NCFMF Video: How to Reduce Drag

[sendler]

Wow! A rod has 10 times the drag of an airfoil.

[betasniper]

Glad I did that antenna relocation to under the bodywork.

[RedDevil]

First results, if it can be named so, from the wing shaped antenna sleeve.

Arriving at work after 35 km the rear edge had split open in the middle; apparently the glue failed. The sleeve had slid up slightly and the point of the antenna stuck out of the gap. So I took it off.

Version 2 had internal bracing to give it a better wing shape, all in bagel box plastic, but it meant more glue was needed to keep all in place. Tried to speed up the drying time in an oven, but overcured it so it deformed enough to just bin it.

Version 3 had internal bracing by simply adding extra folds to create a triangular shape inside the wing, providing a large glueing surface while mimicking the ideal wing shape quite well.
I blew against its leading edge with the antenna inside, and against the antenna without the wing, and sure enough the wing did reduce drag noticeably even in this crude handheld windtunnel substitute.
Looked much better on the car too. Stuck quite firmly to the antenna.
5 km on the highway, doodling along between the semis, I heard a buzzing sound, then a nasty pop (even felt that, but that might be imagination) and off went the plastic sleeve, onto the A12.

So even though the stalk is quite short on the Insight, the force on it is substantial so any aero work on that does bring benefit and needs sturdiness.
Version 4 will be secured firmly, that's for sure.

[freebeard]

The buzzing sound was vortexes shedding on alternate sides of the winglet. You'll see that in some of the other videos. Think: Tacoma Narrows Bridge.

Make a fin of solid foam so the sides don't flex, and put the antenna at 30% of the chord, instead of clear at the front. That will give any vortexes less leverage.

[RedDevil]

Thanks for the tips.
It did not buzz initially, it only started just before it came off completely.
It already had the stalk at roughly 30% btw and its internal structure made it quite rigid; the trailing edge was a glued double layer. But I will use a solid wing in the final version.
Maybe I'll give it a slight shark fin shape, expanding the (bulky) base forward. Cant do much on the back of that as the spray nozzle sits there and the hatch needs to open fully.

[freebeard]

Maybe I'll give it a slight shark fin shape,

[RedDevil]

So here is 4up. Same design as number 3, but slightly narrower and it now has 3 flaps with holes that fold over the antenna bolt, so by screwing that down both antenna and wing sleeve are fixed sturdily.


Again I folded the plastic back end like a double layered flat triangular box to create the wing shape and make the back end rigid.


It looks quite crude from the top, but down from that the shape improves to being just mildly crude.

So will it reduce the antanna's air resistance by 90%?
Who knows. I'd be happy with just 50%.

The force on the (unwinged) antenna is quite big at highway speeds. A 50% reduction in air resistance for the antenna might save 0.1% or 0.2% in total fuel usage.
The wing sleeve weighs almost nothing. The whole bagel box was just a few grams.
As the total cost was maybe just 1 cent for the glue I reckon this mod will have earned itself within the first tank full...!
Going for 100 mpg one tiny step at a time...

[sendler]

The next experiment would have been nice to see how drag with the airfoil increase with angle of incidence.

[RedDevil]

Originally Posted by sendler

The next experiment would have been nice to see how drag with the airfoil increase with angle of incidence.

I've been thinking of giving it a little bit of play so it could adapt like a vane.
But not too much, so in really strong sidewind it could act like a sail and net some forward thrust

[Eddie25]

mind blown! definitely going to look at doing something with my antenna and window wiper arms. would also like to see what happens when the pole is at somewhat of an angle as the antenna on my car is at a very inclined angle. however the first part of my antenna is flexible so might change it as per pic.