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Originally Posted by MazdaBrain  I would have thought the short stubby one will Increase your drag as opposed to decrease. The short stubby one would create a bigger distribuance at the back of the airflow and also because of the 'skin effect'/greater surface area. For example, all supersonic planes are all thin by default.
Anyway, I doubt changing from one type of antennae to another would make that much difference as the car only travels in relative low speeds and it won't alter the drag coefficient.
The irony is, from F1, we are all told that drag = down force = good. In reality, the speed that normal car travels, we are unlikely to lift off any time soon, therefore, the spoiler = more drag = more fuel burnt = more down force on the back wheel when most Mazdas are front wheel drive. In short, we are wasting money. |
Naah, I think you've misunderstood drag my friend. Downforce is generated by the deflection of the spoilers, however a side effect of producing downforce is that more drag is produced. It's not the other way round. You can still generate downforce at low speeds, but this Downforce produced (<115km/ph) is not really worth it as the resulting drag force it creates does not make this whole scheme efficient at these speeds.
The point is that spoilers on everyday cars are NOT used to generate "downforce" you don't need downforce at these speeds. You only need downforce to counter the uplifting forces generated at higher speeds. normal cars don't usually travel at these speeds (unless ur a hoon ofcourse LOL)
As per above explanation, it's not worth it due to the inefficiencies.
Most car manufacturers put spoilers on their cars for 2 reasons: -
1. Aesthetics ofcourse
2. The air stream profile behind most cars is typically very turbulant. This causes drag, and at speeds around 115Km/ph and upwards, this drag creates fuel inefficiencies. The only way around this is to taper the back of the car like a teardrop shaped airfoil. This is not practical. It'll be like the Jetsons all over the place LOL!.
The other way to do this is to very abruptly end the surface continuity towards the back of the car. To do this, the back of the car would have to be at 90 degrees to the car body. Basically picture a loaf of bread with the back end sliced off. Most volvo station wagons in the late 90's were like this. Obviously this will look silly. So to artificially create this effect, spoilers are placed to provide that sudden dis-continuity. Good example are the new M3 tail lights. They purposefully continued the shape of the body towards the rear of the lights by making the lights protrude out the end. Note this produces the 90 degree discontinuation effect.
If ever you have a station wagon/hatch or similar shaped car and drive through a dusty road you will see the rear windscreen coated with dust. Years ago they trialled spoilers at the back of the Dakar race cars to reduce this effect. It worked!! The reduction in turbulance at the back of these cars meant less dust swirling around to dirty the rear windscreen. This greater improved rear vision. People still question why Dakar race cars have spoilers when average speeds are only 110km/h through the desert. Well, it's to provide better fuel efficiencies at these higher speeds, by reducing the drag/ turbulance at the back. This is turn produced less of a dust cloud behind the car, better rear vision, and a cleaner rear windscreen.
As for the stub verses the wire, definitely the stub is more efifcient. The total surface area of the M2 wire antenna is actually very close to that of the stub's. Then there's also a higher disturbance profile on the wire type antenna. The leading edge is longer on the wire antenna vs the short stub having only a short leading edge, creating a shorter disturbance profile. This leads to less drag.
To demonstrate this, we use water which is a fluid just like air, however it is more dense, so the effects of drag are more evident. If you had both antennae in your hands, try dipping the entire length of the long wire antenna into water, then move this through the water keeping it verical. Notice the drag? The wire bends! Now try the stub. Dip this in water, then move it through the water at the same speed. You will definitely feel less drag. Notice how fighter jets have short wings, whereas commercial aircraft flying at lower speeds have longer wings? Shorter and thinner wings = less drag. Longer and fatter wings = more drag. In the antennae's case, definitely would favour the short stubby. I'm still not sure how it looks though.
Photos anyone?
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Originally Posted by Enigma um i see one on the rood of my Mazda 6 so your statement is incorrect. Also see other makes and models with similar aerials. |
Definitely agree with Enigma there.
The spirals around the antennae are great. Due to the WFC, most manufacturer's are cost cutting so no more of these ones in the newer models.
The spirals are wind deflectors. They have these exact same spirals on tall industrial chimneys! They divert the jetstream of air upwards therefore reduce bending on the antennae/ chimney. By doing so, it reduces drag.
VW are only trying to cut costs!
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