Originally Posted by Andy852

The HobbyKing bungee launcher yesterday, trying some different geometry combinations and velcro amounts.

Using old planes as test subjects.

Hi Body, just curious? What size of EDF is that F/wing, are you running it on 3 or 4S? I bought yesty in the S/H junk shop this weird looking Delta wing set up for 90 mm fan, I'm going to make it as a bungee launcher as well, there is bit of issue with the CofG with heavy motor at the rear so going to extend the nose a bit as the easiest solution.

Originally Posted by jofro

What size of EDF is that F/wing, are you running it on 3 or 4S? I bought yesty in the S/H junk shop this weird looking Delta wing set up for 90 mm fan, I'm going to make it as a bungee launcher as well, there is bit of issue with the CofG with heavy motor at the rear so going to extend the nose a bit as the easiest solution.

64mm EDF running on 3S, plenty of powder, but not very fast.

Stable, smooth flyer.

Andy, what are your thoughts on the Hobbyking launcher generally, and can you show a picture of the hook on your plane(or some pictures of various hooks...)?

I'm kind of off the idea of a bungee at the moment, and in any case winter is here unfortunately, so I'm in for a lenghty winter flying lull.. I still may order the HK just to mess around with. Still have this one plane I really like, which I just can't hand launch consistently....

Originally Posted by Herrsavage

Andy, what are your thoughts on the Hobbyking launcher generally, and can you show a picture of the hook on your plane(or some pictures of various hooks...)?

I'm kind of off the idea of a bungee at the moment, and in any case winter is here unfortunately, so I'm in for a lenghty winter flying lull.. I still may order the HK just to mess around with. Still have this one plane I really like, which I just can't hand launch consistently....

Herrs - I am not using any hooks, just a piece of Velcro (you can see the piece of blue Velcro in my photos).

I think I am using too much Velcro, as the test subjects have trouble releasing sometimes.

I am just messing around, it is some cheap fun if you have some old, damaged planes to practice with first.

Originally Posted by Andy852

64mm EDF running on 3S, plenty of powder, but not very fast.

Stable, smooth flyer.

With that sort of model one would wonder why bother to use launch ramp. By the time you set it up you could have 10 hand launches. The wing loading might be some 20 grams per decimeter.

Position of my catapult set up.

That's not even a hook, but a (relatively speaking..) giant long piece of wood with a notch in it...

Originally Posted by jofro

With that sort of model one would wonder why bother to use launch ramp. By the time you set it up you could have 10 hand launches. The wing loading might be some 20 grams per decimeter.

Yes, I have flown it 100s of times via a hand launch, but I wanted something to "test" on the bungee launch ramp.

Originally Posted by Herrsavage

That's not even a hook, but a (relatively speaking..) giant long piece of wood with a notch in it...

What ever you call it, it serves as a hook, also the take off and landing skid in models I don't use landing gear. The most important thing is, I never, ever had a failure launching because of its simple release as it passes the tension.
Just putting finishing touches to my latest birdie with no idea how it will go.

Nice. What glue do you use to isntall that long "hook"? My experiences with epoxy thus far have been crap... Mix it, apply it, ends up weak and useless...(tried to repair a couple Parkzone cowls. Did not work well... Tape would have been as effective - and no less ugly...)

5 to 30 min. Epoxy is my best friend. Sets as quick as I like if warmed up also mixed with powder if needed. Preparation is the trick, some foam needs to be cleaned with metho spirit, also I always pin contact surface.
What you call piece of wood is 3mm light ply epoxied to the body after some 5-6 mm grove is cut out in the foam for proper seating.
If not in hurry I often use liquid nails either water or terp based depend no surface, good idea to check it first so the foam won't be eaten.

Use of ramp depends on what terrain you are flying of ... I fly of rough fields and a Ramp is needed.

The hook - no need for anything other than a simple affair ...

Here's hooks as I fit :







They could be replaced by Ply if necessary.

Epoxy works IF set in ... but better is PU Glue (Gorilla Glue) ...

As to ramp use ... used properly it provides a good angle and launch system ...

Catapult Launcher April 18-2012 compilation (3 min 48 sec)

Nigel

Little piddle on 3S/1800 I just throw by hand , what a waste of time setting up ramps. Are you serious or just kidding?

Originally Posted by jofro

Little piddle on 3S/1800 I just throw by hand , what a waste of time setting up ramps. Are you serious or just kidding?

Jo ... if you want this argument again ... I'm not interested .....

Nigel

Lets look at Bungee launching and various systems and any advantages.

Many reasons why we would want to use one, it could be that like me - you do not like hand launching despite many years of doing it. It could be due to size or design of the model. It could be due to torque reaction in high powered models such as my Parkjet NFS.

The choice of how you bungee is often dictated by the flight site - if like me you fly off predominantly rough sites - then a ramp system gives you clear launch. If you fly of smooth surfaces such as short grass - then you may elect to not use a ramp.
Each has its place and reason.

Taking my own circumstances, and having used Hi-Starts on Thermal Gliders for many years - it was a natural progression to look at similar for those models that proved to have some 'quirks' on hand launching. The NFS project where quite small models were grossly overpowered created launch problems that just made hand launching a nightmare. Imagine 1kw via a 3500KV motor / 5x5 prop on back end of a Parkjet and you start to understand TORQUE !!
Tests were conducted and an exit speed (unpowered) of my ramp was measured at 117KPH ... that was well above flight stable speed and meant literally zero torque reaction with minimal run length. (The compilation video above shows the Parkjet pusher prop going of on one of its 700W 200KPH test flights).
Moving up - I launched larger models and had 99.9% success rate of it. I have to deduct 0.1% due to failures - not due to ramp or bungee - but model / myself.

Having looked at various designs and online sketches of ramps and systems - I combined what I considered best .. modified ... developed a system that only takes a couple of minutes to set-up. In fact I have been in the air as fast as others without bungee ... by time they sort holding and stance to launch - I'm releasing my trigger ! It really is a place on ... hook line ... open throttle and go. My bungee line is placed at 27 paces ... to give tension I need for up to 1.5kg models on 6mm Bungee ... I have 8mm for larger and that is set at 27 paces as well.

The ramp and set-up allows me to fly from literally any location and have reliable launch under MY total control. There are times I consider just using bungee along the ground - but given that it only takes so short a time to put the ramp and G'TEE a launch - I am used to using it and that's it.

Others who have developed FPV and other hard to launch 'vehicles' have taken my system and been rewarded with success. Do not mis-understand - my design is based on others and my modifications to suit me better.

If you do not fly of rough or unsuitable ground - then you can choose ramp or no ramp - its all down to situation and what works.

OK onto a point that rarely gets mentioned but in my mind is important. Hook design.

If you use a system that carries tension BEFORE release - then it needs to be structurally secure in the model. It is carrying tension that the hook is holding. This is common with a single line system. It also means that you are most likely having to hold the tension by tethering the model.
My design uses a twin line system where the tension is carried by the trigger and the line to model is not. Therefore the hook only has to be strong enough to resist the tension as it pulls model through the air ... this is significantly less than the single line system. As example - my F16 has simply a bent wire hook passed through a hole in bottom of the intake under the fuselage and taped in place. I can remove it easily.

Some are worried about the trigger line being longer than the model line ... I have never had it catch a model - because it has a metal ring and flag at its end which causes it to 'fly' much lower than the model.

See the lower left of the photo .... if photo does not show - its attached below



The position of the hook is also at a point that allows pitch control to be used if needed .. but actually gives the model a good slope angle of the ramp without my need to pull up more than a very small amount ... no need for switchable pitch etc.
Too far fwd and model can start spinning on the line like a top ... too far back and it can pitch up violently ... so I advocate about 40 - 60% distance nose to CoG.

I am always open to questions if anyone thinks I can help. I am not worlds expert on this - just one who has had good success from such over 50yrs of RC. There are many other designs / ideas out there with and without ramps / rails / launch additions ... its what suits the pilot and model.

When I launched my NFS Parkjet on first test - I shouted 'Truly Independent' having had all the failures of hand launching such a beast ...

It really is a great addition to RC flying to have a system that can launch models without need for assistance reliably time after time ...

Good luck to all .....

Nigel