Introduction: Model Glider Bungee Launcher



This is a how-to on building a Bungee or Highstart Launcher for model gliders: no gas or electric motors are used just a re-usable length of rubber tubing and some fishing line.

And it's very inexpensive too: less than 30 bucks for a small set up.

I use this to launch my six foot wing-span model glider hundreds of feet in the air. This will also work if you have a gas or electric model plane and wish to conserve fuel at takeoff.

The video above gives you an idea of how this works, launch and release of tow line, including shots from the camera I installed on-board giving us a bird's eye view!

But please read all of the instructions before proceeding.

Successfully flying and landing an RC plane is beyond the scope of this instructable, so in the video I thought I would add some more excitement and show what you don't want to CRASH into!   Plus, there's a little how-to on getting your plane out of a tree ;-)

I hope you enjoyed this instructable.  Questions, suggestions and comments are welcome!.
 
Brett @ SaskView

Step 1: Overview

No rocket science here. Basically you are using a very big elastic band and some string to catapult your plane into the air!

50 to 100 feet of rubber tubing is anchored to the ground at one end. A tow line is connected to the free end of the tubing.

At the other end of the tow line is a ring that goes over the tow hook mounted on bottom of your glider. The tow hook is located just behind the center of gravity of the glider. The tow hook usually is adjustable and can be moved forward or ahead within a slot and tightened down. This is to allow fine tuning so that a steep enough launch angle is achieved.

To launch launch your glider using a bungee requires the pilot to start walking backwards stretching out the tubing until there is enough tension for launch.

You then throw your glider into the air and the high-start rapidly hurls it sky ward at steep angle at a steep angle. This all happens without pulling back on the stick. The only radio control input during launch is left/right as needed to keep the glider from veering off to the side.

As your plane passes over the anchor point, the tow line slips off of the tow hook and the plane is free to fly on it's own.

When learning to use this method of launch it's best to get the hang of things gradually, so the first few attempts don't try to go for height and therefore use less tension than what you would for maximum altitude. As you get more comfortable with catapulting launching you can start increasing how far back you stretch the bungee, and how much tension you use when launching. The reason for this is because the high-start launch is quick and it's very easy for a beginner to lose control and smash their glider, and possibly cause injury.

I've attached a video tutorial called R/C Glider High Start Tutorial With Mike Smith that's gets into more detail and is well worth watching.

Step 2: Anchor

A dog stake or other ground anchor for the tubing.

A piece of wood to help you screw in the dog stake (put it though the triangle shaped handle and then you screw holding the ends of the wood.

A carabiner or other quick release clip to make attaching the tubing to the stake easier.

Step 3: Rubber Tubing

50 - 100 feet of rubber tubing. UV resistant if possible. Normal surgical tubing isn't UV resistant, and it will get brittle after too much time in the sun. Tie a key ring to each end and tape or heat shrink them too as shown in the photo.

For my set up it was 50 feet of UV resistant latex tubing purchased on ebay for $20
3/8 inch outside diameter 1/16 wall.

This is for BIG PLANES over a pound, and is a very fast take-off on my glider.

For smaller, lighter models weighing in at under a pound, 20-100 feet of 1/4 outside diameter tubing is good. And you may not need much if any tow line for tiny park flyers.

You'll notice I'm not giving exact numbers because as long as you have very stetchy tubing with enough pull, your highstart will work!. The longer the tubing, the more gentle and higher your launch will be.

What is important is that you'll be pulling 5 to 10 times the weight of your plane on the tubing to provide take off. If you have less pull than the weight of your plane, no take-off.

For me 8 - 10 pounds will get a good launch because my plane weighs two pounds.

To get higher launches you can use more pounds of pull or add more tubing.

The higher the pull/weight ratio is, the quicker and more dangerous your launch will be.

Step 4: The Tow Line

200 - 400 feet of 20-50 LB fishing line.

Again no need for exact numbers. Length is usually 4 - 6 times the length of tubing you are using but sometimes you don't have that large of a take-off area.

How many pound test: I use 25 Lb test. When I'm pulling back on the bungee I stretch the tubing until there's about 8 - 10 pounds of pull, so there is little chance of the line breaking.

You can use too much line, but more often that never happens as how many football fields do you have to use... Sometimes you may not have a long enough area to launch, in which case you can use a shorter line and stretch the bungee more that you normally would. This will make for a faster, quicker launch, more prone to failure and never as high.

My setup has 200 feet of tow line and several other lengths of 50 feet. This way, I can vary how long the tow line is, depending on how big my launch field is. I've found on my set-up, 350 feet of tow line will get the best results.

Tie fishing swivel fasteners at the ends so you can easily clip your tow lines and bungee together.

Kite string can be used but I find that fishing line works better as it has some elasticity which helps get a better launch.


Step 5: Tiny Parachute or Kite Tail

A 12 inch parachute or a kite tail of streamers tied to a small ring.

This will be attached at the end of the fishing line where you hook it to you plane.

The reason for having this is twofold: when the line releases, any wind will carry the line back towards your launching position, and you won't have to walk as far when retrieving the line for you next launch. And it helps you find the end of your highstart. The fishing line is sometimes invisible...

If you're using a parachute you'll need a small key ring mounted at the top and botton.


Step 6: Hose-reel (Optional)

A great way to store, unwind and wind up the bungee launcher.

You could also use other things for transport and storage of your highstart, such as a large cardboard tube...

Step 7: Assembly

Very Simple:

Clip one end of the swivel on the tow line to your reel and roll it up.

Once the tow line has been reeled up, clip one end to the bungee tubing's key ring and roll up the tubing.

Make sure that you aren't stretching the tubing as it's rolled up because this is how you store and transport your highstart, not how you launch. Storing the tubing stretched will cause the tubing to lose elasticity, and that's no good.

Gather everything up and head out to a big field.

Step 8: Deployment

Check to see if there is a model airplane club in your area, that has it's own field, or has a suitable location and permission to access and fly there. Never use private property unless you have permission.

Safety Is Important: A large open field is required as you will need hundreds of feet of unobstructed space to deploy the bungee launcher. The area that you fly should not be near any airports, buildings or populated areas. Make sure you are following local laws pertaining to model airplanes. Don't ruin this sport by attempting to fly in areas close to were people are. A glider that weighs a couple pounds can severely injure or even cause a fatality if it crashed at high speed.

Place your anchor at the upwind end of your field. You always want to launch into the wind.

Make sure your anchor is firmly rooted in the ground. Give it a serious tug to make sure it won't pull free. If it does come loose when you're launching, you will have a dog stake projectile heading your way. Make sure there are no people near the launching area because of this possibility.

Take note of the above step. Failure to do so may result in a serious injury.

Connect one end of the tubing to the anchor and unreel it away from the anchor towards your take off postion. When you come to the end of the tubing, clip the fishing line onto it, and start unreeling the fishing line.

Once you have unreeled the fishing line, clip the parachute or kite tail to end.

If using a parachute, attach the lines end of the parachute to the fish line.

Hook the other chute ring to the tow hook of your glider, and start walking backwards. As the tension builds up, keep a firm grip on the plane. When you've reached the point where the tension is enough, it's time for launch.

Throw the glider forward and a bit upwards. When starting out, it's best if you have a helper be the one launching, so that you can have your hands on the radio, ready for the launch.

Remember to always launch your glider into the wind. If the wind shifts after you've un-spooled, don't be lazy and ignore the above advice: adjust the highstart so that you'll be launching into the wind. If you launch with a cross-wind, you'll be asking for trouble.

Thanks for checking out this instructable! Questions, suggestions or comments are welcome, and if I've left anything unclear please let me know.

Step 9: The Glider I'm Using

Carl Goldberg Gentle Lady
78 inch wing span
31 ounces (880 grams) including 6 ounce camera (170 g)
2 Channels

www.carlgoldbergproducts.com

Here's a short video showing it:
http://www.youtube.com/watch?v=755GyoYkUJw

Comments

author
BenjaminG42 made it! (author)2016-04-22

OK! Thank you for the tip, I didn't know that. But I'm surprised by the hook being behind the center of gravity, I alwys read not to go behind the CG. Tomorrow I will back a bit the hook and try a softer sandow. I belive my 6 mm sandow is too powerful for a so light glider. I 'll let you know aboiut the next launches!

author

Usually it only needs to be a tiny bit behind the CG.

author
BenjaminG42 made it! (author)2016-04-21

Hi, I'm trying to bungee launch a mini glider of 60g TAW ( anout 2 ounces) with that method. I use 8 m of fishing line and 3 meters of 6mm sandow. I stretch to 2 or 3 times the weight of the glider but I never can't get this climbing slope. instead my plane is accelerating for 2 or 3 meters and then releases the hook whimle she's only 1 meter height!

How do you get this climbing slope on departre? By puling the stick?

author

I've added the info about tow hook location and not needing to pull back on the stick.

author

No. That steep angle happens without pulling back on the stick. The tow hook is just behind the center of gravity and can be adjusted forward or back to fine tune the launch angle. The only control input is left/right to keep the glider from vearing off to the side.

author
matt1606 made it! (author)2010-02-23

 agreed with both of you two. someone really needs to make a banshee bungee and show everyone how to. ive been trying to find bungee but i cant get any anywhere

author

you can also find the tubing for this on hobbyking.com, $6ish each.

author

There's lots of latex tubing available on EBay.

author
goud553 made it! (author)2011-01-15

can i buy bungee tubing at my local ace or lowes , homedepot or ANY OTHER tOOLS AND SUPPLIES SHOP OR do i have to go on ebay cuz id like to get my glider fliing like tomarrow

author

it's a bit late now, but you can use rubber tubing from dive shops, just be prepared, it is EXPENSIVE

author

Not that I've seen.

author
hrheault made it! (author)2012-06-17

Where would i best put the hook? The bottom, yes, but if not the bottom, where?

author

by the way, just in case you are new, the center of gravity should be about 25% back from the leading edge of the wing. that is, one quarter of the way back from the front of the wing to the back of the wing.

author

Bottom is the only place, just in front of the center of gravity on your plane. The CG is the balance point along the fuselage. Any other spot will most likely not work.

author
lr10cent made it! (author)2012-03-01

Another good anchor for a hi start of this size is a large automotive lug wrench. $1 at the junk yard. I'm talking about the kind that has a chisel point at one end and a bend near the other end. The bend allows you to work it back and forth to get it in or out of the ground. It would be better if it was a right angle, but that's not how they're made. Even with the angle it has, you can still pound it in if the ground is frozen, depending on how wet it was when it froze. We have some soft, wet ground at one end of our field, but this stake still works fine, even when it's thawed, with the 3/8" OD tubing I use.

author

Good tip.

The thing to keep in mind is you want the anchor firmly embedded when using the launcher. If the anchor pulls free while you are stretching out the bungee it could cause injury.

author
black42799 made it! (author)2012-01-14

THANKS FOR TAKING THE TIME TO EXPLAIN ALL OF THIS, I really like the spool idea to keep it all from getting tangled up, NICE JOB AND THANK YOU.

author

Thanks!

author
UATradition made it! (author)2011-11-28

That's the glider that I started my r/c life with about 14 years ago - The Gentle Lady !

author

Well chosen name too: slow, easy to fly, loves trees...

author
01glide made it! (author)2011-11-22

What year is that transmitter? It's got to be at least 25 years old.

I'm missing something here. This high-start system has been on the market even longer. When I built my first plane in the 80s, the same Gentle Lady, the high-start system sold for about $30. It included everything needed to launch right away: the surgical tubing, non-stretch line, metal rings, parachute, reel, spike (for wood fence posts), and a clamp (for any surface: metal post, fence, tailgate, etc).

I guess the new thing could be the dog anchor.

Here's a link for the current kit.
kit http://www3.towerhobbies.com/cgi-bin/wti0001p?Q=1&I=LXYXK4&P=N

author

Who said this was new? I never said in the instructable that I invented this. I suppose I should have mentioned that it's been around as long as model airplanes.

Sure, you can go out and buy a ready made high-start, or you can build one from scratch like I did.

As far as I know, this is the only instructable on High-starts and that's why I uploaded it.

author
goofy102938 made it! (author)2010-08-31

the camera shots from the plane are amazing

author
Waren-Neutron made it! (author)2010-08-31

such a good plan

author
Arkwebdragon made it! (author)2010-05-04

How many paces do you usually put on it before launch?

author

Never really measured it, but I'm guessing 60-80 feet.  The important thing to keep in mind is not how far you back up, but how much tension the bungee is applying to the glider.  Stretch the bungee back until the desired amount of pull is reached.

For my glider, I launch it using about 8-10 pounds of pull.  Step 3 talks about this.  How much pull YOU use will depend on the size, weight, and type of plane.

When starting out, you can use an angler's fish-scale to get an idea of how much stretch is needed.  Once you get a feel for things the scale isn't needed.

author
huntjulien made it! (author)2009-11-29

were  do you live.??? im a saskatooner...

author
travis7s made it! (author)travis7s2009-12-01

Me also from Saskatoon, but originally from Assiniboia.

author

Regina!  Small world, huh?

author
huntjulien made it! (author)huntjulien2009-11-30

guess so... hope to see you flying sum time...

author
kicker109 made it! (author)2009-06-13

thats a fair sick glider! you should make it an R/C (unless it already is). it would be so much more easyer than a discus or throw start. good job.

author

Thanks! It's RC but the way I fly you wouldn't know it.

author
cool! made it! (author)2009-05-07

My RC attempts are failing :) Nice instructable

author

Thanks Cool! That's why I originally got a cheap tiny camera to put in my plane. I was having so many crashes I figured it would be one or two more flights before I totalled it, so why not get some cool footage. That was more than two years ago. Other than landing in trees, it seems to have changed my luck. One thing that really did help was www.flying-model-simulator.com I practiced on the sim until I wasn't having any virtual crashes. I highly recommend using this free program and a 5$ USB game pad or compatible transmitter.

author
cool! made it! (author)cool!2009-05-07

Im having tech problems right now.
I should really try gliding, but takes too much space for me
right now im flying electric, but either the ESC or motor is broken.
I have a nice durable foamy right now, really easy to repair from my many crashes.
Once I broke the Fuse in half, repaired in 5 with hot glue :)
Here is the model:
http://blackdogrc.com/blackdogrc/eppCherokee.jsp
Ps Devon from BlackDogRC is really nice.

author

Cool,.. cool!

author
Opcom made it! (author)2009-05-02

That's one of the coolest things I've seen in a while!

author

Thanks! Exactly what I thought when I first saw a highstart launch.

author
mweston made it! (author)2009-04-23

Wow, I have never seen anyone launch a glider like this. Me and my dad have been flying planes and gliders for a few years and this is much different - I like the idea a lot! I never saw a full picture of the plane, so I don't know if it has servo controls (I know the idea is green and no battery power though) but that would be a heck of a lot of fun. Keep up the good work

author

Thanks msweston! Of course the receiver and transmitter use rechargeable batteries. There are two servos to control the elevator and rudder. I've added step 9 to this instructable showing the glider and a short video of it. Check out the League of Silent Flight: www.silentflight.org for more info on high-start and other cool green ways to soar. Catching a thermal updraft with your glider will get you hooked on this unique sport.

author
mweston made it! (author)mweston2009-04-24

Cool, love the idea - might go try it on a smaller scale this weekend if its not too windy

author
maxpower49 made it! (author)2009-04-23

did you make the plane or did you buy it either way i would like either a site or instructions

author

I built the glider from a kit. It's from Carl Goldberg Products Ltd and the model is called Gentle Lady. You can also get it "Almost Ready to Fly" too. www.carlgoldbergproducts.com

author
stevenscorsese made it! (author)2009-04-21

very cool - loved the camera view from the plane!

author

Thanx!

author
LUCCHINA made it! (author)2009-04-21

That's very smart!

author

Thanks, but you're too kind! I learned this from The League of Silent Flight, they're the smart ones...

author
Euphy made it! (author)2009-04-16

This is a great project, the film is ace!

author

Just checked out Recycled Cardboard Lamp. Very creative, sir!

author

Thanx Euphy!

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