Title: Re: world's fastest model plane
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This is probably too far off the soaring topic...but
anyway...
Turbines do nto increase substantially the amount of thrust
with speed. Some Ram air effect happens, but on the type of turbine we
have that is not that much of an increase. The thing that it does do is
maintain a MUCH higher amount of thrust at any speed. For example: a
DF may produce 12 lb of static thrust (0 mph) but at 200mph it may produce only
1lb of thrust. A Turbine will produce the same static thrust of 12lb but
will produce probably 11-12lb of thrust at 200mph! This makes continous
acceleration possible...and VERY high speeds possible.
Jason Werner
> I remember reading that the turbine powered RC jets are
the
> fastest, but because of the danger, no one
will sanction
> an actual speed contest with the
turbines. "Demonstration"
> runs have
been made at around 280mph, but these were made (snip)
I was told that the problem with turbine engines is that
their thrust increases with airspeed. Propellor and ducted fans are the
opposite - as you get faster the engine gets less efficient so they're
inherently self limiting.
I can understand why the AMA is a bit nervous about
turbines. Our radios have a nominal range of a half mile or so and we all
know just how difficult it is to orient even a big sailplane at that kind of
distance. A jet flying at that 'demonstration' speed is going to go out of
visual and radio range in about 10 seconds.
Its probably pointless to figure out exactly how fast a
model could go. By redefining the word 'model' and increasing the budget a
bit (OK, rather a lot) we could probably make missiles that go well above
the speed of sound. All this would do is replicate the ME163 and X1..X15
programs half a century or so after they were first done. I can see the
attraction in this but to me its just not the same as seeing how fast you
can make a sloper go - you could say that soaring is an
artform.
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