Stormeflyers
Slope Soaring Pedal Bungee Launcher
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This is an inherently and potentially dangerous tool, even when used correctly. The builder/user will assume all responsibility for any harm or damage, and will use it at his or her own risk. Stormeflyers assumes no liability nor responsibility for any mishaps. "Let's face it, in this hobby we use high-amperage electricity, we play with high-powered motors that spin razor sharp carbon propellers, we use toxic glues and fuels, and we use plenty of very sharp and very hot tools"
Cutting list and materials
2 pcs x 24" x 5 1/2" x 1/2" Plywood (Sides)
1 pc x 24" x 4 1/4" x 1/2" Plywood (Base)
1 pc x 33" x 4 1/4" x 1/2" Plywood (Pedal)
1 pc x 4" x 2" x 1/2" Plywood (Hinge riser/spacer)
10 black drywall screws, 1 1/2" long
1 x 4" x 1/4" Coach bolt & washer & nut.
2 x Tent pegs
3 x I" diameter harness rings
1 x 18" x 1/4" metal ground stake
2 x kitchen worktop connector blocks
8 yards of 3/16" bungee cord
Strong twine or Dacron.
Construction is very simple if you understand how a bungee launcher works. Essentially by pressing down the rear of the pedal with your foot, the pedal rotates on a hinge and rises up at the front, which in turn releases a harness ring which is under tension from a bungee cord staked into the ground.
The harness ring is released and your model is launched from the launcher. The reason the entire launcher doesn't move forward is because it is held in the ground with tent pegs
Double click to enlarge photos
Lets begin the simple construction.
Base
Sides
Next glue and screw the two sides to the base making sure the sides are vertical. You will note that the sides on my bungee are sloping. The sides are 5 1/2" high at the front and 3 1/2" high at the back. The incline was found to greatly enhance launching a model as it enabled it to gain height much quicker without any user input.
Pedal
Plane a couple of shavings off one edge of the pedal so it fits between the launcher sides without binding, then shape the front and back of the pedal, again drill a 1/4" hole in the centre set back 1 1/2" from the front of the pedal to correspond exactly with the hole in the base. You will need to make this hole slightly larger
than the base.
Hinge Riser
Measure 16" from the front of the pedal and mark with pencil, next screw your 3" hinge parrallel to this mark with the hinge pin parrallel toward the rear of the pedal, Next open your hinge at 90 degrees to the pedal and screw the other side of the hinge to your your 4" wide riser. You should now be able to close the hinge flat with the riser secured below. Screw from the hinge countersunk faces...........Doh!
Next mate up the pedal onto the base lining up the holes at the front and operate the pedal, noting that it does not bind at the sides or around the top of the coach bolt. If your pedal binds at the top of the bolt, simply cut the excess off with a hacksaw. What you want is that when the pedal is fully depressed it clears the top of the coach bolt by 1/2", you will find that you will need to file the pedal hole larger due to the arc of the pedal, an elongated slot front to back is better than a gaping hole!
When you are happy with the position and the pedal moves freely mark the base where the riser (hinge spacer) mates up, lift off the pedal and drill a couple of pilot holes through the base to enable you to screw the riser to the base, then apply a bit of glue to the bottom of the spacer, refit the pedal and secure with a couple of screws from the underneath of the base.
Lastly you can give your launcher a couple of coats of varnish, when dry attach your two worktop blocks (one either side near the front) I also ran a strip of cross weave packing tape along each top rail to protect the models covering on launch.
Bungee chord set up
Simply make a loop at both ends of your bungee, but make one with a harness ring in it. Then attach another harness ring to this one. From this one attach your strong twine, I use only about 5" and finally attach this to your last harness ring (this is the one that you secure to your model's hook)
Rigging the Bungee
Find a suitable location, into the wind of course..........Doh! and drive in your groundstake at an angle away from you, slip over the bungee loop and pace back approx 11 to 12 yds, you should now get a good feel of the tension of your bungee chord as you walk back to the launcher. Attach the first harness ring to the coachbolt, making sure your launcher is secured to the
ground properly with the tent pegs, or you just might see all your hard work scurrying away from you over the ridge. Carefully place your model on the launcher and attach the last harness ring to the model's hook.
You are now ready to commit the art of Bungee!!!!!!
Under tension and ready to Launch
Remember to drive the front main anchor stake well into the ground at an angle away from the launcher, the bungee chord automatically drops to the very bottom of the stake under tension, which is the correct position for the bungee chord.
Some launcher designs use a concrete nail to secure the harness ring to, I soon replaced this with an inverted coach bolt as the threads act as a grip on the harness ring release hook, greatly reducing any possibility of a misfire. I found a concrete nail far too unreliable; with one particular occasion when the bungee misfired off the nail as I was attaching a model and the metal release ring caught my knuckles, to which my friends learned some new Anglo Saxon expletives. I looked down at my hand expecting to see fingers missing.
Never ever leave a bungee launcher tensioned at the slope unless you have a model on it to launch, if it misfires and someone is at either end of the tensioned bungee chord, someone could suffer terrible injuries even with a ribbon attached. Make sure you know there are no persons or animals below the slope before you launch. You just might be greeted suddenly by their unexpected presence in the line of fire with disastrous results. If children, including your own are around leave the bungee in the car.
Used correctly, a bungee is invaluable to launch models. The model is flying as soon as it leaves the launcher, so you aren't going to stall or dump a model in the ground because of a lousy hand launch or slip. This will also benefit electric models, simply launch with the motor off then switch on when you are well into the air, this saves lots of battery power for your flight. Variations of the launcher can be made with a wider body and using dowels, these can even be used with models with IC engines and no undercarriage to great effect.
To the uninitiated, when under tension people think a bungee launch will rip the wings off a model..........the reality is the launch is so smooooooth! and when seen modellers wonder why they never thought of it before. We nearly always use bungee launchers, especially in very strong winds, otherwise we could not safely launch our models without them being spat back into the slope and breaking into bits. Once away from the ridge and out of the turbulence the gliders are rock steady.
Lift off!
"Bearing in mind; you are launching a trimmed model aren't you?.........................Doh!"
We have frequently launched a model off the bungee only to find the lift had unexpectedly dropped, but due to the considerable height gained by the launch, we simply flew a circuit and landed under full control. You could not have done that with merely a hand launch, I have witnessed a few stuffed models from a hand launch with insufficient lift. Even with no lift at the slope, you can just crank up the bungee tension and fire your model into space, then see who can be the first to do the most circuits or stunts or rip the covering off the wings!
Stormeflyers accept no liability or responsibility whatsoever for any harm or damage caused. The builder/user will assume all liability and responsibility for and will use it at his or her own risk.
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