Shortening the suspension lines

[crazy 0]

What would be the flight characteristics of a canopy with suspension lines shorter than the factory setting, for instance a stiletto 135 with the suspension lines from a stiletto 120? If you have actually tried it, which canopy was it? What was the effect on the performances?
BB
Come

[freeflir29 0]

You would probably wind up with an unstable canopy. Line trim, especially on smaller canopies, is critical to the way it flies. I'm just guessing though.....
"Here I come to save the BOOBIES!"

[LawnDart21 0]

Under normal wind conditions, it would fly normally, even with normal toggle input, but once you started to use riser input or hard toggle turns, you'd notice significant buffetting, and if it were flown through choppy air, you'd experience buffetting as well. Liken it to a car driving with all flat tires. If you drive slow enough, the car will still turn and stop, etc, but if you pick up speed or drive over bumpy terrain, the car will lose it's control proportionately to the increase in speed and or bumps in the road. Just curious, do you suspect that your lines are too short?
"I live to EFS"
Tom

[eames 0]

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Under normal wind conditions, it would fly normally, even with normal toggle input, but once you started to use riser input or hard toggle turns, you'd notice significant buffetting, and if it were flown through choppy air, you'd experience buffetting as well.

I'm curious as to how you know this. Have you flown a canopy with a non-standard lineset? Do you test fly canopies? Are you intimately familiar with the design and testing process of a certain manufacturer? Please provide more information.
I know that happens on certain canopies with short brake lines, because I've seen it and experienced it. But how do you know that's what happens with an entirely different lineset?
Jason

[faulknerwn 36]

I've never tried it on freefall canopies or ellipticals, but CRW jumpers regularly have different length lines on their canopies. I've got 2 Lightning 113's - one with 8 1/2 foot lines and one with 9 foot lines. I like how the one with the longer lines flies better - it seems to pendulum out a bit more in the flare and lands softer. The rotation guys who jump _really_ short lines definitely have to work harder to get good landings. The shorter lined canopy also seems a bit more "twitchy" I guess - it seems to react a touch faster to toggle input.
W

[riggerrob 558]

The biggest problem with a Stiletto 135 with 120 lines is that the canopy would be trimmed flatter. Which means that it would fly slower. Since it would be flying slower, there would be less forward speed to convert to lift at the bottom end, resulting in a shorter surf or no surf at all! In a worst case scenario, he sweet spot would be so tiny that you would not be able to land with both legs intact.

[polarbear 1]

It wouldn't neccessarily have to change the trim angle. You could shorten the lines without changing the trim. If you just took a line set from a 120 and threw it on a 135, then yes, it would have a flatter trim.
A canopy with shorter lines will not have to throw you (the pilot) around in as a big an arc, which will result in quicker handling and recovery. The canopy will have a sharper anhedral (it won' be as spread out over your head), which may make it harder to get slowed down as much when landing.
Assuming you don't change the trim angle, its hands-off natural speed should stay about the same. If you change the trim angle, the performance could feel very different.

[LawnDart21 0]

How do I know this? Hmm, let's see, it was part of the Evolution Canopy Flight School ground school that I attended. The person that stated the info on performance of canopies with complete line sets being too short, not just brake lines, was Jim Slaton of Icarus's Team Extreme, and arguably the best canopy pilot on the planet and the most knowledgable test pilot around. The car analogy was his directly. As for what you personally have experienced, all I can say is welcome to canopy flight, most, if not all manufacturers have their "stock" brake settings shorter than what would be appropriate for riser turns. It's safer that way. That is why you see so many high performance canopy pilots lengthening their brake lines. Because "hooking" on front risers with standard brake line settings, almost always results in slight tail closer from lines not being long enough, and when the tail starts to close in a dive, you get buffetting. Go flame somewhere else dude and keep your ego in check. I only have 500 jumps, but I took the time to learn from the best.
"I live to EFS"
Tom

[roq 0]

I altered and tested several canopys with short lines and same trim (eliptical 85 ft and 120ft, square110 and 252 accuracy, and kites) and my conclusions is follow:
More previsible opennings but also more sensitive.
More easy to keep a longer arch recovery.
Slightly more fast
less drag
less swinging balance and pendulum
flare a little more difficult to control but more long because less drag
Canopy in general with same good carateristicas of the normal canopy but more sensitive outputs and inputs for jumper, and need to lose chest strap for more large anhedral curvature of the canopy. With scenery of line twist, the canopy centrifuges less but is more sensitive .
All of the my canopys are short lines with same original trim.
Never to use short lines of the short canopy of same model, because drastic alterations in trim and profile.
Small lines should be made exclusively by the factory.
Roq

[eames 0]

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Go flame somewhere else dude and keep your ego in check.

Calm down.... I wasn't flaming. I really wanted to know the answers to those questions.... The fact that short line sets causes buffetting is not some piece of trivia I see thrown around a lot and I wanted to know how you would know that. Even though it probably doesn't always cause buffetting... but who cares? Jim said it does.
Oh, and thanks for the "welcome to canopy flight." I really know nothing about it, and I'm glad that a knowledgeable person such as yourself is here to set me strait.
Jason

[LawnDart21 0]

The funny thing is Jason, after I read your post, which I guess I incorrectly interpretted as a flame, and posted my reply, I read a couple of your past posts on swoop competitions.......I started laughing at the very same thing. "Welcome to canopy flight......lol" Oops. Anyways, yeah, we were talking about canopy line sets and how the correct size line sets are very important and what can happen if they are too short. That wasn't to say all canopies with short line sets would absolutely experience buffetting, but that it was very likely to occur, especially in turbulent winds. Anyway, misunderstanding resolved, my bad.
"I live to EFS"
Tom

[billvon 2,400]

>What would be the flight characteristics of a canopy with suspension lines
>shorter than the factory setting, for instance a stiletto 135 with the suspension
>lines from a stiletto 120?
You'd see several effects.
First off, the canopy would be more cathedraled i.e. more 'curved.' This makes it less efficient, since you are increasing the curve on the sides of the canopy, and only that part of the canopy that is horizontal generates lift. It would be like shortening the canopy slightly but keeping the same amount of drag. This would also make it tougher to land since you will get less lift in the flare.
Secondly, you'd get some trim errors. The line lengths are calculated so that they hold the canopy essentially flat; if you change the lineset to a lineset that's supposed to go on a smaller canopy, you may introduce a "step" into the canopy, since the D lines (for example) may now be too short. Note that, since the line attach points are farther apart than the lineset expects, the C lines may be fine or even too slack. In a severe case you might actually see one line group waving in the breeze, and a big "crease" in the canopy. This also isn't too good for efficiency.
Finally, you'd probably get some increase in directional stability, since the drooped tips are part of what gives a canopy yaw stability.
It is worth mentioning that line length is a tradeoff. Too long, and you get a very efficient flat wing, but lots of line drag and reduced yaw stability. Too short, and you get low line drag, but an inefficient wing. This is one reason that spreading your risers helps increase efficiency - you reduce cathedraling without lengthening the lines.
-bill von

[crazy 0]

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Small lines should be made exclusively by the factory.

Do you mean that manufacturers agree to do this kind of modification? Until know i thought that these were always home made.
From what you say, it looks quite good... Do you know if there is any competition swooper flying with shortened suspension lines?
Come

[SkydiveMonkey 0]

Couldn't you have a line set with shorter centre lines, but comensating with slightly longer lines going to the outside cells (compared to the normal shorter line set)
Adrenaline Junkie Skydive Monkey

[eames 0]

It really did sound like I was grillin' you, I apologize, but I swear all those questions popped into my head.... If you had answered "yes", I was going to ask you for some war stories. Hadn't really considered the "no" reaction.
This thread caught my interest 'cause I have a custom sized Xaos-27 coming and I was wondering how they determined the line lengths for custom sized canopies. Chris informed me that the lengths scale, to a point, with the canopy size. Meaning that an extremely small canopy or an extremely large canopy may not scale, but generally, canopies of a given design are in proportion.
But how do they come up with that scale? Trial and error? Pick the sweet spot between too long and too short?
Jason

[billvon 2,400]

>Couldn't you have a line set with shorter centre lines, but comensating with
> slightly longer lines going to the outside cells (compared to the normal shorter
> line set)
Paragliders do this for just that reason, so I tried it a while back with my Sabre 150. Hardest opening I've ever had in my life. Reason - if the outer lines are longer, the slider does not sit flush against the stabilizer bumpers, and the canopy is not reefed the same way.
On the other hand, if you could open your canopy then somehow "release" the outer lines, allow them to become six inches longer, then it might work. If I ever get a decent sewing machine I might just try this . . .
-bill von

[roq 0]

I know some makers that can make that alteration, but I won't say who.
But if you are interested ask the maker of its calote. He can agree who knows ?
I don't know swopers of the professional circuit with shortened lines. But I have three canopys with shortened lines (85) with more than 300 jumps with very good results.
Roq

[crazy 0]

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Paragliders do this for just that reason, so I tried it a while back with my Sabre 150. Hardest opening I've ever had in my life. Reason - if the outer lines are longer, the slider does not sit flush against the stabilizer bumpers,

Please can you explain a bit more? If the lines are adjusted so that the bottom of the ribs is straight, I don't see why the slider wouldn't sit against the bumpers.

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and the canopy is not reefed the same way.

On a stiletto 135 with suspension lines of a 120, at low (~1 lb/sqft) wing loading, the owner said that it opened a bit faster and that the possibility of closed end cells was reduced significantly (unfortunately i couldn't try it).

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On the other hand, if you could open your canopy then somehow "release" the outer lines, allow them to become six inches longer, then it might work. If I ever get a decent sewing machine I might just try this . . .

Why not put a bigger slider?
Come