the landing gear well. If the CG hook is within the landing gear well, retracting the gear on tow interferes with the towline. Even if the glider has a nose hook, retracting the gear on tow is not recommended, since the handle is usually on the right cockpit side and switching hands to raise the gear can lead to loss of control on tow. A CG hook, as compared to a nose hook, makes a crosswind takeoff more difficult since the glider can weathervane into the wind more easily. In addition, a CG hook makes the glider more susceptible to “kiting” on takeoff, especially if the flying CG is near the aft limit. This can present a serious danger to the tow pilot. 

## Water Ballast 

To maximize average cross-country speed on a day with strong thermals, water ballast can be used. The gain in speed between thermals outweighs the lost time due to slightly slower climbs with water ballast. If thermals are weak, ballast should not be used. If strong thermals become weak, the water ballast can be dumped. In any case, water ballast should be dumped before landing because heavy wings are more difficult to keep level on the ground roll, and a hard landing is more likely to lead to damage with a heavier glider. Water dumping times vary but are typically between 2 and 5 minutes. 

Water ballast is carried in the wings in built-in tanks or water bags. The latter works well but has been known to have problems with leaks. Filling and dumping systems vary from glider to glider, and it is vital to be familiar with the ballast system as described in the GFM/POH. Filling without proper venting can lead to structural damage. Care must be taken to ensure that both wings are filled with the same amount of water. If one wing has a few extra gallons, it can be lead to ground loops and loss of control on takeoff, especially in the presence of a crosswind. 

Water expands when going from the liquid state to the solid state. The force of the water ballast freezing can be enough to split composite wing skins. If anticipating flying at levels where the temperature might be below 0 °C, follow the GFM/ POH recommended additive to avoid freezing. 

Some gliders have a small ballast tank in the tail, as well as ballast in the wings. Tail ballast is an effective means to adjust for a CG that is too far forward. It should be used with caution, however, since the position of the tail ballast tank gives it a long arm aft of the empty CG. A careless calculation can lead to too much water in the tail tank and a flying CG that is aft of the limit. 

## Cross-Country Flight Using Other Lift Sources 

Many world distance and speed records have been broken using ridge or wave lift. Under the right conditions, these lift sources can extend for hundreds of miles from sunrise to sunset. Ridge or wave lift is often more consistent than thermals, allowing long, straight stretches at high speed. 

Cross-country flight on ridge lift poses some special problems and considerations. Often, the best lift is very close to the ridge crest where the air can be quite turbulent. Great pilot concentration is needed over several hours close to terrain in rough conditions for longer flights. On relatively low ridges, (e.g., in the eastern United States) ridge lift may not extend very high, so the pilot is never too far from a potential off-field landing. These are not conditions for the beginning cross-country pilot. In milder conditions, gaps in the ridge may require thermaling to gain enough height to cross the gap. Ridge lift can provide a place to temporarily wait for thermals to generate. For instance, if cumulus have spread out to form a stratus layer shading the ground and eliminating thermals, a wind facing slope can be used to maintain soaring flight until the sun returns to regenerate thermals. 

Wave lift can also provide opportunities for long and/or fast cross-country flights. Most record flights have been along mountain ranges; flights in excess of 2,000 kilometers having been flown in New Zealand and along the Andes. In the United States, speed records have been set using the wave in the lee of the Sierra Nevada Mountains. In theory, long-distance flights could also be made by climbing high in wave, then gliding with a strong tailwind to the next range downwind for another climb. Special consideration for pilot physiology (cold, oxygen, etc.) and airspace restrictions are needed when considering a cross-country flight using wave lift. 

Convergence zones can also be used to enhance cross-country speed. Even if the convergence is not a consistent line but merely acts as a focus for thermals, dolphin flight is often possible, making glides over long distances possible without thermaling. When flying low, awareness of local, small-scale convergence can help the pilot find thermal triggers, enabling climb back to a comfortable cruising height. 

It is possible to find ridge, thermal, wave, and even convergence lift during one cross-country flight. Optimum use of the various lift sources requires mental agility but makes for an exciting and rewarding flight. 

