This Performance discussion is broken into Wing Loading, and Glide Ratio.

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This info is considered Public Domain, so use it as you wish, but not for commercial purposes.  It was created to increase the joy and enjoyment of flying gliders/ soaring. WARNING: All info is unsubstantiated, so use it at your own risk.

Wing loading.

Wing loading can be increased by pulling g's.  If you want to keep your wing loading to a minimum, then don't pull back on the stick so much.  Of course you need to put the airplane where you want it, so there is a tradeoff, but you need to fly with a delicate hand if you want the best glide ratio.  Don't be playing fighter pilot by pulling lots of unnecessary g's when you can accomplish the same action through gentle maneuvers.

Wing loading is a function of the size of the wing, compared to the weight that the wing it is supporting.  That is, we are talking about a certain sized wing (e.g. a 15 meter wing with 115 square feet of surface area) in relation to the weight at which the airplane is flown (e.g. a 625 pound ship with a 175 pound pilot weighs a total of 800 pounds.  The wing loading for this sample ship is 800 divided by 115, which is almost 7 pounds per square foot.  Most contest flying allows up to 9 pounds).

Weight may be increased by making the pilot heavier, or by adding lead weights under the
pilot, or by adding water ballast. Any of these may change the center of gravity, which will
then also affect the gliding performance of the glider.

The higher the wing loading, then the slower the ship will climb in a given thermal.

The best glide ratio of a given ship at a given weight is a certain speed. If the weight of the
glider is increased (i.e. the wing loading is increased), then the best glide ratio will only be
achieved by flying at a faster speed.  The glide ratio remains the same, but the speed to achieve
that glide ratio is now different.

The lift over drag ratio (L/D) does not change due to the weight of the glider. It is a function of the shape of the wing.

Higher wing loading will allow you to fly further if the lift is strong, because you can now cover more distance in a given three or four hour flight because you have a faster ground speed.

Higher wing loading will prevent you from flying as far as ships with lower wing loading if the lift is weak, because you will spend much more time circling in lift while the lower wing loaded ships will be climbing faster, and will already be cruising to the next turnpoint.

On days when the lift is weak rather than strong, you will not travel as far of a distance.

The decision to fly with extra weight is determined by the strength of the lift.

The strength of the lift is one thing that determines what percentage of the time you will spend circling in thermals,  versus cruising between thermals.

Location of lift will also determine what percentage of the time you will spend circling in thermals,  versus cruising between thermals.  If you can run below cloud streets, or along lines of convergence, you will not need to stop and circle as often.
 

Glide Ratio (L/D)

L/D is an abbreviation for Lift over Drag.  It is also called run over rise as well as glide ratio.  It is merely a term that allows you to compare distance traveled horizontally with the altitude traveled vertically.

If we say a glider has a glide ratio of 30 to one, we are saying that for every foot of altitude the glider descends, the glider will travel forward 30 feet.  To make the info more useful, we usually state the calculations in terms of how far can you travel for a given height.  If you have an extra 1000 feet of altitude to lose, and you glide straight ahead in calm air, you will travel 30,000 feet forward.  If you think in Statute Miles, that is 30,000 ft / 5,283 ft = 5.7 miles.  Thus you will travel 5.7 sm while losing that 1,000 ft of altitude.  Since many of us do calculations in nautical miles (approximately 6,000 ft per nautical mile), we just divide the 30,000 by 6,000 and we know we will travel five nautical miles while losing that 1,000 ft.

Given several ships with the same wing loading, and flying the same speeds during cruise, the one
with the higher L/D will lose less altitude between thermals.

An L/D of 30:1 gliding over 10 NM (10*6000 ft) will lose 2000 ft (60000/30).

An L/D of 40:1 gliding over the same 10 miles will lose 1500 ft (60000/40).

An L/D of 50:1 gliding over the same will lose 1200 ft (60000/50).

The time it takes to fly a fixed distance is dependent on the average ground speed.
                                   Time to cover a Distance Vs Ground Speed

The wing loading determines the speed at which you fly to achieve the best L/D. Generally,
for a given ship, a full load of water increases the required indicated speed by 7 to 12 knots.
Thus for a 65 kt speed, you will gain 10 to 15 % faster ground speed.

If it takes 10 to 15 % longer to climb, then two same model ships - one with water and one without water, will finish at the same time. However, the ships will not be using the same thermals at the same time.

                 Your glide ratio determines how much you will have to climb
                         in order to cover a certain distance.

If a 20:1 glider makes 6 climbs of 4500 ft each he will have climbed 27,000 ft.
If a 40:1 glider makes 12 climbs of 4500 ft each, he will have climbed 54,000 ft.
Each glider will finish at the same time (one flying 90 NM and the other flying 180 NM), if they cruise at the same speed.

The time it takes you to climb is one factor in determining your ground speed.
The number of times you have to stop to climb is another.
The ground speed you fly between thermals is another.
The higher up you are, the greater your true airspeed will be for any given indicated.
The higher your true airspeed, the higher your ground speed, for any given wind.

If you stay in a thermal after you have stopped climbing, then for each minute you remain
there, you will be further behind the others.  It is important to keep moving if you are trying to cover more distance.

Staying in a thermal after it has decreased to 75 % of its strength is not a recommended
thing to do. Each minute longer in that thermal means it will take you longer to get home.