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Hand Towing

Michael Lachowski - reprinted courtesy of Model Airplane News

Hand towing is easy, enjoyable, and it makes for great competition. This month, I'll tell you what you need to start hand towing and how to tow easily even in calm air.

HandTow.jpg (17087 bytes)

Hand towing is an interesting way to launch sailplanes. Many people think that hand towing requires substantial athletic abilities, but actually, it's quite easy. You've probably launched an airplane on a high-start. You stretch the high-start and throw the sailplane. To hand tow, you don't need to pull anymore than on the high-start pulls, so strength isn't much of a problem. With a good breeze, you can keep the model on the high-start by flying from side to side. The high-start stretch stays uniform, and the end of the line doesn't move. It works the same way for hand towing. With a breeze and a line with some stretch, you can stay on the line while the tow man stands in one place.

The official name for hand tow sailplane contests is F3J. This event is a man-on-man thermal duration contest. Flying is done in groups, and you fly as long as possible in a 10 minute working window. You don't want to fly more than 10 minutes, because there's a 30 point penalty for exceeding the time limit, and landing points don't count if you land after the 10-minute working time. F3J Rules evolved from the British Open Class soaring rules, and they include a 100 point spot landing on a FAI-style graduated landing tape. (This includes a 15-meter spot landing. Landing within 1 meter is worth 100 points, within 2 meters is worth 95 points, and this decreases to 30 points at 15 meters.) After several qualifying rounds, the top pilots fly in one group for two fly-off rounds, which are 15 minutes long. Scores from the qualifying rounds don't count in the final standings, so the objective is to get into the fly-off rounds. This is a different philosophy from that of AMA-style contests.

EQUIPMENT

You'll need one or two models and some tow lines for F3J. Model selection is interesting, because you'll want two different models to suit the time of day and the lift conditions during the fly-off. In good lift conditions, you'll need to launch as quickly as possible to maximize your flight time. If the lift is really good, a 2-meter design is perfect. During the early morning and in fly-offs, a larger model is more suitable.

High performance is important, so a large, high-aspect-ratio model is a good choice. The original British Association of Radio Control Soarers (BARCS) Open Class rules allowed a generous "in/out" type of landing, so some pilots used models with spans as large as 16 feet. This is a little too large to land well on a FAI spot landing, and it's impossible on an AMA spot landing, so you shouldn't see too many 16-foot-span models at F3J contests. Some of the larger AMA thermal duration ships would perform quite well in F3J. They are light, strong enough for hand towing, and they land very well.

Use monofilament line for the towline. It stretches more than braided lines. If you're flying a gas bag, such as an Olympic, you can use line as light as 40-pound test. The lighter line has more stretch and less drag during tow. For larger models and stronger wind, consider line up to 150-pound test. I normally use 120-pound test line, and I use the 150 for stronger winds. More than 100 pounds of pull from the model is needed to break a 150-pound test line. A strong wind can make it a challenge to hold on to the line. The official line length is 150 meters, and you can launch that high on a good tow.

Here are two ways to store the line: the cheapest way is to buy one of those orange spools designed to roll up electrical power cords. (Some fliers use these spools for winding high-starts.) Or, buy a hand winch that's designed to rewind quickly and store the towline. Graupner makes one (I bought my hand winch from Slegers International.)

COMMUNICATIONS

Communications between the tow man and the pilot are critical. You'll need to establish two signals: one to tension the line and one to start towing. Raising a hand might be a signal to tension the line, and lifting a leg is a good signal to start running. Allow the tow man to build some line tension before you throw the model. You should throw it firmly to avoid stalling at the start of the launch. The model will rise just as if it was launched from a high-start. Plan your release from the tow line before you fly over the tow man's head. You can get a respectable zoom from a hand tow in wind, but start it much earlier than you would with a winch launch.

TOWING TRICKS

What do you do when the weather is calm? Even high-start launches are bad when there isn't any wind during launch. I have an easy solution to that problem... use a pulley system. Instead of running with the end of the towline, stake it to the ground. The line runs through a pulley with a handle. The tow man runs with this pulley to tow the model. For every foot the tow man moves, the model moves forward by 2 feet. The pulley system doubles the speed, so you don't have to run as fast, and almost anyone can provide a good tow even in calm conditions.

The disadvantage of this technique is that you reduce the length of the line. The increased line tension accelerates the model upward during the tow and the increased velocity more than compensates for the loss in line length. You can easily launch a 2-meter model in calm air in 15 seconds. For the really aggressive types, the pulley tow can be used in wind. Use a strong model, strong line, and two tow men to pull. The Germans used this technique to launch their F3B models at Interglide '92.

Hand towing is easy, and it requires very little special equipment. Contests are easy to organize, because everyone supplies his own launch equipment. Get some club members, and give it a try. Flying in groups is always more fun, not to mention some one-on-one flying.

 

 
 
     
 
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