Do "vented" tailgates help on 5th wheels?

Stefonius wrote:

45Ricochet wrote:

N-Trouble wrote:
Ever see the Mythbusters episode where they tested mileage on a truck with both tailgate on and off? The truck with the tailgate on got better mileage. MYTH BUSTED...

I wish they had done a test with a 13' high wall above the bed pushing all that air into the bed :W
A must have? no. More MPG most likely a toss up. Make hitching up easier? yes

Agreed. Mythbusters did not do a test with a fifth wheel attached. The airflow is vastly different in that case. I have had things sucked out of the bed with a solid gate. With my current gate (made out of steel tubes), nothing in the back of the truck moves so much as an inch as long as the fiver is hooked up. With the bed empty, it's a different story.

Your comment about items getting sucked out of the bed with a solid tailgate is exactly why you get better mileage with a tailgate in place.

Quoted from Mythbusters:
Closing the tailgate actually improves fuel efficiency because it creates a type of airflow called a separated bubble within the bed of the truck. As wind rushes over the moving truck, that bubble of slow-moving air deflects it over the raised tailgate. By guiding surrounding air over and across the bed of the truck, that vortex effect prevents added drag.

However, driving with the tailgate open eliminates the bubble effect, pulling the air toward the truck bed and creating more drag rather than deflecting the wind. Some gas-conscious pickup drivers still swear by leaving their tailgates open, but science sides with leaving it up.

I got a vented tailgate for free and like it since it makes hitching/unhitching easier and eliminated the vacuum that sucked things out of the bed.

N-Trouble wrote:
Ever see the Mythbusters episode where they tested mileage on a truck with both tailgate on and off? The truck with the tailgate on got better mileage. MYTH BUSTED...

Maybe somebody else has access to the full study but I seem to recall that there was a difference between short bed and long bed trucks. The short beds would come out better with tailgate up and the long beds better with tailgate down.

I would still use one even if I got slightly worse mileage.

What they found in the mythbusters episode was that if there was something solid blocking the airflow (like a tailgate), a high pressure area would immediately form and after that, the air would just flow over it. Therefore, no measurable difference in gas mileage between tailgate up and tailgate down. Same would be true with towing the fiver as far as the bed of the truck is concerned. However, you still have airflow around and under the trailer. That would seem to be fairly consistent between tailgate/no tailgate, but I have never seen it run through a wind tunnel to find out for sure. My guess would be that the air resistance of the fiver would be so much greater than anything in the bed that you wouldn't notice the fraction of a mpg you might get anyway. However, I have a notched tailgate for the ease of hitching and unhitching and as someone else has noted, things have been sucked out unless they are tied down.

joe

45Ricochet wrote:

N-Trouble wrote:
Ever see the Mythbusters episode where they tested mileage on a truck with both tailgate on and off? The truck with the tailgate on got better mileage. MYTH BUSTED...

I wish they had done a test with a 13' high wall above the bed pushing all that air into the bed :W
A must have? no. More MPG most likely a toss up. Make hitching up easier? yes

Agreed. Mythbusters did not do a test with a fifth wheel attached. The airflow is vastly different in that case. I have had things sucked out of the bed with a solid gate. With my current gate (made out of steel tubes), nothing in the back of the truck moves so much as an inch as long as the fiver is hooked up. With the bed empty, it's a different story.

Tom&Dee wrote:
It may not help with economy, but it does cut the turbulance a lot in the bed with a fiver on.

X2. I've lost a few things out of my bed from turbulence. Now, almost everything is tied down, especially if it's under the nose of the FW. I lost a set of those hard plastic wheel chocks and never got over 60 on a 10 mile trip in calm weather.

Lyle

Dunno about the fuel mileage, but the site at the last KOA we stayed was so short the truck had to be backed under the hitch when parked at the site. With a regular tailgate you'd have had to either leave the tailgate down all the time or be in and out of the cab a dozen times.

Tom&Dee wrote:
It may not help with economy, but it does cut the turbulance a lot in the bed with a fiver on.

What are you basing this on? I have a vented v tail gate. I have had a 12x12x2 inch wood block made from 2x6's and 3/4 plywood that I use for the landing gear on my 5th wheel sucked out of the bed at 55 mph. It takes a lot of turbulence to do that. If something is not tied down I do not carry it in my truck bed. I can not testify what happens with a standard tailgate. Had the v gate from day one.

gmcsmoke wrote:
fuel economy pulling a 5 ton brick down the road :r:

+1