How much water for a 1000K attempt?

I am working on the planning for a 1000K attempt. One question I have
is how much water should I launch with in my Ventus B? I can carry up
to 40 gallons (150 liters), but for a 1000K flight I will need to
launch in early weak conditions, followed by strong conditions latter
in the day.

Options would be to launch with 20 to 40 gallons. Twenty to thirty
would probably give a good balance for early climb and later running.

Any suggestions for an optimum balance?

Thanks,

Tim

At 04:54 01 August 2005, Ttaylor At Cc.Usu.Edu wrote:
I am working on the planning for a 1000K attempt.
One question I have
is how much water should I launch with in my Ventus
B? I can carry up
to 40 gallons (150 liters), but for a 1000K flight
I will need to
launch in early weak conditions, followed by strong
conditions latter
in the day.

Options would be to launch with 20 to 40 gallons.
Twenty to thirty
would probably give a good balance for early climb
and later running.

Any suggestions for an optimum balance?


The optimal, assuming strong enough conditions to support
1000k, is full water - so long as you can stay aloft
early in the day. The slower climb in the first 1-2
hours of the day is more than offset by the faster
cruise for the peak 6-7 hours later on.

9B

Andy Blackburn wrote:
At 04:54 01 August 2005, Ttaylor At Cc.Usu.Edu wrote:

I am working on the planning for a 1000K attempt.
One question I have
is how much water should I launch with in my Ventus
B? I can carry up
to 40 gallons (150 liters), but for a 1000K flight
I will need to
launch in early weak conditions, followed by strong
conditions latter
in the day.

Options would be to launch with 20 to 40 gallons.
Twenty to thirty
would probably give a good balance for early climb
and later running.

Any suggestions for an optimum balance?



The optimal, assuming strong enough conditions to support
1000k, is full water - so long as you can stay aloft
early in the day. The slower climb in the first 1-2
hours of the day is more than offset by the faster
cruise for the peak 6-7 hours later on.

Take off full, dump until you can stay up, just like at a contest. If
you can stay up easily when full, you are either flying in a great
place, or you took off too late!


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Eric Greenwell
Washington State
USA

Fill it to the top go early get high go fast and get home.

There is no substitute for wing loading!



ttaylor at cc.usu.edu wrote:
I am working on the planning for a 1000K attempt. One question I have
is how much water should I launch with in my Ventus B? I can carry up
to 40 gallons (150 liters), but for a 1000K flight I will need to
launch in early weak conditions, followed by strong conditions latter
in the day.

Options would be to launch with 20 to 40 gallons. Twenty to thirty
would probably give a good balance for early climb and later running.

Any suggestions for an optimum balance?

Thanks,

Tim

My two longest flights ever -- 970 and 930 km -- were at the highest
wing loading I could get.

If you're doing a flight as long as 1000km, you're going to be spending
the vast majority if your time (at least 70%, more likely 80% or 85%)
on course, not turning in lift. So top of the tanks, get high, and have
fun!!!

-tuno

Full water and wait for launch until you can stay up with full water.
The majority of the day will be strong conditions - you need the water
then more than you need an early launch. Wait until it is "cooking".
I have flown 23 flights of 1000 km + at Bitterwasser, Namibia (Africa).

wrote:
Full water and wait for launch until you can stay up with full water.
The majority of the day will be strong conditions - you need the water
then more than you need an early launch. Wait until it is "cooking".
I have flown 23 flights of 1000 km + at Bitterwasser, Namibia (Africa).

I'm sure that is right for Bitterwasser, but if Logan, Utah (I'm
assuming Tim is talking about flying from his home area), had those
kinds of conditions, I don't think Tim would be asking the question! The
various responses to his question suggest the best answer is "it depends
on your weather and the speed of your glider". I haven't flown at Logan
enough to know it's weather, but here in the Columbia Basin of
Washington State, it will take an early start in weak conditions. The
strong part of the day just isn't long enough and strong enough to fly
1000K. No has done it yet, but some have made 800+K.

Tactically, one should take off with full ballast early enough to have a
chance of completing the flight, and drop whatever it takes to stay up.
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Eric Greenwell
Washington State
USA

At 18:48 02 August 2005, Eric Greenwell wrote:
Tactically, one should take off with full ballast early
enough to have a
chance of completing the flight, and drop whatever
it takes to stay up.

That's one approach - but keep in mind that the difference
in climb rate between full and empty (in a 45-degree
bank) is less than 50 fpm.

Furthermore, the McCready-derived XC speed differential
for full versus empty water is 6-9 knots. The actual
difference with streeting, etc. may be greater. That
amounts to about an hour less time on course with water
versus without. To break even without ballast you'd
have to make about 80 miles before you could get started
on course with ballast.

I'm thinking this would only be true if the day developed
with either very weak (0.5-1.5 knots climb, dry) or
very narrow thermals for a very long time (1-2 hours).
Under those conditions I don't think you're making
80 miles even if you have Helium in your wings.

I'd recommend taking tows until you can stay up with
full water.

9B

Andy Blackburn wrote:
At 18:48 02 August 2005, Eric Greenwell wrote:

Tactically, one should take off with full ballast early
enough to have a
chance of completing the flight, and drop whatever
it takes to stay up.


That's one approach - but keep in mind that the difference
in climb rate between full and empty (in a 45-degree
bank) is less than 50 fpm.

The _sink rate_ in calm air might differ only that much, but I've seen
much bigger differences in climb rate in contests, due to the width of
the thermal and the ability to maneuver. In addition, the glider with
the lighter wing loading can often continue up another 400-500' in good
lift, while the heavier can't. And this is with climb rates in the 2-4
knot range, not just really weak conditions.

I've experienced these differences in gliders only 1 pound/sq ft apart
in wing loading. It's not necessary to be empty to have a worthwhile
climb advantage in modest conditions.


Furthermore, the McCready-derived XC speed differential
for full versus empty water is 6-9 knots. The actual
difference with streeting, etc. may be greater. That
amounts to about an hour less time on course with water
versus without. To break even without ballast

I wasn't suggesting Tim fly without ballast, only that a partial load
might be a better choice if he could start 30-60 minutes earlier.

you'd
have to make about 80 miles before you could get started
on course with ballast.

If you flew 6 hours in good conditions, you'd have an extra 36-54 miles
over the empty glider. If it got started an hour earlier in the
conditions we often have, it could make that 50 miles pretty easily by
starting downwind.

I'm thinking this would only be true if the day developed
with either very weak (0.5-1.5 knots climb, dry) or
very narrow thermals for a very long time (1-2 hours).
Under those conditions I don't think you're making
80 miles even if you have Helium in your wings.

I'd recommend taking tows until you can stay up with
full water.

I think it depends very much on your weather and your glider. I'm sure
that's good advice for Tonopah and other strong areas, but I don't think
it will work here in the Pacific NW. Tim will need to experiment some,
and, I hope, report back to us in a year.

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Eric Greenwell
Washington State
USA