021 at 12:12 PM.
Jan 22, 2021, 02:26 PM
B for Bruce
BMatthews's Avatar
If the servo stays locked over for the FF turn my thought was that the down trim would be triggered to click in by the first triggering of the rudder to come off the FF setting. You'd latch whatever trigger setup to put the stab into the FF setting before the launch. And upon using the Tx the first time the movement of the rudder tab to neutral or slightly the other way would release the stab to snap to the higher speed glide. So no timer function needed. Then it stays in that trimmed down state until you reset it before the next flight.

This is partly suggested by the fact that if the model is set to glide in circles right at the minimum sink and minimum speed setting then even straightening up from there will slow the model down enough to probably go into one of those long slight repeating stall modes. And that's not a good trim setting for fighting back upwind.

As for how much turn to use? I think you nailed it with the idea that you'd want to slightly overcorrect and go into a moderate slight turn the other way. This would ensure that you have full control even if your "straight line" is in fact a slow S turning wiggle all the way back. Otherwise if you only go back to dead straight and the model is upset to the side towards the turn your only option to correct for that is do most of a full turn around. And once again having to do that isn't going to aid with fighting your way back upwind. So by all means overcorrect past straight ahead by some small amount.

I assume that with the moveable rudder tab and likely some manner of triggered down trim tab or stab rest shift that you'll need a whole new tail group as opposed to the setup for flying FF matches where you're limited to RDT. Or are you strictly using this for casual sport flying?
Jan 22, 2021, 05:36 PM
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The chances of me making a contest are slim to none unless they start a club here in Austin and find a flying site. But anything I do to make it more fun as a casual flyer will be quickly reversible.

I'm going to stick with minimal mods until I determine how much penetration it will have. It's not like I'm going to pick this plane out of my hangar to fly on days when the conditions are marginal anyways. I just want to get more time on some FF models after building them almost exclusively for a couple of years now. None of them have seen full power launches except for the E-36 on a 5 sec run.

My Torontonian Wakefield is next on the list of conversions if this one works out.
Last edited by edfmaniac; Jan 22, 2021 at 06:44 PM.
Jan 23, 2021, 04:00 PM
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I need to do a little more fine tuning in the power pattern but the glide and amount of control is in the ball park. Perfect right hand glide pattern with no radio input and just a little turn to the left when the rudder is activated. Making it go straight is very easy with a simple on/off cycle every couple of seconds.
Jan 23, 2021, 07:55 PM
B for Bruce
BMatthews's Avatar
That sounds perfect for what you're trying to do.

Just a thought.... you know that there's a FF forum here on RCG? Likely this whole thread would have been more at home over in that sub forum.
Jan 23, 2021, 08:37 PM
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Quote:
Originally Posted by BMatthews
Just a thought.... you know that there's a FF forum here on RCG? Likely this whole thread would have been more at home over in that sub forum.
Of course the purists in the FF community would question why I'm posting about rc related stuff in the FF section of an rc forum. LOL It's now an rc controlled electric powered self launching glider in their eyes. Is there a single channel sub-forum??


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