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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-12-2009, 05:08 PM   #61 (permalink)
A madman
 
brucey's Avatar
 
Join Date: Mar 2008
Location: WV
Posts: 1,018

Pequod - '17 Subaru Outback
90 day: 22.79 mpg (US)
Thanks: 73
Thanked 183 Times in 98 Posts
Send a message via AIM to brucey
I'll try testing it tonight, but I dont think this idea works practically. At least not the way I've built it. It's too heavy, too awkward to use, a ***** to put on and off, and way too big to store anywhere. Nice concept.

I think I'm going to start from scratch again and have a kammback permanently on the car to get the right angles going and go from there.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-12-2009, 08:49 PM   #62 (permalink)
T-100 Road Warrior
 
BamZipPow's Avatar
 
Join Date: Apr 2008
Location: The Woodlands, TX
Posts: 1,920

BZP T-100 (2010) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 24 mpg (US)

BZP T-100 (2011) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 23.66 mpg (US)

BZP T-100 (2009) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 19.01 mpg (US)

BZP T-100 (2012) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 25.45 mpg (US)

BZP T-100 (2013) - '98 Toyota T-100 SR5
Last 3: 25.79 mpg (US)

BZP T-100 (2014) - '98 Toyota T-100 SR5
Last 3: 23.18 mpg (US)

BZP T-100 (2015) - '98 Toyota T-100 SR5
Last 3: 23.85 mpg (US)

BZP T-100 (2016) - '98 Toyota T-100 SR5
Last 3: 17.62 mpg (US)

BZP T-100 (2017) - '98 Toyota T-100 SR5
90 day: 20.78 mpg (US)

BZP T-100 (2018) - '98 Toyota T-100 SR5
90 day: 20.19 mpg (US)

BZP T-100 (2019) - '98 Toyota T-100 SR5

BZP T-100 (2020) - '98 Toyota T-100 SR5

2012 Scion iQ - '12 Scion iQ Base
Thanks: 3,479
Thanked 1,395 Times in 968 Posts
Send a message via ICQ to BamZipPow
Found something interesting...at least from an inflateable point of view...

Balloons.net makes those inflateables you see around...they even have some clear ones.

Probably be kinda expensive though...but it would be a cool approach.
  Reply With Quote
Old 11-13-2009, 03:09 AM   #63 (permalink)
A madman
 
brucey's Avatar
 
Join Date: Mar 2008
Location: WV
Posts: 1,018

Pequod - '17 Subaru Outback
90 day: 22.79 mpg (US)
Thanks: 73
Thanked 183 Times in 98 Posts
Send a message via AIM to brucey
OFFICIAL RESULTS:

Weather Conditions:

45°F | °C
Current: Partly Cloudy
Wind: N at 3 mph
Humidity: 48%

Method:

Cruise was set at 55 and run on my 1 mile test track. A - B 3 times each, cancelled with cruise and resuming with resume. I put the boat tail on and duct taped a few areas where I felt it could be catching. Then did another A-B 3 times, and went back, took it off, and did ANOTHER A-B 3 times.

Data:

NO TAIL:

A: 33.2
B: 33.4
A: 33.2
B: 33.2
A: 33.4
B: 33.3

TAIL:

A: 33.6
B: 33.4
A: 33.5
B: 33.1
A: 33.4
B: 33.0

NO TAIL:

A: 34.7
B: 33.3
A: 32.9
B: 33.3
A: 33.5
B: 33.4

Results:

GORRAMIT

Pretty much a wash.

Its interesting that the best AND the worse results came from the same run set, in the same direction.

Other than that, it seems I've made a 4 foot rolling blind spot. And I now have enough data for myself to start over pretty much from scratch.

*sigh*

It would have been really useful for the trip to Cape Canaveral this weekend for the shuttle launch. Hopefully I can rig up a kamm quickly and drag it down.

Last edited by brucey; 11-13-2009 at 03:21 AM..
  Reply With Quote
Old 11-13-2009, 07:13 PM   #64 (permalink)
Cd
Ultimate Fail
 
Cd's Avatar
 
Join Date: Feb 2008
Location: Austin,Texas
Posts: 3,585
Thanks: 2,872
Thanked 1,121 Times in 679 Posts
That was certainly unexpected !
Sorry to hear about those results.
It would be interesting to see some tuft testing to see what is happening back there.
  Reply With Quote
Old 11-14-2009, 11:12 AM   #65 (permalink)
EcoModding Lurker
 
Join Date: Feb 2008
Location: campbell, ca
Posts: 8
Thanks: 0
Thanked 0 Times in 0 Posts
dont give up so easily

Hi,
I'm not surprised too much by the 55 mph data. If you tried it at 45 I suspect it would have gotten worse as the boattail would just extra weight. Since at 45 the wind resistance becomes insignificant compared to the other losses. However, if you tried it at 65 or 70, we might see that although the mpg goes down in both cases, it would go down less in the case of the boattail.

Could you rerun the tests at 65 or even 70?
  Reply With Quote
Old 11-14-2009, 12:28 PM   #66 (permalink)
Cd
Ultimate Fail
 
Cd's Avatar
 
Join Date: Feb 2008
Location: Austin,Texas
Posts: 3,585
Thanks: 2,872
Thanked 1,121 Times in 679 Posts
Quote:
Originally Posted by dluck View Post
Hi,
Since at 45 the wind resistance becomes insignificant compared to the other losses.
Um..........."insignificant" ??
  Reply With Quote
Old 11-14-2009, 12:52 PM   #67 (permalink)
Wanderer
 
Sorrow Six Star's Avatar
 
Join Date: Nov 2009
Location: Birmingham
Posts: 90

Winona - '86 Subaru XT DL
Thanks: 20
Thanked 4 Times in 3 Posts
lesbaru! I like it!

the boat tail makes the OB look like a Chinook.
  Reply With Quote
Old 11-14-2009, 02:28 PM   #68 (permalink)
T-100 Road Warrior
 
BamZipPow's Avatar
 
Join Date: Apr 2008
Location: The Woodlands, TX
Posts: 1,920

BZP T-100 (2010) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 24 mpg (US)

BZP T-100 (2011) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 23.66 mpg (US)

BZP T-100 (2009) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 19.01 mpg (US)

BZP T-100 (2012) - '98 Toyota T-100 ext cab - 3.4L/auto SR5
Last 3: 25.45 mpg (US)

BZP T-100 (2013) - '98 Toyota T-100 SR5
Last 3: 25.79 mpg (US)

BZP T-100 (2014) - '98 Toyota T-100 SR5
Last 3: 23.18 mpg (US)

BZP T-100 (2015) - '98 Toyota T-100 SR5
Last 3: 23.85 mpg (US)

BZP T-100 (2016) - '98 Toyota T-100 SR5
Last 3: 17.62 mpg (US)

BZP T-100 (2017) - '98 Toyota T-100 SR5
90 day: 20.78 mpg (US)

BZP T-100 (2018) - '98 Toyota T-100 SR5
90 day: 20.19 mpg (US)

BZP T-100 (2019) - '98 Toyota T-100 SR5

BZP T-100 (2020) - '98 Toyota T-100 SR5

2012 Scion iQ - '12 Scion iQ Base
Thanks: 3,479
Thanked 1,395 Times in 968 Posts
Send a message via ICQ to BamZipPow
Some data I'd like to see is the weight of the boat tail along with the new angle/rake of the car with the boat tail installed.
  Reply With Quote
Old 11-14-2009, 04:01 PM   #69 (permalink)
EcoModding Lurker
 
Join Date: Feb 2008
Location: campbell, ca
Posts: 8
Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Cd View Post
Um..........."insignificant" ??
Yes, insignificant for a car, not insignificant if you are peddling a bicycle. The boattail effectiveness is proportional to square of the speed. At low speeds where there is little if any energy being spent to push air out of the way, or sucking it back in behind you cannot get any benefit. Also the boattail length/curvature will create a sweet spot for a particular speed. If its not long enough there were still be drag as a vacuum is created behind the boattail. However being longer than necessary will start to add drag back and unnecessary weight.
  Reply With Quote
Old 12-06-2009, 10:58 PM   #70 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
dluck: even at 45 mph, probably half or more of the power required to go down the road is lost to aero drag.

Have a look at this tool: Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com

Quote:
Also the boattail length/curvature will create a sweet spot for a particular speed.
Cd is effectively constant for our purposes - the shape either works, or it doesn't, regardless of speed.

__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



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
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Vibe Kammback / Boat tail trikkonceptz Aerodynamics 9 01-19-2014 09:59 AM
Project: Geo Metro boat tail prototype - 15% MPG improvement @ 90 kph / 56 mph MetroMPG Aerodynamics 500 05-10-2012 10:30 PM
Trailer Hitch Boat Tail? superchow EcoModding Central 16 04-26-2010 02:35 PM
Subaru Outback Prototype Boat Tail Test Results brucey Aerodynamics 10 10-02-2009 05:03 PM
Rear Wheel Boat Tail Fabrication 2003protege Aerodynamics 1 07-24-2008 05:16 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com