Electric talk

Grapher expresses some interesting views

Reading your issue 41 and in particular looking at the electric powered content, I am stimulated to throw in what I hope will begin some informed discussion from which we may all learn something.

 

I have been using electric power for about 18 months.  When I tell you that I began model flying in about 1950 you will see that electric power has been a very recent interest.

 

A Junior 60 was my first effort and I thoroughly enjoyed that aircraft (and still do) but after an initial period of excitement I soon reached the "cooling off stage".  I wanted something that I could better compare to an i/c powered model for, say, climb rate and general performance.  So as to measure the differences I began by building another Junior 60 equipping that one with an SC .30 engine.  Flying either of my 60's reveals very quickly that the performance of the electric aircraft leaves much to be desired.  That, by the way, is on its second Graupner Speed 600BB geared 3:1, 7.2V running on 7 Sanyo 2000MaH cells.  It must be said if only to pre-empt someone else, that I do know that one can worship at the high altar of "building light" but I find that to be a tedious business.

 

The worst thing about the electric puzzle is fathoming your way through all the self-appointed guru's who freely dish out advice whether informed or not!  I'll cut out the tortuous paths trodden in my search through the electric wilderness but suffice to say that my conclusions now are:

 

1.  I bought a cheap (£30-ish) charger.  Big mistake!  Now I have a Robbe Infinity 2 (about £150) and through that my batteries can now be properly maintained - a very important practice.  My batteries can "talk to me" through this sophisticated charger and there are of course other brands.

 

2.  I listened to those who said that there really was no need to buy expensive, brushless motors unless I was wanting to compete.  I tried about five different motors and they were all disappointing on performance - climb particularly.  By this time I am talking about my 2.8 metre Reichard Elipsoid.  I then chucked caution to the winds and bought a Jeti Phasor motor and Jeti speed controller costing about £175 total.  The transformation was as they say "truly electric" which when you think about it is entirely appropriate in this case!  Using the Phasor I can get to thermalling altitude in about 20 to 30 seconds and typically get say 30 minutes flying (subject to good air of course) landing with but 1/3 of battery power used.

 

Summing up, then, I would say to the budding electric flyer that there is a choice to be made by those who simply can't afford the high cost of running a stable of aircraft powered by both sources.  Going in to electric as a "cheap option" is a big mistake.  Spend what you would on i/c power buying brushless motor(s) adding a good charger - meaning about £150 worth.  Buy a good field battery for re-charging and in this respect I have found a conventional car battery to have been fine for sport use.  Then you will get a truly comparable performance.  I am pretty near convinced too that a rev counter and a watt meter are essential kit (objectively driving the selection of the optimum propellor).  When funds become available I'll get these too.

 

Graham McAllister has been a great source of advice for me though he'll probably disagree with some of what has been said.  So too has John at Gliders in Newark.  I am certainly not a competition flyer and I would say not even a very accomplished pilot but I do like engineering excellence in anything - brushless motors deliver that.

 

If you publish this Reg, I really do hope that we get some exchanges contributed by folk who possibly think I have written some tosh.  However, I would expect to be able to test what they say by duplicating their claims in the field as anyone could test my own statements.  Just buy an excellent Elipsoid and try it with three different brushed motors, two different gearboxes and then a Jeti brushless Phasor 30/3.  Then consider what you would have saved if you had just bought the Jeti which requires no gearbox (immediate saving for example about £60 for the two gearboxes I did buy).

 

Now one might say that I was daft buying all this kit to which my reply would be a question really.  "How can one avoid it when there is so little sound guidance available?"

 

Anybody got some helpful comments on what Grapher is saying? Some practical advice on this subject from some of you with considerable experience in electric flying would really be most welcome.