Hoss

I noticed a 6 mpg increase in fuel mileage as well as a gain of 42 HP and 120 lb-ft of torque when I started lowering my tailgate.

Shovelhead

OK,....Who left the door unlocked again?.........

Hoss

Didn't Jack tell you?? I have a key.

HOHN

The best shape for aerodynamics would be a custom shaped cap that had a sloping roofline that went from the top of the cab roof to the top of the tailgate, like a ramp. The sides could either be flat and triangular (and make a square edge at the roofline) or slighly sloped inward and rounded at the point where it meets the roofline-- the latter being a little better.

In aerodynamics, the trailing edge shape matters much more than the the leading edge shape. Imagine you had a cube that had a cone attached to one side, kinda like this <::

Now, would it be more aerodynamic to have the cone pointing INTO the wind, or AWAY from the wind??? Common sense seems to tell us that pointing the cone into the wind would be best. But windtunnel testing will show that that opposite is true. The best aerodynamics are achieved by focusing NOT on how the air is initially disturbed, but rather on how it is allowed to be put back into place.

Ever seen the cone fixture attached to the rear of the space shuttle when it is riding piggyback on its 747? This is the idea.

Huge improvements in the aerodynamics of Class 8 rigs could also be realized though the use of a similar rearward-pointing rounded cone, like a hemisphere.

The eddy currents mentioned by another poster are better with the tailgate up. The "air pocket" that forms acts aerodynamically almost like a a tonneau, though much less effective.

Keep in mind the fundamental idea of aero-- air is unique because it is both compressible and elastic. Thus, a blunt surface facing the wind will develop a high-pressure "node" that makes the flat surface perform as if it were domed. The high pressure pocket "steers" the airflow around it, just as if the sirface were more aerodynamic.

There's no such effect on the trailing edge, so that's why it's MUCH more important to the overall drag picture.

I'm thankful for my US Air Force Academy education, as I got to take classes on this kind of thing and it was a lot of fun.

Justin

Mcmopar

If you want fuel mileage go buy a Volkswagon diesel!! If you want a truck-pay up. Stacy from trucks said that when you have a truck there are two garantees.

1) scratches
2) filling it up all the time!!

Shovelhead

Aerodynamic tests run by a few Pro Stock racers in the 80s proved that the Pinto body was actually more "slippery" if turned around backward.

I PASS GAS

That's probably what you would see if you took a jackhammer to that concrete bed liner of yours!

FiverBob

Them thar are Texas increases.

This thread makes one reconsider the vented fiver tail gates. However, what happens when the fiver (over the bed) messes up that air flow and drives it down into the bed? HHMMMMM.

Think I will keep my stock gate - - well, unless I have a senior moment while hooking up some day.

SHARPMACHINE

Maybe Hoss should fill his hole bed with concrete!! This should give him good winter traction and mileage like a bed cover. Of course the weight may have negative side effects... just my .002

scuzman00

Ya'll need to watch out.... I have it by good sources that Hoss is currently working on a new hydraulic jacking system that actually lifts his bedliner up to tonneau status. Engineering stats aren't in yet but I have heard that piston bore and ram length are currently frustrating the designers, not to mention that the local Caterpillar dealership in Big D are at a quandry as to the whereabouts of 2 D-9 blade rams that have dissappeared .......

Hoss

True, but then I wouldn't have a bedliner.

Hoss

Hmmmm....that's a thought, but I think it might push the weight limits of my truck.

Hoss

thebestofindica

http://www.cartalk.com/content/colum...ctober/05.html