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 Post subject: Re: How are strutless kites doing ?
PostPosted: Wed Jul 30, 2014 5:50 pm 
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Quote:
The Cloud leading edge buckles when overpowered. A friend has a quiver and complaines about it.


Not true. I've had the 17m C2 in about 25kt and no buckling at all. Maybe your friend underinflates.


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Wed Jul 30, 2014 6:08 pm 
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i can get the cloud to buckle at 200 lbs in overpowered conditions, that being said its the best 12m for its wind range and i will probably never have a strutted 12m again


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Wed Jul 30, 2014 7:39 pm 
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I've had some momentary buckling in powered up strokes through the power zone as well. But I have had that on a strutted kite too. Could be under-inflation, but I pump mine up as much as I dare to.


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Sat Aug 02, 2014 6:05 pm 
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Location: NW Florida
Rode the Airrush strutless the other day in the gulf. Was enough wind to ride my turbine but the current was carrying me downwind and I was doing a bunch of walking. Airrush was obviously much lighter in weight & was more efficient - meaning as I started riding it picked up speed and moved fwd and I was easily staying upwind. Also turned much much faster than turbine.
It liked to be very sheeted out & I had all the speed and pressure I wanted - substantially more than when I was on my turbine.
Dealer did say that its top end was not as good as the turbine's & I can believe that is true. I will also be interested to see about the reliability of the strutless designs in general. They seem to require quite a bit higher bladder pressure than strutted lightwind designs, I wonder if that will affect their reliability over the years?
--Anyway all in all, for very light days it was a fun kite


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Sun Aug 03, 2014 1:52 am 
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knot_moving wrote:
Rode the Airrush strutless the other day in the gulf. Was enough wind to ride my turbine but the current was carrying me downwind and I was doing a bunch of walking. Airrush was obviously much lighter in weight & was more efficient - meaning as I started riding it picked up speed and moved fwd and I was easily staying upwind. Also turned much much faster than turbine.
It liked to be very sheeted out & I had all the speed and pressure I wanted - substantially more than when I was on my turbine.
Dealer did say that its top end was not as good as the turbine's & I can believe that is true. I will also be interested to see about the reliability of the strutless designs in general. They seem to require quite a bit higher bladder pressure than strutted lightwind designs, I wonder if that will affect their reliability over the years?
--Anyway all in all, for very light days it was a fun kite


I ride with my BRM Cloud firmly inflated...but not really high. The BRM Clouds have a substantially smaller diameter leading edge than all my other kites. The stress on a cylinder under pressure is called "hoop stress"...like the hoops on a barrel. So the stress on the hoop and the stress on the wall of a leading edge, and the stress on a seam of a leading edge at any given pressure are all a function of diameter. Decrease the diameter, markedly decrease the stress...ie. decrease the tension on the seams. The formula can be found here:

http://www.engineersedge.com/material_s ... stress.htm

So, narrowing the leading edge so radically as in the Clouds does create advantages and raise challenges. The flying bridle each side has some 7 attachment points to keep the shape. I pump it up firm. Same as I did my Cult. Though I split a Cult leading edge seam (at the largest diameter area as you'd expect), the Cloud doesn't feel stressed (just as struts are under less stress than leading edges). The narrow leading edge makes it a fast kite that can move forward fast and maintain higher apparent wind than my Cult.
Also....it seems to me that struts work on the canopy...in ways that can be advantageous, or not depending on what characteristics we're looking for (it is not a for or against proposition...just different). But the struts don't stabilize the leading edge, right?

I went out yesterday on my 17m Cloud. Wind picked up...then some squalls with gusts over 20mph (I usually like to ride it in 9 to 14mph winds optimally). Letting the bar out my full reach, I feel less pull than with my 13.5 cult or 13.5 rrd vision. I mean down to almost no pull. I'm am not saying I like to fly it in that much wind. But without the fixed camber inducing of the struts, the kite can way more depower as the canopy can flatten right behind the leading edge. Again...the kites characteristic may not be for everyone...to each his own. But when I am trying to decide which size kite....I can now more freely choose a bigger size with less fear I'll get hammered if the wind surges. Long story short, the Cloud has a remarkable high end.

There are lots of hypotheses about the long-term structural stability and wear of strutless kites. Since the Cloud seemed the be the first, premier, one to follow, it is the one people have wondered about. My theory is the the whole kite...leading edge and canopy...will last longer than my other kites...but it is just a theory. I have used my 17m Cloud about 40 sessions and loaned it out about 15 times. It has been in the water, reef break, shore break many times. I see no signs of wear or stretch yet. But still it's a bit early to really say honestly....so I'll report back after 200 sessions for it to be more meaningful.


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Sun Aug 03, 2014 5:55 am 
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lobodomar wrote:
Quote:
I've had the 17m C2 in about 25kt

i'd love to hear more about that experience. my c1 becomes a handful at around 17


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Sun Aug 03, 2014 11:08 am 
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darippah wrote:
lobodomar wrote:
Quote:
I've had the 17m C2 in about 25kt

i'd love to hear more about that experience. my c1 becomes a handful at around 17


Like Herbert, I also found out that the high-end of the C2 is higher than other kites I have flown. To achieve it, a bar with long depower travel is necessary. But it's kind of a survival high-end, since with all that luffing the kite becomes a pig to turn due to increased drag. Upwind also becomes highly compromised, but still doable with the right fins/outline. I haven't flown the C1 to compare.

Regarding buckling, I have to admit I never really loaded the kite in such conditions. But I would never intend to load any other 17m kite in those winds as well, so for me the leading edge rigidity is more than satisfactory.


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Sun Aug 03, 2014 11:53 am 
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As Herbert said, a smaller diameter L/E will have reduced stress at a given pressure. So the pressure used should be higher on a thinner L/E, without increasing the stress.

So the C2 Cloud would use a higher pressure than the C1, due to the bigger diameter of the C1 L/E.

The Clouds are very light, so the guidance in this video would not necessarily apply to other kites. As a guide to what pressure to pump to, Greg suggests that you should be able to hold the C2 kite at one end without the L/E buckling.



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 Post subject: Re: How are strutless kites doing ?
PostPosted: Sun Aug 03, 2014 6:20 pm 
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How is the bar pressure with c2 17 compared to c1, anybody know?
Especially sheeted out/higher end of wind range?


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 Post subject: Re: How are strutless kites doing ?
PostPosted: Mon Aug 04, 2014 3:42 pm 
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Location: NW Florida
herbert wrote:
knot_moving wrote:
Rode the Airrush strutless the other day in the gulf. ... They seem to require quite a bit higher bladder pressure than strutted lightwind designs, I wonder if that will affect their reliability over the years?
--Anyway all in all, for very light days it was a fun kite


I ride with my BRM Cloud firmly inflated...but not really high. The BRM Clouds have a substantially smaller diameter leading edge than all my other kites. The stress on a cylinder under pressure is called "hoop stress"...like the hoops on a barrel. So the stress on the hoop and the stress on the wall of a leading edge, and the stress on a seam of a leading edge at any given pressure are all a function of diameter. Decrease the diameter, markedly decrease the stress...ie. decrease the tension on the seams. The formula can be found here:

http://www.engineersedge.com/material_s ... stress.htm

So, narrowing the leading edge so radically as in the Clouds does create advantages and raise challenges. The flying bridle each side has some 7 attachment points to keep the shape.


I do enjoy that amidst all the emotional posting there is real high quality info on this forum as well! The smaller leading edge diameters on the newer generation light wind kites bodes well for all apparently! Also gives me encouragement to really "pump it up!" when using my smaller kites.


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