aerodynamics & 5th wheels

[ron]

you might try a v shaped or wedge between the 5th wheel and the tailgate, close to the bumper. attach it to the camper and include a bottom panel and tight to the underside of the overhang to throw the air to the side in that area. Might help

[AndyL]

Kinda pondering that, there's actually a bunch of stuff I'd like to try out, but full scale testing gets expensive... so, I have a feeling, I'm about to start some scale model testing in the near future... got a 1:24 ram printing on the reprap now, working on a rough model of the 5th in sketchup - time for some wind tunnel testing...

And now have more Fab time, truck won't be ready until next week now... fml

[aerohead]

Originally Posted by AndyL

Kinda pondering that, there's actually a bunch of stuff I'd like to try out, but full scale testing gets expensive... so, I have a feeling, I'm about to start some scale model testing in the near future... got a 1:24 ram printing on the reprap now, working on a rough model of the 5th in sketchup - time for some wind tunnel testing...

And now have more Fab time, truck won't be ready until next week now... fml

Pat Nixon,who ruled Texas Tech's Aero Lab fiefdom,put a VHS video together for me in 1990 from their pickup/trailer studies.
The best of all configurations was always the bulbous nose on the trailer.Kust like KamperBob has on his rig.

[AndyL]

Has that ever been published? I'd love to see it

[aerohead]

Originally Posted by AndyL

Has that ever been published? I'd love to see it

General Motors staff published an SAE Paper on it in 1963 I believe it was.They used the Guggenheim Aero Lab at Cal Tech to do model studies.
I believe that paper is mentioned over at the full-boat-tail-trailer thread.
With Texas Tech's video footage you can just observe what the smoke does,given different leading edge add-on devices.
In elevation profile,the bulbous nose wins.And from data also at the above mentioned thread,the bulbous nose wins in crosswind hands down.
All this is in Hucho's books also.

[AndyL]

Well some real world testing in... 32km highway round trip (3 secondary highways), with some blustery weather... Secondary highways, so wasn't fighting traffic, tried to keep accel/decel rates the same, cruise to keep the drift down...

Working off the dashboard lie-o-meter, here's the numbers:

Truck - no 5th, 13.2L/100
Truck & 5th - 21L/100
Truck w/ deflector & fifth 18.7L/100
Truck w/ deflector (duct tape to fill cab to deflector gap) & fifth 18.4L/100

Ran 2 tests of each configuration (except the duct tape - it only got a single test) was +/- 0.1L/100 on restest

I'll leave the duct tape off 5L of fuel on this upcoming week's run - isn't worth having to look at duct tape.

[slowmover]

Truck w/ deflector (duct tape to fill cab to deflector gap) & fifth 18.4L/100

Glad you're on the way. A gasser has some problems to overcome versus a few of the early 2000's turbodiesel 1T trucks. Pulling all-aluminum aerodynamic travel trailers from 28' to 34' (8k to 12k weight), a fairly common number is 14.7L/100 on level Interstate (these are 55' to 63' combination rigs).

The best I've seen is reports in the low/mid 10's for Airstream trailers below 23' pulled by Euro TD SUV's.

You and KamperBob and Skyking are all up to some good work. The potential for a 5'er is definitely high, and, [my guess] that will eventually pull away on the lowest fuel burn numbers.

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[KamperBob]

12% better FE from your short cap is a nice win.

Originally Posted by AndyL

Well some real world testing in... 32km highway round trip (3 secondary highways), with some blustery weather... Secondary highways, so wasn't fighting traffic, tried to keep accel/decel rates the same, cruise to keep the drift down...

Working off the dashboard lie-o-meter, here's the numbers:

Truck - no 5th, 13.2L/100
Truck & 5th - 21L/100
Truck w/ deflector & fifth 18.7L/100
Truck w/ deflector (duct tape to fill cab to deflector gap) & fifth 18.4L/100

Ran 2 tests of each configuration (except the duct tape - it only got a single test) was +/- 0.1L/100 on restest

I'll leave the duct tape off 5L of fuel on this upcoming week's run - isn't worth having to look at duct tape.

[slowmover]

Found a nice pic on several forums of a slick two-piece "wing", but could not find any more information:

Here, at TurboDieselRegister

EDIT: Tried to find more information about this, but came away only with:

AIR FLOW
PH# 1-877-655-3244
WEB SITE= Wind-Tunnel-Designs.com
e-mail save @2wtd.com



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[MTrenk]

Not to be rude, but I'm just going around telling everyone that designing your own vortex generators without an engineering degree is a bad idea. Pretty much ANYTHING other than VG's in the aero mods section I think is viable for amateur ecomodders, but after studying vortices, there's no way anyone without access to CFD, extensive wind tunnel hours, or time to get a mechanical/aerospace degree is going to be able to reliably design their own effective VG's. If you want to try go right ahead, but chances are you'll hurt more than you'll help, especially if you're just eyeballing it.