Another leap forward ...

[Michael]

RC electric flight has seen several improvements over the last 30 years: electronic speed controls, geared motor systems, brushless motors, lithium polymer batteries, and much lower prices (mass produced products from Chine).

Well, without much fanfare, it seems another quiet revolution (pun intended) has taken place. Years ago, our models flew for 2 or 3 minutes.

Things are changing in a big way.

I was on Hobby King's website and noticed a new 60" pusher flying wing.
What got my attention was the stated flight duration on a single battery charge: 30 minutes plus!

As far as I understand, that far exceeds nitro/gas models.

http://www.hobbyking.com/hobbyking/store/__33295__Phantom_FPV_Flying_Wing_EPO_Airplane_1550mm_PNF_.html

[pmackenzie]

I have a slightly different take on this

Back in the late 80's/early 90's typical electric duration for a well built model would be 6 to 8 minutes.

If you recall EMFSO had a design contest for an aerobatic model that would fly for 10 minutes.
It was won by John Bec-Hansen's Fer de Lance. It had to be stretched a bit for the last 30 seconds, but
was a very nice flying model.
Second was Csaba Lemak's Bumble Bee. It had a geared ferite motor and easily flew the 10 minutes with sport aerobatic performance throughout the flight.
Both models used 1400SCR cells.

When the Eco8 helicopter came out it would easily do 12 minutes on Nicads.

When Lipos first came out they were rated 3C with 5C burst, so to replace a NiCad pack you typically used 8000 mahr cells. They were still lighter than a NiCad pack, but not by a huge amount.

My 40 size Nosen Citabria would do three 8 to 10 minute flights on a single charge of its 4S8000 TP pack.
My Logo 10 on the same pack flew for 20 minutes. There was video floating around of a Logo20 doing 25 minutes of 3D.

So why do we only get 8 to 10 minutes with normal models now?

A bunch of reasons.
- Power levels have increased. Now we want unlimited vertical and 3D performance, not sport aerobatic.
- Models are heavier, since the batteries and motor are lighter. You don't have to be able to build light anymore, everything works pretty well.
- We now only use part of the capacity available to avoid damaging the cells.
- in the race for higher "C" ratings Lipos have actually gotten heavier compared to the earlier cells. Power density is up, but energy density is down.
-The power systems are less efficient than the old standard Astro cobalts, particularly at part throttle.
  Cheap outrunners have great power to weight, but relatively poor efficiency.

In other words, nothing remarkable about 30 minutes.
A light efficient airframe, light weight lower C cells and modest power will get that.

Pat MacKenzie

[Gregor77]

The old dynam catalina with two 2200 3s packs could do 25 mins on one flight.  But by that time. I was bored. Lol.

[Michael]

I have a slightly different take on this


In other words, nothing remarkable about 30 minutes.
A light efficient airframe, light weight lower C cells and modest power will get that.

Pat MacKenzie

Everything you say is true, but it's no longer in the realm of careful light building.

The difference now is that's it's available off the shelf, ready to fly, and cheap.

It's mainstream.

[Gregor77]

All hail the king! 

[flying saucer]

I would have to agree with Pat, however where there has definitely been a breakthrough is in the very large models sucks as quarter scale 25lbs+ that can now easily be flown using standard electric components. As I understand it, even a few years ago this would have been unheard of.

[Michael]

Which part of Pat's post do you feel you have to agree with, and why?

What do you mean, "even a few years ago"?

I was flying an 18  pound 1/4 scale model 7 years ago with an off-the shelf power system, and I wasn't close to being at the leading edge of that part of the hobby.

[pmackenzie]

Shorter version - 25-30 years ago we could fly over 10 minutes on batteries with 1/3 the energy density.
lipos ~10 years ago allowed 30 minutes with the same models, but we have instead stuch with 10 minute flights but at higher power

Csaba made the world's first electric paraglider 7 years ago with what was essentially off the shelf R/C motor, esc and battery. Duration - about 30 minutes.

http://www.marksparaglidingpages.com/index.php?action=news&newsid=188

Pat MacKenzie

[Michael]

The ability to fly an electric model airplane for 30 minutes is not what I consider the "leap forward".

In fact, years ago, my first ever purposely-designed model using lipo cells flew for 45 minutes.

The availability of a mass-produced ARF electric model airplane, for under 100 dollars, that anyone can buy and fly, that is advertised with a standard flight time of 30+ minutes, is new to me.