ECL column

[robertc]

Steve,thanks for being volunteered.
Feel free to use any info I have posted in this forum.
I have built three electric control line planes (ECL) and info on two has been posted here.
For many the intial question seems to be motor control. Perhaps the first question should be are you to fly alone or with a friend?
If you fly with a friend the simplest is probably one I used on my first ECL plane.
This consists of a switch mounted on the fuselage for the assistant to turn on and let go when you are ready and a fuse installed to protect the motor in case of a nose over. At the end of the flight when the battery was sagging I would put the plane down with motor still going and walk over and switch off. If it nosed over there was never enough power left to blow the fuse or cause a problem.
Control method number two was for flying on my own.
I used coated steel fishing trace instead of regular control lines. A switch on the control handle turned the motor on and off. No motor power was going up the wires just a short circuit from the switch to operate a relay in the plane.
Control method number three has been built for a friend who wanted to use his regular control lines with a hand launched plane. The model is a geared S400 with folding prop.
I have built an auto- cut system that is started by pushing a momentary switch mounted on the plane. The motor will be stopped when the battery drops to a pretedermined voltage level. I have not added a fuse to this system because, if the motor is stalled ,the voltage depression this causes trips the auto-cut.
***Conclusions ***
In the interests of safety I like the ability to terminate the flight on demand when flying in a public park.
When flying with friends at the club field I don't find it essential. My intial thoughts were to have full speed control when I started but it is no longer a priority.
*** What use do I see for ECL now that I have tried it ***
1: Ideal for those who like to build scale models,see them in the air but do not want to go to radio.
2: A defined competition aerobatic electric schedule. Define a pattern and set a clearly understood and easily policed rule. e.g.RULE 1- the model shall be powered by a maximum of of 10 nicads or NiMH cells no larger than sub c size and flown on lines between 49 and 51 foot in length. RULE 2- there shall be no other rules.
regards
Bob

[philc]

Before we start setting rules, I'd like to see some suggestions for decent performance. Unless I'm missing something, 10 cells can deliver performance similar to an anemic glow .15 engine in an overweight, kind 'a small plane. Hardly something for even semi-serious stunting.:confused:

[steve lewin]

I think Bob was suggesting a special class for purpose built ECL planes. I like the idea, particularly keeping it small and therefore relatively cheap.

So what are your ideas for performance ? Must the model be of a minimum size ? Does it have to fly on 70' lines ? Bob suggested a set pattern to fly. Do you want to help us define the pattern ? E.g. I'm guessing that an overhead cloverleaf is going to be tricky.

If your ambition is for a PAMPA size model flying the full schedule then, from all I've seen in Stunt News and elsewhere, that is just about possible now but will cost lots of money. A good geared brushless motor and about 20 cells may get close. But with the state of battery technology there is no way to compete directly with the power/weight ratio of IC. That's true in all areas of electric flight, we do something different.

BTW size isn't everything :). All the competent stunt fliers I know can fly the full schedule with a 1/2A model.

Steve

[philc]

I guess I would like to see something that can fly about like a Ringmaster on a Fox 35 for about 3 min. Most Ringmasters are overweight and don't stunt well, but do a nice job for sport flying. Any less performance and a competition would be more about who can keep the plane in the air than who can fly a good pattern. Any suggestions on specific motors, batteries, etc?

Since electrics rapidly lose power throughout the flight, the pattern will have to take that into account and not waste time. No wasted level laps that's for sure.

How about this-
take off(1 lap)
one level lap
start reverse wingover
in the first half do the overhead eights
pull out inverted
complete last half of reverse wingover
at end of wingover, do the cloverleaf
recover upright and complete a level lap
horizontal square eights
recover upright
outside loops starting at 45deg
inside loops from level flight
landing

This puts the high horsepower maneuvers up front.
By doing a maneuver on each lap no time is wasted. Putting the square eights in the middle will really tax the plane but it is a low altitude maneuver, so it shouldn't risk a crash too much. Finishing out with some round maneuvers on the last of the power will put some emphasis on flying the plane with minimal power.

This pattern works out to about 10-12 level laps and the equivalent of another 20 or so in the maneuvers. With a lap time of about 5 seconds that would work out to 2.5-3 min. flight time, which seems to fit the battery life available.

[Ray Lowinski]

I've been avoiding this forum but it's nice to see that someone is actively pursuing the ECL. A very good friend of mine, Wil Hinton, has been trying to get me back into CL and this just might do it. Wil used to be a writer for PAMPA in the member profile column.

I have a scratch built combat type ECL on the shelf right now. just haven't got the nerve to really try it. :o 05 Cobalt on 7-1700's and planned on 54' lines.

One thing I have tried to remind people in other forums is that Stunt builders have an absolute obsession with how light the plane can be. When you see a 720 sqin, .60 size plane in the 60+ oz range it is impressive.

I just may have to dust off the old Excaliber plans and do an ECL.

Keep 'em hummin'

Ray

[philc]

A couple years ago I put an SR 7 motor on 7 SR 1000 cells in a 9 ounce combat plane(airframe) with 450 squares. All up weight was about 28 oz. Used direct drive and a 7/5 APC prop, mostly. .012x52 foot lines. It would fly about 2 min. For the first minute it could do a couple low level loops or a couple figure eights. If everything was just right it probably could do eight loops. Then it would cruise for another 40-60 seconds.

[Ray Lowinski]

That's not exactly performance to write home about. OTOH that's where we get our kicks isn't it? Experimenting is half the fun.

BTW what is an SR7 in layman's terms?

Keep 'em hummin'

Ray

[robertc]

Phil,Steve is correct on all counts. I am simply suggesting a set of rules that could be easily policed. It is merely the concept I am pointing out not saying my suggestion is the best way to go.
I find if you keep to a simple rule format it allows maximum experimentation ,variety and progress.
I dont fly control line stunt or anything else . I am just proving concepts for myself so I can advise others around me from first hand experience.
What an IC plane can do has nothing to do with an electric class. But let us say for instance that you select the current schedule for an IC engine model and apply that to (say) my proposal. It is most likely that no one can achieve anywhere near the performance of an IC engine model at the moment but the idea is to set a goal for experimenters to work towards. Just as they did when IC engines could not pull the skin off a rice pudding.
These rules could just as easily be applied to say team racing where the crew has to rush out and do a battery change mid race.
Hope that clarifies my thoughts.
Thanks for yours. Keep them coming.
I think there is a certain fun to be had with battling the pull on the lines and it would be nice to see it continue for the next generations in a world where noise around suburban areas is simply not acceptable.
Regards
Bob

[philc]

The SR-7 Motor is SR batteries heavy duty ferrite motor wound for 7 cell. They also have a SR-10 for 10 cells.

Sorry to see that nobody has any suggestions for a motor battery combo- I'd like to see something that could deliver between 180-250 watts to the prop, probably geared, probably somewhere around a 11/7 or 12/8 prop, run at least 2 min, and weigh less than 25 oz.(motor, battery, harness). Anybody have any suggestions? I haven't been able to find it.

[dave_lilley]

An Astro 805G can do that.

By itself, it weighs 4.3 oz and uses a 8x2400 pack, which weighs 18oz. Geared at 3.3:1, it turn a APC 12x7 prop at 7000 RPMs with about 300 watts of power. The AUW of the whole power system should come in around 25-26 oz.

There are many other, cheaper systems available.

An Endoplasm on ten cells and 4.6 gearing can turn a 12X8 APC prop at ~7800 rpms. The two extra cells add ~4 oz, but I don't know what the gear and motor weight. Overall, it may come out the same.