Sunglide

I would like to see a new class in soaring competition
in the future. I am thinking of a class where one is
allowed to utilize electro-solar energy beside the
usual ways to generate lift.
As things goes today we use slopes, waves and thermals
to keep us flying and that governs the way our glider
are built and the way our competitions are constructed.
I think it is time to think new and move ahead.
If FAI would declare a competition for, lets say, the
summer of 2008 in witch glider equipped with solar
panels and electric motors could race it might promote
the industry to develop new machines.
I am just a layman, not an engineer, so please take
this as my humble vision of things to come. I really
don’t know if this is possible but I believe it is.
Imagine a modern 18 meter glider with solar panels
on all available surfaces and a fixed electric motor
in the nose or on the fin. Just like a modern electric
model glider. The power from the solar panels would
probably not be sufficient to make the glider climb
but well to enormously extend the gliders effective
glide ratio. When you are thermaling under a cloud
the solar panels would probably not deliver very much
power and so the motor would just spin along, neither
puling nor inducing drag. When you leave the cloud
to speed on to the next thermal the panels will be
exposed to the sun and the motor would start to pull.
There would be no need to fold the propeller blades
and no need to fold the motor in to the fuselage since
the motor at all times would produce thrust to out
weight the induced drag.
Maybe it is possible to make a system like this to
function as a generator in a strong thermal. If you
carry batteries you might be able to charge them by
letting the motor windmill while you climb and then
use that energy in the final run. Of course batteries
could also extend your glide range extensively in the
same way as a turbo if you screw up far from home.

I don’t think it would be a big problem to keep track
of how much power that is gained via the solar panels
and how much power that is taken from the batteries
if that would be an issue with the rules of a competition.
A big competition could maybe promote the industry
to start thinking and developing and gliding as a whole
would take a step further.
Finally, I apologise for my English. It is not my mother
languish.

Finally, I apologise for my English. It is not my mother
languish.

No need to apologize. Your English is better than some around here
that have spoken it all their lives as their mother language - and some
of them can't read/write it at all. Most of us in the US don't have a
second language so your already one up on us.

But back to the intent of the post.

I think the idea is a good one. Unfortunatly I just don't see it
happening until the technology needed is reduced in price considerably.
The model builders have some pretty efficent and probably powerfull
enough motors to be practical but I just haven't seen anything in the
way of solar panels that have the combination of output/weight/cost to
use in such a sailplane. If they exist I'd sure like to know about
them. A practical solar/electric sustainer motor might go a long way
to making soaring, in general, more popular.

Till then small turbines running on BioDiesel may be the best way in
the near future to make enviromentally friendly motorgliders.
==============
Leon McAtee
Bablefish.com .. second language for the ignorant

A diana needs an effective power of approx 55N*30m/s= 1650 watt

*Total usable surface for solar panels 8 M^2
*Max sun power about 1250 watt/m^2. Let`s say, average European
conditions: 350 watt/M^2.
Ordinary solar panels have a coefficient of about 12%. Best available
are 25% but perhaps they`re way too expensive (about 250.000 euro`s for
the Nuna for example)

Let`s say 18%, that`s a reduction of sink of about 30% (at 100 km/h)
leading to a glide ratio of 1:72. Heck, that`s more than the Eta!!!


Also take a look at:
http://www.solar-flight.com/med_res_wing_mount_copy.jpg

Doesn`t look too bad although I prefer the Diana...