On Jul 4, 7:56*am, T8 wrote:
On Jul 4, 8:29*am, Scott Alexander
wrote:



I have been told over the years two consistent things: when trying to
achieve the fastest possible cross country speeds, *1. Try to minimize
circling as much as possible and 2. Fly the true maccready airspeeds
between thermals.

But these two things contradict. *The first couple days I flew at
Perry this year, I flew true maccready airspeeds between thermals.
The lift was strong, 5-7 kt thermals to 6-7,000 feet. *So I flew about
70-80 between thermals. *My average speed was then in the upper 40's.
Then for the later part of the contest, in the same weather
conditions, I delibertly did everything I could to reduce my %
circling. *I flew 50-70 kts between thermals and drastically reduced
my circling. *I had one flight with 15% circling and my resulting
average speed was 52 mph. *So by slowing down I had a faster speed.

I understand that thermal density plays a big part in deciding what
speed to cruise at. *If the thermal density is lower, it may be best
to stretch out the inter thermal glides to stay in the altitude power
band. *I fly faster when the lift sources are obvious, gaggle, clouds,
birds, smoke. *But when the lift is invisible, I slow it down to
stretch out my glide. *I also slow waaay down if there's no good
landable fields insight....for safety.

So is there a balance between % circling and true maccready speed to
fly? *What are some things that can flex your true maccready speeds up
or down?

Must read classic:

http://www.betsybyars.com/guy/soarin...a/72price.html

I recall a talk a few years ago at the convention by Carl Herold
titled something like "If you fly MacCready you will lose". Pretty
rough title that drew a lot of people to the talk. The main idea was
that you have to base your speed to fly on your actual climb rate, not
the vario reading or the average of the vario reading but what is
actually happening to the glider. Also, by staying higher for longer
you take advantage of true airspeed benefits of flying in thinner
air. At the time Carl was flying pretty impressive cross countries in
his Nimbus while circling something like 10% of the time, or less.

Typically in the Cherokee I set the ring at about half of what the
Vario is saying and figure that is a good number. I think that % of
time circling is more important than speed between thermals. No
forward movement is going to kill average speed a lot more than being
off by 5 or 10 mph for a little while. I've been working a lot more
on minimizing my circling time on recent flights.

I noticed that on your second day at Perry your average climb was
actually down in the 250 fpm range but your interthermal speeds seemed
about the same as the day before when the average climb was over 450.
I'm no expert but I'd guess that is why you spent 40% of the time
circling on day 2 vs 25% on day 1.

Funny, the guy flying probably the slowest glider on RAS trying to
talk about how to go fast.