Tension knots and firm openings. Two things skydivers are not lovers of. And canopy manufacturers even less so. It all started with one or two Leia pilots experiencing these issues, followed by some investigation by JYRO (previously NZ Aerosports), which finally resulted in a modified lineset for Leia. That was after much trial and error, a lot of testing and a fair bit of head scratching. We asked our R&D team to answer a few questions about the process they went through and give a short history.
How did it all start?
It started with a small group of people who were having tension knot issues and some others having firm openings. Mostly they were camera flyers affected. Given the amount of Leias out there and the amount of jumps on it, it was considered statistically insignificant at the time.
What Changed?
We decided it was still worth asking around and investigate further. In doing so, we received more feedback about tension knots. Although the number affected was still the minority, it was enough that we needed to act on it.
What was next?
We sent a survey to all our Leia customers to gather feedback. We included a range of questions about gear, jump numbers and DZ location. From this we gathered around 200 responses, giving us enough data points to compare many parameters.
What did the data show?
For the most part, it showed there was no significant correlation between a skydiver’s gear and their rate of tension knots. For example, your d-bag type, whether it was magnetic, semi stowless or standard, had no impact on increasing or decreasing your chance of a tension knot. One parameter that did show a trend was line size/thickness. We found that around 90% of people having tension knots had our thicker 550lb Vectran line.
What actions were taken next?
The first thing was to discontinue our 550lb Vectran line since that line type had the highest volume of tension knots. We now only offer our 400lb Vectran line on Leia. This is a temporary solution and we are currently working on a thicker line type as an alternative.
Next, we looked into how people were packing their Leia. We compared packing techniques in a group of Leia pilots (no tension knots vs. high rate of tension knots) to see what differences there were. From this we developed a packing guide and video for Leia. The main takeaways for packing your Leia:
- good line tension is essential during the entire pack job
- smaller line stows to avoid excess loose lines
Problem solved then?
Unfortunately not! This only helped reduce the rate for some, while others continued to have tension knots. From here we began to watch many opening videos – both when a tension knot occurred and when one didn’t. We used slow motion and 360 videos to get the best picture as well as studying photos when a tension knot occurred.
What did you discover?
From this, we discovered the tension knots were almost always happening between the brakes and the C3 and C4 lines, which on Leia are span-wise (left to right) and not cord-wise (front to back). At first we thought it was a cascade point on the brake lines that was the issue.
This began a testing campaign of new designs trying to avoid interference of the cascade on C3 and the brakes. Basically, we tried moving the cascade up and down each line to separate them. This had limited success so next we made a new design that removed the cascade from the brake line. This also had limited success.
Where to from there?
It was back to looking at the videos and going in a different direction. We noticed there was a phase during the opening where there was slack on C3 and C4 so we decided to shorten C4 to help keep tension during the opening. This was a big step in the right direction to reducing the tension knot rate. It also had the advantage of sitting the slider in a better position during the opening, which helped to make the openings softer and more predictable.
Time to release it then?
First, we had to get multiple pilots on varying sizes with varying wing loadings from all over the world to test it out. The feedback was positive, but some people felt that the roll sensitivity of the canopy had increased. We solved this by modifying the A4 and B4 lines to flatten the lobe and counteract the role sensitivity.
Now that the modification had been proven safe the next step was beta testing. This is where we send it out to a wider range of pilots for a more diverse range of feedback over a longer period of time.
From thousands of beta test jumps and positive feedback we concluded that the modification was successful, we had managed to keep Leia’s flight characteristics the same but also reduce the tension knot rate and improve the openings.
Now is it time to release?
On March the 28th 2023, after 2 years of R&D, thousands of test jumps and working closely with our Leia pilots from all over the world, the Leia line modification was released. It was a slow and trying journey but the results are definitely worth it. A massive thank you to all those who helped develop the modification, from those who filled in the survey to those in the heart of the testing phase, it was all made possible because of your input.
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Feature image Photo Credit: Matt Walker. JYRO sales person, funky sock wearer and all round good fella.
Blog images provided by test jumpers, Leia customers and screen-grabs of the Leia Mod Explained video.
KEEP READING
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Research & Development: Tales from JYRO Test Jumpers
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