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Electric Stunt => New electronic technology => Topic started by: Air Ministry . on April 21, 2018, 07:04:20 AM
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Anyone ever tried a Rubber Powered Control Line Ship ? Tried a few stunts with it ?
Would it be possable now with some electric limiter / goveoner , somewhat like Igors ' G ' thingo ,
to get a big grunty rubber band motor to ' tick over ' for 6 1/2 minutes , maybe coasting downhill . :-\
Some huge ultra light models what Id have thought , maybe a C F ( Helicopter boom ? ) Motor / Fuse Crutch ,
a wing spar , the rest pretty much ultra light F F type costruction .
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The Olde Morane , eindeker , Tabloid , Bristol Scout & suchlike , or thereabouts . Perhaps.
Old Comet Rubber F2B at 400% would be 60 inch span .
just a thought , thinking it might now be achievable , even if multiple sequetial ' motor tubes ' for flight duration .
any Wakefiels of FF rubber buffs know some sums on output/ duation etc . . .
Turn of the century there was a 6 ft span Folkerts FF Rubber thing with a 24 inch prop , Fairly basic lines for strength to weight .
naff All Weight , naff all load at high G square turns . Deadly serious on this .
supose someone will tell us the price of Perelli Rubber & we'll go into cardiac arest . >:(
(https://outerzone.co.uk/images/_thumbs/models/117.jpg)
flogged from Outerzone
(https://outerzone.co.uk/images/_thumbs/plans/4199.jpg)
(http://test.fiddlersgreen.net/aircraft/Antoinette/IMAGES/Antionette-VII.jpg)
or some other hieneous contraption . :-\
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Methanol specific energy: roughly 50MJ/kg (Mega Joule, from Wikipedia (https://en.wikipedia.org/wiki/Energy_density#/media/File:Energy_density.svg)).
LiPo specific energy: roughly 500kJ/kg (From Wikipedia (https://en.wikipedia.org/wiki/Lithium_polymer_battery)).
Twisted rubber band specific energy: roughly 6.6kJ/kg (from Wired (https://www.wired.com/story/how-much-energy-can-you-store-in-a-rubber-band/), of all places).
So, no. A rubber band would have to weigh about 75 times more than a LiPo to have the same energy, and then the plane would weigh too much.
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If you take close look at F1B you will see that a rubber motor can beat a piston engine or an electric motor, but only for a few seconds.
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It HAS been done, and even demonstrated at a Tucson VSC many years ago. Keith? Any detail on date and "guilty party?"
I think the model was an early Stanzel low-wing design, like their later G-Shark types. It did work, apparently well. I don't recall if the flier tried any figures.
A problem with most rubber powered flight is the initial power burst. It lasts only the first several seconds after prop release, then settles down to a fairly long decreasing plateau. Most indoor FF rubber models, so I hear, land with a few turns still in the motor, but not enough power to maintain even level flight.
Of course, another problem for rubber power is duration. That ukie didn't stay up anywhere near long enough to do many figures, and glided in with the prop free-wheeling with all or most winds spent.
Those Stanzel models were either before, or about the same time that, U-Control (Jim Walker's patent) got popular. Stanzel and others tried variations to avoid 'licensing' fees to use Walker's system commercially. It makes an interesting buncha pages in Charles Mackey's great book, Pioneers of Control-Line Flight.