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Old Jan 27, 2013, 10:46 AM
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SoaringDude's Avatar
near Sacramento, CA
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Improved bungee setup?

Last year at Visalia I saw and used a bungee setup that had a spacer line between the parachute and the tow-hook ring (see attached pic). I've done a ton of zoom bungee launches and always hooked the plane directly to the top parachute ring. But I've also had close calls where a steep zoom almost tangled the parachute in the plane's tail-feathers. So I assume the spacer line is to keep the parachute out of the tail's way. Seems like a good idea.

EDIT: After thinking about this on the way home from the field today I think the new attached pic shows the bungee setup I used at Visalia. Only restriction is that the spacer line and tow ring should be as light as possible so it doesn't completely collapse the parachute. I'll try it soon & report back.

Chris B.
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Last edited by SoaringDude; Jan 27, 2013 at 04:21 PM. Reason: Changed pic to what I think I used at Visalia
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Old Jan 27, 2013, 10:49 AM
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Woodstock 1's Avatar
Ireland, County Kerry, Kerry
Joined Dec 2005
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Edit: Drawing edited, so issue falls away!
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Old Jan 27, 2013, 10:59 AM
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near Sacramento, CA
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Originally Posted by Woodstock 1 View Post
What stops the parachute from opening and deploying fully while the plane is going up? Chris
An embarrasingly good question. Maybe I missed a detail on the one I used. Kinda why I'm asking before I try it.
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Old Jan 27, 2013, 11:00 AM
dare to thermal
Mannheim, Germany
Joined May 2004
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Chris,

IMHO remove the spacer line - itīs not necessary
Hook the top tow-hook ring first an then the bottom ring. The parchute is folded under the fuselage during the launch .
And if you hit the tail with the parachute, the dive was too long.

Bernd
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Old Jan 27, 2013, 04:24 PM
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near Sacramento, CA
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I just changed the original pic to reflect what I'm pretty sure I used at Visalia. It's worth some experimentation so I'll try it soon.
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Old Jan 27, 2013, 04:53 PM
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United States, CA, Midway City
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The chute should't deploy while going up the line if there's slight tension on the bungee and the plane is not flying towards the staked end because the plane is "dragging" the chute through the air. The relative wind of the chute is closer to 90 degrees to it vs 180 for normal chute operation.

I would recommend against an extension after the chute as it could pose more trouble than good really. Just practice to come off the line with some tension on the bungee.
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Old Jan 27, 2013, 06:02 PM
Registered User
Sarasota, FL
Joined Jan 2006
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I agree with fnnwizard. I had to put an extension on my launch set-up when a friend launched his Allegro 2-meter. Without it, the tail feathers got hooked into the chute or line. The extension (about 7") solved the problem and the chute never opened on launch. There was always enough line tension to keep the chute closed.

Besides the chute is traveling at flatter angle until the plane releases and then it comes down vertically and then opens.

Phil
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Old Jan 27, 2013, 06:19 PM
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near Sacramento, CA
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Tuan and Phil,

Really appreciate the feedback. I've never tangled any of my planes as I've learned from a few other's dramatic mistakes. But I have been teaching some guys in our club how to use a bungee with their bigger planes. I was thinking an extension might be a nice training add-on until they get the zoom duration + angle thing dialed in. There may be a reason why few do this but I'm still going to experiment a little (with my backup plane )
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Old Jan 27, 2013, 10:16 PM
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United States, WA, Seattle
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[QUOTE=SoaringDude;23946639]Last year at Visalia I saw and used a bungee setup that had a spacer line between the parachute and the tow-hook ring (see attached pic).... But I've also had close calls where a steep zoom almost tangled the parachute in the plane's tail-feathers. So I assume the spacer line is to keep the parachute out of the tail's way.

Guys,
The bungee you used at Visalia was mostly likely a SASS Club bungee that I built for the club. A little history on the set up. Most of my flights begin with a zip start launch. As a matter of convenience they are quick to set up. But more important to my purposes, as the launch height achieved is very low, they demand the most of one's piloting skills. First to make a proper read of the air as to when to launch and where to go once up, and second, as the launch is low, you have to make the most of your flying skill to get up and out.

Having made literally thousands of zip start launches, I think I have buggered them up just about every way imaginable over the years. The extension is the resultant "fix" to minimize the most common snafus you can create with a poorly executed zip launch. Primarily it places the parachute shrouds well ahead of the nose so as to preclude any part of the plane becoming wrapped up in them if you dip too deep prior to the zoom. A secondary advantage to the design is it gets the chute out of your grip area. I find I can grip the plane much better without out a collapsed, slippery chute between my hand and the plane. The plane is much more secure in my hand as I walk back tensioning the line.

I have found that with this setup, when I do mess up the launch, the extension is what the plane ends up flying into and more times than not the line will slide free of the plane and allow me to fly clear. The extension consists of about 3'-5' of parachord. I use a parachute with no ring in the top and tie directly into the chute shrouds. My personal set up does not use a ring to attach to the plane. I tie a loop and connect the loop to the tow hook. The reason for this is (again learned the hard way) when the plane flies into the line, the ring has a tendency to help wrap the line around the plane. Sort of like the way you might swing a set of car keys on a lanyard around in a circle and then let it wind its way on to your finger. Same thing happens on the plane. So without the ring, the chances of the line clearing the plane is greater. And that ring will really dent your plane when it smacks a surface! Additionally, no rings in the system = less weight the plane has to haul up the line = higher launch. So there you have it.
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Old Jan 27, 2013, 10:27 PM
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fnnwizard's Avatar
United States, CA, Midway City
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One of the reasons for the chute where it normally is, is to actually help get the ring off the hook.
If you do experiment, maybe have the chute at 2+ fuse length away.

If a pilot has a tendency to over run the parachute in a dive and the extension is not long enough, it could be possible for the chute to end up flirting with the tail more often than without the extension.
In an extreme cast the chute could be hitting the tail before the ring comes off... if the dive was too severe, no tension and in some wind etc. Just thinking of some instances I have been in to share
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Old Jan 27, 2013, 10:59 PM
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near Sacramento, CA
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Quote:
Originally Posted by m.vance View Post
Guys, The bungee you used at Visalia was mostly likely a SASS Club bungee that I built for the club. ...
Mark, awesome post and thanks for solving the mystery. Your explanation for the extension makes great sense to me. I also think Tuan's suggestion of an even longer extension sounds good with the caveat that the more extension you use the more it will keep the chute from floating in lighter breezes.

Thanks again.
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Old Jan 27, 2013, 11:33 PM
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[QUOTE=fnnwizard;23953704]One of the reasons for the chute where it normally is, is to actually help get the ring off the hook.

When done properly, zip starting, high tension competition winch launches and F3J launches could easily do without the chute completely. Other than helping to blow the line a little closer thus shortening the retrieve walk, and providing a bright color in the field to assist in locating the line, the chute has nothing to do with the line release.

A properly executed high tension zoom style launch maintains as much line tension as possible, utilizing the highly loaded line to snap release at the moment of highest wing loading as the plane rotates towards a vertical flight path. More tension=higher launch. The parachute is just along for the ride in this system.

If you muck up the timing however and dive too deep into the bucket, the tension is released and the line becomes slack. Now the chute can open and pull the line off the tow hook at just the opportune moment for the tail to fly right into the chute and tangle. So if you are using a chute in a zoom style type of launch, a small one is better than a big one
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Old Jan 28, 2013, 01:03 AM
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fnnwizard's Avatar
United States, CA, Midway City
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[QUOTE=m.vance;23954190]
Quote:
Originally Posted by fnnwizard View Post
One of the reasons for the chute where it normally is, is to actually help get the ring off the hook.

When done properly, zip starting, high tension competition winch launches and F3J launches could easily do without the chute completely. Other than helping to blow the line a little closer thus shortening the retrieve walk, and providing a bright color in the field to assist in locating the line, the chute has nothing to do with the line release.

A properly executed high tension zoom style launch maintains as much line tension as possible, utilizing the highly loaded line to snap release at the moment of highest wing loading as the plane rotates towards a vertical flight path. More tension=higher launch. The parachute is just along for the ride in this system.

If you muck up the timing however and dive too deep into the bucket, the tension is released and the line becomes slack. Now the chute can open and pull the line off the tow hook at just the opportune moment for the tail to fly right into the chute and tangle. So if you are using a chute in a zoom style type of launch, a small one is better than a big one
Hi Mark, how are you doing. I didn't realize you had responded when I post my reply. I agree completely with you. For our purposes the chute is just there to shortened a few steps to retrieve and makes it easier to see the end. It can also help tell you if there is a slight bit of tension on the line at release with a "pop" sound of the chute opening.
I know what you mean by moving it out of the way for grasping the fuse to launch. On my histarts with high tension (at least 40lbs of tension), I hook the chute like how they do in F3B so it literally dangles behind the hook and the chute/line joint with a loop is where the tow-hook attaches to. Of course there is some risk to this method of ours as with a lot of tension, I know I can't always get my throwing hand down to the stick fast enough... and usually that's where the tension left on the histart is trying to pull the plane down and I can end up over-running the chute if over diving.
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Old Jan 30, 2013, 07:16 PM
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Harbor City, CA
Joined Oct 2003
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I used to set up my aerofoam "mega bungee zipstart" like Tuan did with an F3B chute....
But, after I witnessed an FAI team pilot using it by hooking the whimpy F3B chute apex to the hook (with the chute in tension), I decided that this was too complicated a task.
Now I use a more normal heavier chute (from Mr Kite) with ring on top.

If I am going to tangle the chute, it really means that I rode the bungy way too long. You want to bump a ping before the rubber is limp. If so, and you aren't crazy agressive, its pretty near impossible to get wrapped in the chute.

One of the best things about having a chute on the end of the line, is it lays out downwind, and this time of year, the wind in SoCal tends to "clock around" with the time of morning, and so it tells me which direction to walk and stretch the bungee for launching directly into the wind (unless there was a large thermal influence at the time of the last launch).

The idea of a "leader" is interesting, I would think for the most snag-free arrangement, you would want to skip the ring, and just have a knotted loop of the line there.
Is that how you guys are doing it, or are you using a ring?

I think it would be interesting to also try no chute, maybe just a streamer, and no ring, just the loop tied into the line.
I would think that this would give least drag on launch under tension (like the 1/10th of 1% matters?), and more important, be the most likely to come off the plane, should you manage to tangle with it in the first place.

R,
target
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Old Jan 30, 2013, 07:33 PM
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Quote:
Originally Posted by target View Post
The idea of a "leader" is interesting, I would think for the most snag-free arrangement, you would want to skip the ring, and just have a knotted loop of the line there. Is that how you guys are doing it, or are you using a ring?
Target, yes, Mark's OP refers to using a tow hook loop on the extension, not a ring.

By the way, I found 50 ft. of "550 Paracord" (3.18mm dia, 150lb working load) at Lowe's for $6.70. This is probably pretty close to what Mark uses for his extension. This size paracord gives plenty of clearance for tow hooks. It ties into a nice secure tow hook loop using a Yosemite Bowline knot. Be sure you can pull hard on either side of the loop cord and not have the loop slip into a smaller one. The Yosemite Bowline knot is easy to tie wrong if you've had too many beers.

Chris B.
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Last edited by SoaringDude; Jan 30, 2013 at 07:46 PM. Reason: Added knot caution
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