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

[thatguitarguy]

Originally Posted by MetroMPG

Oh, yeah - a varnished cedar strip boat tail would look fantastic on a black car!

Why just the boattail??

[Nerys]

oh yeah I am imagine chris craft on wheels! has to be mahogany though! I love mahogany!

that wooden car is sick! must weigh an awful lot! but looks so nice.

[thatguitarguy]

Originally Posted by Nerys

oh yeah I am imagine chris craft on wheels! has to be mahogany though! I love mahogany!

that wooden car is sick! must weigh an awful lot! but looks so nice.

900 lbs! 55-70 mpg Check it out" Tryane II

[Nerys]

man oh man I wish I had the time skill and most importantly MONEY to do something like that. What a machine!

[discovery]

May be one day i'll try to fit it on my cars, waithing to see all the results. This is realy cool project.

[MetroMPG]

Originally Posted by Cd

Oh wait ... I didn't think about the frame under the cardboard.
I guess you couldn't just cut an adjustable section out could you ?

It's not really a simple change. I'd have to revise the internal bulkheads too. Also, getting curvature into the top would require bending the top aluminum tubes. Willing to do that.

Originally Posted by Frank Lee

Right or wrong, I'd increase tapers until I see sign of turbulence, than increase until "laminar". Otherwise you may just end up with extra unneeded length. With unneeded length comes extra unwanted skin drag as noted in recent discussions re: crx and del sol tails.

I have no problem admitting that the design isn't optimal. I'm inclined to revise once more, this time tapering/curving more aggressively toward the end. Average the results of v.1 and v.2 if I see separation, keep v.2 if I don't.

As you see it now, I've got maybe 12 hours in it. It's a lot of work! It's also fun, but not in the recent temps when the fingers start to get icy.

OH, and I'll have to go buy another roll of the good, sticky $5 duct tape. Used 1.5 rolls already. This is getting expensive!

Oh wait... I just realized I know where I may be able to use a heated shop. That would drastically increase my modding season. Will report back.

[Bicycle Bob]

How about adding a small, adjustable extension that you can progressively bend down? You could watch for turbulence at the middle as a test section without fussing over the sides, and get an angle to aim for when building v2.

[wagonman76]

Originally Posted by Frank Lee

With unneeded length comes extra unwanted skin drag as noted in recent discussions re: crx and del sol tails.

Mine appeared to add extra skin drag too when I added the bolt on tail extension. Didn't get a pic before taking it off but it was the same horizontal and vertical slopes as the rest of the tail and went out another 16 inches or so.

[MetroMPG]

Lots of giggling from a gaggle of school kids going past while I was kludging this together.

Comment from one of them: "are you making a dragon? It needs wings!"



Above: radiused the leading edge of the wheel boat tail.





I realize it's not very practical, in terms of hitting stuff. But wanted to go big or go home.



Surprise, surprise, attached flow behind the wheel (at least on the outside - didn't capture the inside).

You can compare this to the image a few posts up, without it. Comparing the videos, I'd like to say there's less turbulence on the lower tufts now. It's only subjective, but logic says this should help.

One thing I can say for sure: this boat tail business is bad for the economy. There's a house construction site on the road I've been using, and when I go past everyone stops working to stare at the car!

[MetroMPG]

Here's the "before" pic.



Be careful drawing conclusions just from these screen grabs. I could probably find a frame where they appear to be laying relatively still, if I tried.