Variable Pitch Prop Spring Design and Re: Article, "Fliagra" F1d.

From: Fred or Judy Rash <frash_at_chartertn.net>
Date: Fri, 25 Mar 2011 22:26:02 -0400

Ignacio and Mark and All,

Disclaimer: I don't fly F1D or anything requiring much indoor expertise.
Neither do I have an engineering degree. However, I did once about 35
years ago try to design a twanger tow hook for towline glider using a
fishing scale. The engineering handbooks have the spring design
equations. If you know what you want, and have a couple of points that
are close, a few hours with a spreadsheet might help a lot. Use your two
points, also try 6 turns of 0.007 wire. Also remember that the diameter
of the winding form is a variable that you can play with. I don't
remember the equations, but it was not incomprehensible.

Tapio Linkosalo once posted that the indoor model should reach the
ceiling at the inflection point in the torque-turns curve, so maybe the
prop has returned to its lower pitch setting at about that point on the
torque-turns curve. I hope that I quoted him approximately right.

Please let us know if it works! Thanks.

Fred Rash

On 3/25/2011 9:15 PM, Mark F1diddler wrote:
>
>
>
> --- In Indoor_Construction_at_yahoogroups.com
> <mailto:Indoor_Construction%40yahoogroups.com>, "izgo" <izgo_at_...> wrote:
> >
> > Mark, sorry I'm bring back this old tread, but its very interesting
> for me, and not much else found using yahoo search feature.
> >
> > I like to know about the springs, if you have managed to make a
> conclusion on best springs for CatI (maybe CatII too) VP tunning.
> >
> > Thanks!
> > Ignacio-
>
> Sorry, since that article I haven't had much opportunity for pure F1d
> experimentation. All the spring configurations I've tried for low
> ceiling (from 4 coils of .008" wire to 9 coils of .009" wire) have too
> fast a rate at the wrong time in the flight profile. I want a spring
> that closes steadily (or at least more slowly) from 2 minutes after
> launch to about 25 minutes, and doesn't bump ceiling.
> Mark F1diddler
>
>
Received on Fri Mar 25 2011 - 19:26:07 CET