All FLPHG stuff goes here
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By W9GFO
#386884
freeflight wrote: How much less efficient are we going to see? 50%?
I don't know. I would guess 30 to 40 percent. I would be quite impressed if it were less than a 20% difference.
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By TjW
#386912
Watson wrote: This is kind of embarrassing, but I don't know if you know that gasoline HAS to catch fire when in use. While electric systems don't even need to have a spark to work.
This is kind of embarrassing, but I don't know if you know that gasoline DOESN'T burn unless it has oxygen. While batteries have the oxidizer built right into them, like a rocket engine.
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By Watson
#391119
I have finally tested my E-JetPack!

Here is the footage of the 1st flight:
http://youtu.be/eCcmfe26Iis

It was only a trial run, in order to check if everything worked well together. So, I was winch towed to 500ft, turned the engines on in flight for a little bit, then turned off and landed.

I still need to make some adjustment to the structure that holds the ducted fans (it was pushing down my helmet), but the glider had a very noticeable speed up (the GPS tracking is a bit off though).
By blindrodie
#391130
:mosh: :mosh:

8)
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By DMarley
#395331
Too bad watson's flying Cuisineart just doesn't accelerate enough air fast enough for their to be enough thrust to allow for climb performance. Any climb performance. I know for a fact that if he geared these same two motors down to drive a 48" to 50" diameter prop, he would get some usable thrust. A medium sized pilot requires at bare minimum of 8 kW of power to see a usable climb in an aircraft with very high aeroelasticity such as a flex wing Hg. But, that power has to be put into the air in the most efficient manner possible. The larger and slower rotating the propeller is, the more efficient the energy transfer. At least at the airspeeds we are talking about (zero compressability). The propeller tips must not approach mach for any efficiency to be had. Even if one was to enshroud a large enough prop, the form drag of the shroud would negate any benefit, especially while soaring. The only conditions in which a shrouded prop or fan makes sense is when approaching mach airspeeds (compressible flow).

Watson most likely spent way too much for those larger fans, and now has discovered that fans are terribly inefficient at low airspeeds. Next time, please do more research, and run the numbers. Derive your information from believable sources (NASA, NACA, research papers, etc.) rather than manufacturers that want to make a buck off of gullible people and modellers. Read research papers and engineering texts to find the algorithms to calculate thrust. It ain't rocket science. If you have to, brush up on your calculus, physics, and trig. It ain't rocket science. That's why you saved all your texts from college, right?! :)
By Roadrunner
#395358
These Electric powered launch Engines look pretty cool. Heck, I for one, would likke to give one a try.