prop formula

Fri Oct 22 08:59:38 AKDT 2004

Here we are in an event which could easily be mistaken for highly technical in nature ... but it's really an aerial beauty contest. 

Feeling foolishly philosophical

Dean Pappas
Sr. Design Engineer
Kodeos Communications
111 Corporate Blvd.
South Plainfield, N.J. 07080
(908) 222-7817 phone
(908) 222-2392 fax
d.pappas at kodeos.com

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Jeff H. Snider
Sent: Friday, October 22, 2004 12:03 AM
To: discussion at nsrca.org
Subject: Re: prop formula 

I don't want to try and decide what portion of any endeavor is art
and what is science.  The Wright brothers were dilettantes very short
on art but long on luck.  Any less lucky and physically talented
people would have failed to fly that contraption of theirs.  A great
deal of money and time was recently spent demonstrating that fact,
unfortunately for all the people involved.  (If you ever have a
chance to visit the Curtiss Museum in Hammondsport NY, along with
a huge and wonderful display of aviation history there's an infectious
undercurrent of distain for all things Wright.)

I'm in favor of art, and I believe a good scientist is just a kind
of artist who keeps good notes and follows a very strict methodology.
What I said was "Maybe by then science will have more fully displaced
art."  Meaning with a full molecule-by-molecule simulator a scientist
could create and test a new airfoil in under a minute, instead of
weeks painstakingly crafting a model and testing it in a wind tunnel,
so we can accumulate a lot more facts and rely less on intuition.
Science never eliminates art, but I'd rely on facts and technology
in place of guesses any day of the week.

I haven't in fact seen a good Analog Engineer.  I didn't know they still
existed.  But then I've been a software guy too long and all that
hardware stuff just appears on the loading dock courtesy of FedEx.
Nobody actually builds it, do they?

I am indeed flying Intermediate next season.  I'm desperately trying
to remember all the maneuvers in the correct order before competing
this weekend at BARKS.  Thank heaven for the simulator.  It has
paid for itself in YS 30% fuel alone by now!

	-Jeff

P.S.,
In terms of progress and a by-the-molecules simulation of air, the
numbers don't leave much room for error.  Take the number of molecules
in a liter of air (3e22), the radius of the space a molecule has
to itself at an instant of time (30 angstroms), the speed of the
molecules (3e12 angstroms/second), and you find the need to do 3e33
calculations per second.  Today we can do 3e9 calculations per
second, so we need to get our computers 1e24 times faster to compute
this liter of air in realtime.  Of course it takes more than one
calculation per molecule, and conversely of course really smart
algorithms can reduce the number of necessary calculations by maybe
a factor of billion.  But just to keep things simple, if computers
double in speed every 18 months, and it takes 80 doublings to reach
1e24, that's 120 years.  If I'm off by a factor of a billion, it
takes 75 years.  And unless we forget the "supercomputers", the
supposed fastest in the world was running at 36 teraflops in
September: 1000 times faster than today's desktop computers, meaning
the scientists get there 15 years ahead of us desktop computer guys.
If I live to be a really old scientist, maybe I'll see it happen.
For now I'm just trying to leave myself enough space for a half
decent cobra with half rolls and get my outside loop to end anywhere
near the same altitude where it started.

P.P.S.,
To take the fun out of a seemingly silly assertion and simultaneously
demonstrating my analytical bent one last time:  Supposing I stretch
my fuel to get 60 minutes flight time out of a gallon (this is a
140DZ we're talking about), and supposing I get a great deal of
$16.50 per gallon on my fuel (this is YS 30% fuel we're talking
about), I only need to have flown 12 hours on the simulator to equal
its cost in fuel.  I would guess I average at least 20 minutes a
day, so it pays for itself in fuel alone in 36 days.

John Pavlick writes:
> Jeff,
>  Science displacing art? Obviously you haven't seen a good Analog Engineer
> design and test an RF circuit. The only thing missing is the Dragon's Blood
> and Eye of Nute. Your method of studying problems is refreshing though. I
> wish some of the Engineers that I have worked with subscribed to this method
> of thinking, rather than "Plug and Pray". You will be a formidable adversary
> next year (I suspect that you will be flying Intermediate). If only I can
> turn you to the "Dark Side"...
>  I was thinking of trying a 3-blader myself. For now I just want to get
> something reliable / proven to practice with. I have to re-train myself to
> fly the 2 meter planes s-l-o-w-l-y. My lasting impression of Pattern comes
> from watching Tipo's and Curare's with retracts and pipes. I still can't
> believe these new planes don't tip stall when they're landing as slowly as
> they do. I have to make a conscious effort to concentrate on a new
> technique. I don't think the prop will be a major concern yet.
>  As far as technology / progress goes, you might be wrong on that
> calculation. Some of the things we do on desktop computers today were not
> even possible on super computers a decade ago. Besides, all of this CAD CAM
> stuff is nice but keep in mind that the Wright Brothers didn't have any of
> this. You can't wait for technology to catch up with your creativity - come
> on, get out your slide rule...
> 
> John Pavlick
> http://www.idseng.com
> 
> 
> > -----Original Message-----
> > From: discussion-request at nsrca.org
> > [mailto:discussion-request at nsrca.org]On Behalf Of Jeff H. Snider
> > Sent: Thursday, October 21, 2004 6:18 PM
> > To: discussion at nsrca.org
> > Subject: Re: prop formula
> >
> >
> > Thanks for the feedback.  Nothing that can be done with paper
> > and pencil, or keyboard and cpu, replaces going into the field
> > and making some real world observations.  But having an
> > analytical brain and being a former student of Math and Physics
> > I really like being able to calculate my way through a problem.
> > Plus having a theory to support what I see happening in the
> > air does a world of good for my rate of improvement as a pilot.
> >
> > I missed reading about Jim Woodward and his 18x10 prop.
> > Where was that?
> >
> > About multi-blade props.  APC's website says they roughly weigh:
> >  17" 2 blade .07 lb
> >  16" 3 blade .10 lb
> >  15" 4 blade .46 lb!
> > Is that a typo?  Does a 4-blade add over 6 ounces to your
> > nose?  I'm ready to give this multi-blade bandwagon a test
> > ride, but no one is flying a half-pound prop!  Are they?
> >
> > As Dean says, this is fun stuff!  I need to read up on
> > that guy Renard.  Anyone have a suggestion for a good book
> > on the subject?  I have "Model Aircraft Aerodynamics" or
> > something similarly titled, which gave me my first exposure
> > to the amount of art pervading the science of aerodynamics.
> > (By my calculations, at the present rate of improvement
> > in technology we're 120 years away from being able to use
> > our desktop computers for a full and complete molecule by
> > molecule realtime simulation of air flowing over a wing.
> > Maybe by then science will have more fully displaced art.)
> >
> > 	-Jeff
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