Sailplaners depend on nature to keep their planes in the air, but nature needs a little help to get to that flight-sustaining lift. Handlaunch guys with their featherweight planes can use muscle power to get to 50 feet or so. Slopers can toss their plane off a cliff and get wind power just a few feet away.
But thermallers with bigger planes need some extra help for a good start. Beginners do well to use a hi-start for that something extra. Hi-starts are relatively safe, can be used by one person, and work well with limited size planes. If you accept the rule of thumb that you need 4 pounds of pull per pound of plane, it is easy to get a 2 pound 2 meter plane up on an appropriately sized hi-start. 4 and 5 pound planes begin to tax your pulling power. More than that, you are limited in launch height with the good old hi-start. Sooner or later it sinks in that a 600 foot launch gives you an exponentially greater chance of finding a thermal than a 400 foot launch. That’s why we use winches.
Winches are powerful tools to get bigger planes, as well as smaller ones, to higher altitudes. When combined with retrievers they are also convenient tools. You don’t need to chase lines all over the field. But, conventional winch setups work best with two or more experienced people on the flying line- one to pilot the plane and the other to work the retriever. “Auto-retrieve” systems (Bill Groft is building one) can be used by a single person.
Along with all that power comes some liabilities. The purpose of this missive is to help those who may have limited experience understand and deal with the liabilities, and thus limit the chances of an outing becoming a frustrating and perhaps injurious experience instead of a happy one. The liabilities we see are:
· Winch launches can break planes not specifically designed for such.
· Planes can pop-off the line at low altitude, presenting hazards to the pilot and others nearby.
· Winch lines can break, creating similar hazards if they break with the plane at an early stage of the launch.
· The retriever line can tangle with the plane and prevent its release.
· The retriever line will bow in a headwind and blow back over the launch line if the retriever is not promptly started. It can land in trees in a crosswind
· The harness represents a personnel hazard if the retrieve is not properly controlled.
· The solenoids in the winch and retriever circuits can stick closed, preventing the motors from stopping when the switches are released.
· When rewinding the winch line after a flying session, the winch line can slip under the brake belt and create great tangling turmoil.
· The winch brake can stop functioning, resulting in more turmoil.
· The retriever line can break
· The swivels on the lines can wear out and create line tangles.
Thoughts on how to deal with these liabilities:
Planes not designed for full-bore winch launches should be launched with intermittent tapping of the pedal switch, so launch speed is limited and thus the plane is not exposed to the full fury of the winch. These planes probably won’t withstand much of a zoom, if any, at the release point.
Pop-offs will occur at times in spite of the best efforts of the pilot. The pilot must be continuously alert to such possibility and be prepared to adjust the controls quickly to prevent the plane from hitting others, or from crashing. Spectators, too, should be alerted to the possibility of pop-offs, and should be prepared to duck if the plane heads their way. Pop-offs can result from too steep a launch angle, from a towhook location too far back, or from a bent towhook. Trim the elevator to limit the launch angle, if that is the problem. For most planes, the towhook should be ahead of the center of gravity by a quarter inch or so. Keep the bottom of the towhook parallel to the bottom of the fuse. If it’s bent the chances of a pop-off are increased. A poor throw of the plane, especially in crosswinds, can create pop-offs as well. Keep the wing level when throwing the plane.
When a winch line breaks, the plane’s ascent will be slowed suddenly and the winch motor will unload. Usually, the sound of the motor will clue you that the line has broken. It is important to stop the winch promptly in such event, to avoid running the broken end of the line through the turnaround. If the plane is at low altitude it may behave similar to the way it behaves in a pop-off. At higher altitudes the pilot will have ample time to control the plane and may even get a normal flight out of it. The worst time for a line break (or knot failure) is immediately after the pilot releases the plane from his or her hand. When fixing a line break the granny knot will not do. A “double fishermans knot” is appropriate. The knot is better known as the blood knot. See www.creeksideflyfishing.com/blood_knot.jpg for a diagram on tying this knot.
The potential for the retriever line tangling with the plane seems to be greatest in windy conditions, as well as when the harness line which connects to the plane is short. It is recommended that this section of line be kept around 5 feet long, or more. Maintaining tension on the winch line during the launch is helpful. If the line goes slack the chances for the retriever line to foul the plane seems to increase. If the retriever line does foul the plane, stop the retrieve immediately. That gives the pilot the best chance of landing the plane undamaged.
The bowing of the retriever line in a headwind can be a real hazard if the person operating the retriever is not alert. If the retrieve is not started promptly, the line can easily blow behind the launch area and descend to or near the ground. If this happens it is important that the retriever not be started until an inspection of the line position with respect to objects and people is made. It is easy to snag a person or plane on the ground and create line burns or worse if a bowed line is low and the retriever is started unmindful of the hazard.
The harness used to connect the plane on launch can be a hazard during the retrieve if the retriever is not stopped in time. The job of the person handling the retriever is to make a safe retrieve, not to watch the plane. After the pretty plane releases from the launch line, forget the plane-watch the line. Too many times the retriever is run until the harness winds up on the wheel. This can break the lines and release the harness and rings to inflict damage on personnel nearby. This potential for injury is not theoretical, it has happened. Don’t get a bruise the shape of a ring on your back, or worse; watch the line, not the plane.
If the solenoid switches on the winch motor stick shut during a launch, the motor will not shut off when you take your foot off the pedal. Not a good situation. The knife switch above the battery near the motor is for use in such a situation. It is up to the retriever operator to pull the switch open promptly if such a happening occurs. It is not a likely occurrence on our winches, as they are equipped with two solenoids, one of which is redundant. The retriever motor has only one solenoid. The knife switch should also be opened at the end of the flying session, after the line has been wound in and the wagon is ready to return to the Birdhouse.
As to rewinding the line after the flying is done. During the rewind, while you are guiding the line onto the spool, keep your eye on the spool at all times while the spool is rotating. There is a strong temptation to look behind you during the windup to see if the end of the line is approaching. This is a surefire way to get winch line under the brake belt. Winch line under the brake belt is not only a mess to clear out — sections of the line next to the spinning pulley can overheat and break during the next outing. Keep your eye on the spool whenever the spool is rotating.
If the winch brake stops functioning, there will be another type of rats nest to untangle. Malfunctions of the brake are often caused by wear on the belt, or by the angle of the front belt grip. Wear on the belt can result in the brake arm sliding to the bottom of its slot, and this will restrict the belt from tensioning. The cure is to loosen the set screws in the front grip and force the belt down a half inch or so, and then retighten the set screws.
If the retriever line breaks, find the ends of the line and tie them with the fisherman’s knot.
Swivels are on the line for an important purpose. The retriever operation puts a twist in the retriever line which can transfer to the winch line as well. Properly operating swivels will release most of the twist. If the twist is not removed the retriever line, and sometimes the winch line, can develop birds nests of sizeable dimensions. It is important to have the swivels in the lines and to replace them when they do not swivel freely under tension. Use ball bearing swivels equal in size to those you are replacing. Spares are kept in the Birdhouse, or in a container in the tool box. If there are no spares, get some. Be sure to use braided lines on both winch and retriever, not twist lines.
Setting Up the Launch Wagon
The end of the winch line should have a loop in it two to three inches long, secured by a bowline knot. This end of the line goes in the bottom of the turnaround and out the top, so the line going to the plane is the top line. After running the line through the turnaround, secure the loop end to a bolt or nut on the wagon and run the turnaround out to or near the end of the line. It helps in running the line out if the winch brake is held in the released position. After the turnaround is staked, pick up the top line with the hammer and separate the two lines on the way back to the wagon. (On a windy day with a cross wind these lines can twist around each other if they are not separated, and foul the first launch)
The launch harness should look like this.
Some people will be horrified to hear this, but if the retriever is used the chute can be inserted in either direction. If the retriever is not used, it should be installed as shown. If inserted opposite to that shown, it will not catch on weeds etc on the field, and will be less subject to ripping. It will not open during launch, as some fear; there is too much tension on the line for that.
The line to the turnaround has a loop in the end, secured by a bowline knot. This loop can be slipped through the eye in the snap swivel, looped back over the snap and thus keep the swivel fastened to the line. It will still be easily removed when the flying is done. Removal of the snap swivel is important before you wind in the winch line. The snap swivel will not go through the turnaround undamaged. If you run it through the turnaround, buy a new one.
The harness line to which the plane is connected should be heavy, and it is recommended that it be 5 feet or more in length to minimize the chance for the retriever line snagging the plane during the launch.
After the harness is hooked up, plant the arch over the retriever line. Be sure it is arranged so the winch will not pull the plane through the arch. That’s a tight fit. When using the retriever keep some tension on the retriever line all the time. Failure to do this can result in several loops of line sloughing off at once and creating bird’s nests of exasperating dimensions.
When connecting the battery cables on the retriever, be sure to get the negative terminal connection tight. Because of some peculiarities in the setup, if the negative terminal is not tight there is a ground wire on the winch motor which will overheat when the retriever is running, with possible damage to the motor.
Line up the wagon so the winch line winds evenly across the spool. An uneven windup can result in line running off the spool if it is severe. In any case, an uneven windup will result in variable tension and variable line speed on the launch. Once the wagon is lined up, stake the wagon tongue to keep it that way.
Don’t forget to open the knife switch after the flying session, and stow the cables so they don’t fall off and drag on the ground on the trip back to the Birdhouse.
In spite of all the potential for trouble, the launch wagons will get your plane high and often if the pitfalls are avoided. Happy launching!