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Old 05-07-2014, 05:13 PM   #613 (permalink)
aerohead
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instabilty

Quote:
Originally Posted by botsapper View Post
I'm sure I'm not the only one who view these 'aero' templates to be very narrow in their scope. The almost '2D' shapes are almost always tested and highly scrutinized with just straight head winds. Pragmatic 'optimal' forms will surely change when these shapes are evaluated with off-center cross winds. The relatively high & flat sides of some of these shapes will go through erratic yaw movements and have straight line instability. Wind tunnel researchers/junkies & especially HPV designers are always mindful of constantly changing cross winds' effect on their designs. I'd like to see wind tunnel smoke trails, tuft testing or CFD flow visualization art created by off-center sidewinds.
Many have questioned the crosswind stability of the 'pumpkin seed' half-body as embodied with the 'Template.'
GM worked on it in their tunnel with the Solaraycer in 1987.
In Goro Tamai's book he addressed crosswind stability of the 'flattened-torpedo' form.Tamai reported that zero lift or negative lift was easily achieved as a function of body inclination.
Crosswind stability was achieved by the use of a simple spine down the roof/aft-body centerline.
The light weight and large relative surface area of these solar racers required much consideration with respect to stability in storm fronts and proximity to the Australian land-trains.
'Normal' vehicle weights might render the issue moot.
Darko Technologies ought to be able to supply lift as well as drag data on the T-100 in September.We should have some hard numbers by then.
The 'seat-of-the-pants' stability meter registered 'stable',on the salt at 105-mph.She felt fine in crosswind at 108-mph in 2007 on the interstate.We've had very strong wind lately and 75-mph in 30-mph crosswind was just fine.
Having the low,slant-back,wrap-around nose and double low fins behind the rear tires (after Morelli,1978) seem to be the ticket to a good ride.
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