Significant points, Peter... well explained.Peter_Frank wrote:Interesting...
Not in the upwind legs of a race, which are all about low aoa. (and the vented canopy is just extra parasite drag)El Rudo wrote:
On the OR kites, the vents do work.
They only "open" at high AoA.lobodomar wrote:Not in the upwind legs of a race, which are all about low aoa. (and the vented canopy is just extra parasite drag)El Rudo wrote:
On the OR kites, the vents do work.
Exactly. Even in the closed position, the vented canopy (net+outer ripstop) adds extra drag and weight.Kamikuza wrote:They only "open" at high AoA.lobodomar wrote:Not in the upwind legs of a race, which are all about low aoa. (and the vented canopy is just extra parasite drag)El Rudo wrote:
On the OR kites, the vents do work.
The initial idea of the OR designers was to put the vents more towards the LE. Tell tale testing showed that they would be more effective towards the TE, to suck the flow back on to the canopy at higher AoA's, like Bille describes above. Airplane wings are designed to perform with AoA's differing only a few degrees. Kites fly with way bigger AoA variations depending on what you do with them.lobodomar wrote: Exactly. Even in the closed position, the vented canopy (net+outer ripstop) adds extra drag and weight.
BTW I own a 2011 OR razor, so had my share of first hand experience with the venturi system. It's a nice kite, but in my opinion the venturi is a marketing thing, something to stand out from the crowded kite market. Think about airplane slots: they are close to the LE, not to the TE like on OR kites. It's close to the LE that you need to energyze the boundary layer so that it keeps attached to the wing along the chord. Plus most of the lift is produced in the first half of the kite (center of pressure is usually at about 1/4 of the chord).
But of course OR didn't put the vent in the front, I doubt that a naturally vented (instead of mechanically open-close) slot would not screw up the kite's aerodynamics in a such a critical zone. They put it in the back, where it can do neither harm nor good.
A quantifiable but (very?) small amount of drag perhaps . . . but does the positive outweigh the negative?lobodomar wrote:Exactly. Even in the closed position, the vented canopy (net+outer ripstop) adds extra drag and weight.
Think about airplane slots: they are close to the LE, not to the TE like on OR kites. It's close to the LE that you need to energyze the boundary layer so that it keeps attached to the wing along the chord. Plus most of the lift is produced in the first half of the kite (center of pressure is usually at about 1/4 of the chord).
But of course OR didn't put the vent in the front, I doubt that a naturally vented (instead of mechanically open-close) slot would not screw up the kite's aerodynamics in a such a critical zone. They put it in the back, where it can do neither harm nor good.
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