Project: Geo Metro boat tail prototype - 15% MPG improvement @ 90 kph / 56 mph

[Cd]

Awesome !
Perhaps you could get your wife to video the car from the side of the road using a more high res. video camera.

( It sure would be less work, and it would show more areas of the tail rather than just one section. )

( Also, you wouldn't have to worry about telephone poles, cyclists, trees, little old ladies... )

[MetroMPG]

Originally Posted by Cd

would be interesting to see how much turbulence is on the very back and underside. ( like behind the wheels )

I think we know there's going to be turbulence behind the wheels!

But I am planning to tuft the bottom boat tail surface and see what it shows. I'm expecting turbulence over all of it, with no belly pan.

When do you plan to add minitails to your mudflaps ?

Ummm.... Tuesday, June 21, 2011.

I don't know! Eventually. After I lower the car... eventually.

Also, I know that you didn't get good results with your bellypan test, but as you mentioned, the cardboard was drooping down during the test. Do you ever plan to redo the test ?

I had that one botched test (the one with the droop), then I re-did it with just an A-B comparison, 3 bi-directional runs each. It showed about a 2% improvement at 90 km/h (56 mph).

Since I have the prototype boat tail built, I'm going to put the belly pan back on, fair the rear control arms into it (they stick waaay down below the plane of the floor pan), and then test the works.

I suspect the bottom of the tail is useless without the belly pan, so might as well see what all the bits are worth together. I suspect the effect of belly pan + boat tail (assuming the bottom angle isn't too steep) is greater than the sum of the individual mods' effects.

Originally Posted by Nerys

quick shot of BLACK spray paint and it will even have a nice 20ft finish.

I thought about painting it, but this is just for testing. The "good" version will be black.

Originally Posted by Bicycle Bob

Will we see little fairings behind the mud flaps, too?

Yep, eventually. See above.

The thing about the concave rear is to encourage a single large vortex to form there.

A little confused about that. How can we have a single vortex shed off the rear of a vehicle... unless you mean one that's rotating on an axis parallel to the "transom"? (As opposed to parallel to the direction of travel, which would necessarily mean a pair, wouldn't it?)

[Cd]

Originally Posted by MetroMPG

• the boat tail literally stops traffic. A guy actually came to a halt in his Chevy Avalanche in the middle of a turn in an intersection to gape - blocking through traffic from two directions.

[/LIST]

I fully expect to see your car all over the internet
I think you need to make the ecomodder.com logo clearly visible and prepare for the massive amount of traffic that we are going to see here !!

[orange4boy]

Looks like you are ready for launch. You will have to get used to the gawking, pointing, laughing. Nice thing is you can laugh right back.

SWEET!

I think Bob means one big elongated magical doughnut shaped vortex. Mmmmm... doughnut...

[MetroMPG]

OH! One of THOSE vortices!

http://www.youtube.com/watch?v=IyAyd4WnvhU

[Cd]

Thanks for posting that !
Reminds me of what I had read sometime ago about the Air Force experimenting with using supersonic shock waves as a weapon.

Regarding the back end vortex, even if the concave rear end doesn't do much, it can't hurt right ?

[MetroMPG]

Originally Posted by NeilBlanchard

How far out does the boattail extend?

The cardboard ends at about 1.3 m / 51 in. from the end of the Kammback.

Then I glommed the tail lights on the back of that, for another 12 cm / ~5 in. Overall it's about the length of a Toyota Camry now. Maybe a few inches more.

Cd - the way I have the tail lights stuck on would make it difficult to do the concave transom, otherwise I might give it a shot.

[Rokeby]

Originally Posted by MetroMPG

OH! One of THOSE vortices!

In a smaller size, camouflaged as a tail pipe, it would be very useful to
express displeasure to tailgaters.

[Nerys]

oh man I SO WANT ONE OF THOSE CANON"S !!!!

so your getting 70mpg highway? ?? how exactly are you doing that?

[majestic]

This is the best implementation of a boattail I have seen yet.

I would love to see you make a more permanent version, so I did a little photoshop, hope you don't mind!