hi there every one well i built my first bungiw launcher today if i could figure out how to post pics i will do so but i am wondering what sort of weight ratio to use for the launch i dont want to stuff around with trial and eror to much as the jets dont take to kindly to ground impact any help would be great thanks

here are the pics hope it works

I have tried anywhere from 3:1 (min) to 5:1 (max).

A cord tension equal to five (5) times the AUW of the plane will work. You can gradually reduce the tension in the cord as you gain experience.

Where have you located the launch hook?

do you mean the launch hook on bungie ? if so at the rear as you can see in the pic in will run a Y lead off the bungie to the foot release and one to the plane will take some more pics next week when i go to use it

Great stuff but can you post pics or provide detail on the bungie part of this? I mean are you still attaching a bungie to a stake some 30ft out and just using this as a ramp or is this a "self contained" system. I've been trying to come with something as well because I can't hand launch worth a darn and very few at the club "volunteer" to help as well.

Take a look at this article. I think it will answer all your questions

http://www.rcgroups.com/forums/showthread.php?t=404254

I'm using the surgical tubing from Home Depot it came in 1o foot lengths I tied 2 together. I'm using about 100 feet of tension to get a good solid launch. I started at 75 feet and it just din't have the enough tension. The Panther a just a bit over 3 pounds and it ggets off the launcher in a hurry. Mike

Here's the actual bungee withe the nylon cord and rings attached. Mike

One question about your launcher. The third picture with the plane positioned on the launch rails bothers me. Isn't the release supposed to be at the front of the launcher so there is no slack in the launch cord? With the release under the plane as in the picture, it seems when the release is activated there will be some slack in the line that the bungee will quickly take up and then yank mightily on the launch hook (risking damage to the fuse). Am I not seeing this clearly?

RCMiket, where did you get the candystripe F9F? I know I've seen one once bumbling around websites, but I can't remember where it was? What are the dimensions on your launcher? I'm working on a Ziroli Turbinator-E and I need to build a launcher for it. I like the looks of yours!!

http://www.ejf.com/index.php?main_pa...roducts_id=676
EJF Talk to Robert hes bringing in the whole RC Lander line. Great EDF. I'll post some more info on the launcher. >Mike

Kingcobra,

The bungee is set up so there is no slack in the cord.

Okay, so what am I not seeing/understanding? I'm going to be fabricating a launcher, too, and as I understand it, the bungee is attached to a ring which will go over the vertical upright pin on the launcher which, in the 3rd picuture of the top set of photos, is under and slightly behind the plane on the launch rails. Then there is a line going from the ring to the tow hook on the fusesage, which in that picture would have to go up and forward to meet the criteria that it is in front of the plane's CG. So it seems it could be a problem securing the line to the plane/launch hook. It doesn't look like there is enough room on those rails to slide the plane back to take up any slack that might be in the line once the ring is popped over the vertical pin and the bungee line contracts. In the pictures of Mike's launcher, the release is on the front of the launcher and the plane is positioned on the back of the rails so there is no slack in the launch line. That doesn't seem to be the case in the launcher at the top; but maybe it is just a misleading perspective of the photo, too.

Its pretty simple but I understand how confusing it is because I've been there. If you need any help in any way please just let me know. I did mine with the "it looks about right" mind set. I'd be more than happy to post dimensions or anything else you might need. Mike

Mike, I'd like to hear the specs and tips on constructing yours. I noticed too that you have some postings on another bungee launch thread. In that one it looks like you've replaced the tops of the front vertical supports with cut open T's to extend the launch rails. And maybe give it a bit more vertical height? What prompted the modification? CC

I have the same thing as RCMiket but on the tow end, I have 2 nylon cords. Shorter one is connected to the tow ring whilst the longer one is used to take up the tension. Hence, no stress on the tow point till its released.

The modified launcher was raised in elevation for a better launch angle. The foam was causing too much drag on launch so I went with the cut open T's, works great now no issues. I'm gather the specs and will have them up in a while. Mike

I tried using the surgical tubing in cold weather. It doesn't retain any elasticity when it gets close to freezing. I went with 3/8 inch woven bungee 30 ft long, stretched to total of 45-48 ft, with 20-23 lbs tension, based on a fish scale I bought at walmart for 5 bucks. (I am using the JePe dolly with wheels. On my first launch the hook was too tight on the dolly bar, and the horizontal part of the hook was too long, so it didn't release. I cut it down to 1/4 inch past the bend, and extended the length to the fuselage, and have had no problems since.)