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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 06-10-2014, 06:07 PM   #1 (permalink)
EcoModding Lurker
 
Join Date: Dec 2011
Location: Austin,Texas
Posts: 14

A.J. - '04 Honda Civic LX
90 day: 41.47 mpg (US)

bruce - '08 Kawasaki Ninja 650 R
90 day: 46.52 mpg (US)

Big Blue - '09 Ford F-150 LX
90 day: 17.33 mpg (US)

dr - '13 Kawasaki DR650
90 day: 55.32 mpg (US)
Thanks: 2
Thanked 64 Times in 9 Posts
Boat Tail Construction-Civic Sedan

After viewing the 'redneck boat tail' I have decided to make a boat tail. I have overlayed the template on images and they seem alright. Can anyone tell me if they are wrong in an way? I was not sure if the side taper was done correctly.

For materials,

I will probably build the frame as a tubular structure. I was thinking Metal conduit or PVC piping? For anyone with PVC experience, do you think it would be strong enough to support the weight? This seems easier since I can use a heat gun and bend it to the right shape.

I want to build the frame and then cover it in foam. After sanding/filing the foam, I want to fiberglass it with probably two layers of 4 oz cloth. Does this sound reasonable?

For the rear section, I will probably use 10mm coroplast that I have lying around.

Please give suggestions and point out problems if you can

Attached Thumbnails
Click image for larger version

Name:	AJ side donex small.jpg
Views:	54
Size:	40.2 KB
ID:	15173   Click image for larger version

Name:	AJ final top small.jpg
Views:	46
Size:	25.6 KB
ID:	15174  
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 06-10-2014, 06:27 PM   #2 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
plan-view contour

Here is the Cd 0.12,1959 MG EX 181 streamliner and its contour.

Here's 'Template' plan-view I'm recommending
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
NeilBlanchard (06-11-2014)
Old 06-10-2014, 07:05 PM   #3 (permalink)
Master EcoModder
 
redneck's Avatar
 
Join Date: Jun 2009
Location: SC Lowcountry
Posts: 1,795

Geo XL1 - '94 Geo Metro
Team Metro
Boat tails and more mods
90 day: 72.22 mpg (US)

Big, Bad & Flat - '01 Dodge Ram 3500 SLT
Team Cummins
90 day: 21.13 mpg (US)
Thanks: 226
Thanked 1,353 Times in 711 Posts
Quote:
For materials,

I will probably build the frame as a tubular structure. I was thinking Metal conduit or PVC piping? For anyone with PVC experience, do you think it would be strong enough to support the weight? This seems easier since I can use a heat gun and bend it to the right shape.

I want to build the frame and then cover it in foam. After sanding/filing the foam, I want to fiberglass it with probably two layers of 4 oz cloth. Does this sound reasonable?

For the rear section, I will probably use 10mm coroplast that I have lying around.

Please give suggestions and point out problems if you can

I think PVC is to flimsy. It is also heavy and would be hard to attach. A 10' stick of 1/2" EMT weighs around 2.2 lbs. is rigid and can be bent easily, but will have to be welded.

A big plus for using 1/2" builders foam is that one side has aluminum foil and the other side a plastic film. The aluminum foil side will keep the fiberglass resin from making contact with the foam and melting it.



>
  Reply With Quote
Old 06-10-2014, 07:17 PM   #4 (permalink)
Drive less save more
 
ecomodded's Avatar
 
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
TEAM VW AUDI Group
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
Man, a 10' length of EMT sure is light , I guess being a 1/2" it is very light.
Sweet
__________________
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun
__________________



  Reply With Quote
Old 06-10-2014, 08:58 PM   #5 (permalink)
EcoModding Lurker
 
Join Date: Dec 2011
Location: Austin,Texas
Posts: 14

A.J. - '04 Honda Civic LX
90 day: 41.47 mpg (US)

bruce - '08 Kawasaki Ninja 650 R
90 day: 46.52 mpg (US)

Big Blue - '09 Ford F-150 LX
90 day: 17.33 mpg (US)

dr - '13 Kawasaki DR650
90 day: 55.32 mpg (US)
Thanks: 2
Thanked 64 Times in 9 Posts
I unfortunately don't have immediate access to a welder. Do you think I could braze/solder it or would there not be enough adhesion?
  Reply With Quote
Old 06-10-2014, 10:20 PM   #6 (permalink)
Master EcoModder
 
redneck's Avatar
 
Join Date: Jun 2009
Location: SC Lowcountry
Posts: 1,795

Geo XL1 - '94 Geo Metro
Team Metro
Boat tails and more mods
90 day: 72.22 mpg (US)

Big, Bad & Flat - '01 Dodge Ram 3500 SLT
Team Cummins
90 day: 21.13 mpg (US)
Thanks: 226
Thanked 1,353 Times in 711 Posts
.

It should be mig welded. Mig is easy to learn and can be used for many different welding projects. There are 115v flux core mig welders for $200 or less that will do the job.

Or, find a friend who has one and get him to help for beer and burgers.

>
  Reply With Quote
Old 06-11-2014, 03:37 AM   #7 (permalink)
Not Doug
 
Xist's Avatar
 
Join Date: Jun 2012
Location: Show Low, AZ
Posts: 12,186

Chorizo - '00 Honda Civic HX, baby! :D
90 day: 35.35 mpg (US)

Mid-Life Crisis Fighter - '99 Honda Accord LX
90 day: 34.2 mpg (US)

Gramps - '04 Toyota Camry LE
90 day: 35.39 mpg (US)

Don't hit me bro - '05 Toyota Camry LE
90 day: 35.79 mpg (US)
Thanks: 7,217
Thanked 2,217 Times in 1,708 Posts
Could you not just build it out of foam and then fiberglass it?

http://ecomodder.com/forum/showthrea...ect-13533.html
  Reply With Quote
The Following User Says Thank You to Xist For This Useful Post:
aerohead (06-12-2014)
Old 06-11-2014, 01:07 PM   #8 (permalink)
EcoModding Lurker
 
Join Date: Dec 2011
Location: Austin,Texas
Posts: 14

A.J. - '04 Honda Civic LX
90 day: 41.47 mpg (US)

bruce - '08 Kawasaki Ninja 650 R
90 day: 46.52 mpg (US)

Big Blue - '09 Ford F-150 LX
90 day: 17.33 mpg (US)

dr - '13 Kawasaki DR650
90 day: 55.32 mpg (US)
Thanks: 2
Thanked 64 Times in 9 Posts
For the side taper:

I have overlaid both my original template and the suggested template on the car. Will the original not work because it is too aggressive of an angle for the air to stay attached? The suggested template seems pretty flat or maybe I did not line it up correctly. Obviously I would rather have a flatter angle with no air separation versus a steeper one but I also want the cross section to be as small as possible at the end.
Attached Thumbnails
Click image for larger version

Name:	top compare small.jpg
Views:	36
Size:	29.5 KB
ID:	15176  
  Reply With Quote
Old 06-11-2014, 03:01 PM   #9 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,861
Thanks: 23,922
Thanked 7,207 Times in 4,640 Posts
too aggressive?

Quote:
Originally Posted by bs25942 View Post
For the side taper:

I have overlaid both my original template and the suggested template on the car. Will the original not work because it is too aggressive of an angle for the air to stay attached? The suggested template seems pretty flat or maybe I did not line it up correctly. Obviously I would rather have a flatter angle with no air separation versus a steeper one but I also want the cross section to be as small as possible at the end.
If your car was actually a half-body,the sides would be identical to the top.With this,the flow velocity and pressure along the sides would be closer to the top flow.
With the CIVIC,the airflow over the greenhouse is faster,and at a lower pressure than at the sides do to the way the streamlines are divided at the nose and windshield.
With less body camber,and higher pressure,the side flow cannot support attached flow over as radical a curvature as on top without triggering separation.
The more gentle curvature of the 2-D strut of minimum drag (second image,center table) has the sectional density necessary for a more gradual pressure rise which will not jeopardize the boundary layer.
A number of the lowest drag cars ever constructed happen to use this more gentle 2-D section profile for their plan view boat-tailing.
Until more data comes along I believe it to be the safest bet.
Here is Kamm's research model for Jaray-type rear ends.The longest, most gentle plan-view contour netted him the lowest drag.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
The Following User Says Thank You to aerohead For This Useful Post:
COcyclist (08-28-2014)
Old 06-11-2014, 05:43 PM   #10 (permalink)
Too busy for gas stations
 
Superfuelgero's Avatar
 
Join Date: May 2013
Location: The intersection of TN/MS/AL
Posts: 460

Turtle - '92 Honda Civic Vx
Team Honda
90 day: 67.09 mpg (US)

Rolla - '10 Toyota Corolla Le

Beast - '91 Chevy V2500

Bus - '01 VW Eurovan MV

Speed - '93 Harley bored and storked Harley w/ turbo/ nitrous
90 day: 53.09 mpg (US)

Cal - '68 Ford Mustang GT/CS
Thanks: 87
Thanked 176 Times in 114 Posts
Quote:
Originally Posted by bs25942 View Post
I unfortunately don't have immediate access to a welder. Do you think I could braze/solder it or would there not be enough adhesion?
Most schedule 10 pvc will bend with time and heat cycling. Schedule 40+ may work, but is very sensitive to uv.

For the emt:
Straight sections: Sleeve, epoxy and rivet
Joints, flatten, then epoxy and rivet. Works best if pipe continues to on (think a continuous square, flattened at corners).
Removable sections rivnut instead of epoxy and rivet.

__________________
Shooting for 600 miles of range at 65-70 mph out of a vx.

  Reply With Quote
Reply  Post New Thread


Thread Tools




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