On May 18, 5:33*pm, "noel.wade" wrote:
All -

I've been flying with the assumption that flying slow in cloud-streets
is always a good idea. *But in looking at some of my OLC flights I
wonder if my logic is faulty and I'm hurting my speed. *Anyone with
lots of OLC or contest experience care to offer feedback? Details
below...

My thinking has always been that your forward speed in a circling
climb is effectively "0" (slightly more or less than 0, based on wind;
but call it 0 for the sake of argument). As a corollary, anything you
can do to maintain or gain altitude while retaining forward progress
on-course is a "win".

Therefore, I've always been slowing down in cloud-streets or under
large clouds with apparent extended areas of lift. *If I'm anywhere
near cloudbase (say, less than 1000' or so), my logic has been that
I'm not gaining enough altitude to stop and circle with that zero
forward speed. *Instead I try to maximize the lift by flying straight
ahead (or slightly curving my path to stay in the zone of lift) at
slow speed (say 50 kts).

Rough math to support my thoughts:
With a cruise speed of 75 knots and a time-in-climb around 25%,
average forward speed is roughly 56 knots (75% x 75 knots). *This is
so close to the 50 knots (while flying in a cloud-street) that it
seems to support my behavior... *But maybe I'm missing something?
Maybe the gains I'm getting are not enough to offset the slower cruise-
speed during these times? *I should point out that I fly in pretty
strong thermal conditions at my local site (Ephrata, WA).

I could throw in all of my various caveats and details and thought-
processes, but rather than make this a really long post I'd love to
get some thoughts and feedback. *Anyone have pointers, ideas, see
fallacies in my process, etc?

Thanks,

--Noel

Check out this site by Bob Hanson. He made a java app that directly
deals with your question with a cloud street strategy feature.
To get to that feature, look for the dropdown menu that says "These
Conditions" and choose the option at the very bottom "Cloud Street
Flight Strategy Comparison".
http://www.stolaf.edu/people/hansonr/soaring/spd2fly/

Essentially, it brute forces a lot speed to fly calculations to try to
find the optimum theoretical speed. With the given conditions it
finds the best results out of the batch it then takes the
corresponding airspeed and outputs it to the table. Some interesting
numbers it comes up with... Of course the results are subject to
interpretation based on real life results, like MacCready theory.

~Andrew