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

[MetroMPG]

Originally Posted by 3-Wheeler

Of course don't ask about how much time the sanding/glazing/priming and painting will take.

Jim: this is why I ruled out a foam/fiberglass approach. The kammback is a resin-soaked cardboard/fiberglass sandwich, and I spent 75% of my time trying to make it look nice after it was functionally done. The body work tested my patience .

Also, I don't think the finish turned out all that great relative to the time I spent. To add insult to injury, it's peeling/bubbling in spots!

[gone-ot]

...I'd get a replacement backlight/hatch assembly from a junkyard and attach the boattail permanently to IT, then simply bolt / unbolt the whole she-bang to do A-B testing.

[Piwoslaw]

Originally Posted by Old Tele man

...I'd get a replacement backlight/hatch assembly from a junkyard and attach the boattail permanently to IT, then simply bolt / unbolt the whole she-bang to do A-B testing.

But then it wouldn't easily fit for storage in the car...

[Wonderboy]

But then it wouldn't easily fit for storage in the car...

I think the point is that in this case, it may be much easier to slap something on there permanently to test it and see if the results make it worth the time and effort to make a fancy one that will detach and fit into the hatch. A whole hatch may be pretty cheap too depending on the junkyard. I know there are plenty of that generation hatches in the yards around here.

[Tango Charlie]

Originally Posted by MetroMPG

I've spent a silly amount of time standing around looking at the back of the car.

Heh, I think we've all been there.

Can't wait to see what you come up with. I think you will find that the internal bracing can be minimal if you let the coroplast skin carry the load; i.e. monocoque construction.

[botsapper]

Your requirement of having the boat tail stowed in the car was a challenge. We had earlier concepts of rigid or semi-rigid boat tail appendages mainly supported by extended hitch connections. So a folding inflatable could be attached ala bike rack straps & a rigid spar to hold the rear lights/license assemblies. The inflatable form could theoretically have the optimum airflow shape. Inflatable aerospace tech has been updated from earlier Goodyear airplane studies. The exciting 'Mars airplane' studies depend heavily on reliable inflatable airfoil engineering solutions. The tech has already been used in the Pathfinder projects.

http://www.youtube.com/watch?v=WZbR3...eature=related

Goodyear have taken early tests & concepts of inflatable airplane platforms. A compact rescue package designed for downed pilots/operators that could be air-dropped. They could then be deployed & flown to their freedom and back to friendly lines. However watch out for catastrophic deformation at extreme speeds.

http://www.youtube.com/watch?v=ywPkL...eature=related

[MetroMPG]

Originally Posted by Wonderboy

I think the point is that in this case, it may be much easier to slap something on there permanently to test it and see if the results make it worth the time and effort to make a fancy one that will detach and fit into the hatch. A whole hatch may be pretty cheap too depending on the junkyard. I know there are plenty of that generation hatches in the yards around here.

I've thought that a junkyard hatch would be a good thing. Speaking just of the Kammback: I could integrate it better into one that I didn't mind welding/cutting up/bondo-ing/etc. It could be lighter, plus I could lose the rear glass and enclose with plexi.

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I'll probably skin the boat tail with cardboard for testing before doing anything more complicated. (removable panels, coroplast)

EDIT: but I won't be able to work on this any more until the weekend at the earliest.

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Cd asked me via PM if I knew the car's current Cd. I don't. I went out one day this summer to do the Instructables "measure your Cd" coastdown test, but the numbers I got didn't fit very well in the curve used to figure out Crr and Cd, so I didn't bother finishing it.

[MetroMPG]

Botsapper: inflatable would be fantastic.

[Piwoslaw]

Inflatable boattail

[botsapper]

These ideas just keeps going around. Let's see some eco-prototyping!!!

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