Winter / Focus / Prop Drag

[Larry Diamond]

This has been a very interesting thread on Prop Drag Vs Idle..

Couple of thoughts...

1) From a non-engineering mind or non-aerodynamics mind, Stop Vs Idle seems
to be about the same as a motor vehicle. The vehicle slows better when the
tires are not in a skid.

2) If there is enough interest there is a way, not only to prove
this theory, but show it's predictability with Prop Disc Size, Idle speed, #
Blades, and to a limit that nature allows, Temperature and Humidity. Also to 
show the relationships on how one effects the other or how a subset effect a 
single item, or etc...

The question is, "Who is willing to take this on?"; and, is it of any real 
value
for us to understand. For my skill level the answer is "no". For the Top 
Guns and Designers of Pattern Aircraft, this may be some interesting data to 
have.

Here is what I think the experiment would take.

A) A committed top pilot and caller (Troy N., Dave L., etc...) that feels 
this is needed data and is committed to flying the same exact way, with 
precision, to gather the best data. Precision would mean time Vs throttle 
setting, altitude, attitude, etc....

B) Flight monitoring system that can down load data to a PC for collection
and archive. Accuracy and repeatability is critical.

C) A team of folks that can work together to collect the data and keep the
pilot performing the sequences the exact same way every flight and every
attempt.

There is a scientific process that (if successful) will not only allow for a 
single solution, but will also offer a formula for a given platform by 
changing a predetermined set of variables. The formula will also be good for 
parameters beyond what was tested.

The key point here is, "This is a long tedious process and the level of 
detail
required, not only to task but also documentation, is very intimidating to
most." However, if done correctly...It works with very predictable 
solutions...

The down side...

The formula will not be the same for every plane, even if it's the same 
model
with the same set up built by the same person with the same jigs and tools 
and using the same fuel. However, the relationships should hold true for 
similar airframes.

Upside...

We would know that it's a scientific based conclusion and can offer
what has the most effect, # Blades, Idle Speed, etc...

Depending on the desired output, it can take from days to literally months. 
The more complex, the longer it takes.

I would be willing to offer some assistance and guidance, but would not 
tackle on my own.

If you think you might be interested in this project, let me know off the 
list.

Larry Diamond
NSRCA 3083
AMA 5024


----- Original Message ----- 
From: "Del Rykert" <drykert at rochester.rr.com>
To: <discussion at nsrca.org>
Sent: Thursday, December 04, 2003 7:59 PM
Subject: Re: Winter / Focus / Prop Drag


> If you are looking for irrefutable proof go up in a full scale or for R/C
> take a clean design with low idling engine up and do some downlines. Bump
> you idle trim up on some and leave it as low as you can on others. Will be
> more pronounced with 4 cycles turning big side blade props.
>
> For more proof..  Ever see what happens to a model that kicks back up in
> the
> air but the prop stays on windmilling...  You can't fly it any more except
> like a ton of bricks.. If that doesn't convince you nothing will. I flew a
> friends model that it happened to. It only broke the prop on landing in
> weeds as it landed on its nose.
>
>      Del K. Rykert
>      AMA - 8928
>      NSRCA - 473
>      Kb2joi - General
>
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