Winch Launching

[Ollie]

The winch is one of the most versitile launching tools available because the tension and speed are fully under the control of the person running the winch throughout the launch. When a winch is operated by a skilled and prudent person it is capable of launching the vast majority of sailplane models safely and efficiently. It is the skill and prudence of the operator that determines whether the wings break. Several people on this forum have stated or implied that some models are not winchable when they can be if the winch is properly operated.

Even the unskilled can use a winch safely by putting a weak link in the line. Tie a few inches of 10 or 15 pound test monofilament line between the regular launch ring and a second launch ring. Hook the second ring to the model. If the monofilament breaking strength is properly chosen, then it will break before the wings fold.

A student can practise controlling the winch without risking a model. Hold the launch ring in the hand so that it can pull out of your grip without taking any flesh with it. Use a work glove if your hands are tender. Lean back a little and begin tapping the foot switch with a steady rhythm but so lightly that the switch doesn't close. Keep up the rhythm while gradually increasing the force of the taps until the switch closes for the briefist possible pulses. The tension on the line is best regulated by the length of the pulse, not the rhythm of the taps. In this way the peak tension on the line is limited while the average tension is increased as the pulse width increases. In other words, use pulse width modulation while tapping the winch with a constant rhythm.

[emersunn]

Good tips. I am in fear of winching my new big plane (my first non-HLG) - I do not know the ins and outs of the pedal, how strong our clubs winches are, the elasticity of the line, etc . . . This post is very helpful.

I will be using a stong hi-start to get a feel for the plane's strength first. Then I will step up to the winch. Of course the guys at the club will be helpful and encouraging. Even so, I have seen beginners and pros kill some nice planes on those winches!

[Ollie]

You will loose your fear of the winch when you master it with the safe practise exercise. You should be able to pulse the winch while holding the ring and carry on a conversation with someone for minutes at a time. By that time you will have trained your reflexes to control the winch without having to concentrate completely on what you are doing. That leaves enough of your attention left to fly the plane. The same training principle applies to flying. With enough practise, all you have to think about is what you want the plane to do and your unconcious reflexes take care of the details. Skill comes with practise, practise and more practise. Skill and prudence displace anxiety and risk.

[Ollie]

The diameter of the core plus the line build up thickness on the core of the winch drum affects the maximum speed of the winch line at any given tension. No matter what the the effective diameter, the average speed of the line can be controlled from zero up to maximum by how the winch is pulsed. The skill and prudence of the winch operator can be sufficient to prevent folding wood sparred wings no matter what the diameter of the drum core plus line build up.

I don't want there to be any misunderstanding. It is the winch operator that counts far above all other considerations for protecting weak sparred wings.

Drum core diameter and line build up are important considerations for matching the winch to wind conditions when launching planes like competitive F3B models that can take all the power and speed that the winch has to offer. FAI legal winches for F3B typically have wide drums to limit line build up during launch, quick change drums for a variety of core diameters and less power available than some Ford long shaft motor based winches. In competition these winches are used to build maximum line tension before release. The tension on the line is so high that it hums. The operator can judge how close the monofilament line is to breaking by the tone of the line hum. BTW, the quick change drums also allow for the use of various diameter monofilament line to match a variety of launch conditions.

The typical Ford long shaft winch can have at least three different motor configurations of varying power. Even so, a prudent and skilled operator can safely launch a wood sparred wing on any of them.

[ICTHRMLS]

Originally posted by Ollie
It is the winch operator that counts far above all other considerations for protecting weak sparred wings.
Good balance is essential too since you are trying to be pulled over during spool up (line tension) while leaning slightly backwards holding the plane in one hand & the X-mitter in the other when suddenly you initiate a throwing motion that mirrors a tennis serve while following through to reach the x-mitter stick to control the sideways launch..... all this on pretty much one leg. OR - you can stand flatfooted all out on the winch pedal and watch your wings snap. It helps to make sure the pedal is on solid level ground along with a balanced stance that will allow a rapid tapping of the pedal if needed. We often turn the pedal sideways to avoid having our foot "overcenter". A good winch operator can launch any plane safely - technique is more important than drum diameters. :cool:

[thelocust]

Just last weekend, I winch-launched one of my own planes for the first time. A couple of things I learned:

Have your weight on your back foot, and your front foot near/on the pedal.

Hold the plane back like you are chucking a spear. The combination of weight on the back foot and plane held back lets you get a good throw that won't send you reeling forward.

Before you throw, but with the plane in yer hand, tap the pedal lightly a couple of times so that you get the feel of the tension before throwing.

I like to tap 3 times to get the tension up, tap tap tap - THROW! Remember to not put the pedal down! Pulse that thing, and watch the wing.

Try doing a tap while just standing around. I quickly learned how hard drummers have it with the kick-drum pedal!

Throwing the plane is terribly, terribly important, especially for the bigger birds. I have seen 2 planes in recent weeks go nose-in from stalling on launch. It's damned scary and violent!

If your club has a beater foamie or something, try launching with that first -- I am fortunate to have a club that has a couple of Highlanders, so that made the learning curve much less steep (and much less expensive).

[Ollie]

It gets a lot safer and easier with a two man launch. One man throws the model and the other man operates the foot switch. Either can hold the transmitter and guide the plane up the line. This launch method avoids a lot of the athletic coordination needed for a one man launch. This method has become the preferred way for geezers such as myself who's balance, athletic ability and coordination aren't what they once were.

The two man launch is a useful stepping stone to the one man launch for beginners as well.

Hey ICTHRMLS,

I'm still trying to decypher your handle. Does it mean that you can really see them? Does it mean that you fly so high that your plane comes down icy? Does it mean that you fly thermals in icy weather? Is it all of the above?

Regards, Ollie

[RCFlybry]

Some great info here.. especially for those of us that are just getting started in winch launching. I did have one question however and I'm sure that it's mostly relative to launching technique and the plane you are launching but, How high are you guys maxing out on a winch launch anyway? Is it actually possible to hit say 800 feet or more?
Ooops that was 2 questions. :-)

Bryan

[ICTHRMLS]

Ollie - It was meant as a take-off :rolleyes: of the Sixth Sense movie ("I see dead people") but I like the other two as well!! :D :D :D

BTW, I landed once on a beautiful spring day & my plane WAS freezing cold.... no ice but it was noticeably cold. Someone tried to explane ;) it by refering to the lapse rate of the atmosphere or something like that. Any OllieLogic to that??? :cool:

[ICTHRMLS]

Typical winch launch height is about 500 feet but that all depends on total line length and distance to turnaround stake. Gee.... a 2,000 foot turnaround would be very cool to try out!!!!

[shoe]

Originally posted by ICTHRMLS
Typical winch launch height is about 500 feet but that all depends on total line length and distance to turnaround stake. ...

check out Jim Bacus' website for some experiments he did with a data logger
http://www.jimbacus.net/blog/2003/6/14.html

All of his launches were at least 600ft, I'm not sure but I think that was on standard braided line, mono line can get you a little more if you know how to use it.

[Ollie]

As far as launch height is concerned, it usually increases with distance to the turn around pulley in light wind conditions. The AMA rule book limits distance to the turnaround to a maximum of 300 meters, which is about 984 feet, for AMA competition or record trials. I think the LSF achievement programs uses the same criteria.

On a windy day it is possible to launch a lightly loaded, large sailplane without using up any line to speak of. Allowing for line sag due to the wind, I think a 900 foot launch without a zoom is possible. A plane like the Bubble Dancer can pull line off the winch drum under windy conditions. In that case the launch height is limited mainly by the patience of the launcher and the excess line length on the drum. Not only that but the BD is stiff and strong enough to do a full tension zoom. Even with a shorter distance to the turnaround and the right plane, on a windy day, almost any height to over 1500 feet is attainable even from a small field starting with 2000 feet or so of line on the drum. It violates the spirit of the rules to use such tactics. Maybe that is why the FAI requires competition winches to have devices to prevent unreeling. For FAI competition the distance to the turn around is also limited to 150 meters.

[shoe]

Originally posted by Ollie
For FAI competition the distance to the turn around is also limited to 150 meters.

It's a fine point but I think F3J is limited to 150m and F3B 200m.


The main point is you can get a LOT of stretch in 150-200m and gets tons of energy from it, resulting in impressive zooms.

[thelocust]

I was out at the field just recently here in Louisville and Gordy was around with his ELV altimeter doo-hickey, and I seem to remember 600 foot launches.

However, for those of us without such things can use the old method of determining height! If you assume that the plane releases right above the turnaround, and you happen to have a protractor and a scientific calculator with you....

[ICTHRMLS]

Originally posted by thelocust
If you assume that the plane releases right above the turnaround, Now there is a recipe for disaster.... SNAP!!!:eek: