Towing with a cap / topper vs empty bed.

I tow a car hauler flatbed (not enclosed) regularly with a sxs and atv from Seattle to Moses Lake, WA. The three instances directly below are all talking about 70-72 mph the entire way.

Before canopy, with a full tank of gas, I would regularly have my low fuel light come on within a couple miles of Moses Lake, multiple times just as I exited the freeway.

I got new tires, Duratracs, to replace the original Rugged Trails and I could no longer make it all the way on a single tank (or at least it was so buried down by the E i was afraid to try).

Once I put a canopy on I was consistently able to make it with 1/8th of a tank remaining.

Now that I have an AT Habitat and I'm more loaded down and heavier toys... I throw that out the window and drive much slower. This last trip I probably averaged more like 55 (45-50 up the pass and out of vantage) with top speeds of around 65 during the trip.

The standard canopy (was a Leer) definitely helped my mileage in a noticeable manner while towing. I'm sure it will help you out.

 

Great idea. Golf balls are dimpled for aerodynamics. They keep a buffer of air vortices between the ball and the air they are working against. Honda tried a fairing with dimples on the front at the Suzuka 8 hours race years ago. Same principle.

 

Lots to think about.

 

That's exactly what I found out on my old truck. When I bought my new truck I didn't purchase a cap. Also a cap makes it harder to back the trailer up in the dark.

 

Driving at 55 instead of 70 will half your mpg a lot more than anything else.

 

I have had caps on and off my trucks since early 1980's. They will make a difference, maybe 1-1.5 mpg depending the trailer, but not enough to justify the cost for just that purpose.
Little aerodynamic changes do make a difference. Just look at the over-the-road trucks with flush hubcaps, mirrors and aero deflectors. But, that's an accumulation over many miles.

 

No it won’t. Unless you have TRIED IT with a third Gen and a trailer my size and can prove me different. I have tried different speeds. The only thing that saves substantial fuel is holding a higher gear. While travelling at or under 80kmh (49mph) it will hold 5th. You can’t do this safely on highways rated at 100kmh (62mph) with many travelling at 120kmh (75mph).

There is a reason I specified real world testing experience vs theories when I first posed the original questions in my original post. Theories can be 100% correct but have zero relevance in this discussion. Improving aerodynamics is the goal here as it will allow the truck to hold a higher gear and THAT will result in better economy and more importantly less noise and more comfort. Just because a slower speed has less aero drag and better economy it doesn’t make it relevant. I could go cross country and never go above 50kph / 30mph but that is simply not realistic or even plausible.

To be quite clear the goal is to be able to reduce aerodynamic drag enough to consistently run a higher gear and reduce motor screaming which makes for a more pleasant drive. The benefit of better fuel economy while still a major concern is not the primary focus. The issue truely is about reducing drag so that higher gears can be used. Everything else comes into place after that.

 

I don't think your going to achieve that with just a cap.

 

I get around 15 MPG with my 5x8 V nose and cap on my truck @65 MPH give or take. I have no data for no cap, sorry. Just providing some towing info for ya.

 

I have a Turbo-Diesel Chevy Colorado Crew Cab with slope-nosed aluminum camper so the back of my topper is the height of my travel trailer. I have also done quite a few easy aero mods to get the air moving smoothly across the truck, topper, and trailer. I usually drive 65 as drag goes up by the square of the speed. I get right around 20 mpg. That mini-Duramax has plenty of torque and comparatively sips the diesel.

 

I still have (but will soon sell) an EZ Hauler Aluminum 20x8.5' cargo trailer with the V nose. Pulls like a dream behind any full size pickup I've owned without a topper (my prior 4G pulled it empty just fine, but when fully loaded it was too much for that truck - definitely too much for my new to me 3G).
But as soon as I bought an Excursion so I could haul the entire family and dogs when we were headed to a MX track, and tried to pull that same trailer, I was finding a lot of side to side wiggling that just wasn't there with an open pickup bed. And worse when a semi would pass us.. I never had anything else to pull it with besides my trucks with no topper, so I couldn't ever deduce that the shape of the Excursion was the issue, or if the Excursion itself was flawed (I bought it used but it was a super low mile pristine example, and added new tires, a sway bar and other items to help with towing but nothing fixed our issue with the V Nose trailer). Or, if the V Nose of the trailer didn't like the enclosed back of the Excursion vs an open pickup bed. I always figured it was something with aerodynamics since Excursions are used to tow regularly and never heard anyone complain about them as tow rigs except for fuel economy with the thirsty V10's.

 

If it was wagging the tail like you are describing my first thought is tongue weight and how you balanced the trailer. For years I pulled a trailer for work and once I hit the hwy in a blizzard and took both lanes of the hwy just to keep out of the ditch and center median. I pulled over and moved the equipment inside and the problem went away. My other thought is wheelbase of the truck. Excursion should be plenty long enough so my thoughts go back to weight distribution and tongue weight.

 

We used that trailer almost every weekend for racing and practice. We kept our stuff in it most of the time, in the same places since I had customized racks and tie downs for everything we took with us. The loading wasn't different between truck with open bed vs Excursion. I did have the same thought you did after my first trip with the Excursion, and played with trying to change tongue weight and side to side weight inside the trailer to see if it would help. Even got a Weigh-Safe hitch to mess around with that more formally, but nothing seemed to help the wiggling when it was hooked up to the Excursion. I eventually gave up and sold the Ford; still have the trailer 10 years later and its only had these issues behind the Excursion. I still chalk it up to some aerodynamic glitch between the two. Perhaps its not a topper vs open bed issue in its entirety, but perhaps the height of the Excursion caused the wind to hit the trailer just wrong(?) to cause the wiggling motion. It was stock height, but still a tall rig!