Aerocivic - how to drop your Cd from 0.31 to 0.17

[3-Wheeler]

Hi Robert,

Thanks for that picture!!! It's nice to have something to look at!

Using the 8-bolts is something that sounds good. Maybe utilizing some of the holes by the rear tail lights would be good too. Just enough fasteners spread around to make an effective attachment to the car, and make it strong in both the vertical and horizontal axis's.

Hey, I appreciate the offer to crawl around in the back of the car, but with some practicality in mind...

...A boat tail that pivots to one side the car will allow one to grab maybe some built in "handles" or "grab-holds" on the inside opening of the boat tail, and allow it to be lifted from the pivoting pins.

Maybe the pins could be like house front door hinges that are not "interlinked" and slide apart easily.

I hope this information is helping anyone else that is thinking about making a boat tail, since I don't want to take over Mike's thread.

Jim.

[3-Wheeler]

Mike,

Have you gotten any snow down there yet?

Just wondering how the under side panels are holding up.

Jim.

[basjoos]

Haven't had any snow yet here in Greenwood, SC but the western NC mountains got close to a foot of snow and I got a chance to test out the new Nokian snow tires driving around up there. This isn't the first time I've driven the car in snow and haven't yet had any snow-related problems with any of the mods.

[TOOSTUBBORN2FAIL]

just curious, with your low cd, ever have any problems going downhill, as far as not having enough brakes?

reason i ask, is i barely have any mods done, (estimating a cd of .31-.30 and frontal area of 20 feet), and going down the grapvine, with the car in 4th, the car will still accelerate to 75 mph, which is 10 mph above the speed limit. In neutral, it'll top 100. The grapevine is also a very bad place to speed as there are highway patrols hiding everywhere.

Last trip down, i was able to coast 15 miles in without gas, and without dropping below 55 mph. 7 of those miles were at a 6% decline, and those miles were pretty hard on the car. I had it up to 4000 rpm while engine braking, and i assume it will only get worse as the aero gets better.

Ill be making another trip down it in a couple months, with an extra 100 pounds in the car, and a few more aero tweaks (going from removed side mirrors, full grill block, no antenae, no wipers, and gap fillers on the rear tires, to all the above plus rear wheel skirts, front gap fillers, and wheel disks).

[3-Wheeler]

Originally Posted by TOOSTUBBORN2FAIL

...Last trip down, i was able to coast 15 miles in without gas, and without dropping below 55 mph. 7 of those miles were at a 6% decline, and those miles were pretty hard on the car. I had it up to 4000 rpm while engine braking, and i assume it will only get worse as the aero gets better...

One possible way to help the situation would be to create some spoilers on the sides of your boat tail let's say.

Remember that old TV show Knight Rider? He had all kinds of stuff that would pop out, supposedly to make the car faster.

In your case, the spoilers would help slow you down until you get to the bottom of the long hill.

Just an idea...

Jim.

[Tango Charlie]

How about some wind-powered generators like on that silly Forever electric car. You could make them extend out of the trunk when going downhill, sort of a poor-man's regenerative braking.

[aerohead]

Originally Posted by TOOSTUBBORN2FAIL

just curious, with your low cd, ever have any problems going downhill, as far as not having enough brakes?

reason i ask, is i barely have any mods done, (estimating a cd of .31-.30 and frontal area of 20 feet), and going down the grapvine, with the car in 4th, the car will still accelerate to 75 mph, which is 10 mph above the speed limit. In neutral, it'll top 100. The grapevine is also a very bad place to speed as there are highway patrols hiding everywhere.

Last trip down, i was able to coast 15 miles in without gas, and without dropping below 55 mph. 7 of those miles were at a 6% decline, and those miles were pretty hard on the car. I had it up to 4000 rpm while engine braking, and i assume it will only get worse as the aero gets better.

Ill be making another trip down it in a couple months, with an extra 100 pounds in the car, and a few more aero tweaks (going from removed side mirrors, full grill block, no antenae, no wipers, and gap fillers on the rear tires, to all the above plus rear wheel skirts, front gap fillers, and wheel disks).

I like to descend into Chama,New Mexico at 1:00 in the morning with the driver door stuck out like an air brake and my knee locked.
It's also a great way to swat the 1,200-lb elk standing in the highway.

[basjoos]

Since most of my driving is in the 55 to 70mph range, a speed range below the drag wall of my stock vehicle (and WAY below that of my aeromodded vehicle), I haven't noticed any noticable increased tendency for the vehicle to overspeed on the downhills and to require more braking than before aeromodding. But if I were coasting down the hills at 100mph, I would notice a bigger difference, since that speed would be well within the drag wall of a stock Civic CX, whereas the drag would be just starting to make itself noticable on the Aerocivic. At that speed the Aerocivic would require more friction/engine braking, but the Civic CX would be increasingly air braked by the increasing vehicle drag.

Even on the hottest summer day, I've never had any problems with brake fade on the longest, steepest grade around here, a 1000 foot drop off the Blue Ridge escarpment, the steepest parts of which are a 3rd gear hill climb.

[3-Wheeler]

Hi Mike,

How long is your boat tail?

In other words, how much longer is your current design past the location of the old bumper?

Metro made his boat tail, if memory serves, about 51 inches.

Thanks, Jim.

[basjoos]

The boattail adds 3 and a half feet of additional length to the rear of the car, of which two and a half feet of that is additional interior cargo space.