The Freewing 1026... its just too awkward to hand launch!KaPANG! What are you launching?
Cheers!
LitterBug
Just a few things to be aware of!This should be a pretty short build thread. After all it's mainly some plastic water pipe and some bungee rubber!
Here's my very (very very very) rough sketch..
View attachment 130453
I will lower the overall height was thinking about that too. The string I drew was incorrect in arrangement and I make that a bit clearer tomorrow and I've seen some add a small rubber ball on it to reduce that snapping effect. Not sure about the reduction of the angle - seen several simular systems where the initial 5-7 degrees was increased to around 15, which is what this was 'designed?' to be. It will be easy to make less/more anyway.Just a few things to be aware of!
The ramp pieces will bow downwards under the tension of the bungee at launch so you end up with a "Ski jump" type profile during launch and with very small planes and too much tension it is possible to damage the wing underside or even break them due to the sudden increase in upwards angle at the end of the ramp..
As the release point/treadle, and bungee cord, (under tension), are not in line with the slope of the ramp. On release the initial pull on the aircraft will have a very large downwards component.
If you do not coat the ramp pieces in something very low in friction you will scar the wing undersides and after a few launches start sawing through the wings!
If you are open to suggestions I would suggest that you drop the ramp angle to 5 degrees and reduce the overall height so that the bungee does not have such a severe angle when it snaps to full tension on the towed/still stationary plane.
Finally ensure that the string(?) to the treadle is considerably longer than the string to the launch hook. If there is not such a difference it is possible, (happened here quite often until the message got through), the released treadle string is whipped upwards as the bungee tension changes its focus form the treadle to the tow hook and can strike and become entangles in the aircraft rearmost control surfaces.
Good luck with it all!
Have fun!
What we use here which is the result of efforts of most of the club members is actually a simpler system than you currently have envisaged.I will lower the overall height was thinking about that too. The string I drew was incorrect in arrangement and I make that a bit clearer tomorrow and I've seen some add a small rubber ball on it to reduce that snapping effect. Not sure about the reduction of the angle - seen several simular systems where the initial 5-7 degrees was increased to around 15, which is what this was 'designed?' to be. It will be easy to make less/more anyway.
What do you think of adding some of that smooth pipe insulation along the runners? seen that a few times on other bungee catapults. What would you suggest to use?
Thanks for the input![]()
You are correct that a launch "Dolly" could be used but like all things as you increase complexity you introduce other concerns and issues.I have never built one but anyone done one or tried with a sliding bed that the aircraft sits on? Bungee cord is now attached to the bed so no downforce on the aircraft so then it doesn't matter what angle you have it at. I tend to make things more difficult then they need to be and 50% of the time it doesn't work anyways.![]()
I raised a thread on something similar. It was a bungee system for ground launching aircraft, (NO RAMP), and it works very well still even on the large EDFs, (greater than 3Kg). Whilst it still used a treadle the use of the treadle is purely optional and without it it becomes a cheap histart system!I wonder if you could do this even more simply? Why not a high-start type setup with a single bungee attached to a string. Anchor one side of the bungee to the ground, tie the other end to the string, and the final end of the string gets hooked on the aircraft. Walk backwards to stretch the bungee and then release when the tension is right. I've been wanting to try something like this but I don't have the appropriate bungee material.
I raised a thread on something similar. It was a bungee system for ground launching aircraft, (NO RAMP), and it works very well still even on the large EDFs, (greater than 3Kg). Whilst it still used a treadle the use of the treadle is purely optional and without it it becomes a cheap histart system!
See: https://forum.flitetest.com/index.php?threads/the-best-20-i-invested.53587/
Have fun!
Yea, it was just all nice and "laser cutable"...Of course I have already checked out those links and the foot release is a shameless rip off
It's definitely going to break down into bits for easy transport. My car is not huge 🤣🤣curious if you are going to leave sections unglued for transport, or is it "just the right size" to toss into the back of the car?