DIY - Strutless bow kite

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Re: DIY - Strutless bow kite

Postby windstoked » Wed Jul 17, 2013 7:31 am

Great post, Rey.
The weak point you indicated in your kite is the same area I see more in 3-strut kites than 5-struts, especially when boosting.
The pressure situation with your bladder is a challenge. Because the tension on the wall equals the pressure times the radius (LaPlace's Law), you can't put as much pressure in a kite with a fatter leading edge. However, a fatter leading edge gives more support, so there's a trade-off. Perhaps making the leading edge fatter at the weak points, but keeping it the same elsewhere would help.
How about reinforcing the leading edge at the weak points with a baton like in a sail? It would add minimal weight, although it would make storage less optimal.
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DIY - Strutless bow kite

Postby sc-surfer » Wed Jul 17, 2013 10:14 am

Aloha wrote:I think we may be witnessing the birth of an 11 that pulls like a 13 but depowers like a 9 especially if Monte is getting involved



And drifts like an inner city teenager in a mini car.... :-)


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Re: DIY - Strutless bow kite

Postby reyrivera » Thu Mar 06, 2014 7:07 pm

It has been awhile since I posted something here, finally caught up with work and now back to kiting.

Finally found some time working on this thing. Turned out to be two simple fixes: First, I pulled out the bladder and trimmed it down to a 6 inch diameter. Too much plastic to make the bladder rigid. Second fix was adding an inch on the bridal. The pulley was wedging itself on the connecting points.

I now have a working prototype. I will start working on a bigger version for this season.
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Re: DIY - Strutless bow kite

Postby sflinux » Thu Mar 06, 2014 10:53 pm

Cool project Rey. It would be cool if you could post a gopro helmet/hat cam of the prototype flying.
Hard to give advice without seeing the kite fly... but looking at your bridle, I can see the front bridle putting a heavy load on the shoulder with that V bridle in hard turns. You may want to try a RPM style bridle to support the leading edge better. May want to try your stock bridle without a pulley too (just larkshead a pigtail on your V bridle), to see the difference.
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Re: DIY - Strutless bow kite

Postby reyrivera » Fri Mar 07, 2014 1:19 am

Good observations, that is what is causing the initial issues. Increasing the lengths a bit distribute the pressure across the bridal points. I am trying to build a really simple short bridle system, trying to avoid long and complicated bridles that causes tangles.

When I was a regular at Scott Creek, I always had to deal with tangled bridles when I ride my slingshot bridled kites whenever I crash on the surf. Of course the solution was to not crash the kites on the surf, but I'm just an average rider.

I got frustrated with the bridles so I switched back to C kites and the Caution mayhem kites.

I will try your recommendations and change the bridles and play with its characteristics. Currently I like the way it flies, hovers a little bit, so its perfect for my riding style.

Anyway, as promised here are a few files if people are interested:

3.5m.Phoenix.strutless.sle.zip
This is the project file for the strutless design, can be opened with surfplan. Unzip it and open with surfplan

3.5.m.Hybrid.overlay.pdf
PDF version with 2 struts, older version, but exactly the same cut but includes two supporting struts.
Attachments
3.5.m.Hybrid.overlay.pdf
(115.43 KiB) Downloaded 19 times
3.5m.Phoenix.strutless.sle.zip
(1.84 KiB) Downloaded 12 times
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Re: DIY - Strutless bow kite

Postby reyrivera » Wed Mar 19, 2014 8:26 pm

10.5.m.png
10.5.m.png (161.42 KiB) Viewed 150 times


It was a bit tricky to create the same design but different sizes. I made the 4 meter version a bit too simple. Adding additional panels so the patterns would fit on a printer made me re-design the canopy slightly. I'm still tweaking the design to match the smaller kite, its a learning process. Goal here is to make an identical version but bigger size.

Here's a teaser, the 10.5 meter kite is green, on the right, compared to the original 4 meter kite on the left.
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Re: DIY - Strutless bow kite

Postby pipedragon » Thu Mar 20, 2014 4:06 pm

Wow seriously impressed. I can barely sew a button on.
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Re: DIY - Strutless bow kite

Postby sflinux » Fri Mar 21, 2014 7:24 am

Curious as to why you have a smaller aoa in the wingtips.
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Re: DIY - Strutless bow kite

Postby reyrivera » Fri Mar 21, 2014 9:50 am

sflinux wrote:Curious as to why you have a smaller aoa in the wingtips.


I wanted the kite to go fast and stable. I picked a low aspect ratio of 3.5 so the kite is stable when it hovers at 11 or 12 o'clock. For the wingtip angle of attack (AoA), I picked -1, I want it to accelerate and move faster forward.

In terms of riding, i.e. I'm riding on a strapless board about to change direction. Have enough speed, so I let the kite up at 11 and have it hover there for a tad longer while I switch stance (have some coffee, fart a little bit, you get the idea). As soon as I'm ready, I can then swing the kite forward the other direction to gain speed.

Does it make sense?

I have two favorite kites, the Naish Boxer for its stability, and the Caution Mayhem for its fast angle of attack. I'm trying to get the two features together based on how I ride.

The one last problem I had was the kite going far out the window. I made some guesses and adjustments, so I think its almost ready for production. I also made the leading edge bigger, 36 cm diameter. Now I'm thinking that leading edge is a bit too fat.

Keep the comments and questions coming, most of the stuff I'm doing are educated guesses.

I'm putting together a grocery list now, my wife is going to kill me when she see the final bill.

Here's what the kite will look like, I also attached the preliminary surfplan model.

10.5.m.strutless.png
10.5.m.strutless.png (60.04 KiB) Viewed 87 times
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10.5.m.Hybrid.sle.zip
(1.81 KiB) Downloaded 8 times
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Re: DIY - Strutless bow kite

Postby ozchrisb » Fri Mar 21, 2014 3:53 pm

Do you have a triple step sewing machine? The machine in the photo looks similar to the sailmakers one I have, but mine only zig-zags no triple. Not that I'm sure you actually need it, just curious about where you might get one from.
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