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

[Tango Charlie]

Save it for the Ecomodder Hall of Fame.

[JackMcCornack]

Originally Posted by MetroMPG

So, the last thing I'm going to do to the boat tail is document it: take a few more pictures and a bunch of measurements.

Could you give us a picture close-up of how you attach your yarn to your car? Even from a distance it looks so neat and tidy, it looks like you're buying yarn fasteners by the roll from Edmund Scientific, McMaster-Carr, or Tufts R Us. I use the painter's-tape-and-prayer method myself, but I like yours better.

[silverinsight2]

Originally Posted by MetroMPG

I'd only radius the aft portion of the wheel arch with half a noodle. I'd extend the front/top surfaces out flat toward the tire. Probably minimal gains on an Insight though - they paid attention to the wheel arches in their design. (I'm assuming you drive an Insight from your username.)

Thanks for the links. I saw somewhere that the front wheels & engine cooling were 30~50 percent of a cars total drag. I was thinking of minimizing the the outflow of air around the front wheels by minimizing the gap.

Maybe I'll try it on my own Insight next summer, it should be easy enough to do.
I also agree with Frank and the rest...leave the tail on throughout the winter. Long term testing will find weakpoints. Again congratulations on your significant gains.

[Frank Lee]

I'd like to see this with a tail:



It would be short and sweet!

[Christ]

Imagine the Miata sitting next to it with a fastback... It'd almost look identical to the Metro shape-wise, and no actual body modification would be needed.

That way, it meets Carlos' specs! :wink:

[gone-ot]

...but the Miata has a much more upright windshield, nowhere's as sloped and that Geo has (modded?!?).

[MetroMPG]

Originally Posted by JackMcCornack

it looks like you're buying yarn fasteners by the roll from Edmund Scientific, McMaster-Carr, or Tufts R Us. I use the painter's-tape-and-prayer method myself, but I like yours better.

Sorry to disappoint, but I'm using painter's tape too. Well, these tufts were stuck to gooey electrical tape, then onto a square of painter's tape. I save the tufts for the next project.

[MetroMPG]

Originally Posted by Frank Lee

I'd like to see this with a tail:

So would I. I keep coming back to that image & daydreaming. Reduce both Cd and A, and it looks great too (to my eyes).

EDIT: Old Tele Man - yes the entire roof has been chopped at the base of the A pillars and leaned back. It's a creative job.

[Christ]

Originally Posted by Old Tele man

...but the Miata has a much more upright windshield, nowhere's as sloped and that Geo has (modded?!?).

That Geo's been completely redone. If you check that link back to the main site, you'll find that it's been modded for drag racing, and the windshield's been raked back a bunch, so that the OEM windshield could be used with the chopped top.

Windshield angle isn't really a notable part of aero, from what I've read/learned.

I believe HotRod magazine did an aero spot where they covered it, because the windshield angle of most cars is already in the "ideal range", raking the windshield would only reduce frontal area. This isn't necessarily a bad thing, though.

Originally Posted by MetroMPG

So would I. I keep coming back to that image & daydreaming. Reduce both Cd and A, and it looks great too (to my eyes).

Darin -
You ain't the only one, buddy.

[NeilBlanchard]

I could not sit in that chopped Metro...

The irony is, a low car like that almost doesn't need a boattail; while a tall car definitely needs one! But a lot of height means a longer boattail...