CivicTail project: ginormous aerodynamic tail on '07 Civic sedan

[WD40]

How much rear overhang are you legally allowed to have?
I can't find anything in the B.C. motor vehicle act that defines overhangs front side or back.
I have read on some forums that 12" on front and 48"on back is allowed as long as they have marker lights.

[MetroMPG]

~54 mpg US.

That's one-way today on wet roads, light rain, just above freezing, negligible winds. That's a best ever on a trip I've done before with the car, AND driving faster with more cruise control use. (I like spending some of my aero dividends on shorter travel time.)

Lots of rubbernecking and smiles directed this way. Fun.

Full trip report later tomorrow!

[MetroMPG]

Originally Posted by Cd

What's the plan with the end of the tail ? ( the section that gets too 'fast' )

A simple spoiler at the end of the tail would bring the effective shape closer to the template.

Also, IIRC you mentioned that here seemed to be a lot of turbulence from the wheel wells [...] This has me puzzled, since the wheel gap is so small, and you have wheel covers on.
Care to explain more on this ?

I think it's as simple as: no wheel-to-arch gap (ie. a rear fender skirt) is better than a small gap.

In the video I took, the difference in flow on the side of the tail with the fender skirt on is clear as day. I was a little surprised too.

[MetroMPG]

Originally Posted by WD40

How much rear overhang are you legally allowed to have?

I'm not sure about added length regulations.

Like you, I've also read multiple references of a 48" limit. This tail is less than that, at about 44 inches beyond the rear bumper.

[MetroMPG]

A non-scientific comparison of this weekend's results against another trip, pre-tail:

This weekend's round trip results with the tail in place:

• Trip length: 177 mi / 284 km round trip, 1 person, approx 10% city, 90% rural roads (50 mph / 80 km/h limit),
• Average speed: 39.5 mph / 64 km/h, 60 mph max (posted limit on the majority of the drive: 50 mph / 80 km/h). Note: that includes time stopped, and reflects going through 1 small city, several small towns, hamlets.
• Driving style: cruise control on the open road (with some engine-on coasting down steep enough hills), engine-off approaching stops/turns, where practical.
• Conditions, there: light rain, just above freezing, negligible winds. Return: dry roads, just above freezing, gusty (up to 40 km/h) crosswinds.
• Results: 52.4 mpg (US) round trip = 4.5 L/100 km (54.3 there, 50.4 back)

A previous round trip, pre-tail, but with the 15 mods in place:

• Trip length: 168 mi / 270 km round trip, 3 people, approx. 10% city, 45% freeway (100 km/h / 62 mph posted limit), 45% rural roads (80 km/h / 50 mph limit)
• Average speed: 40 mph / 64 km/h (per ScanGauge, includes time spent sitting still). Includes going through 1 small city, 1 town, 1 medium city.
• Driving style: mostly with cruise control on the open road (close to the speed limits -- a little over, a little under, depending on traffic).
  Engine off coasting, where practical (approaching stops/turns).
• Conditions: windy (gusts to ~40 km/h), temperature -2 to +2C, roads dry or damp.
• Results: 44.3 MPG US = 5.3 L/100 km = 53 MPG Imp.

But note these trips don't make for an ideal comparison -- it's unlikely this thing is worth an 8 mpg improvement in identical conditions. Even though the trip length, average speeds & ambient temps were close, they were on different routes, with different loads. The pre-tail trip carried more people & probably had a higher "rolling average" speed.

I'm just comparing them out of curiosity until I get some better controlled numbers. (A speed vs. mpg set that can be compared to pre-tail speed vs mpg).

The "as-good-as-possible" testing (A-B-A) will come sometime later.

[niky]

Man, you've outdone yourself... absolutely incredible work!

Makes me wish I were half as handy with cardboard as you are!

[OG VX]

Amazing work! Beautiful shape and craftsmanship.

[aerohead]

Originally Posted by MetroMPG

I'm not sure about added length regulations.

Like you, I've also read multiple references of a 48" limit. This tail is less than that, at about 44 inches beyond the rear bumper.

In the USA,'rigid' tails are limited to 48" overall length.
Inflatable tails can be 60".
Not sure about Canada.

[aerohead]

Less filling and tastes great!
Let's see if Reddit latches on to this one Darin.

[MetroMPG]

Thanks, Phil. I'd be surprised if we didn't share the same regs on added length.

--

Waiting for testing-friendly weather for A-B-A. There's nothing on the near horizon -- it's been really windy the past few days.