How To Make a Safe Glider Bungee or Hi-Start

RCGroups user rowdy01 put together an instruction sheet on how he makes his bungee launchers for 3-4M sailplanes.

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Make Your Own Bungee Launcher

RCGroups user rowdy01 put together an instruction sheet on how he makes his bungee launchers for 3-4M sailplanes. It's easier than dealing with a winch setup if you just want to practice by yourself. Making one that is safe and functional is important so this guide is a great for making one for yourself. I wanted to get it into an article to share with more people. Thanks to Kevin for putting this together!

Firstly the rubber tube which is brought off gym fitness equipment suppliers and itís the silver one which is the strongest. You require 9 metres. Its called Theraband

The next required is 6 x 6mmx75mm nylon anchors and suitable nylon cord that will go through the centre of the nylon anchor.

Prepare nylon anchor by sanding or dremel the ends so they are close to the size of the outside diameter of the rubber tube. Then thread some nylon cord through the anchor (approx. 500mm length) and tie a good double knot at the anchor end.

Cut tube into three even lengths at 3 meters then spray anchor with hair spray and while wet thread into tube using as lubricant. Then bind with binding wire right down to the end of the anchor (close to the 75mm)

Wrap the length of the wire wrap with insulation tape to cover all exposed wire wrap. Do this on all ends and the bungee rubbers have now been completed.

Heavier cord is used for the anchoring or staking down two rubbers to one heavy cord and one rubber to a second.

The other end is connected to the 60 metres of heavy winch nylon with sleeve and a chute at the far end again with conventional sleeve.

Note the pegs we use are 500mm and must be hammered well in so as not to allow heads to rotate and ropes slip off.

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May 18, 2020, 11:03 AM
Registered User
I have a similarly constructed high start, I used heat shrink for the end wraps instead of tape.
May 19, 2020, 12:29 PM
CR5
CR5
Registered User
Sorry, I got lost somehow.
Are you anchoring 2 bungees to two separate ground anchors then both of the other ends of them to a single bungee with the 60m of rope with the parachute on the end of that?
May 19, 2020, 12:51 PM
RCG Admin
Jason Cole's Avatar
Thread OP
I believe that is correct. That provides a little extra safety in case one of the anchors or line fails.
May 19, 2020, 09:46 PM
Registered User
So as I understand it, this a 'Y' configuration, with the tail of the Y connected to the towline-'chute-glider. Correct?
May 19, 2020, 09:58 PM
Going in circles.
GliderJim's Avatar
It's being discussed in another thread. Someone posted a diagram at my request. Not a Y. Just 3 strands so that one can break without endangering the pilot.

Diagram

The idea being that 1 strand is dangerous, 2 strands is better, but if one breaks it's possible for the 2nd one to go immediately after, but with 3 strands this is less likely.

Post 296 for more info...
https://www.rcgroups.com/forums/show...anceled/page20

Post 280 for pictures of what can happen if you find yourself on the receiving end of a metal ring launched at you.
May 20, 2020, 05:59 AM
Registered User
Pappyjkns's Avatar
Interesting! I use a single line hi-start which when fully extended is probably some 700 - 800 ft in length. I've never worried about the anchored end hitting me because it just too far away. This is something different and I will have to explore it further as I am moving into larger 10 to 12 ft wingspan sailplanes. I've only tried a winch once and understandably, I was rather nervous about using it. It just so easy to overload a wing structure. this "Y" setup might be a good alternative.

Cheers!
Lyle
May 20, 2020, 06:07 AM
Registered User
Pappyjkns's Avatar
Another thought.....(yes, it can happen! : ) With this setup, if the wind shifts....which it inevitably does, you would have to either reset one stake or risk launching with the wind off at an angle. With the hi-start you have some latitude in that you can move your launch location left or right depending on the wind shift.

Regards,
Lyle
May 20, 2020, 09:37 AM
Going in circles.
GliderJim's Avatar
This hi-start is about 10 feet of rubber and 200 feet of line. You don't need a big field, but it's designed to create a LOT of tension, therefore the extra safety features such as no metal rings and the redundancy of 2 stakes and 3 strands of rubber.

Joe Wurts posted a couple of photos of his that uses 4 strands of rubber for even more power.
https://www.rcgroups.com/forums/show...&postcount=304
May 20, 2020, 09:46 AM
Registered User
4 strands of the silver?

I have a traditional high start setup with 100 ft of the silver rubber and it will launch with pretty good authority. I have launched 85oz airplanes with no problem.
May 20, 2020, 01:22 PM
Scale Aircraft = Scale Crators
mikejr83's Avatar
So this discussion came about because I built a zip start with rubber left over after re-working my primary high-start after it failed. The zip-start failed. Post 280 is my back after the line between the anchor and the rubber broke.

My original highstart had a large amount of rubber, purchased from GravesRC.com as a kit, and broke from age. This original break was a non-issue because the length of mono on the end. I took the left over, which was too short to provide the power to launch my 4m Xplorer at a good tension and turned it into a parallel setup similar to above. To make equal lengths of rubber I had ~2m left over.

I took the left over, which had one of the plastic plugs and metal eyelets for connection, and made a small zip-start. The difference being that it wouldn't be for full launches, max 10 steps, get me to approximate landing pattern height, for launch, land, launch, land, repeat practice. I used winch line to tie from a concrete spike to a the remaining plug and then added 7m of mono on the other end of the rubber.

Anyhow, I like the multiple rubber idea as it does make it safer.
May 20, 2020, 09:22 PM
Flying in OZ.
iflylilplanes's Avatar
At what length does a Hi-Start become a catapult/zip-start? just curious. I've used hi-starts since the late 1970's, had hi-starts let go on me (lost count) and never had to worry, the rubber looses energy in the first 50', never had a use for a short 30' - 40' catapult/zip-start.

Cheers,

Dave
May 21, 2020, 06:19 AM
Scale Aircraft = Scale Crators
mikejr83's Avatar
Quote:
Originally Posted by iflylilplanes
At what length does a Hi-Start become a catapult/zip-start? just curious. I've used hi-starts since the late 1970's, had hi-starts let go on me (lost count) and never had to worry, the rubber looses energy in the first 50', never had a use for a short 30' - 40' catapult/zip-start.

Cheers,

Dave
Not sure. I called my contraption by that name because it just felt like it was correct. The idea behind my zip start was not to launch a model to a height to hunt of thermals but to get it it to approximately the same height I'd be going downwind for the landing pattern. Some people just throw their model for landing practice. I found that I was spending more time working on setting up the approach from a sub-optimal throw than actually getting the model lined up as it would look like in a "real" landing.
May 21, 2020, 09:46 PM
Flying in OZ.
iflylilplanes's Avatar
Ok, I've always hand launched for landing practice, even managed a 25 minute flight from a hand launch once with a own design 12' floater (never had a name) just bounced of little puffs of lift till it gained a 150' altitude then went hunting for bigger and better thermals.

Thanks,

Dave
May 23, 2020, 05:23 PM
Registered User
gliderguide's Avatar
https://www.walmart.com/ip/Pet-Champ...Stake/20369862


Something like this is much safer as an anchor. It has way more grip on the ground, the tube can rotate around the shaft without fear of it pulling off a free end. Different sizes are available and you donít need a hammer. Plus, they stick up a little which helps keep your rubber from fouling. I always put a small bit of bright covered ribbon on mine. Shows wind direction easily and limits people walking into it. Doesnít stop them...

I like the idea of a very powerful small launcher. Itís hand for launch n spot land practice, or for hunting thermals at low levels which is a good skill to have. I made a similar unit but with very lite theraband for dlg launch. Iíd call it more a catapult in my usage though. For me it provides horizontal speed which I translate to vertical like a dlg launch, but without and knee or back stress.


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