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

[JackMcCornack]

Man, MetroMPG, when you tackle a project you get right on it, eh? Remarkable work and you gotta love the results.

Originally Posted by MetroMPG

Easy to build. Harder to sell, I suspect.

Selling new products for out-of-production cars is a rough row to hoe. That boat tail in fiberglass would end up retailing for more than Metro blue book value. Surely some auto manufacturer will come out with another no frills high efficiency econobox to match our beloved Suzukevy Swiftros, and when they do maybe you should make a removable boat tail for them.

[orange4boy]

I'm Christ, and I stand behind this statement 100%.


This post paid for by the Committee to Agree Needlessly with Obviously Correct Statements. CANOCS is a non-profit organization.


My mama always told me I had a firm grasp of the oblivious.

And in the interest of staying OT: Darin, your boattail is very boatish! and tail like also, but not very boxy or moatish. So yay for you.

You guys can delete these posts later right?

[Christ]

Originally Posted by orange4boy

I'm Christ, and I stand behind this statement 100%.


This post paid for by the Committee to Agree Needlessly with Obviously Correct Statements. CANOCS is a non-profit organization.


My mama always told me I had a firm grasp of the oblivious.

And in the interest of staying OT: Darin, your boattail is very boatish! and tail like also, but not very boxy or moatish. So yay for you.

You guys can delete these posts later right?

Man, I hope so...

[Piwoslaw]

Originally Posted by Christ

Something like a thread for the various templates we use?

That's not a bad idea, but I was thinking about an "Aeromodding Bicycles" or "Boattailed Recumbant Bikes" thread.
But a DIY forum with a template collection is sooooo much better

[JeepNmpg2]

Congrats on the great results, your thorough engineering paid off.

I do have a question through: Is it still more effiecient to go full conical VS bluff boattail? I understand that lengthening your vehicle out and reducing the tail cross sectioning does happen with both, but how much more efficient could it be with the full tail?

BTW, I'm not raining on your parade, I just want to know for my own design purposes (I drive a box on wheels.... enough said). I really don't want to go all the way through the design process and have to rethink everything in the end.

[silverinsight2]

Kudos on your achievment, is a front wheel skirt next?

[Cd]

Thanks for being so thorough with the testing on you 'tail.
Those results are absolutely incredible.

Now that you have reached this far along, do you think you have reached the point of diminishing returns ?

I look at the back of the 'tail and wonder if a solar powered fan would help your wake even more.

( O.K. maybe not .... but the Aptera has one )


silverinsight2 The wheel skirt on the front was tested earlier ( on one side ). It was a very clever design that fit almost flush with the body of the car, and used a simple system of slick plastic and nylon banding.
It looked promising, but the results weren't that great on this particular car ( the wheel wells do not flare out like most cars )
They have since been removed.

[Cd]

silverinsight2 The fabrication of the front wheel skirt was documented on another thread. For some reason, I'm clueless to find it.

[silverinsight2]

I couldn't find the thread either.
I was actually thinking of a tight form fitting closed cell poly "pool noodle" to fill the fender gap. Plus moonies.

[alohaspirit]

Originally Posted by MetroMPG

Conditions:

Grenadier Island Past 24 Hour Conditions
Date / Time (EST) ... Conditions ... Temp (°C) ... Humidity (%) ... Dew Point (°C) ... Wind (km/h) ... Pressure (kPa) ... Vis (km) ... Wind Chill
15:00 ... N/A ... 2 ... 59 ... -5 ... calm ... 101.8 ... N/A ... *
14:00 ... N/A ... 2 ... 57 ... -5 ... W 2 ... 101.7 ... N/A ... *

Speed: 90 km/h (56 mph)

Route: straight & practically level 1.6 km stretch of 2-lane highway, no other traffic ahead of me in my lane, infrequent oncoming vehicles in the other lane.

A = boat tail on
B = boat tail off

Readings in MPG (US):

    east    west    avg    
A    66.4    62.6    64.5    
A    65.2    62.8    64    
A    65    64.4    64.7    64.4 (avg these A runs)

B    56    56.6    56.3    
B    55.9    56.5    56.2    
B    54.3    56.3    55.3    55.93333333 (avg B runs)

A    65    64.3    64.65    
A    64.2    64    64.1    64.375 (avg these A runs)

64.39 A avg (all A runs)
55.93333333 B avg

15.1% improvement, A over B

for +8.46 mpg

I had to bump this up