Correction....I mistakenly typed trailing edge re. the electrified Lazair. It is of course powered with tractor motors off the leading edge. I had thought the concept would lend itself well to Carbon Dragon/ULF-1 with pushers off the trailing edge ala Espirit DD 1.
Michael
On Dec 19, 2012, at 11:21 PM, Michael McKeown wrote:
On Dec 19, 2012, at 10:45 PM, russell wilson wrote:
regenerative braking to generate electrical power on a sailplane is pointless......once a prop starts windmilling it becomes an air brake not the size of the prop but the entire disk area...you will generate moor drag much moor than you will get back in lift/electrizerty.
Well, not so crazy really....and it is being done. The idea is to use a motor cruiser glider like a sailboat. Sailboats use the electric motor when the wind isn't right, and use a regen prop in the water when the wind is cranking to recharge the batteries for when the wind is wrong and the motor needed again. In a motor cruiser glider, one can ride a mountain wave up to 20K, then regen back down to 5K. In between cloud streets cruise with the motor, but then when you're over a ridge or under a cloud street, use nature's lift to get up, then regen back down again and use that new electricity to once again cruise under power to the next lift band.
the idea of turning the prop over to match air flow so the prop gives no drag .....how will you manage this when you have diferent air speeds all the time?
How will I? I'm not. I said I read about a plane that is doing this. I'd have to dig around to find the reference, but it was just in the last couple of weeks I read about the plane. And yes, more or less my understanding of how they are doing it is connected to airspeed and electronically telling the controller how much power to apply to turn the prop at the right speed. I don't know (and I don't think the article made it clear) if they are taking the data from literal airspeed, or perhaps measuring drag at the motor (if there is a regen current being created, that could be measured and enough power supplied to the motor to cancel the regen effect).
I am excited by the electrified Lazair. Twin pushers off the trailing edge of the wing using large size model airplane motors. I believe he says he did his complete installation including chargers for about $5k, and he's flying off water on floats and the performance looks great. Keep in mind in his video that shows the one long take off run that he hadn't learned yet how to get it on step. Watching him fly ridge lift from a tree line with power just above idle is pretty cool. I think an installation that like would lend itself well to a Carbon Dragon/ULF-1 type plane.
Michael McKeown
Starflight Composites
www.starflightcomposites.com 