Stiletto brake length

[skyjumpenfool 2]

Here is a question for you rigger types. I just picked up a good used Stiletto 135 to replace an older Stiletto 135. When changing out the canopy, I noticed the brake lines are different in the two canopies...
The length from the center of the finger trap to the toggle on the older stiletto is 14.5 inches. The same length on the newer canopy is 13 inches. I've looked at PD's line trim chart...
http://performancedesigns.com/docs/linetrims/ST_089-170LT.pdf
but that left me a little confused. I'm going back out to measure the rest of the lines, but maybe someone can tell me why these line lengths might be different?

Birdshit & Fools Productions

"Son, only two things fall from the sky."

[pchapman 279]

Lots & lots of people have brake lines that are adjustable at the toggle end, and/or have had replacement brake lines installed locally, so I'm not sure why variation would be unexpected? It's not uncommon for someone to ask for a few more inches on their brake lines.

(Now another lesser factor is that the line trim chart is revision D, so there have been minor changes over the years, although I have no idea if that particular dimension ever changed.)

[skyjumpenfool 2]

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Lots & lots of people have brake lines that are adjustable at the toggle end, and/or have had replacement brake lines installed locally, so I'm not sure why variation would be unexpected? It's not uncommon for someone to ask for a few more inches on their brake lines.

I get that. But, since the older stiletto opened, flew, and landed beautifully, should I be concered about 1.5 inches difference in brake length? Will it open harder? Will it surge on opening? Spin? Any thoughts?

One last question, does riser length/design affect brake line length?






Does riser length/design affect brake line length?

Birdshit & Fools Productions

"Son, only two things fall from the sky."

[pchapman 279]

Well if the brake set loop (cat eye) is in the same place it won't change the openings, where ever the toggles are...

With Stilettos generally lined with Spectra, there will be general trim changes so it is hard to know what to do if the brake line length down to the cat eye has changed. Everything will have changed. I'm no expert in trim changes, but usually I leave things fairly much alone unless the jumper says that the openings are getting squirrely in some way.

A bad thing to do when replacing brake lines on an older Spectra lined canopy is to lengthen them right to factory spec, because now they're out of whack with the way the rest of the lines have shrunk. If putting on new brake lines, I've tended to lengthen them a bit from the shrunk state of the existing lines (both counteracting the shrinkage, and given them a little extra because they'll shrink in time), but not go nearly as long as the factory spec.

While I won't comment on all the possible aerodynamics arguments about different riser lengths, clearly different length risers will place the toggles a different distance from your body. That'll influence how far you have to reach up, and how far down you pull for the flare or stall point, relative to your body.

[piisfish 140]

are the risers the same length ? people with different arm length need different brake line length

scissors beat paper, paper beat rock, rock beat wingsuit - KarlM

[davelepka 4]

The lower steering line will have no effect on the opening, that's the upper steering line (the brake fingertrap being the split between upper and lower).

The length of the upper is really only relative to the length of the other lines. Given the condition of the other lines, the upper may not match the factory numbers and the canopy might still open well. The 'ideal' is that all the lines are on the factory spec, but somtimes you don't get that.

The lower, provided that it's long enough to allow for full flight with no tail deflection, and front riser turns with the toggles in your hands with no tail deflection (if you do front riser turns), then the length of the lowers can be whatever the pilot wants. Riser length, arm lenght and personal preference will all come into play when setting the lowers.

Of course, the other consideration is the flare/stall point. If the lines are too long, you'll never get a full flare out of it. On the flip side, you'll never stall it either.

What you really need to do is just hook it up and jump it. See if the lines are long enough to allow for full lfight and front riser turns, and short enough to allow to 'reach' a full flare and just barely reach a stall. Once you have the lwoers set, you may have to reset them in a couple jumps as the line set stretches and shrinks from use.

[skyjumpenfool 2]

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are the risers the same length ? people with different arm length need different brake line length

I transfered the newer canopy to the same risers. So, the risers are the same ones.

I'll check the length of the upper steering line and go from there. Thanks

Birdshit & Fools Productions

"Son, only two things fall from the sky."

[riggerrob 643]

The real question is about the difference between the A and steering lines.
Note that PD insists on taking this measurement with the brake locking eye on the same nail as the front connector link.

On another matter, the quickest way to determine the age of a line set is to compare the lengths of the "A" line son one side of the canopy. When the outboard line is more than 3 inches shorter than the center "A" line, replace all the lines.

[jonathan.newman 1]

PD puts out a diagram on how to measure line lengths. It's on the same page where you pulled the trim chart.

The dimension you are looking for is BK-TOG, or brake setting to toggle. Put your cat-eye on a pencil, and pull the pencil and toggle apart. The distance from pencil to toggle is what you should be measuring; and for the 135, 16.5 inches is "spec".

I've seen spec lengths shortened by 6 inches for a jumper who likes his canopies "Tight, tighter! I like 'em tight" (NOT RECOMMENDED) to swoopers who have asked for 6-8 inches more than spec.

The way to check is to jump it. If in full flight, you can move your toggles 2-6 inches before the tail of the canopy begins to move you are fine. If the tail moves as soon as you touch the toggle, then it's too tight. Lengthen the BK-TOG.

And on the other end, if you're a swooper and your canopy starts to... well, if you're a swooper, then you know all this by now.

[skyjumpenfool 2]

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PD puts out a diagram on how to measure line lengths. It's on the same page where you pulled the trim chart.

The dimension you are looking for is BK-TOG, or brake setting to toggle. Put your cat-eye on a pencil, and pull the pencil and toggle apart. The distance from pencil to toggle is what you should be measuring; and for the 135, 16.5 inches is "spec".

That is the measurement I used. It's 1 1/2" short.

Quote

I've seen spec lengths shortened by 6 inches for a jumper who likes his canopies "Tight, tighter! I like 'em tight" (NOT RECOMMENDED) to swoopers who have asked for 6-8 inches more than spec.

The way to check is to jump it. If in full flight, you can move your toggles 2-6 inches before the tail of the canopy begins to move you are fine. If the tail moves as soon as you touch the toggle, then it's too tight. Lengthen the BK-TOG.

And on the other end, if you're a swooper and your canopy starts to... well, if you're a swooper, then you know all this by now.

I'm not a swooper! I have enough vises, thank you very much.

OK. I got 2 jumps on it before the plane started breaking thru the ice on the runway today.

Jump 1. Tossed the PC. Nice soft opening shock. As the end cells inflated, the canopy started turning hard to the right. I tried to keep it flying straight with harness input but it turned 540 degrees before the turn stopped. I had my hand on the L Rear riser, but it was flying straight before I needed to apply input.

Visual canopy check. Check and collapse slider. then, when I released the brakes, it did another hard 90 degree turn before flying straight. At this point, I took a quick peak at my handles... just in case.
Control checks... all good. Brake line check... not much slack. As soon as I touch a toogle, the canopy turns. I played around with it and all seemed good. So, at about 2500 ft. I stalled it. It stalled very quickly and recoverd very nicely. Suspicions confirmed, brake lines need more length. After that, I flew it very conservatively to a nice soft landing, being carefull not to stall on landing.

Jump 2. I tossed the PC and had a soft, straight on heading opening. In fact, probably one of the nicest openings I've ever had. I was very careful when releasing the brakes not to cause any turn. Everything went very nicely. The canopy flies beautifully. Again, powerfull flair and soft landing.

My conclusion.. Not sure what caused the initial turn on jump 1 (probably me?). Shit happens, right? As for the turn after releasing the brakes, I'm thinking mybe I was too aggressive (with short, touchy brake lines) and caused that turn by not pulling down evenly.

On jump 2, I was more aware of body position on opening. Also, I was way more carefull when unstowing the brakes. I could just keep flying the canopy as is and learn to fly it. But, I'm thinking I'll probly lengthen the brake lins and go from there. Any other advice is always welcome.

Birdshit & Fools Productions

"Son, only two things fall from the sky."