On May 18, 3:33*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

Noel,

The best way to think about this is to do a few thought experiments.
First you need to say what is the average climb you expect for the day
that you are willing to take, lets say 5 knots. What is the speed you
can achieve with that if you were in pure MacCready flight mode.

There are side by side cloud streets one with a 5 knot thermal every
10 miles and one one where you can fly along at 50 knots for the whole
flight. Which one will get you home faster? What speed would you fly
between the thermals on the one street.

Now combine the two together. How would you fly differently? You can
fly faster than you have in the low lift under the street, but take
advantage of the stronger cores every few miles by being below the
clouds enough to make it worth while to stop and turn in the strong
stuff. If it is a really good street you fly faster but only pull up
in the strong cores and climb back to cloud base without turning.

Reichmann covers this well in the section on Dolphin flight models and
concludes:

"For dolphin flight a new theory results which contains the "classic"
theory as a special case. The speed ring and similar devices retain
their validity. Thus, according to the theory, the ring is set
exactly the same for "classic" flight (apart from possible tactical
considerations, of course). It has been proven that "force" dolphin
flight causes cruise-speed losses."

So you speed ring or speed to fly vario is going to tell you to slow
down in lift but not all the way to climb speeds if you are cruising
with a MC 5 and your in one knot lift.