I think this is the link Herbert posted.knot_moving wrote: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.herbert wrote: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: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
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.
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.