benefits of bigger turns

[raymod2 1]

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)

metrics:

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)

[keithbar 1]

Entry gate speed 84 plus mph.God is great .beer is good. swoopers are crazy

i have on occasion been accused of pulling low . My response. Naw I wasn't low I'm just such a big guy I look closer than I really am .

[Di0 2]

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.

[daffes 4]

Even though you can reach your terminal speed with a smaller turn, doesn't a bigger turn give you more time to think and do several small corrections during the turn without compromising the top speed?

[raymod2 1]

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.