markbaur

Let's see... There was the slider-on-a-round streamer, the two x-slider-on-a-round streamers, and the daisy-chained hooked-up backwards deployed-from-a-grocery-bag round. Several cases of broken brake lines, all landed with rear risers. Tension knots once. Tore the bottom out of a home-built canopy a couple times. Snapped the center A-lines once. A couple tandem line-overs. I plan on having a malfunction on my next jump -- but hope to get lucky again. Mark

Rock-climbing shoes. Slick soles for surfs, narrow for easy jumpsuit changes, flexible for feeling the step. One size larger than any self-respecting rock-climber would wear, just for comfort. Plus another size larger so I can wear socks. Next pair will be yet another size larger so I can put in padded insoles for more comfort.

Is there test data to support this? The usual configuration of the pilot chutes should be one above the other, with the lower one providing most of the drag. In the early 80's, some jumpers tried using two spring-loaded pilot chutes on their mains in an attempt to improve their openings, but they went back to single pilot chutes when they found no discernable difference. Poynter suggests that the pilot chutes interfere with each other. Mark

The wink says you're not so serious, but ... the vario just gives an indication of the strength of a thermal (or, if you're unlucky, the rate of sink). You still need to do some calculations to figure out the best speed to fly, which is dependent also on weight and expected thermal conditions along your route. Mark

And yet asymmetrical flap extension also causes a roll away from the more extended flap. Let me propose this explanation instead: pulling down on one brake line increases lift on both sides of the canopy. The side that is pulled down experiences an increase in induced drag, but the other side accelerates (a result of inertia), and therefore produces more lift with less induced drag. Mark

Not quite. The folks in the soaring community have made a fine art of calculating best cross-country speeds, that is, the speed to fly to achieve maximum range. As a starting point, the two important speeds are the best glide speed (the speed which results from minimizing combined drag, given assuming no-wind conditions), and the minimum sink speed (the speed which gives you the most time aloft, what the airplane pilots call maximum endurance speed). With a tailwind, you'd like to reduce your airspeed from best glide to something closer to minimum sink. With a headwind, you need more speed to get more range. So far, this corresponds with our canopy experience. We use airspeed as a proxy for angle of attack, and for our canopies the angle of attack (the angle between the mean chord line and the relative wind) is in large part built in by the suspension line lengths (although some posters have pointed out that the mean chord line, and thus the angle of attack, changes when you pull on a riser or brake line). Many -- but not all -- canopies are rigged for best glide. I jump an Icarus 93, which is rigged for a speed faster than best glide, so in some light headwind conditions slowing down results in better range. Mark

For those instructors doing AFP and who have used both Strongs and Vectors, do you have an instructional preference for one rig or the other? That is, leaving out issues like ease of packing or harness comfort, which system is more likely to produce a good freefall student? Mark

I'm still not sure this is the explanation. If pulling down a toggle produces far more drag than lift, then why does my canopy glide farther in brakes than in full glide?

Actually, it's not at all like a Kitfox. In a Kitfox, if the left flaperon is deflected down, the left wing goes up and the aircraft banks right. On my parachute, when I deflect the left side of the trailing edge down, the left side of the canopy goes down, and I turn left. I looked at the Skydive Arizona canopy book, but I didn't see an explanation for this apparent contradiction in performance: pull down both sides to increase lift, pull down one side to decrease lift on that side.

I observe that pulling down on both brake lines increases both lift and drag. I also observe that pulling down one brake line, even a little bit, results in that side of the canopy being lower than the other. Why does pulling down on both brake lines make more lift, and pulling down just one make less? I understand stuff like drag coefficient, adverse yaw, pendulum stability, Vno, Va, etc., as they apply to airplanes, helicopters, and gliders, so I'm looking for an explanation in those terms.