Truck Aerodynamics

[kenh]

I agree about gaps making lots of drag. 'Cause I'm an airplane guy I read a lot about that. In one of the publications about drag, I think it was from NASA.it stated a depression will cause more drag than a projection of equal size. Now they were talking about relativity small things hear but you get the idea. ALSO the leading edge (grill area) is not nearly as important as the the trailing edge (tailgate) in creating drag. The trailing edge is MUCH more important. A sharp trailing edge is best. I can relate and have personal experience in this on a much smaller scale. I used to race RC planes. We would take a standard propeller and modify to suit our needs. I had a prop, well several, that while worked OK were not turning the RPM I wanted. We wanted about 23,500 on the ground and I was about 500 RPM short A fellow competitor looked at them and told me to sharpen the trailing edge to razor thin. I didn't get my 500 rpm but did gain about 100 rpm. He said the rest was up to me and redesigning my prop.! LOL

So if we could sharpen out tailgates a bit....... OH and all those trailer tails on semi trailers..... DON"T work. They just to help create even more vacuum to hold back the truck.

OK, back to the original thread and enough of my ramblings/rants!!!!

Ken

 

[thegawd]

thanks for sharing your real world experience Ken. that's so cool man, I highly value your knowledge and read everything you post... Ramble Away

 

[kenh]

thanks for sharing your real world experience Ken. that's so cool man, I highly value your knowledge and read everything you post... Ramble Away

Thank you! Please DO let me know if I start to become obnoxious.

ken

 

[thegawd]

LMAO!

 

[Steve Addy]

Very interesting lol. I heard a rumor that gmt400 burb gave you better mpg then gmt400 tahoe. Also I personally like the air dam with tow hook look. Looks complete. But then again I wonder why gm didnt do it for the 2500 +models. Unless they didnt care about efficiency?

Isn't that air dam difference a 4x2 vs a 4x4 situation? I have never noticed a 4x4 without hooks, but TBH never really looked all that intently at it.

I did not know that about the race trucks Ken but to be honest I dont really follow any racing but I do enjoy rally racing. of course when fractions of a seconds means a win or a loss, theres nothing better than real world testing.

she says the soft tonnue covers are better than hard because they will form to the air movement. she did not talk about bed toppers but she talks about a lot of things that will apply. in theory most toppers are built to move the air efficiently and one spot of concern would be the gap between the topper and the cab. it pulls the air down in between messing up the flow.

she dosent relate in terms of mpg but rather how all these small things improve the overall performance of the vehicle.

Al

I think with camper shells (toppers) that conform to the pickup cab you're better off, but for toppers that protrude out past (sides and top) the profile of the cab you're worse off because they create a blunt surface.

Would be nice if someone created a product that could be attached to the topper that filled the cavity between the topper and the cab, but with so many topper differences that would be hard to do. I'm not just talking about a seal, but something that could soften the transition between the two in the case of a profile mismatch between camper and topper.

I would also venture a guess that fiberglass toppers are best since they're built to match the profile of the cab rather and the angle of the rear window rather well, aluminum, not as much.

Steve

EDIT: I'm curious about the skirts they run under the semi trailers that angle out and in front of the rear trailer wheels? I recall back in the 80's someone explored this on cars a bit but IDK what ever became of it.

 

[drewcrew]

Isn't that air dam difference a 4x2 vs a 4x4 situation? I have never noticed a 4x4 without hooks, but TBH never really looked all that intently at it.



I think with camper shells (toppers) that conform to the pickup cab you're better off, but for toppers that protrude out past (sides and top) the profile of the cab you're worse off because they create a blunt surface.

Would be nice if someone created a product that could be attached to the topper that filled the cavity between the topper and the cab, but with so many topper differences that would be hard to do. I'm not just talking about a seal, but something that could soften the transition between the two in the case of a profile mismatch between camper and topper.

I would also venture a guess that fiberglass toppers are best since they're built to match the profile of the cab rather and the angle of the rear window rather well, aluminum, not as much.

Steve

EDIT: I'm curious about the skirts they run under the semi trailers that angle out and in front of the rear trailer wheels? I recall back in the 80's someone explored this on cars a bit but IDK what ever became of it.

About the skirts on semi's, if they really made a difference UPS would have them on their trailers. I would bet that UPS has already researched this and found them not worth the money. I have never been an employee of UPS but have been an employee of their competition.

 

[Steve Addy]

About the skirts on semi's, if they really made a difference UPS would have them on their trailers. I would bet that UPS has already researched this and found them not worth the money. I have never been an employee of UPS but have been an employee of their competition.

I did a quick check and this is what trucknews says about it:

"The answer, thanks to the highly respected testing of FPInnovations' Performance Innovation Transport (PIT), is that most do save fuel, though the savings vary. ... side skirts reduced fuel consumption by an average of 6.69%. trailers with trailer undercarriage devices reduced fuel consumption an average of 1.43%"

I would still bet that UPS and others have figured out that the cost of the product plus the install labor isn't worth the savings, or that the cost will be just barely recovered during the life of the trailer. I've seen more trailers rolling now with the undercarriage covers (black sweptback covers) that attempt to smooth out a bunch of irregularities, it looks like they claim those can potentially reduce consumption by 1+%.

The article is here if anyone wants to have a look.

Steve

EDIT: Honestly I've been thinking about a larger front lower air dam for the C3500, nothing part of a kit or anything but just wondering if something a bit lower than standard would make the MPG any better.

 

[SUBURBAN5]

Isn't that air dam difference a 4x2 vs a 4x4 situation? I have never noticed a 4x4 without hooks, but TBH never really looked all that intently at it.



I think with camper shells (toppers) that conform to the pickup cab you're better off, but for toppers that protrude out past (sides and top) the profile of the cab you're worse off because they create a blunt surface.

Would be nice if someone created a product that could be attached to the topper that filled the cavity between the topper and the cab, but with so many topper differences that would be hard to do. I'm not just talking about a seal, but something that could soften the transition between the two in the case of a profile mismatch between camper and topper.

I would also venture a guess that fiberglass toppers are best since they're built to match the profile of the cab rather and the angle of the rear window rather well, aluminum, not as much.

Steve

EDIT: I'm curious about the skirts they run under the semi trailers that angle out and in front of the rear trailer wheels? I recall back in the 80's someone explored this on cars a bit but IDK what ever became of it.

As far as hooks yes 4x2 vs 4x4 now air dams I thought were only 1500. 2500 and 3500 i thought were not install with dams from tthe factory lol

 

[PlayingWithTBI]

As far as hooks yes 4x2 vs 4x4 now air dams I thought were only 1500. 2500 and 3500 i thought were not install with dams from tthe factory lol

Here's my 88 C1500 with tow hooks and valance from the factory.

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[SUBURBAN5]

Here's my 88 C1500 with tow hooks and valance from the factory.

You must be registered for see images attach

If that was not an extra then that's awesome. I know my dads 98 suburban wasnt stock with that neither moms 99 tahoe. But I'm sure they could of added it whenever they bought it