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Launch Bungee Spec


Mel Jones
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I did make my own using 8mm (?)silicon tubing from HK, 80Lbs BS monofilament fishing line, a small parachute purchased from some model web site and a dog spiral stake, and it worked really well. Total length was about 90m. I think in competitions where multiple models are launched at the same time, they tend to use electric winches. Anyhow, here is a video of me launching my 2m Whisper on the bungee from the top of a big hill when there was very little slope lift.

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Mel,

I took your question to mean what are the rules for bungee specifications in competition. I cannot answer that.

If you are asking what works, in addition to what the guys have already said, it depends on the weight of your glider.

My first attempt using rubber tubing was far too viscious for ~250 gram models. I bought a made up set which may be this, plus a good ground stake from a kite shop. The Graupner web site appears to be down so I cannot find the details. I think mine was only half the price now quoted.

Germany is the home of RES competiton, with emc-vega a well known supplier of Hi-Starts. Absurdly expensive but it will show you the range of options.

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  • 4 months later...

Mel--My high start bungee I made years ago is made of 100 ft of surgical tubing and 400 ft of kite string. The id is 5/16 " and the od is 7/16". It launches my "Bird of Time" 3 meter sailplane with ease, but then again it is a relatively light model. Two meter ships too, but less stretch. It has been two years since I flew it ,but if my memory serves me, about 80 steps ( for around 200 ft or more total stretch) or until the wood starts to creek. Could be wrong on the stretch,--senior moment !

My big question is just how big/heavy my next sailplane can be with this system?

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  • 8 months later...

Silicon tubing seems to be very expensive. As a new comer to Hi-start I have been trying to find information on various sorts / types of "rubber" to use. On one sire it said that the cheaper bungee cord provided and explosive start but soon ran out of steam. Has anybody used this product, if so to what effect?. I was thinking of 2 x 10 meter lengths of 8 mm bungee, attached in parallel, to 100 meters of 45 kg mono filament line. This I think will launch gliders up to about 2.5 kg. Any comments welcome. smiley

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I have a 2.7m Art Hobby Odyssey full-house glider and I use 8mm cloth covered rubber bungee to launch it using 35m of bungee and 100m of 90lb monofil.

It is quite a rapid start and, with marginal wind, it can run out of steam but it still gives enough height to pick out some lift. With a bit of breeze then it's fine because it kites up especially if I weave it with the rudder to keep tension as it goes up. Once it goes over the top of the climb I put it into a shallow dive then 'ping-off' to gain even more height.

I also used to use it for a Bird of Time quite happily, so long as too much up wasn't held in because the original only had a centre join of 2 x 6mm rods which used to increase the dihedral by the end of the climb.

I have had the red 9mm silicone bungee in the past and I found that it started to break quite often after some time in use, even though stored in the dark, and ended up knotting it together so I stick with 'roof-rack' bungee now. It's not too expensive if bought off the reel from ship's chandlers or sailing clubs.

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We have used this from hobby king. It was used to replace a damaged section on a members old bungee where the outer layers on the reel had perished. It works really well and should get a 2.5kg glider up OK, although the height you get will depend on if there is a decent headwind or not.

Great fun and we recently used it to launch a members 4m Algebra he had just acquired, he'd only brought it to the field to do a couple of hand launches to check the trim, he had never done a bungee launch before, I laid out the bungee and two launches later he was sold.

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Not quite a glider...but it took quite a few attempts and wood glue to get the launch to consistently work.

cal_0190.jpgcal_0191.jpg

It weighs 5.6 Kg and due to being a pusher needs to attain flying speed ASAP

I am using a combination of bungee cables to achieve 20 M free and close to 35 M extended with the best part of 25 Kg at launch!

One of the less successful launches.

_njt2129.jpg

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Thanks Frank,

I have ordered the red from Hobbyking and the blue is now on my Christmas list. HK reckon that the red will launch 3 kg so lets see. I have a BOT which I bought for pocket money off E-Bay and was given 2 more vintage gliders for free. One is 2 meters and the other is 2.5 mtrs, both have polyhedral wings and look fantastic. Cant wait to get them in the air. Hopefully this time next week. laugh

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  • 7 months later...

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