On 07-22-2008 crexcrex said this about his VG's -
Quote:
Originally Posted by crexcrex
The buisness of airtabs is to sell you as many as you do not need, 21 is a case of overkill, 21 would be great for a semi! before i can comment re number of tabs on the roof how many inches at the widest point? I have seen them and not impressed i beleive that you will find that your drag will go up..............if i had the cash i would bet on it.
I made nine shark fin style for a crx and have installed them and used them and can feel the effect on the highway and city as the air rushes over the roof the fins divert the air down onto the glass and off the back............to reap the full benefits of the vortex generators i can only conclude that i will have to install a air wing.......not a spoiler.
I can only suggest that you check citroen the pro's on aerodynamics and arrive at your own conclusion.................speaking for my self i usually coast down this bloody hill each day. prior to using the vortex generators i would coast at 50 miles per hour and with them 60 with a head wind or not...........I made my own vortex generators and am satisfied.............bottom line is too may will cause more drag.
I am sure this entire matter is and will be open to debate.
Your typical vortex generators are four inches apart and one inch from the edge of the vehicles roof.
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Now he says this -
Quote:
Originally Posted by crexcrex
There is no possible way that i can let the subject of air tabs be discussed over and over, the bottom line is that after three months of using Voretx Generators in all possible configurations.............they do not work period! they in fact apply down force and do not attribute to any significant gain in gas mileage.
three months of using vortex Generators tell me one thing and that is to let them use them on Delta winged aircraft as they have no place in the world of cars that are land bound..............
If you can visualize a mini gate attached to the vehicles turret, the gate may well allow some air and wind through the gate but the vortex generators actually block the wind and air from travelling smoothly and effectively over the turret.
When i finally removed the vortex generators one could litterally feel the down force previously applied by the vg's allow the rear end to run free and unencumbered by the mini fence.............
I am sure there are many here who will continue to play with vg's till such time they realixe that it induces drag rather than reduce it.If anything i have learned that vg's would be great on the sides of a truck trailer as it would reduce the amount of sway thus keeping the truck trailer steady.
I wish the best to those who keep trying with vg's. The vg's were applied to a crx, yes! the good old Kamm Back.
I have no furteher commentts on vg's i now consider the subject closed and leave it to those who feel that it may be of benefit to thier vehicles
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So were you confused then or now about VG's. If you could coast at 60 instead of 50, then you could at least increase your FE by longer EOC'ing. But we don't know, because you don't have any fuel logs.
VG's do not "produce downforce", they create a vortex or swirl of air, thus increasing the speed of the air and resulting in a decrease of air pressure, allowing the flow to remain attached. Low speed aircraft use them to maintain flow across the upper surface of the wing during high angle of attack flight. They are not used to smooth out the airflow behind the plane, like airtabs are designed to do in the case of a large square box truck that has alternating swirling vortices coming from the sides of the box (motorcycle riders know this well). Those vortices create a suction drag and by using the airtabs to force those vortices further aft of the box, the suction drag is reduced. Check out the videos from the Valdez Alaska Fly-In STOL competition sometime. Cubcrafters Carbon Cub tookoff in 19ft. and landed in 53ft.
CubCrafters: <font color="F1AB00">UPDATED!!!</font> CARBON CUB THE HIGHLIGHT OF THE MAY DAY FLY-IN AT VALDEZ.
The problem that people have here on EM is they use them in ways that are never going to do any good as far as FE goes. Mitsubishi has shown a slight increase in FE with all their extensive testing, the average joe slapping a few homemade VG's or airtabs here or there will probably never see a measurable improvement.
A&P and Hypermiler