Re: Increasing duration in F1D - prop settings and back-off

From: John Kagan <john_kagan_at_hotmail.com>
Date: Mon, 19 Mar 2012 03:35:53 -0000

Hi Tapio,

Launching with no backoff is a good goal. There is a lot of energy in those top end turns - much more than cruise or descent turns. You want all of that energy. Energy = time :)

I recommend charting the RPM during a flight. That will give you a clear picture of when the prop starts and finishes changing, and how much it changes. This is a more accurate method than watching the climb - IMO.

--- In Indoor_Construction_at_yahoogroups.com, Tapio Linkosalo <tapio.linkosalo@...> wrote:
>
>
> Last night when making motors (for F1B...) my thoughts turned to
> Belgrade, again. Started to wonder what to do to climb up the ladder of
> duration (I'm currently at 26 mins, so next target should be closer to
> 30...)
>
> Comparing my flight profile to the one that John was flying in 2010, I
> was surprised to see him taking almost 20 minutes to climb to the
> ceiling. My model was at the apex of the flight profile in 10 mins... So
> obviously this is where the missing flight time lures. One thing that I
> need to fix for next summer is to modify my VP's to take higher max
> pitch, currently I'm against the top stop (cannot adjust any further),
> and need to take backoff to avoid hitting the ceiling.
>
> So this is the first question: should I aim to fly with no backoff at
> all, and just add the max pitch to control the amount of the climb?
>
> Second, my props use a "soft" spring with multiple turns. Thanks to very
> informative discussion with the Brits last summer, I now understand that
> this kind of spring works with a rapid movement from high pitch to low,
> and indeed this was showing in my flight profile last summer: after the
> apex at 10 mins, the model started descending, until at around 14 mins
> the pitch changed, resulting in a shallow second climb and then cruising
> down for the rest of the flight. Maybe a "harder" spring of fewer turns
> would enable similar action as Treger was showing, with a long cruise
> not changing much altitude throughout the middle parts of the flight? I
> suppose this would, however, make the adjustment of the spring
> pre-tension much more sensitive than with a softer spring?
>
>
>
> -Tapio-
>
Received on Sun Mar 18 2012 - 20:35:56 CET