DIY hi-start

[Oliver Beams]

I have a 2 meter span thermal glider which weighs about 2 ¼ pounds and I am interested in launching this using a hi-start, although all of the ones that I have looked at seem quite expensive. So my question is it possible to make ones own hi-start and if so what type of materials and sizes should I be looking at? Alternatively does anyone know of a cheep source of a hi-start?      

Thanks, Oliver

[Former Member]

[This posting has been removed]

[ken anderson.]

hello oliver--i had my first go with a zaggi using the method which eric bray describes--only thing is watch out with the dog stake----i've heard of them comming out of the ground!--i preferred to fasten the end of the "bungi"(name) of the high start around a fence or a tree............have fun.

                        ken anderson.. 

[Former Member]

[This posting has been removed]

[Simon Chaddock]

Of course you could go the whole hog and design a radio controlled electric winch!

[Oliver Beams]

Thanks for the advice guys.  As a cheaper alternative to surgical rubber tubing would it be possible to use the round, stranded, cotton covered bungee available off the roll from DIY stores?

Oliver

[Delta Whiskey]

I got a old Gentle Lady kit I've nearly finished, that's been under my uncles bed for 15 or more years, 2.4m wingspan, and will need to start looking at ways to lunch it, so need to consider a bungee too! Is there any guide line to the lenght of rubber / line per wingspan?

[Terence Lynock]

One system I have seen diagrams of developed by a flying club was to fix the doggy stake near you then trail out the bungee away from you, the line attached to the bungee passed around a pulley wheel down the field and then came back to you.

just at the end of the bungee was a stopper so that the bungee rubber couldnt be pulled through the pulley wheel, so you pulled the line back to your launching point which stretched the bungee out and if the doggy stake comes out of the ground some other poor sod down the field gets it.

They found that by using this method the need for a bungee rubber over 60 yards was never needed and because it was stretched until the stop hit the pulley wheel every time you got a constant power output from the thing, I made up three bungees at different sizes for about thirty quid.

Keep Latex tube well covered with talc and store it in a cool place away from sunlight, Latex tends to become sticky or 'grabby' when it is not powdered regularly and I have seen a bungee that was left in a cupboard under the stairs for two years that couldnt be unrolled because all the turns on the spool had glued themselves together,

 

regards,     Terry

[Terence Lynock]

 

 

Try googling 'exercise bands' and it should give you plenty of references for Latex tube but the stuff also comes in glat strip so make sure you get the tubing and shop around, some suppliers are very expensive whilst others are dirt cheap for the same stuff.

You can start with                                                                                                                           http://the-therapy-connection.com/B0006ZWSIG/M/B0006ZWSIG.htm and this will give you an idea of what you want, the yellow 6mm is OK for smaller models and red 8mm for slightly larger stuff, 100ft of the black will launch Pakiderms  across the Welsh boarder,

 

regards,   Terry

[Guest]

Eric,

if I remember correctly, the old bungees had about 100 feet of rubber and 100 yds of monofilament.  the bungee would stretch to about 2 to 3 times its length developing the power to launch

john

[Bert]

" just at the end of the bungee was a stopper so that the bungee rubber couldnt be pulled through the pulley wheel, so you pulled the line back to your launching point which stretched the bungee out and if the doggy stake comes out of the ground some other poor sod down the field gets it."

 

What hapens if the pulley pulls out of the ground?

 

Bert

[Pete B]

Oliver Beams said:

Thanks for the advice guys.  As a cheaper alternative to surgical rubber tubing would it be possible to use the round, stranded, cotton covered bungee available off the roll from DIY stores?

 

Reply is a bit late, I'm afraid, Oliver.  Your question doesn't seem to have been answered above. Surgical tube is a much better alternative to cotton-covered bungee. The problem with cotton bungee cord is that the stretch is seriously limited by the covering so, if you manage to avoid ripping the towhook out when you stretch it, you get a disappointing short amount of oomph before it has fully contracted. You should get a much softer, more prolonged contraction with surgical tube and, with practice and the right conditions, be able to 'kite' the model a bit to get the maximum height on launch.

I'm starting to sound a bit like a midwife, I think.......

Having said all that, it's fair to say that, having come back into the hobby, the last time I did a bungee launch would have been about 1983...........but I'm sure things haven't changed that much.

Mind you, I'm surprised to find that model shops are still selling the cotton-covered bungee kits! How many of those are now laying around in sheds and lofts, never to see the light of day again??   

 

Pete

 

[Oliver Beams]

Thanks Pete and all others for your help, it sounds as though I will have to use surgical tubing after all.