Some thoughts on Electric C/L

LAST EDITED ON Dec-04-04 AT 06:27 PM (CST)
 
All,
I have been flying electric planes since 1978. Yeah, they were really clunkers back then. Picked them up and put them down several times between then and now. Started really coming into its own maybe 3 or 4 years ago and really bloomed in the last year or so. Now electric C/L has become a real possibility. I would like to share some thoughts for those who have not been through the time, aggravation and $$ of electric modeling. These are in no particular order yet. Mike P., chime in here if I get off track.

-Log on to EZonemag.com and just start reading anything that sounds interesting, especially the Power Systems section. There are a BUNCH of highly knowledgeable people who, very much like this site, are quite willing to help just for the asking.

-EDIT: Electrics have a very well developed cottage industry for limited production high tech motors, gearboxes, aircraft as well as the various bits and pieces necessary to make things work. EZone is the place to find out about this. There is even a "vendors" forum so users can post the the good and not-so-good experiences they have had with vendors. They have a good search engine, and if all else fails find a likely looking area and post the question there. If the moderators think it belongs somewhere else, they will move it for you.

-Get a copy of Motorcalc from Motorcalc.com and learn to use it. You can download it free for 30 days, then you have to pay about $35. Worth every cent. It is great for getting a project vectored in to a starting place and throwing out non-viable set-ups. You will have to adjust for the plane being C/L, of course.

-Buy a good battery charger. Expect to pay $50 or so for a low end lithium-poly "LED status" Charger, around $120 for a very good battery analyzer type charger (Like an Orbit, a Triton or an Astro 109), up to several hundred for a charger for a high end, high cell count charger (like a Schulze). The battery analyzer type can tell you how much charge was put into the battery and what the voltages at the start and finish are. I use both types: an Orbit when I want detailed data about the battery under charge and an Apache 2500 LED status one when I don't.

-Get some type of current measuring tool and use it. Simulate the set-up with Motorcalc THEN test it to make sure. It is REAL easy to over prop a motor and blow the motor, ESC or the li-po battery pack, or even all three (we won't go into how I know THAT...). It is just as easy to UNDER prop a motor, not get the power you need and not know why (been there, too). Astro Flight sells a "Whattmeter" which goes in line with the battery and displays the voltage, current and wattage of the motor under test. I also bought a Sears clamp-on ammeter for $50 and it works well.

-Buy the best equipment you can afford. Big surprise here. There are a lot of "clone" motors out there and while they are affordable, they are not as efficient or as powerful for a given size. The German motors like Plettenberg and Hacker are some of the best made. They are also more expensive. Another big surprise. I think Mike went to a Plettenberg "outrunner" (more on that later) to get the most efficient set-up possible. The same goes for batteries. The industry standard is Thunderpower. There are a couple more companies that are starting to gain on them real fast, though, like Tanic. Buy good wire, plugs and connectors, like Deans Ultra, Sermos or Astro Zero Loss. High current operation puts a big load on the connectors and they need to be sized properly. I use Deans Ultra.

-There are two basic configurations of brushless motors. One is the standard motor which has the magnets inside the windings and can spin at 30,000+ rpm. Obviously, gearboxes (sometimes with as much as a 6:1 or more ratio). The other is the "outrunner", which has the magnets outside the windings and the outer case spins much like a rotary engine. Outrunners do not require a gearbox and are less flexible than the first type. They take more "fiddling with" but can give very good (and very quiet) performance.

-EDIT: Igor reminded me (THX!!!) in another post that I forgot to talk about props. Props for electrics are very different than those for nitro. Electrics seem to like bigger props with undercambered blades much like the four strokes. Also the optium blade shape is much different than tht for nitro. APC and GWS have some of the best generally available electric props, with APC having the most in a usable Stunt size. There are a number of other "specialty" props, mostly folding ones made for gliders that are highly developed and very efficient.

-A Mel D. "rule of thumb". A quick way to tell if you have an optium match for motor, prop, ESC and battery pack is that the the motor is very warm, bordering on hot, the battery pack is medium warm and the ESC is warm too. This means all parts of the system are working together and close to the limits of their respective performance limits. Which means you have the lightest possible power system. This is no surprise to this group, but the way to then get the most out of a set-up is to get a good match between the power system and the airframe. It is very interesting for me to say this to this community, because highly experienced C/L guys already KNOW this better than most electric hobbyists will ever understand it. It is just a question of applying that knowledge to electric power.

Wow, this is a lot bigger than I thought it would be. Sorry if it is too long.

later,
Mel D>

EDIT: And it just got a little longer.....-mhd

I postulated that electric Stunt CL was approaching feasability not too long ago.

It is very interesting to hear the details and that kind of pragmatic advice on where to go to get up to speed on developments.

I'm building a gas ARF now just to get back in the air.

In the long run, though, I still think electric ARF is the future of CL as mass market opportunity.

I know that is at odds with the core appeal of the sport to a lot of us--building (in some cases designing) your very own flying machine and enjoying the smell of burnt castor in the morning. But I suspect that electric ARF CL can be the 'version' of the activity that can gain wide spread acceptance among the NextGens.

Thanks for the pointers and advice.

Cy

I too expect to make the change to electric. I'm just waiting for someone else to develop the technology.

Yup!

I'm with Al!

BIGS

" What constitutes the dignity of a craft is that it creates a fellowship, that it binds men together and fashions for them a common language. For there is but one problem - the problem of human relations."

>I too expect to make the change to electric. I'm just
>waiting for someone else to develop the technology.
>
>Al

My sentiments exactly. There is no end to the good that can come to this world if no one cares who gets the credit. grin.

Tom Morris and I got excited about Electric Powered Stunt Ships after the successful adventure with the electric stunter in Advance at this year's Nats. But when we totaled the cost of the items to get a stunt ship in the air we both backed off. It exceeded $600.00. A good bit of that was for support equipment etc.

It is coming and I will most likely not be around when it reaches an acceptable level on the expense.

What an audience Jim Walker would have generated with three control line electric powered fireballs flying at the same time.

He would have had onboard, airdriven battery chargers for sure. lol

Thanks, Mel.

>Thanks, Mel.

Good Lord! With his latest Impact I count three different engines being slated for the thing so long has it taken to build so far. Now there is yet another diversion in the form of electric power.

Al Rabe has the best idea: Wait for the development of a full package.

I say this as one who has watched, or at least looked askance, the development of electrics since the very first when the Boucher brothers were still friendly enough to each other to actually be in partnership. Alas, this did not last long. As predicted by all who know them both, and I do, although not well.

The difficulty I see here, call it a challenge if you wish, is that while a lot of stuff in the form of batteries, motors, ESCs, props, etc. is available off the shelf in many cases, we have some really intriguing needs in a CL Stunt power plant. "Unique" would not be the wrong word for the situation.

So while, from all I've seen without actually having witnessed an electric CL model fly, indicates very strong potential for the equivalent to a 25-powered, 500-inch profile type of model and corresponding performance, the demands of upper-level performance at the U.S. Nationals will be a much, much different challenge to deal with. Primarily because our current (no pun) power plants and airframes are so highly developed.

I'm thinking the electronic trickery required to match electric motor output to maneuvering speeds required throughout the pattern are not only going to be unique to our event (read: expensive) it will be difficult for the average guy to make it work properly and reliably.

I mean, look at the hundreds of posts dealing with the simple act of placing a bellcrank in proper position within a CL model! Sure, Rush mucked it up some in one of the most hilarious pranks ever seen on SSW (my sincere congratulations!), but that was a very basic issue.

Especially compared to some sort of feed-back loop designed to punch in an extra 83 revs 2.8 feet from second corner of hourglass figure.

Some of you have seen computerized RC units and just rolled your eyes at the complexity. Well, I don't agree, find them to be a dandy tool. But I have not yet lugged a lap top computer to the RC field, and I think that's exactly what is in our future when/if electrics hit CL Stunt in a big way.

And yes, I know about Jason's electric RC Pattern model. No one who is already serious about CL Stunt, understands the requirements, is bothering to replicate what works for him, the application is that different.

I have been waiting for more details on an electric control line plane ever since the wife got me the Cox Bearcat several years ago. The drawback is only one battery pack that takes six hours to charge for one 5 minute flight. When the technology gets it affordable and working I will try it. Right now too many Fox's to wear out. Later, -DOC

Well, I have judged a full-fuselage, good-looking electric airplane flown in competiton. It was Walt Brownell's airplane flown in the Broken Arrow Contest in St. Louis last September. Walt was not in practice and it was only the airplane's third flight Even so, a respectable pattern was flown, with nice square corners. I could not see that the airplane was lacking in power in any way. Other than the quietness, it seemed to me no different from an IC powered airplane.

I couldn't agree more that it's going to be a big part of our future.

The best part is that we will be able to hitchike onto other people's development. Battery improvements, lower prices, lighter weights will all come with or without us. An engineer/ stunt flyer friend says it won't take much more than a chip to add the equivalent of our "2-4 break" to hold even speeds.

Bet you a nickel somebody also comes up with a way to add engine noise to an electric for those who just can't live without it.

Time will tell!

I guess you guys know that if anyone wants to see electric power develop further it is me!!! I can't wait to see what people come up with. I look forward to the day that I can ask someone "what motor are you running?" or "how many cells is that?". There are far more advantages to electric than there are disadvantages (both in performance and noise). In the next year or two most of the disadvantages will go away and make it a truly competitive power source.

If you talk to Jason Schulman he will tell you in R/C pattern there are more advantages to electric than there are to glow. Thats why he flys electric. He has shown this to be true. I think in the next few years we will find this true in C/L aerobatics also.

As always I will be persuing electric flight. I look forward to reading about what others have done!!!