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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 07-13-2011, 09:01 PM   #1 (permalink)
EcoModding Apprentice
 
Join Date: Jul 2010
Location: Tucson, AZ
Posts: 245
Thanks: 111
Thanked 154 Times in 63 Posts
Aero RV (custom boat tail for '95 Ford E-350 Class C motorhome)

About a month ago I decided to build a boat tail for my 95 E-350 Ford 25 foot turbo diesel Class C motor home. I read the aerodynamics study NASA did at Dryden Air Force base back in the late 60’s on the squared off E-150 van about 20 times, as well as several other studies, drew up some plans and three weeks later and some serious sweat the prototype is done and tested.
Photos of the process are posted below. I used ½” square tubing for the ribs. I determined the shape I wanted, hammered out a ‘control’ rib, taped it to the bench and then built 28 more just like it, so the four sides have the same shape coming inward. Next I built the rear frame, then made it bigger, then added ribs one at a time until I had the shape.
The basic frame weighs about 75 pounds, which is about 25 pounds heavier than the rear bumper that was removed, so there is a net gain of about 25 pounds plus the weight of 5 sheets of coroplast, and a bunch of aluminum pop rivets.
I tried my best to replicate the rounded corners of the body on this vehicle because it makes sense to me that going from a rounded corner right to a 90 degree square corner wouldn’t be conductive to smooth air flow.
This creates lots of compound curves, which are a pain to cover, but as far as the prototype skin is concerned it wasn’t too bad. The four corners were the worst so I used monocoat to cover them, which is heat shrink plastic made for covering model airplane wings and fuselages, available at most hobby stores. The larger areas are covered in coroplast. You can see in the photos where the panels had to be cut and trimmed to allow for the compound curves. Not much modification considering the shape.
In an attempt to keep the air flow over the roof area good, I also faired the roof A/C housing. According to the tell tales, that worked out really well, although now that I know the overall fairing design is good, now I have to get the A/C to work with the fairing in place. I think maybe if I louver the hell out of the final cover it will be good.
I’ve only done one road test of the new design so far but it was very encouraging. Getting up at 3AM to beat the heat and wind, we (my wife insisted on going, she thinks the boat tail is great, how cool is that?) drove from Tucson to Phoenix, which is about 1,000 feet lower elevation, to Apache Junction, a total distance of 135+ miles, one way, with lots of subtle hills and valleys in between. We didn’t use the A/C and we ran right at 57-58mph, since that is the ‘sweet spot’ for this drive line (7.3L turbo diesel Ford, A4OD auto trans, 4.10 tail gear).
The drive up yielded 17.26 mpg, compared to an average of 13.1 for the same trip sans the boat tail. I have to say by the time the tail was completed I was having my doubts this would make much of a difference so I was really happy with that. The return trip we used the A/C the whole way, and had an intermittent crosswind of about 10 to 20 mph and got 14.68mpg. That works out to a two way average of 15.97mpg. Not bad for a first try under those conditions.
Anyway, it will take a lot more testing to know the accurate numbers of course but I’m very happy with the initial results. I also have a ton more work to do before this is anywhere near ideal or finished. I still have to skin the rest of the under carriage. For this test, about the last 3 feet of the belly pan was installed and I’m guessing it was catching some air in there. So far the cost of this extravaganza is about $225 for materials, which was way worth it just for entertainment value, for me as well as my friends. If I had 5 bucks for every time someone has said, ‘What the HELL is that?’, the materials would be paid for. : )

Attached Thumbnails
Click image for larger version

Name:	Aero RV 1.jpg
Views:	1747
Size:	114.3 KB
ID:	8968  Click image for larger version

Name:	Aero RV 5.jpg
Views:	1700
Size:	111.6 KB
ID:	8969  Click image for larger version

Name:	Aero RV 9.jpg
Views:	1517
Size:	120.6 KB
ID:	8970  Click image for larger version

Name:	Aero RV 13.jpg
Views:	1478
Size:	71.7 KB
ID:	8971  Click image for larger version

Name:	Aero RV 16.jpg
Views:	1359
Size:	79.7 KB
ID:	8972  

Click image for larger version

Name:	Aero RV 17.jpg
Views:	5142
Size:	74.5 KB
ID:	8973  Click image for larger version

Name:	Aero RV 23.jpg
Views:	1412
Size:	83.2 KB
ID:	8974  Click image for larger version

Name:	Aero RV 30.jpg
Views:	1827
Size:	83.8 KB
ID:	8975  Click image for larger version

Name:	Aero RV 34.jpg
Views:	1962
Size:	65.5 KB
ID:	8976  Click image for larger version

Name:	Aero RV 37.jpg
Views:	3362
Size:	89.3 KB
ID:	8977  

  Reply With Quote
The Following 41 Users Say Thank You to orbywan For This Useful Post:
aerohead (07-14-2011), ausias (01-26-2013), BamZipPow (07-14-2011), bespurcell (02-01-2015), bikeprof (08-11-2016), bondo (07-17-2011), Cd (07-14-2011), ChazInMT (07-13-2011), cleanspeed1 (07-17-2011), dennyt (07-14-2011), dpero (07-14-2011), ECONORAM (02-28-2013), elhigh (01-06-2013), FORDF250HDXLT (07-27-2011), Frank Lee (07-14-2011), GeekForLife (01-19-2013), HHOTDI (01-12-2013), HyperMileQC (01-06-2013), JamesKatt (01-20-2013), JasonG (09-29-2015), jime57 (07-13-2011), Joggernot (08-04-2015), katiep (07-14-2011), landsailor (07-14-2011), larrybuck (07-14-2011), mikeyjd (03-08-2014), nat@asis.com (01-07-2013), Nero9 (09-13-2011), noxman (03-02-2013), rbrowning (09-09-2011), silverclip1 (02-13-2013), skyking (07-14-2011), slowmover (07-17-2011), Snowman9000 (02-08-2016), Sven7 (08-15-2012), Synchronicity (08-16-2012), t vago (07-13-2011), thatguitarguy (07-15-2011), UltArc (11-23-2014), Weather Spotter (07-15-2011), wyatt (07-14-2011)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 07-13-2011, 09:12 PM   #2 (permalink)
Coasting Down the Peak
 
skyl4rk's Avatar
 
Join Date: Jun 2008
Location: M I C H I G A N
Posts: 514

Toyauto Pickup - '94 Toyota Pickup 2WD
90 day: 36.32 mpg (US)

Versa Base - '09 Versa Sedan 1.6 Base
Team Nissan
90 day: 41.69 mpg (US)
Thanks: 27
Thanked 41 Times in 34 Posts
Very nice job, professional.
__________________
Nissan Versa Aeromods
  Reply With Quote
Old 07-13-2011, 10:06 PM   #3 (permalink)
Master EcoModder
 
skyking's Avatar
 
Join Date: Apr 2011
Location: Tacoma WA
Posts: 1,201

Woody - '96 Dodge Ram 2500 SLT
Team Cummins
90 day: 23.82 mpg (US)

Avion and Woody - '96 Dodge/Avion Ram 2500/5th wheel combo
90 day: 15.1 mpg (US)

TD eye eye eye - '03 Volkswagen Beetle GLS
90 day: 49.05 mpg (US)

Mule - '07 Dodge Ram 3500 ST
Thanks: 464
Thanked 441 Times in 281 Posts
nice job man. This is another inspiration!
How about some other pics of the rig, it looks pretty slick.
I've been looking at mini split heat pumps as a replacement for failed AC units. It would get them off the roof, you could hang them on the back of the rig. They are also a great deal more efficient.
__________________




2007 Dodge Ram 3500 SRW 4x4 with 6MT
2003 TDI Beetle
2002 TDI Beetle

currently parked - 1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears

Last edited by skyking; 07-13-2011 at 10:13 PM..
  Reply With Quote
Old 07-13-2011, 10:24 PM   #4 (permalink)
Master EcoModder
 
Join Date: Oct 2008
Location: Mid-Atlantic
Posts: 491

OurInsight - '06 Honda Insight
Thanks: 170
Thanked 68 Times in 43 Posts
Great job! Wish I had you here in Richmond to work on my diesel pusher.

I think you might be a bit unfair to yourself with your math. If your baseline was without A/C, then that is the only data that really counts. But I certainly know how difficult it is to get good data. Initially, I think it looks very encouraging.
  Reply With Quote
Old 07-13-2011, 10:27 PM   #5 (permalink)
EcoModding Apprentice
 
Join Date: Jul 2010
Location: Tucson, AZ
Posts: 245
Thanks: 111
Thanked 154 Times in 63 Posts
Aero RV

Here are some more photos of the process. I wasn't aware they made heat pumps for RV's, Skyking, do you have any info on that? I'd love to get that big pile off the roof. Thanks.
Attached Thumbnails
Click image for larger version

Name:	Aero RV 6.jpg
Views:	1242
Size:	95.1 KB
ID:	8978  Click image for larger version

Name:	Aero RV 18.jpg
Views:	1148
Size:	67.8 KB
ID:	8979  Click image for larger version

Name:	Aero RV 19.jpg
Views:	1061
Size:	68.5 KB
ID:	8980  Click image for larger version

Name:	Aero RV 24.jpg
Views:	1011
Size:	62.8 KB
ID:	8981  Click image for larger version

Name:	Aero RV 27.jpg
Views:	1063
Size:	58.1 KB
ID:	8982  

Click image for larger version

Name:	Aero RV 29.jpg
Views:	983
Size:	70.9 KB
ID:	8983  Click image for larger version

Name:	Aero RV 33.jpg
Views:	978
Size:	66.3 KB
ID:	8984  Click image for larger version

Name:	Aero RV 35.jpg
Views:	1117
Size:	77.4 KB
ID:	8985  Click image for larger version

Name:	Aero RV 36.jpg
Views:	1118
Size:	75.6 KB
ID:	8986  Click image for larger version

Name:	Aero RV 7.jpg
Views:	987
Size:	99.7 KB
ID:	8987  

  Reply With Quote
The Following 7 Users Say Thank You to orbywan For This Useful Post:
aerohead (03-19-2016), BamZipPow (07-14-2011), bespurcell (02-01-2015), HHOTDI (01-12-2013), mcrews (08-13-2015), skyking (07-14-2011), slowmover (07-17-2011)
Old 07-13-2011, 11:57 PM   #6 (permalink)
Master EcoModder
 
skyking's Avatar
 
Join Date: Apr 2011
Location: Tacoma WA
Posts: 1,201

Woody - '96 Dodge Ram 2500 SLT
Team Cummins
90 day: 23.82 mpg (US)

Avion and Woody - '96 Dodge/Avion Ram 2500/5th wheel combo
90 day: 15.1 mpg (US)

TD eye eye eye - '03 Volkswagen Beetle GLS
90 day: 49.05 mpg (US)

Mule - '07 Dodge Ram 3500 ST
Thanks: 464
Thanked 441 Times in 281 Posts
Mini Split Air Conditioner AmericAire 120000 Heat Pump

They are not specifically designed for RV's but a quick search and you will find plenty of folks "down under" who have retrofitted them on Rvs with great success. They have extreme heat and also extreme rough road conditions in Australia, so I consider that a good testament to the durability.
What gets me going is the lower power draw of the 12,000 BTU units. It is 2/3rds of the rated draw of a typical Coleman 13,500 BTU unit. I suspect that a Honda EU2000i generator just *might* be able to start it.
The other huge bonus is when you are plugged into a full hookup situation. Now you have a 12,000 BTU heat pump, also much more efficient. Keep that propane in your tank.

In your case you would hang the outdoor unit on the back, find a suitable wall and route the line set and cables, and finish off with an Rv skylight to fix the hole where the old AC was.
RV Skylight
__________________




2007 Dodge Ram 3500 SRW 4x4 with 6MT
2003 TDI Beetle
2002 TDI Beetle

currently parked - 1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears
  Reply With Quote
The Following User Says Thank You to skyking For This Useful Post:
HHOTDI (01-12-2013)
Old 07-14-2011, 12:08 AM   #7 (permalink)
(:
 
Frank Lee's Avatar
 
Join Date: Jan 2008
Location: up north
Posts: 11,985

Blue - '93 Ford Tempo
Last 3: 27.29 mpg (US)

ShWing! - '82 honda gold wing Interstate
90 day: 33.65 mpg (US)

F150 - '94 Ford F150 XLT 4x4
90 day: 18.5 mpg (US)

Sport Coupe - '92 Ford Tempo GL
Last 3: 69.62 mpg (US)

Moon Unit - '98 Mercury Sable LX Wagon
90 day: 21.24 mpg (US)
Thanks: 1,368
Thanked 2,889 Times in 1,842 Posts
Looks good; very inspirational!

One question: is the flow any good along the bottom? Seems too much rise down there for attached flow... Looks like the tufts are swirling around in pic 7.
__________________



Last edited by Frank Lee; 07-14-2011 at 01:01 AM..
  Reply With Quote
Old 07-14-2011, 12:53 AM   #8 (permalink)
Master EcoModder
 
larrybuck's Avatar
 
Join Date: Apr 2011
Location: sw Washington (state), a little north of Vancouver
Posts: 1,039
Thanks: 275
Thanked 77 Times in 60 Posts
Congrats on a great start! Perhaps full side skirts soon?
  Reply With Quote
Old 07-14-2011, 02:23 AM   #9 (permalink)
EcoModding Apprentice
 
Join Date: Jul 2010
Location: Tucson, AZ
Posts: 245
Thanks: 111
Thanked 154 Times in 63 Posts
Quote:
Originally Posted by Frank Lee View Post
Looks good; very inspirational!

One question: is the flow any good along the bottom? Seems too much rise down there for attached flow... Looks like the tufts are swirling around in pic 7.
I'm hoping that completing the belly pan will help help the flow down there because it's not very good. I may have to straighten the curve at the bottom some. So far it's only skinned about 3 feet forward from the rear. That could be effecting the flow in itself.
  Reply With Quote
Old 07-14-2011, 02:31 AM   #10 (permalink)
EcoModding Apprentice
 
Join Date: Jul 2010
Location: Tucson, AZ
Posts: 245
Thanks: 111
Thanked 154 Times in 63 Posts
Quote:
Originally Posted by larrybuck View Post
Congrats on a great start! Perhaps full side skirts soon?
OK, I'm new at this, what is a full side skirt? If you're talking about something kind of like a side air dam, I hadn't considered it because we take this vehicle off road a fair amount. The plan is to skin the rest of the undercarriage and fair both duallies and see how that does.

Maybe full skirts would work if they were pretty flexible. If I skin the undercarriage should I also put a front air dam on it, or is that redundant?

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com