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Re: LE Stiffeners

Posted: Tue Jul 25, 2017 9:40 pm
by stefmoris
Hi guys, on my previous generation homemade foil kites (DIY Foil Kite thread) I used Nylon weedwacker line but found it limiting due to the tight radius set in the material as it is wound as it cools. On my latest generation of kites I'm using straight Acetal rods which are stiffer than nylon 6 for a given diameter and so far so good. The rods are holding up well and I have no deformation thus far (and I pack up my kites quite sloppily!) -stef

Re: LE Stiffeners

Posted: Wed Jul 26, 2017 1:06 am
by PugetSoundKiter
Appreciate the feedback. The 19m Speed3 DLX is Black and the indentations may be more visible on dark color fabric. I’ve flown a white 21m Speed3 and some cells flatten/indent a little (compared to being inflated on the ground with a fan) but not like the more worn 19m. Looking at the 19m LE the fabric is soft/smooth compared to the rest of the kite top and bottom side fabric that is in good condition. I agree the dents are due to lower internal pressures allowed by porous fabric. As mentioned by Skywalker7 the design of Speed3 included velcro to close off the center cell, lowering internal pressure, allowing deformation and decreasing efficiency. My center cell is always open. But, this kind of explains why the kite still seems to fly well even with the dented leading edge.

The LE fabric is probably worn the most because it is exposed to the wind directly and abrasion from leading edge down landings/re-launches (no tears on the 19m LE or visible scrapes). Open cell kites inflate better with very porous leading edges… So, I think spending more effort to re-coat the LE of the kite is not going to help. In theory, the more porous the LE is the less differential pressure is between the inside and the outside of the kite. Less pressure difference x area = less force = less deformation. It may not be practical at this point to raise the pressure of the worn kite without excessive re-re-coating and even more weight being added. This leads me back to stiffening the LE with materials and not pressure.

I’ve looked at the Ozone, Flysurfer, and Liquid Force foil kite leading edges with the sewn in stiffeners. It is like weedeater line but it is also shaped. It is sewn into the seam that helps limit movement but having a somewhat ridged form is probably helpful to keeping the LE shaped. It could be spring like and sewn into the seam to keep shape but they appear more semi-rigid. From my limited sewing experience, I’d like to avoid sewing rods into 39 cell seams. I was hoping for a practical solution that others could quickly, easily, cheaply use.

Still brainstorming ideas like maybe Acetal like rods heat shaped to the inflated LE cell shape and coated on one side with flexible silicone rubber caulk/adhesive, that could be peeled off later. I could try this on a few cells to see if the LE shape of cells can be corrected. Then test on several cells to see if there is any noticeable performance improvements realizing we are adding weight and drag. Some more down sides are they could pop off, sand could stick to the adhesive and it’s probably going to look ugly, but I've heard that…“99 percent of success is built on failure."

Re: LE Stiffeners

Posted: Wed Jul 26, 2017 8:43 am
by Regis-de-giens
The problem of Stiffeners is that it won't solve the bad shape of the LE in between Stiffeners which is certainly linked to pressure loss through the porous cloth and will degrade the performance (speed) of the kite; Does the whole LE deform or is it more present in the middle of each cell (as it was on my Speed3)? Re coating only the LE is not an option ; it is either the whole kite or nothing ; Seal N glide improves a bit ( not as much a stronger coating) and has no weight impact ; I also tried a local seamgrip coating of every sews ... time and cost for almost no result.

IMO if you have 400 dollars available, better to buy save your time and in the end your money and buy a new Pansh Aurora light with a new and lighter cloth, with has similar light wind flight abilities and relaunch as a brand new speed4 Lotus ... A bit out of topic but that is what I would do , having experienced several trials to solve a similar problem.

Re: LE Stiffeners

Posted: Wed Jul 26, 2017 3:32 pm
by gwicke
The Pansh Aurora also deforms some around the leading edge, especially when going upwind at the top of the kite's range. I honestly wouldn't worry about it too much. There are several other design factors that contribute to the deformation, most of which aren't easy to change.

If it still bothers you, you could consider buying a second hand race kite like a Diablo 1. The "Kiteracing2hand" group on facebook has many listed for < $1000: