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Old 02-14-2009, 08:34 PM   #13 (permalink)
Frank Lee
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Join Date: Jan 2008
Location: up north
Posts: 12,761

Blue - '93 Ford Tempo
Last 3: 27.29 mpg (US)

F150 - '94 Ford F150 XLT 4x4
90 day: 18.5 mpg (US)

Sport Coupe - '92 Ford Tempo GL
Last 3: 69.62 mpg (US)

ShWing! - '82 honda gold wing Interstate
90 day: 33.65 mpg (US)

Moon Unit - '98 Mercury Sable LX Wagon
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Quote:
Originally Posted by hypermiler01 View Post
Frank, what's up with you and yaw, yaw, yaw? If you are traveling down the highway at 70, and you have say a 5mph crosswind at 45 degrees, the resulting yaw vector is so small as to be negligible.

If you have hurricane force winds at exactly 90 degrees to the road, yaw might be a concern, but most of the time around here, any breeze is so slow that you can barely feel it.

Just look at all the tuft testing pics posted on this forum. Generally the tufts are pointed straight back.
1. Only 55 mph roads here.

2. 5 mph in the plains? LOL! A CALM day is 15 mph and it isn't uncommon to have 30-35 mph winds.

3. And those winds~ are they EVER lined up with where you are going? Seems like I go East-West a lot and of course the predominant wind is from the North.

So... 15 mph x-wind 90 deg. to the road; travelling 60 mph = 11 deg yaw- right?

30 mph wind = 22 deg yaw?

Imagine 10 to 20 deg yaw flowing over your vehicle on a regular basis.

Or when I'm putzing around at 50 mph or less... even more.

That would really screw up boattailing in the plan view wouldn't it?

I get a visual of it whenever I'm in the rain and snow- the drops/flakes go up and off the windshield at an angle, and the behavior of the drops can sometimes be seen to be different on the side glass.

I guess flying C150s and riding motorcycles and bicycles has also made me acutely aware of x-winds. Try lining a C150 up to the runway in a crosswind and YOU WILL APPRECIATE YAW.

P.S. Tufts straight back: I suppose tuft testing is more fruitful on calm days?

Last edited by Frank Lee; 02-14-2009 at 09:43 PM..
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