Power Kite Forum

Cuben Fiber power kite 2.5M

rdcrawford - 2-16-2016 at 06:40 PM

Here's my latest toy. A mid A.R. Cuber fiber power kite at 2.5M

Here's the details.

0.51oz CTF3 Cuben fiber fabric skin and profiles
primary bridles are 90#kevlar core high tenacity polyester sleeve at 0.8mm
Secondary bridles are 200# PTFE impregnated Vectran at 0.9mm
Bridle attachments are 450# Technora tape with a proprietary stiching method that eliminates seam pull.

Kite by Rich Crawford,SBR Kites Colorado
All cordage from John Kiker, Twin-Line USA Colorado

Next up is a high A.R. 2.7M race machine. Same CTF3 fabric but an even lower drag higher tech bridle.

Can't wait to go buggying.



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rtz - 2-16-2016 at 06:48 PM

What's the story/history of that kite?

The Story

rdcrawford - 2-16-2016 at 08:10 PM

Well, I've been designing and building power foils for ~13 years and a good friend of mine introduced me to Cuben fiber. When he asked if we could build a kite out of it, I just couldn't resist. And now, here it is, ready to rock.

I ride a PL comp XR with a little lift kit that I added for the rough terrain where I live and have a full race Libre for the fun flat stuff.

Working on a design for a Kite "dragster" with a certified welding buddy of mine. I'm hoping that with the right buggy and my soon to be race kite we can try to set a new speed record. This Cuben fiber has a lot less surface drag than ripstop so I'm hoping for the best.

Randy - 2-17-2016 at 06:21 AM

Is the cuben fiber hard to sew, or is it pretty much like regular ripstop? Any special techniques needed? Do you hot cut it?


grigorib - 2-17-2016 at 11:31 AM

it's the fiber which makes all of the existing new kites already obsolete!

B-Roc - 2-17-2016 at 02:56 PM

As you get older, you need more fiber. Seems like a win/win if marketed towards an older, male audience :P

Sewing

rdcrawford - 2-18-2016 at 04:10 PM

Working with this stuff isn't very different from Ripstop. Tape adheres to Cuben much better (like don't get it wrong the first time) and actually the curves are easier with cuben as there's a bit more bias stretch than ripstop.

It's still new to me but I think the most important is make sure you know where your stress points are and reinforce accordingly. Corners etc. are very important and as I think I stated earlier, I have a technique that I've always used that makes it so that none of the bridle stress is applied to any seam. It works great. I haven't tested the cuben yet, but with my setup on 3/4 oz ripstop I've tested an individual bridle attachment to 140# with no deformation of the seam near the attachment. I like it lots and with the nonstretch Technora flat braid as bridle attachments that I'm using now I'm even less concerned especially given the tensile strength of cuben. At the end of the day, that's the trick. Make sure that whatever fabric you use, you design around its best qualities.

grigorib - 2-19-2016 at 09:56 AM

The fiber itself is fine :)
Best had an ad on their Hellfish kite which turned out to be a big fiasco. The "obsolete" claim is from that aggressive ad.

Hellfish

rdcrawford - 2-19-2016 at 10:34 PM

So what was the whole story with the Hellfish? I mean really, doing the leading edge with Cuben is a great idea but I don't know how much weight savings overall you're going to get on an LEI or SLE.

windrider1 - 2-20-2016 at 05:55 AM

I remeber when the best hellfish came out. it was supposed to be this super amazing light weight kite and everyone was talking about it being the next greatest thing until the leading edges started exploding on people's kites. I think it may still work out to be a great fabric but may need some reworking and testing. I think we may be at a limit for light kite fabric nowadays I don't knw how much lighter u can get as there are some pretty thin fabric being used on some light wind brands nowadays. anywas it would be cool to get some video up of the cuben fibre kite.

Bigun22 - 2-20-2016 at 01:31 PM

Last fall I proposed to Rich that one of my customers specialized in Cuben fiber and if I could get a few yards could we make a power kite? I wanted something I could take to the beach and relax with a few beers, nothing crazy but very sporty. I am the VP of R&D at Twinline and have developed quite a few specialty cords for agencies with just initials. I told Rich lets use some of these cords and the Cuben fiber for a kite. Last week we flew for the first time in very gusty conditions. It was either very windy or none at all.
We discovered very quickly that this kite performed unlike most mid AR power foils. Only weighing 12.3 OZ and having virtually no bridal drag it shot straight up and began pulling like a locomotive. Surprised the heck out of me, almost did a header.
After making some adjustments we were able to get better control and started to find out what the kite would take. We tried to break it but found that the materials and the way Rich did the seam and bridal attachments held up quite well. We are going to continue with our research then make another high AR version for Rich and his buggy.
There is a video on my companies Twinline Facebook page in calm wind conditions. We did not get any video of when the wind was really cranking. I will be taking a month long R&D trip to the beach this spring and hope to get a feel for the power the kite can produce in better wind conditions. Flying here in Colorado at 5400 feet we have wind speed but 20% less density. Stay tuned.
BTW here is a action photo of some guy just after shoulder surgery doing his PT, hope his doctor doesn't see this.

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Bladerunner - 2-20-2016 at 06:47 PM

Quote: Originally posted by rdcrawford  
So what was the whole story with the Hellfish? I mean really, doing the leading edge with Cuben is a great idea but I don't know how much weight savings overall you're going to get on an LEI or SLE.


I think Best was trying to reduce the size of the leading edge dramatically. They thought that the Cuben Fibre would stand up to the high internal pressure required.

Cuben Fiber full race kite

rdcrawford - 6-13-2020 at 08:43 PM

So the 3.0 high A.R. cuben fiber race kite is done in the design phase. All cordage has been selected using TwinLine supplied vectran and technora. I'm making a new set of flying lines from custom manufactured 325# vectran power lines and 200# vectran brakes.
The Flat A.R. is 4.25, wingspan is 3.6M flat, 23 cells with primary bridle diameters of 0.4mm and secondaries coming in at 0.7mm. The miracle of kick ass materials and cordage.
Coming out to Ivanpah in September with our new kite "Dragster" and Cuben fiber kites to see just what this stuff can do.

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Randy - 6-14-2020 at 05:36 AM

Very impressive work!

Where do you get the cuben fiber material? I think Fly Market had some in the past but not now.

jeffnyc - 6-14-2020 at 09:33 AM

Those look really cool rdcrawford! Looking forward to hearing how it goes on Ivanpah.

Lots of folks here probably don't keep up with the water side of things. The latest incarnation of super light/unripable fabric is Aluula. Ocean Rodeo has a lock on it for I think a year, and already have a couple kites for sale built with it. They're only using it for the frame (on LEIs), with traditional dacron for the sail. I assume it would cost too much to make the entire thing out of it? But they have gotten the kite weight down considerably, and so far the Best fiasco has not happened to them. I'm super interested to see what Flysurfer or Ozone will do with it (if anything) on foils when it becomes widely available.