I really have no time for answering questions at present due to the F3B
WCs departure scheduled early next week, but this one intrigues me.
-----Original Message-----
From: Dick Barker <[EMAIL PROTECTED]>
>What I need now is for Gary Whitney, Joe Wurtz, John Hazel, Dave
R.(Barnyard
>Science), or others to confirm that the numbers makes sense and how it
would
>translate to height on the 11.5 oz plane and on the newer 9oz one.
A few comments... The general analysis looks to be a "quick look" ROM (the
same kinda thing that I do for sanity checking). From a details
perspective,
I'd bet that the acceleration is not constant, but does some form of
asymptotic
taper to zero (otherwise you could keep going around long enough, and you
would need highly swept back wings... :-) ). This makes a dramatic
difference
in the endspeed calculated.
For example, let's assume that the acceleration follows a linear curve, from
max.
at start, to zero at finish (460 degrees of rotation). We will assume the
.625
second elapsed time (seems a bit fast to me, but I've not timed it).
This produces an endspeed of 97 ft/sec.
More reality factors... The acceleration is more likely to be more of a
polynomial
rather than a line, which will bring down the endspeed more. Another caveat
is that the "arm" from nose of Mr. Barker to the CG will decrease due to
the counterbalance requirement (might be a small factor...). There are
lots of "real world" factors that should be understood and included before
dispensing with the "grain of salt".
I make no claims for accounting for
all of the correct input assumptions here, just had to do a quick look at
the problem with a first order cut...
BTW, for an endspeed of 97 ft/sec, if flown well in the climb with a clean
plane,
should get about 90 ft of altitude. This is in agreement with Dicks
practical
experience. With the 84.6 mph, the potential is about 130 ft (using a good
pullout and climb profile, and a Cdo of 0.02), which sounds a bit
optimistic.
Back to building F3B planes....
Joe
PS The Cdo above is only good during the higher speed portions of the
pullout. The slow speed Cdo can be a bit higher :-)... but does not factor
in much of a delta in height. All of the real losses are at high speeds.
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