aerodynamically efficient mirrors

[Otto]

Seems like many vehicles have bigger outside mirrors than needed, and poorly shaped ones (from an aerodynamic efficiency standpoint) at that.

For example, my Ford E-150 van has outside mirrors about 12"W X 10"H, mounted on stalks about 3.5" wide. The mirror housings are, however, somewhat rounded, so that's a start.

But, how big do outside mirrors really need to be? My motorcycles and cars have mirrors about the same distance from the driver's eyes and with adequate rear view vision, but do just fine with a fraction of the frontal area. Even those smaller mirrors have bigger housings and frontal area than needed for the mirrors they enclose, adding ~20% needlessly to frontal area. And, they are not very well shaped from an aerodynamic standpoint, being too blunt and/or angular.

So, I've been looking on eBay and elsewhere for aerodynamically shaped motorcycle mirrors to adapt and install on the van or car. I've seen such for ~$10-30/pair on eBay. Even so, they could stand some improvement, such as streamlined mount stems rather than round ones. How fat does the mount stem need to be, anyway?

Questions: Anybody else here looking at this? What have you found? Sources?

[euromodder]

Originally Posted by Otto

Questions: Anybody else here looking at this? What have you found? Sources?

Yep.
I've seen racing mirrors that have optional clear extensions : http://www.racemirrors.com/
It's like kammbacking your mirrors

[Varn]

I had a fzr1000 yamaha that had two hole mounted aero shaped mirrors.
For round hole mount mirrors, I would go with at least a 10mm stalk They use a standard 10mm thread except some Yamaha round mount mirrors have a left hand thread on one side. You could cut the stalk off to a couple inches and weld on a plate to mount it.

I am thinking of putting tubulators in front of the mirrors on the front fender on my Econoline.

I wonder if 20% of the vehicles aero drag is coming from the mirrors? Seems high.

[Otto]

Thanks for the links and thoughts. I've read probably on this website that outside mirrors may be ~6% of total drag, but if mine are way bigger and draggier than need be, and I can find suitably large enough motorcycle aero mirrors for cheap, why not?

Elsewhere I read that Indy and Formula 1 cars pretty much had been bolting on whatever mirrors were lying around, until recently somebody took another look at this drag source, with good results.

I may find a cheap eBay or similar set of aero mirrors, and make stalks out of aero tubing of teardrop cross-section, or keep the stock round stalks but add teardrop fairings to them. These are only ~1/2" diameter stalks and hold the mirrors in place at 100+ mph, so I am mystified why the car manufacturers use such thick, draggy stalks, not to mention crappy oversized mirror housings.

[Varn]

One thing to consider Otto is interference drag. Two bodies near each other act like one large body. Sometimes a large smooth blended fairing between, in this case, the side of the car and the mirror body, can have less drag than a narrow stalk no matter how aero.

Likewise having a mirror that has the glass face in the convergent area can act as a kamm surface. In effect having a larger mirror fairing and a fairing that is molded into the body might be an advantage.

I agree that some mirrors are pretty oversized. Many have conveniences of remote adjustment and heated. Kind of hard to give up. Hope that you can prove that your motorcycle or race car mirrors are effective on our Tanks.
6% or higher is fairly significant. I will be glad to learn.

Originally Posted by Otto

Thanks for the links and thoughts. I've read probably on this website that outside mirrors may be ~6% of total drag, but if mine are way bigger and draggier than need be, and I can find suitably large enough motorcycle aero mirrors for cheap, why not?

Elsewhere I read that Indy and Formula 1 cars pretty much had been bolting on whatever mirrors were lying around, until recently somebody took another look at this drag source, with good results.

I may find a cheap eBay or similar set of aero mirrors, and make stalks out of aero tubing of teardrop cross-section, or keep the stock round stalks but add teardrop fairings to them. These are only ~1/2" diameter stalks and hold the mirrors in place at 100+ mph, so I am mystified why the car manufacturers use such thick, draggy stalks, not to mention crappy oversized mirror housings.

[ECONORAM]

Interesting. My RAM has large side views as well. I was told Street Scene mirrors were lighter, but I don't know about more aerodynamic. Sounds like another aero experiment in the making!

[Phantom]

Originally Posted by Otto

These are only ~1/2" diameter stalks and hold the mirrors in place at 100+ mph, so I am mystified why the car manufacturers use such thick, draggy stalks, not to mention crappy oversized mirror housings.

I believe the reasons for this is have you ever bumped in to a cars mirror when carrying something or drunk? Did the mirror snap off? Now try that with the thin stalk how does it work? The thin stalk mirrors might be able to handle 100+ mph but is not built for durability/impacts.

The other reason for the size I believe is mostly styling and being able to fit the electronics in it.

[euromodder]

Originally Posted by Otto

I am mystified why the car manufacturers use such thick, draggy stalks, not to mention crappy oversized mirror housings.

The mirrors on street cars are a lot bigger as they are a lot further away from the driver, are often electrically heated, positionable, and also include indicator.
They can survive a bit of a bump too - but racemirrors.com specifically warn their users that their mirrors can't be used to even hang an helmet on !

[NachtRitter]

That warning is specifically for the ones with the Carbon Fiber stalks...

Please note that the Professional mirrors have designed-in Aero mounting stems made of carbon fiber. While this design feature provides an aerodynamic advantage they are also not as strong as the metal stems on the Club mirrors. Care should be taken not to use these mirrors as "helmet hangers" or push locations

[rbrowning]

"But, how big do outside mirrors really need to be?"

I don't know about your E-150, but the Ford Super-duty trucks actually have two mirrors on each housing. The main mirror allows you to see behind / beside you as normal but there is a smaller mirror that is pointed down and is a real life saver when trying to back into a rough spot and you can't see if there is something about to be run over by your rear wheels. For a work truck FE isn't everything.

Have you considered mounting a mirror INSIDE your window? Does your state allow review cameras?