benefits of bigger turns

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Over the years there has been lots of debate over the optimal turn or how many degrees of rotation are needed to achieve maximum speed for a given wing. Competitive pro level swoopers fly anywhere from a 450 degree turn to an 810 degree turn.

I've personally been using a 630 degree turn for about a year and a half. While analyzing my GPS data I have noticed that on most swoops I nearly reach my peak vertical speed after only 270 degrees of rotation.

While training for Nationals yesterday I did an unplanned 270 degree turn and I was surprised to discover that this was my best run of the weekend. It's food for thought and I'm sharing my data as my contribution to the conversation. I was flying a Petra 67 with 206 lbs exit weight for a wing loading of 3.08. The elevation was 5000' MSL and the ground winds were 5-10mph (downwind).

video: https://vimeo.com/159000246

plots: (attached)


exited airplane: 4964 ft AGL
initiated turn: 1374 ft AGL, 444 ft back, -527 ft offset
max vertical speed: 440 ft AGL, 412 ft back, -18 ft offset (94.8 mph)
started rollout: 357 ft AGL, 391 ft back, -27 ft offset (93.5 mph)
finished rollout: 12 ft AGL, -8 ft back, -3 ft offset
max total speed: 175 ft AGL, 293 ft back, -27 ft offset (102.0 mph)
max horizontal speed: 34 ft AGL, 96 ft back, -7 ft offset (89.2 mph)

degrees of rotation: 308 deg (right-hand)
time to execute turn: 11.70 sec
time during rollout: 3.92 sec
time aloft during swoop: 7.26 sec

entry gate speed: 84.1 mph
distance to stop: 628 ft
touchdown estimate: 605 ft (23.6 mph)
speed carve time: ---- sec (---- mph)

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As a person that is learning/reading about swooping and only relatively recently decided that's what I want to do in the sport, please accept my "Fuck Yeah" by looking at those numbers.

Now, as an aerospace engineer intuitively I see how on less performing wings the benefit of bigger turns are limited, since drag increases roughly like speed squared, any wing that is not very efficient (an I mean aerodynamically efficient, as in L/D) will hit its terminal speed fairly soon.
I am surprised to see, though, that you seem to hit this terminal speed on a very highly loaded Petra, which is marketed as benefiting from very large turns.
I'm standing on the edge
With a vision in my head
My body screams release me
My dreams they must be fed... You're in flight.

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Sure, there are other considerations when choosing a turn. A bigger turn gives you more time to adjust but also more time to get pushed out of position by strong uppers. I'll say that one advantage of going from a 450 to a 630 is that the turn initiation height is not nearly as important.

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