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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-15-2019, 10:20 AM   #11 (permalink)
Master EcoModder
 
aardvarcus's Avatar
 
Join Date: Apr 2012
Location: Evensville, TN
Posts: 522

Deep Blue - '94 GMC Suburban K2500 SLE
90 day: 23.75 mpg (US)

Griffin (T4R) - '99 Toyota 4Runner SR5
90 day: 24.68 mpg (US)
Thanks: 164
Thanked 424 Times in 231 Posts
Freebeard,
Thanks for the tip. I have been sanding the shredded surface with an orbital sander as a work around, I don’t really do much foam shaping in the grand scheme of things or I would be more motivated to make/buy additional tools.

Everyone,
Speaking of foam shaping, I got a few of my pieces roughed out of foam last night. I am trying to get the foam blank closer to the final shape to reduce the amount of shaping I have to do, which is taking much longer than expected versus making a large oversized block.

Edit: I forgot to add I got two tanks in for a preliminary baseline (with tire swap and trim removal) showing 23.6 MPG for short trips and 25.6 MPG mostly highway.

Attached Thumbnails
Click image for larger version

Name:	C1.jpg
Views:	16
Size:	32.5 KB
ID:	25883   Click image for larger version

Name:	C2.jpg
Views:	16
Size:	32.7 KB
ID:	25884  

Last edited by aardvarcus; 05-15-2019 at 10:37 AM.. Reason: Added Baseline Info
  Reply With Quote
The Following 2 Users Say Thank You to aardvarcus For This Useful Post:
aerohead (05-15-2019), freebeard (05-15-2019)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-17-2019, 09:01 AM   #12 (permalink)
Master EcoModder
 
aardvarcus's Avatar
 
Join Date: Apr 2012
Location: Evensville, TN
Posts: 522

Deep Blue - '94 GMC Suburban K2500 SLE
90 day: 23.75 mpg (US)

Griffin (T4R) - '99 Toyota 4Runner SR5
90 day: 24.68 mpg (US)
Thanks: 164
Thanked 424 Times in 231 Posts
Trying to keep this moving forward. Got the glueups for the sides done. I am going to add another layer to the inside of these pieces to make it thicker at the front and add some extensions on the back to get to my desired distance. I am hoping to have it shaped and start the fiberglass this weekend.

Question:
When following the AST profiles (AST-II for the top, AST for the sides), if I encounter a bump (e.g. roughly 1/8" bump from trim on the rear of the side windows) do I need to slow up the profile immediately after that (simulating that the angle of that section is less due to the obstruction) or can I press forward following curves as if the bump did not exist? Basically I am calculating the angle of the rear of the vehicle and intercepting the templates based on this angle. If I use the glass/sheet metal the angle is different than if I use the trim.
Attached Thumbnails
Click image for larger version

Name:	D1.jpg
Views:	20
Size:	33.7 KB
ID:	25896   Click image for larger version

Name:	D2.jpg
Views:	20
Size:	37.0 KB
ID:	25897   Click image for larger version

Name:	D3.jpg
Views:	20
Size:	19.4 KB
ID:	25898  
  Reply With Quote
The Following User Says Thank You to aardvarcus For This Useful Post:
aerohead (05-22-2019)
Old 05-17-2019, 01:09 PM   #13 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 12,779
Thanks: 3,095
Thanked 4,162 Times in 3,305 Posts
Dirt doesn't affect drag but rear-view mirrors do. There is going to be some scale, depending on the thickness of the attached flow, below which there's no difference.

It might depend on the angle of the flow to lengthwise of the trim. And it might be possible to over-reach for the optimum.
__________________
.
“Geniuses are just people who had good mothers.”
― Buckminster Fuller
"Momma tried"
― Merle Haggard
_________________
  Reply With Quote
The Following 2 Users Say Thank You to freebeard For This Useful Post:
aardvarcus (05-17-2019), aerohead (05-22-2019)
Old 05-17-2019, 02:03 PM   #14 (permalink)
Master EcoModder
 
aardvarcus's Avatar
 
Join Date: Apr 2012
Location: Evensville, TN
Posts: 522

Deep Blue - '94 GMC Suburban K2500 SLE
90 day: 23.75 mpg (US)

Griffin (T4R) - '99 Toyota 4Runner SR5
90 day: 24.68 mpg (US)
Thanks: 164
Thanked 424 Times in 231 Posts
Freebeard,

For sure I don't want to over reach, but I don't want to under reach either. As the tail is fixed, it is limited in length due to practical reasons. Obviously like everyone I want it to be as effective as it can be in that length.

I am not quite sure I am following "angle of the flow to lengthwise of the trim," could you please reiterate?

What I think I know from Hucho's book was the necessity of window flushness decreased the further back you went, stating that a 5mm inset glass did not increase drag at the rearmost window. That led me to believe the boundary layer was built up enough to accommodate the slight bump. However I don't know if parallel glass and parallel panels with a transition translates to following a taper with a bump.
  Reply With Quote
Old 05-17-2019, 03:28 PM   #15 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 12,779
Thanks: 3,095
Thanked 4,162 Times in 3,305 Posts
Quote:
I am not quite sure I am following "angle of the flow to lengthwise of the trim," could you please reiterate?
[speculation]
  • A ridge parallel to flow would have negligible effect.
  • A ridge athwart the flow would act like a Gurney flap; given enough height, promoting reattachment.
  • A ridge at a 45° angle could trigger a vortex on the lee side.
[/speculation]
__________________
.
“Geniuses are just people who had good mothers.”
― Buckminster Fuller
"Momma tried"
― Merle Haggard
_________________
  Reply With Quote
Old 05-21-2019, 07:55 AM   #16 (permalink)
Master EcoModder
 
aardvarcus's Avatar
 
Join Date: Apr 2012
Location: Evensville, TN
Posts: 522

Deep Blue - '94 GMC Suburban K2500 SLE
90 day: 23.75 mpg (US)

Griffin (T4R) - '99 Toyota 4Runner SR5
90 day: 24.68 mpg (US)
Thanks: 164
Thanked 424 Times in 231 Posts
Got the rest of the foam pieces glued together to form a blank. Transferred AST-II/AST tapers to the blank via shaping to form a few contour lines. Shaped the remainder of the block freehand by eye to form the overall shape. Did lots of test fits to get the overall lines close to right. Shaped out some of the insides of the block to improve rear sight lines. Laid layers of epoxy/fiberglass on the outside and inside of the block.

Current status is that it needs a few patches of fiberglass around some corners and other tricky areas and it will be ready for sanding, prep, and paint.
Attached Thumbnails
Click image for larger version

Name:	E1.jpg
Views:	22
Size:	53.0 KB
ID:	25913   Click image for larger version

Name:	E2.jpg
Views:	24
Size:	46.9 KB
ID:	25914   Click image for larger version

Name:	E3.jpg
Views:	22
Size:	43.1 KB
ID:	25915   Click image for larger version

Name:	E4.jpg
Views:	22
Size:	40.1 KB
ID:	25916   Click image for larger version

Name:	E5.jpg
Views:	40
Size:	38.7 KB
ID:	25917  

Click image for larger version

Name:	E6.jpg
Views:	22
Size:	29.0 KB
ID:	25918  
  Reply With Quote
The Following 3 Users Say Thank You to aardvarcus For This Useful Post:
aerohead (05-22-2019), Joggernot (05-21-2019), slowmover (05-22-2019)
Old 05-22-2019, 11:10 AM   #17 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 9,847
Thanks: 14,604
Thanked 5,222 Times in 3,052 Posts
bump

Quote:
Originally Posted by aardvarcus View Post
Trying to keep this moving forward. Got the glueups for the sides done. I am going to add another layer to the inside of these pieces to make it thicker at the front and add some extensions on the back to get to my desired distance. I am hoping to have it shaped and start the fiberglass this weekend.

Question:
When following the AST profiles (AST-II for the top, AST for the sides), if I encounter a bump (e.g. roughly 1/8" bump from trim on the rear of the side windows) do I need to slow up the profile immediately after that (simulating that the angle of that section is less due to the obstruction) or can I press forward following curves as if the bump did not exist? Basically I am calculating the angle of the rear of the vehicle and intercepting the templates based on this angle. If I use the glass/sheet metal the angle is different than if I use the trim.
Without seeing it,it may be that it merely functions as a trip-strip,actually energizing the boundary layer as vortex generators would.
Volkswagen (Hucho/Buchheim) found that the rear hatch gap of the Rabbit reduced drag,compared to filling it in flush (taping it over) with the body contour.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 05-22-2019, 11:15 AM   #18 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 9,847
Thanks: 14,604
Thanked 5,222 Times in 3,052 Posts
foam pieces glued..............

Oh yeah! Nice work.I don't think you'll have any problem with attached vortices with those edge radii.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 05-23-2019, 10:04 AM   #19 (permalink)
Master EcoModder
 
kach22i's Avatar
 
Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 3,274
Thanks: 4
Thanked 2,080 Times in 1,467 Posts
Quote:
Originally Posted by aardvarcus View Post
Current status is that it needs a few patches of fiberglass around some corners and other tricky areas and it will be ready for sanding, prep, and paint.


This is going along nicely.

__________________
George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com