Drag per aft-body length/roof angle

[Xist]

Meteorologists? The highest form of scientist?

[3-Wheeler]

Originally Posted by aerohead

I think that Hucho would tell you to forget about building the roof,as he is pretty emphatic about not adding frontal area (although Don Bur has been successful);and just boat-tail what you have.

I think that in the case of the wagon shown, there is a steep and rapid transition between the windshield glass and roof top. I would think that there would be air separation there and that it could be handled by building up the roof slightly.

Take a look at the Kia Soul. This roof has an incredibly sharp transition in that same area. Then take a look at a Prius or Gen 1 Insight and see how much "smoother" this transition is.

"Flow has to be attached at the front for the tail to make any difference."

Jim.

[Xist]

Honestly, I think that building up the roof would be an interesting experiment, but what would we call it?

[sheepdog 44]

Take a big sheet of coroplast and duct tape it to the windshield and rear spoiler. Then make cardboard spacers between the roof and coroplast so it's shaped like a wing.

[aerohead]

Originally Posted by 3-Wheeler

I think that in the case of the wagon shown, there is a steep and rapid transition between the windshield glass and roof top. I would think that there would be air separation there and that it could be handled by building up the roof slightly.

Take a look at the Kia Soul. This roof has an incredibly sharp transition in that same area. Then take a look at a Prius or Gen 1 Insight and see how much "smoother" this transition is.

"Flow has to be attached at the front for the tail to make any difference."

Jim.

Hucho talks of 'saturation',and that once the radius of the leading edges will support attached flow,that there's no further drag reduction with increased softening.If the windshield/roof intersection is as rounded as the hood/grille intersection,it seems like it should be plenty,if Hucho's shooting straight with us.Both of these areas are in a favorable pressure gradient,with the oncoming flow tending to hold the boundary layer against the body.

[aerohead]

I found a link while surfing 'wind tunnel aerodynamic testing.' The image is from Mercedes-Benz.
The 'air' patten of the lower green line of the upper flow field suggests a beneficial path surface for an aft-body.
Again,all images are on page-1 at top.

[slowmover]

" . . I take dinner near the interstate each week and can tell you that a lot of the Mesilla Valley Trucking Co. rigs are going by with the Trailer-Tails folded and stowed.I don't know why this is so".

MVT may be an LTL line (less than truckload), and, if there are several customers and consignees in the D/FW metro area then aero aid deployment would be a time-waster; 3-stops to unload, and two more to re-load, for instance.

If a TL line, then there may be a dedicated customer near to Sanger where they are headed. Maybe they have a yard in that area. If they do, then local drivers loading trailers to enable the long-haul crew to drop and hook would also make sense. Etc.

I see them coming out of Laredo, frequently, and all is deployed. The firm does have driver FE incentives in place.

I am a bit surprised not to see more "aero" rigs coming out of Laredo as much of this is dedicated service (fewest changes in conditions for equipment [all Interstate]; long distances travelled; full truckloads), instead what I see more of is maybe an undertrailer diverter and drive axle full covers. Todays conventional tractors are already pretty aero, overall.

Of course what I cannot see is what is under the hood and the drivetrain management system. Electronic logs play a part in this as they constitute a barrier to driver income hours and miles/fuel is more easily predicted.

Many of these trucks will not idle more than 5-minutes within "comfortable" temp ranges for the drivers trying to sleep (the range is too short), and that many rigs now have APU's onboard (CA bans them [a-holes]) which is a better solution. Idle restrictions and E-logs makes fuel cost predictions far easier (dispatch thinks in terms of distance between zip codes at a known total time; if fuel burn differences between drivers is narrowed, then it is an economy).

Even loaded (usually at 74-77k gross) I can easily out-accelerate these "econo trucks' whether they are loaded or empty. But what I do (oilfield service) is drastically different than what they do. Etc.

.

[aerohead]

I added this photo at top of page 1 with others.

[sheepdog 44]

I'm so fortunate to live in an era and country of the free communication of knowledge. The lengths people would go to learn... I would expect this to be coveted in a small exclusive university classroom. And here is Phil Knox freely sharing the mysteries of aerodynamics to anyone who will listen!

Thank you!

[aerohead]

Originally Posted by sheepdog 44

I'm so fortunate to live in an era and country of the free communication of knowledge. The lengths people would go to learn... I would expect this to be coveted in a small exclusive university classroom. And here is Phil Knox freely sharing the mysteries of aerodynamics to anyone who will listen!

Thank you!

It was Sir Issac Newton who said about his contributions,that he was merely standing on the shoulders of giants.
There have been so many altruistic researchers who've devoted their lives to the betterment of mankind,that it would be crime not to pay forward their contributions,especially for those who are gone.
Abraham Lincoln said,"To know and not tell makes cowards of men."
We're so fortunate here at EcoModder.com to have so many, who contribute so much of their human capital,it's a privilege to be part of it.