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Old 03-04-2017, 12:58 PM   #61 (permalink)
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some numbers for a 45-degree 'wing'

*Hoerner assigned Cd 1.03 for a 45-degree-angled structure.
*We know that the hypotenuse,C of this right-angled triangle is 3-feet.
*and from the Pythagorean Theorem : A-squared + B-square = C-squared.
*and @ 45-degrees,A = B.
*then,C-squared = 2A-squared.
*and C-squared = 9
*then A-squared = 9/2,or, 4.5.
*and the square root of 4.5 = 2.121-feet.
*so the frontal area is 6-feet by 2.121-feet,or 12.727-sq-ft.
*and CdA = 1.03 X 12.727 = 13.108 sq-ft.
--------------------------------------------------------------------------
*On say,a 2014 F-150 of Cd 0.402,and 36.0 sq-ft frontal area,we have CdA= 14.472 sq-ft.
*CdA of the truck and wing is 13.108 + 14.472 = 27.58 sq-ft,
*and adding 5% interference drag (as per Hoerner's methodology),we get CdA 28.96 sq-ft.
*The frontal area of the truck and wing is 48.727 sq-ft.
*dividing that into the CdA of the 'rig' gives Cd 0.595 for the pickup driving around with the wing on,but not towing anything.
*This would be like driving six 1st-gen Honda Insights simultaneously.Ouch!

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Old 03-04-2017, 01:20 PM   #62 (permalink)
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Quote:
Originally Posted by aerohead View Post
This was online,but no performance claims were made
I found a sister image to that image - I think.

https://www.rv.net/forum/index.cfm/f...print/true.cfm
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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
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Old 03-11-2017, 01:53 PM   #63 (permalink)
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The three smoke pictures need more explanation to me. Is the one that puts the least amount of smoke in the wake of the camper the best? That would be with the wing in the middle. It also seems like they have less smoke input on that picture and I realize none of them are real pictures in a real wind tunnel but some kind of computer models. The problem with getting the wing back more toward the camper is on a pickup is what happens with the air between the cab and the wing unless you put a cab height topper/shell on first, then the wing on the topper. I'm thinking the topper/shell probably hurts day to day compared to just a bed cover. And is expensive and heavy.

This is the other picture from that Rv.net thread
https://www.tc.gc.ca/media/images/pr..._eng_fig11.jpg
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Old 03-11-2017, 03:08 PM   #64 (permalink)
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more explanation

Quote:
Originally Posted by Hersbird View Post
The three smoke pictures need more explanation to me. Is the one that puts the least amount of smoke in the wake of the camper the best? That would be with the wing in the middle. It also seems like they have less smoke input on that picture and I realize none of them are real pictures in a real wind tunnel but some kind of computer models. The problem with getting the wing back more toward the camper is on a pickup is what happens with the air between the cab and the wing unless you put a cab height topper/shell on first, then the wing on the topper. I'm thinking the topper/shell probably hurts day to day compared to just a bed cover. And is expensive and heavy.

This is the other picture from that Rv.net thread
https://www.tc.gc.ca/media/images/pr..._eng_fig11.jpg
NASA considered creating an aerodynamic singularity,blending the tow vehicle to the trailer of paramount importance to drag,short of boat-tailing

A wing can make zero difference to mpg if it's not positioned exactly and angled exactly.This setup did virtually nothing


All the forebody gaps need to go away for the lowest drag.

Once you have that,then you can consider the aft-body
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Old 03-12-2017, 08:06 AM   #65 (permalink)
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A tonneau is a good start.

I'll assume that a vehicle operator has a handle on annual fuel cost, has reduced cold starts/short trips by combining errands, and has worked out the best routing for commute in 90%+ of driving. Past mechanical issues (steering wander, grabbing brake, etc), there is little left to do which will make a credible gain.

Where aero shows gains to an ANNUAL average mpg is partly to straight ahead and to cross wind effects. Given that highway-only mpg is a significant portion of annual driving. Highway driving that is out and away from a metro area where one lives.

In trailer towing -- as with other things -- it is OEM vehicle design which matters most. Tow vehicle or trailed vehicle. There is no getting around this.

Given that highway travel is in a range from 45-65/mph, that which aids stability has precedence. Muting the effect of crosswinds is highest AFTER combined vehicle brake performance.

The ideal vehicle state at a given rate of travel is in maintaining lane center with little to no steering input. Efforts expended here pay most.

Last is fuel burn reduction where all other issues have been optimized. Too often, I believe, are aerodynamic concerns given weight over the above. As with aftermarket engine tuners, one never solidly confronts the nut behind the wheel. Skewing results of air shaping. The most popular best designed low cost aftermarket Dodge diesel tuner can't really be shown to improve steady state highway mpg. May make the truck more responsive, but the end is that it is no different from tuning the stock carburetor outside factory settings in the 1970s. Gains are to be had, but are never "free".

IMO, treat the combined vehicle rig separately. Unless one is using a trailed vehicle upwards of 30% for annual miles, "simple" changes to the tow vehicle (aerolid, side skirts) and to the trailer (enclosed bottom, skirts) will add margin that noticeably improve wind handling (passing or oncoming vehicle winds the most dangerous).

Getting a "singular vehicle" were it relatively inexpensive would have happened by the late 1970s. Any number of RV manufacturers have gone out of business due to consumer sensitivity to fuel price. There is incentive, but it doesn't make economic sense.

It's the low annual miles towing an RV and near negible effect on annual fuel budget that kills it.

So, if it's good for solo mpg, that's the best approach. If, for the rig, it mediates crosswind problems, that verifies best approach. Yet that is far behind the quality of hitch lash up in terms of results. Safety and FE.

Most RV'ers run few miles. Thus, familiarity, means more also. Being able to predict dynamics in advance. Which is confidence.

I note that thus far are none on any RV forum who casually back under the trailer and take it for a Saturday test run. This is telling. So long as towing remains a special category of activity we'll likely not see acceptable A-B testing (to be generous I'll leave out A-B-A. Anyone serious would incorporate it with a schedule of changes. And devote the time necessary. Not, "well, on our last trip to Lake Goonsquatch, we saw . . . .). This testing is -- solo versus towing -- conducted exactly the same. The benchmark is a 40% drop in FE towing a travel trailer.

Experimenting with light plywood for tonneau length is greatly appealing. Easy A-B testing. Solo and with trailer. May be an optimum length for each situation.
Shortbed and longbed may call for something different. Same for standard versus extended cab. Great room for experimentation.

As a final note, improving in town MPG 20% or more can underwrite vacation towing travel. Start there.
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Last edited by slowmover; 03-12-2017 at 08:20 AM..
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Old 03-13-2017, 09:29 AM   #66 (permalink)
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Quote:
Originally Posted by Hersbird View Post
The three smoke pictures need more explanation to me.
This appears to be their website.

Trucks

Few of the images show up on my old browser and operating system, if there are any graphics of interest please post them. I do not see this particular project.

When I click on "ABOUT" it takes me to a related branch of the business.

Dustin Forensics – Forensic Services
Quote:
We’re a company specializing in the usage, sale and service of 3D scanning as well as imaging devices.
Be sure to view the Justin Ross Harris link for work we have done on that case.

Our Engineers and Technicians have performed thousands of scans in adverse conditions around the world.
Everything from Fire scenes to Homicides.

We are experts in the creation of 3D animations for use at trial.

Click the video below to view the promo video.
I suspect these images I've found have an interesting story to go with them. Hopefully nothing crash or lawsuit related.

I found this doing a reverse image search on Google - first hit.

http://www.icondirect.com/aeroshield-wind-deflector/
Quote:
The Aeroshield can be adjusted to virtually any angle allowing maximum aerodynamic efficiency and easily folds down when not in use.



The above is for 5th wheel trucks, the below for anything else - I guess.

http://www.campingworld.com/category...-deflectors/87
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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

Last edited by kach22i; 03-13-2017 at 04:13 PM..
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Old 03-13-2017, 09:40 AM   #67 (permalink)
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Found another interesting item in Aerohead's Photobucket.

2226.jpg Photo by aerohead2 | Photobucket
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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
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Old 03-13-2017, 01:07 PM   #68 (permalink)
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$350 is a little rich for me, I was thinking I could make one for under $100, maybe more like $15 using some of the stuff I already have lying around. At least it looks like the wind load can't be that bad with just some nylon straps and flat steel braces. I kind of thought it wouldn't be much more than a standard car top carrier
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Old 04-20-2017, 07:31 AM   #69 (permalink)
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Quote:
Originally Posted by kach22i View Post
There is a project thread in this forum on something similar, but as I recall it was intended for trailer use, then easy removal from the truck cab.

I did find this example today, it uses the air slots similar to my roof wing design. I guess I'm not so crazy after all.

Newsletter The Inside Track | ARC
Just thought I would add an image to this topic, a parachute door opening?

Random TRANSPORTATION pictures - Page 1859 - Pelican Parts Technical BBS


EDIT: Caption for the photo............
https://rhk111smilitaryandarmspage.w...omment-page-1/
Quote:
Rear view of the BT-67 Gunship of the Colombian Air Force. Photo courtesy of The Dakota Hunter website.
Quote:
’The BT-67’2
The BT-67 is a refurbished, modernized, and improved version of the Douglas DC-3 which first entered service with the American armed forces way back in 1936. What Basler does is to first get an old DC-3 aircraft, inspect and then do a complete overhaul on it. They then reinforce the airframe, wings and control surfaces to allow the aircraft to handle an increased maximum takeoff weight.
Detail - Crop
https://rhk111smilitaryandarmspage.w...omment-page-1/

Quote:
Rear view of the BT-67 Gunship of the Colombian Air Force. Photo courtesy of The Dakota Hunter website.

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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

Last edited by kach22i; 04-20-2017 at 07:44 AM..
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