How are strutless kites doing ?

[ronnie]

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.

I think this is the link Herbert posted.
http://www.engineersedge.com/material_s ... stress.htm

As you can see in the formula (stress = Pressure x diameter / 2 x thickness), the stress stays constant if the thickness is constant (which we can assume it is), and Pressure times diameter is constant.

So if you pump an 8" diameter L/E to 7 psi, you get pretty much the same stress on the material by pumping a 7" diameter L/e to 8psi.

[aeberl]

It seems that as kites are sheding weight and getting rid of considerable ammounts of material they are also getting more expensive!?&%#"!!
BRM 10m (no struts, no bag, no bar, no pump, no leash) = Rally 10m RTF

[tomatkins]

I recall Bill Hansen commenting on the "stiffness" of a tube... He noted that the rigidity of a tube (columnar structure), like our inflatable kite's leading edge, is proportional to the cube of the diameter... and for that reason, some of the Windwing (Rage model) kites were made with a very large diameter leading edge, so that a conventional (at that time, about 2005) kite (C kites) could have a very stiff leading edge, using the same air pressure as the conventional smaller diameter leading edge kites.

Soooo, it would seem that the reverse would apply to the new very small diameter leading edge kites..... which would mean that the air pressure in these kites would have to be greatly increased to achieve the same rigidity, as the currently produced conventional kite.

In the "old days", the materials could not stand very high pressure, and kites were pumped up to a little over 3 PSI, so they would last longer. New materials and better sewing changed all that. The "Hellfish" explosion taught us a lot... gave the expression "I'm going to blow up my kite" a new meaning. ha, ha

[tautologies]

It seems that as kites are sheding weight and getting rid of considerable ammounts of material they are also getting more expensive!?&%#"!!
BRM 10m (no struts, no bag, no bar, no pump, no leash) = Rally 10m RTF

Dude, this is misplaced anger.
Have you heard about economies of scale? The per unit cost of producing fewer kites is simply way higher. Best thing you can do to bring down the unit cost is to buy a ton of the kites.

[Dave_5280]

I think I saw a strutless kite one day that was over powered in high wind. It was jumping around a lot, looked like it was surging to the edge of the window and then falling back. Is that what they do when over powered?

[ronnie]

It seems that as kites are sheding weight and getting rid of considerable ammounts of material they are also getting more expensive!?&%#"!!
BRM 10m (no struts, no bag, no bar, no pump, no leash) = Rally 10m RTF

The RRD is cheaper than the strutted RRDs of the same size.

[BWD]

I think I saw a strutless kite one day that was over powered in high wind. It was jumping around a lot, looked like it was surging to the edge of the window and then falling back. Is that what they do when over powered?

No not necessarily. Not in normal range at least.
That is what some kites with struts do when overpowered though.
When sheeted far out strutless kites luff and move BACK in the window, in general.
If the end gusts are extremely variable though, say 25 gusting up to 35+,
The kite, any kite may appear to do this, surging around in crazy gusts except maybe a tiny oversheeted one.

Another possibility though is that you were seeing someone riding waves and sheeting out on the wave (kite falls back) and powering up between waves or sections (kite surges forward)...
??

[TheKiteDesigner]

My quick comments about leading edge design, from 10 years of designing kites.

LE size helps with the strength of holding the shape of the kite BUT the bridle plays a greater role in support and buckling of the leading edge in strong winds.

A 12 psi leading edge will buckle if the balance of the bridle is not right

A 6 psi LE will not buckle if the bridle is right

A super thin LE does not work well on kites i feel, I noticed no one is making super thin LE any more, from my experience thin leading edges cause the kite to fly to the edge of the window and past the edge, then Hindenburg much more than a normal leading edge. Super small leading edges just don't feel great. They also lack power as the kite flys to the depower zone quickly.

So if you have a crappy bridle, you can compensate with a thicker leading edge, as you get the balance of the bridle better, you can make the LE smaller, but if its too small the performance of the kite drops in my opinion ( too darty, shoots to the edge of the wind window then loses power and drops, have to be more experienced to keep it in the air when gusty )

So I feel its a balance to get the right size leading edge for the size of the kite that does not shoot to far into the wind window but also does not sit to far back in the wind window if its to big. And work on the bridle positioning to get the balance right.

My 12m Strut less kite turned up today, was only 6 knots but generated alot of power on the beach, have to wait for wind now I think I could get going in 10 knots with a 6ft surfboard at 88kg. Time will tell

[BWD]

Dude, this is misplaced anger.
Have you heard about economies of scale? The per unit cost of producing fewer kites is simply way higher. Best thing you can do to bring down the unit cost is to buy a ton of the kites.

I'm not so sure it is misplaced, maybe a little too intense.
The feeling is understandable, but no need to get too mad, I would say...
The first year pricing was certainly good, from the consumer point of view.
Maybe it was even slightly too low.
Anyway, it helped sell over 100 new strutless kites, from a company that popped up overnight (in the public eye at least) with only youtube and word of mouth, so there must have been something right about it.

The C2 line is on average about 37% more than the C1. It just hurts to see that, as a consumer, even though the new price is still competitive with other kites.
That is not something to be mad about though, and I doubt they would do it if they didn't feel they needed to in order to continue doing business. It may have as much to do unexpected overhead and factory cost (Pryde still I think) as anything else. It would be worse if they went under!

I honestly believe BRM are not out to gouge the consumer and want to bring the best performance, innovation and value they can. Let's hope they can rein it in for year 3, and keep innovating and growing, or other companies will step in (as some are trying to already) and steal their thunder.

[Peert]

I am a satisfied user of a 10m Trip. Looking into buying an extra kite for hydrofoiling so I thought I would give this topic a kick. How are strutless kites doing in 2016?
BRM has obviously paved the way for this concept. Hydrofoil users are happily using the strutless kites because of their light weight. As far as I know there are currently a number of brands offering strutless kites.

1. BRM http://boardridingmaui.com/wind-cloud.html
2. Naish Trip http://www.naishkites.com/product/trip
3. RRD http://www.robertoriccidesigns.com/equi ... otion-mki/
3. Gong http://gongsupshop.com/epages/box1707.s ... 20Ailes%22
4. Storm http://www.stormkites.com/produkte/voyager-2/

The latter two are french brands, not a lot of information available in English, the kites seem to be well priced and relatively popular in the French Hydrofoil-scene.

Airush had a zero before. In their current lineup there is no strutless kite
Liquid force went tried to develop strutless but ended up with just a single strut http://www.thekiteboarder.com/2014/03/l ... echnology/

Who can tell me which strutless (or strutpoor) kite is most suitable for hydrofoil and why? Please tell which kites you have tried/compared. I know foilkites have some advantages over LEI, but they are not affordable enough for me.