Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now

Now available from EcoModder: ScanGauge II fuel economy gauge.  Click for details.  

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 10-24-2009, 11:29 PM   #31 (permalink)
EcoModding Apprentice
 
Bicycle Bob's Avatar
 
Join Date: May 2008
Location: N. Saskatchewan, CA
Posts: 1,275

Appliance White - '93 Geo Metro 4-Dr. Auto
Last 3: 42.35 mpg (US)

Stealth RV - '91 Chevy Sprint Base
Thanks: 44
Thanked 154 Times in 116 Posts
That would depend upon ground clearance and other issues. If departure angle is a problem, turbulators can be added just as the angle is increasing.

  Reply With Quote
Old 10-25-2009, 03:09 AM   #32 (permalink)
aero guerrilla
 
Piwoslaw's Avatar
 
Join Date: Oct 2008
Location: Warsaw, Poland
Posts: 3,302

Svietlana - '05 Peugeot 307 SW
Diesel
90 day: 54.35 mpg (US)
Thanks: 881
Thanked 475 Times in 295 Posts
Quote:
Originally Posted by RobertSmalls View Post
Okay, I suppose it would interfere with your ability to load akward cargo and parallel park. But if you drop the requirement that it be able to be stored inside the Metro, it becomes easier to design and build, since you can use a single rigid frame. Storable in the garage is almost as good. You'd use the boattail on road trips, and leave it at home for commuting.
You're right about a rigid frame being easier to construct and more stable, but being able to fold a boattail and stow it in the trunk is very useful. Not all road trips are of the 'drive to grandma's ranch' type. This summer we drove to Romania and a boattail would have been awsome on the 1500+km trip each way, but once there we were driving around, sightseeing, city driving, parking, etc. The boattail would only be in the way, and we couldn't just take it off and leave it at the border station for two weeks. But if it deflated and packed into a size not much bigger than the rear light assembly in Botsapper's pic, then it could just get stuffed anywhere until it was time to return.
__________________
e·co·mod·ding: the art of turning vehicles into what they should be

What matters is where you're going, not how fast.

"... we humans tend to screw up everything that's good enough as it is...or everything that we're attracted to, we love to go and defile it." - Chris Cornell

Piwoslaw's Peugeot 307sw modding thread

  Reply With Quote
Old 10-25-2009, 06:18 AM   #33 (permalink)
Master EcoModder
 
basjoos's Avatar
 
Join Date: Dec 2007
Location: Upstate SC
Posts: 868

Aerocivic - '92 Honda Civic CX
Last 3: 70.54 mpg (US)

AerocivicLB - '92 Honda Civic CX
Team Honda
90 day: 62.08 mpg (US)
Thanks: 1
Thanked 269 Times in 142 Posts
Quote:
Originally Posted by 3-Wheeler View Post
Nice to hear from you again!

If I am reading what you have said about the relative lack of air on underside of the vehicle compared to the sides and top, it would seem that you could conclude that the taper on the underside of the aerocivic is too steep.

I remember reading in that thread somewhere, that you asked Mike if he had performed tuft testing in that location. How much higher can the 4° go before air detachment would be a concern in this location?

Jim.
The underside of my boattail is steeper than I would have liked it, but I have a sharp approach to my driveway and didn't want to risk dragging the bottom of the boattail. I haven't tuff tested the underside of my boattail. I can't see it when I'm driving and don't have any aeronut neighbors to follow me, observe, and make sense of what they were seeing. But I have noticed that sections on the rear of vehicles that have turbulent flow tend to collect dust and dried deposits of dirt from water/salt spray. The underside of my boattail doesn't collect get dirty, so it can't be too turbulent under there. The side taper helps in allowing air to fill in the space between the road the underside of the boattail.
__________________
aerocivic.com
  Reply With Quote
Old 10-25-2009, 06:38 AM   #34 (permalink)
Master EcoModder
 
NeilBlanchard's Avatar
 
Join Date: May 2008
Location: Maynard, MA Eaarth
Posts: 5,526

Mica Blue - '05 Scion xA RS 2.0
Team Toyota
90 day: 42.98 mpg (US)
Thanks: 1,043
Thanked 1,168 Times in 703 Posts
Hi,

I'll post the image I just made for my thread here as well, because I think it illustrates the issue.

1st possibility is relatively short and curved to a point
2nd possibility extends out to nearly the point where a 15 degree top slope intersects with the 4 degree bottom slope
3rd is a truncated version of the 2nd

__________________
Sincerely, Neil

http://neilblanchard.blogspot.com/
  Reply With Quote
Old 10-27-2009, 01:00 PM   #35 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 15,910

Blackfly - '98 Geo Metro
Team Metro
90 day: 61.51 mpg (US)

ForkenSwift - '92 Geo Metro EV
Last 3: 95.68 mpg (US)

U.F.O. - retired - '00 Honda Insight
Team Honda
90 day: 88.21 mpg (US)
Thanks: 794
Thanked 2,392 Times in 1,280 Posts
Quote:
Originally Posted by botsapper View Post
At the end of the day, it could also serve as the children's slide on the front lawn.
And a gardening hothouse!

Another amazingly good image, botsapper - thanks.

---

I have nothing to report other than when not occupied with a few unrelated tasks last weekend, I sat on my duff. Haven't done any construction yet (aside from the virtual kind in my head - done lots of that!).
__________________
Latest test: Ecodriving comparison: 2014 Mirage CVT vs. Mirage 5-speed vs. '98 Metro 5-spd
Latest project:
Honda Insight boat tail extension (cardboard) tuft video; ABA test +9.7%



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 10-27-2009, 01:15 PM   #36 (permalink)
"Inconceivable"
 
moorecomp's Avatar
 
Join Date: Jul 2008
Location: Mancelona, MI
Posts: 282

My ZX2 - '99 Ford Escort ZX2
Team ZX2
90 day: 37.08 mpg (US)

Her RAV4 - '11 Toyota Rav4 4x4
90 day: 24.52 mpg (US)
Thanks: 2
Thanked 70 Times in 44 Posts
And you can call it the BubbleButt
__________________
moorecomp
Mancelona, MI

  Reply With Quote
Old 10-27-2009, 06:58 PM   #37 (permalink)
Master EcoModder
 
Wonderboy's Avatar
 
Join Date: Jun 2008
Location: Binghamton NY
Posts: 649

CRXFi - '88 Honda CRX HF / XFi
90 day: 38.84 mpg (US)

01 Insight - '01 Honda Insight
90 day: 44.31 mpg (US)
Thanks: 40
Thanked 37 Times in 26 Posts
Quote:
And you can call it the BubbleButt
hahaha brilliant!
__________________
  Reply With Quote
Old 10-28-2009, 06:49 PM   #38 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 5,602
Thanks: 3,780
Thanked 1,641 Times in 971 Posts
dirt could be good

Quote:
Originally Posted by basjoos View Post
The underside of my boattail is steeper than I would have liked it, but I have a sharp approach to my driveway and didn't want to risk dragging the bottom of the boattail. I haven't tuff tested the underside of my boattail. I can't see it when I'm driving and don't have any aeronut neighbors to follow me, observe, and make sense of what they were seeing. But I have noticed that sections on the rear of vehicles that have turbulent flow tend to collect dust and dried deposits of dirt from water/salt spray. The underside of my boattail doesn't collect get dirty, so it can't be too turbulent under there. The side taper helps in allowing air to fill in the space between the road the underside of the boattail.
If the underside of the tail were a little dirty it might have an advantage with high speed stability.
Some race car designs have purposely slanted tails which communicate the low base pressure under the shelf of the tail to the cars underside.
The distance out from the rear wheels acts as a moment arm creating a torque at speed,creating useful downforce albeit with some drag penalty.
  Reply With Quote
Old 10-29-2009, 12:24 PM   #39 (permalink)
Master EcoModder
 
wagonman76's Avatar
 
Join Date: Jun 2008
Location: Northwest Lower Michigan
Posts: 1,006

Red Car - '89 Chevrolet Celebrity CL 4 door
Team Chevy
90 day: 36.47 mpg (US)

Winter Wagon - '89 Pontiac 6000 LE Wagon
90 day: 28.26 mpg (US)
Thanks: 8
Thanked 14 Times in 13 Posts
Quote:
Originally Posted by Old Tele man View Post
...pardon my simplistic analogy, but it sure "looks" like a really bad case of the "...tail waggging the dog..." situation to me.
I remember back in 1989 when a Yugo got blown off our Mackinac Bridge. Hard to say what really happened, everybody's stories were contradicting, some say she was speeding, some say she stopped, some say she started swerving... but one thing was for sure, it was a tiny car driving in high winds. Since then they installed anemometers and close the bridge in high winds.

I can understand one might want to remove the tail. Taking a trip to the city, it can be a lot harder to maneuver in tight spots with a tail.
__________________

Winter daily driver, parked most days right now


Summer daily driver
  Reply With Quote
Old 10-29-2009, 12:29 PM   #40 (permalink)
Moderate your Moderation.
 
Join Date: Nov 2008
Location: Troy, Pa.
Posts: 8,859

Pasta - '96 Volkswagen Passat TDi
90 day: 41.32 mpg (US)
Thanks: 1,342
Thanked 411 Times in 342 Posts
So what about an umbrella frame deal?

Couple pieces of tubing that slip inside each other to make the main "handle" section, a ring that slides up the tubing to open the "chute" section, could be made of thin rods and fabric, would fold up in seconds and could be stuffed in the trunk with no problems. A quick PCV tube frame could be attached to the hatch to connect the loose ends of the fabric.

__________________
"¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"

  Reply With Quote
Reply  Post New Thread

Tags
boat tail, testing

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Project: Rebuilding an '01 Honda Insight as a nonhybrid Fabio Hybrids 158 01-12-2013 11:59 AM
How to get instant fuel consumption from Megasquirt TELVM Instrumentation 11 08-29-2011 02:47 PM




Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com