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In the early 80's we first tried aerotowing but it was to be some 10 years later before we finally got round to some serious glider flying due to trying Scale and Aerobatics first.
We have learnt many valuable lessons through trial and error (we have written an intoduction to Aerotow Training). One of which is not to tow to quickly and another is to use a non stretchable tow line. We started with Dacron (sea fishing line) and using a weak link at the glider end. We had problems with snatching so installed some catapult elastic at the tug end. We then used a fine braid tent guide line and by adding a piece of silicon fuel tubing about 2 ft. long attached at the tug end would take the 'bite out of the line' and therefore smooth out any jerks when the line went slack. At the glider end we use 4 short lengths of Keil Kraft light weight line which is our weak leak should we experience any problems. The length of our line is about 60-70' mainly due to the area of our flying site. We flew at Old Walden last year (June 99) and were watched by an American visitor who had done some aerotowing and he was very impressed. Apparently in the USA they use a much longer line but everything in the US is bigger isn't it! We have had problems with lines breaking, radio glitchers and pilot mistakes but on the whole we now have aerotowing down to a fine art.
We fly 2 main tugs - both are Cubs. One is the Goldberg 76.5" span, powered by a SC91 4stroke. This model is built as the kit dictates but with more power making it a lively and powerful machine. The second tug is the Flair Cub which has been modified by using stringers which as given it a better shape. Other modifications include scale profile, size alerons and flaps.
This allows us to slow down for towing the vintage gliders like the Krick Granua Baby. The Flair Cub is fitted with a SC80 4 stroke and although a little heavier than the Goldberg is capable of towing the Slingsby T21 1/5 scale, weighing some 81/2 lbs and spanning 109". A lovely combination to watch on a sunny evening because the tug uses all the runway and the glider has to be air bourne first. This requires trust and lots of concentration from all pilots. We also fly a Kyosho Cessna 188 Ag Wagon, powered by a SC80 4 stroke, which is a very capable tug and the Krick Klemm 25, powered by a OS40 4 stroke looks good pulling our Granua Baby. One of our biggest gliders that we tow is the Robbe ASW24 weighing 81/2 lbs and spanning 3.5 mtrs at 1/4.5 scale. This looks great and tows up well behind the Goldberg Cub. As a team of 3 we are able to tow up 2 sport gliders behind one tug. For this we use 2 x Global Ridge Runts (unfortunately no longer available) and the tug being a WOT 4. This combination has caused people to sit up and take notice and it's a great feeling once we get air borne.
To achieve the success we have had there are a few points which we have learnt over the years. We find it is very important to talk and listen to fellow pilots. Communication is a must between tug and glider pilots. Experience and good understanding of each other's flying is helpful. You need to work as a team and not solo.
Photograph by Mark Taylor
The position of the tow hook is another important factor. Unlike the full size we cannot tow from the rear of the fuselage just above the tail wheel. We tow from the right hand side of the fuselage and try to keep the release within 2" diameter of both CG and thrust line.
The simple release is worked by a separate servo which pulls out a pin to release the tow line. On the opposite side we have a hard point which we attach the end of what we call the strop. This strop passes through a loop in the tow line and then attaches to the release forming a triangle. The tow line can move from side to side but pull is still coming from the thrust line and CG position. Since using this system of tow line we have sorted out problems of being pulled off course.
In the case of the release mechanism the simpler the better as there will be less to go wrong. A simple wire in a tube that is retracted by a servo to release the line works very well.
Our success with aerotowing hasn't been achieved overnight but with determination we think we've made it. You don't need big aeroplanes and big gliders to have fun at aerotowing.
Glider Tow Video Click on a video of a glider tow from takeoff to landing.
Tug Video The view from the tug from takeoff to landing. Quite a lot of vibration at first, but this does reduce.
Rolling Aerotow taking the aerotow to the next level. This does require the tug pilot and glider pilot to really know how each other fly and lots of experience. Derek Gooch is the tug pilot and Dave Taylor is the glider pilot.
The Pilatus Porter PC6 being used as the tug was built by Derek Gooch (aeromodeller since age 12) - self drawn plans scaled off side on photo of full size which is/has been operated by missionary group in Papua New Guinea (in cockpit is a pilot and native passenger with shrunken head on a stick). 70" span powered by a Laser 80, weighs 8lbs - originally had scale position undercarriage which was too far forward and made takeoffs and landings a nightmare - definitely not good for glider towing! Moved undercarriage back 3" - predictable ground handling now, can be bouncy on landing (probably the pilot). Tows well, no nasty habits unless too steep resulting in stall. The model is also enjoyable sport model. Has split flaps which are very effective. A good fun model for general messing about.
Go on give it a try.
Aerotowing at Old Warden 2014 - Photograph by: Stuart Roberts
Clear of the ground - Photograph by: Stuart Roberts
Final approach - Photograph by: Stuart Roberts
A final check before another flight - Photograph by: Stuart Roberts
A great looking model - that′s the Rhonsperber, not you Dave... - Photograph by: Stuart Roberts