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crossbow warning

 
Post new topic   Reply to topic    Northwest Kiteboarding -> Gorge / Portland / Oregon Coast
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KiteKarl

Since 02 Mar 2005
213 Posts
Stockton, California
Stoked



PostSun Aug 14, 05 10:46 pm    crossbow warning Reply with quote

Got this from a post on the Bay area kite forum. This incident sounds similar to the experience Dan had the other day.

Quote:

yeah, a warning about your Crossbows. Following is the email I sent Cabrinha after an episode at Crissy. Read the whole post and you'll get the full story. Email and response from Cabrinha. It's good, and you should know about it.

Original email:
Umm, yeah, where to start. Problem with the Crossbow 12m? Today was the thrid day flying my Crossbow 12m. I was in the bay, San Francisco, in the middle of everything. Literally a mile from anything. Just spent two hours flying the kite. In fact, I sent you an email yesterday raving about my first two days on the kite. Well, today, issue number one popped up, and vanished at the same time.

Issue: Flying the 12m in 20 mph winds, having a blast. Time to head in. Pulled a fast up turn, back through the power window. Right as the kite was passing the power zone, POW. POW as in the kite seemed to fold in half from the back forward, and turn inside out. Shit. I figured something broke. Ok, wrap up the lines, start the self rescue, managed to flag a boat, got to shore. Layed the kite out, and couldn't find anything wrong. Ok, will have to look into this tonight. Well, here it is, tonight, and I've run the lines/bar out, no problems. No breaks, no tears, no kinks, nothing. The bar and lines look perfect. Ok, I must have missed something on the kite. So, I pump the kite up and check all the bridle lines. Nothing broken, nothing out of place, no tears, nothing. NOTHING! Did I hallucinate?

Question: Is there some sort of flight maneuver I inadvertantly did to cause the kite to suddenly invert from the center strut, fold in half, and fall out o f the sky? This is exactly what happened. When I swam up to the kite, the center strut was pulled 180 degrees backwards, wrapping the kite in itself as it was folded in half. This was a pretty good indication to me that something broke. I found NOTHING! I'll be taking it out tomorrow to see if I can't find something when I fly it. I am baffled. I sure would appreciate some possible insight. The idea of using this kite just became a little sketchy if I can't find anything wrong with it and this happened. I mean NOTHING wrong that I can find. Believe me, I have scoured it. Anyway, I'll know more tomorrow, but am looking for any bit of info you may have.

Response from Cabrinha:
Thanks for contacting Cabrinha Support

The inversion that you experienced usually occurs from insufficient strut and/or LE pressure.

There is a reason why these kites do not have one pump and that’s because the struts need to be a higher pressure than the LE. If you have a strut that is not at pressure the LE can fold on that mark. If the LE is not a sufficient pressure it can roll and also fold in and invert. This usually occurs when the kite is put through the power zone but sheeted out. The low attack angle gets so negative that the canopy starts to blow down from the top side. When you have insufficient bladder pressures the kite simply has no support. BOOM, she’s inside out and in a knot.

Now there is a way to re-launch and get back to the beach if this occurs again.

You have to just play with the rear leaders and try to get the kite to lay out flat again.

Most people in this situation just start pulling on lines and this simply makes the kite knot up even more.

Swimming at it and trying to get it to spin around will get the kite back in the sky.

We have been testing the kite in these situations and it still stands as a 100% re-launch success in even the worst knots.

Result:
As you can see, basically end user error or a leak. I'm paying extra attention to the pressures. Cabrinha has been extremely responsive. This kite has been flying great ever since. Still highly recommended.

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Onad

Since 04 Mar 2005
1435 Posts
Coast<<PDX>>Gorge
XTreme Poster



PostMon Aug 15, 05 12:02 pm     Reply with quote

Thanks for finding & posting this info Karl!

I experienced this exact phenomenon 3-4 times on a 9m X-Bow and perhaps once a 12m (while demo’ing at the sandbar). The worst of the events took place during a down-winder to Rooster Rock on Saturday morning (~11:30AM). The wind was in the 35mph range with higher gusts (see Corbett sensor reading below). I was steering the kite down through the power zone as I was descending from a big jump. Just as I landed, the kite did the POW, POW, POW thing. As the kite tried to right itself (I think I was trying to steer it up) the leading edge wrapped around itself on one side of the kite. The bridle lines also wrapped around the leading edge. The kite dropped to the water and I activated the frontline safety release to prevent damage to the kite. Fortunately, I was close to shore so I swam in and Tonya grabbed the kite. Once we unrolled the leading edge the kite was fine & ready to fly. Not sure that I would have been able to fix the problem in the water by pulling on the lines or swimming toward the kite, as Cabrinha stated in the previous post, as half of the bridle lines were wrapped around the kite.

The leading edge was fully pressurized while the struts were probably at a lower pressure as we had left the struts inflated over night and did not re-pressurize when the kite was re-inflated.

The other times this happened, the kite popped in & out 2-3 times and then righted itself as it shot strait up through the power zone. Fortunately, the kite de-powers instantly so I wasn’t even pulled out of the water.

Tonya has ridden the kite in high & low winds and has not experienced this effect.

Phenomenon seems to happen in higher winds when the kite doesn’t have much rear line tension (supports info Bay area rider received from Cabrinha).

We’ll be sure to watch our LE/strut pressure and report back on this issue. ~Dan & Tonya


This is a NWS sensor located near Corbett. Feedback from sailors / kiters indicates that it generally reads 10-12mph SLOWER than actual speeds on the water.
 This is a NWS sensor located near Corbett. Feedback from sailors / kiters indicates that it generally reads 10-12mph SLOWER than actual speeds on the water.  Corbett.gif 

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