Big project-F250 pulling 20x8.5 enclosed trailer

[Christ]

Darin -

That's what I was talking about, couldn't find the pic. I meant 2 foot, not 2 inch, though... so typo that.

A camper shell would work great, and if you're the kind of person that can modify things, you can actually get the front of the shell to a much more conducive angle without much work, because of the way they're constructed. You can literally remove the trim, peel back the aluminum skin, change the wood frame to a shape that you like, then trim and re-apply the aluminum skin. It's a one day job, at best.

That would also give you cab-top storage space inside the shell, and yet another removable option in case you're driving around w/o the trailer at some point.

I think you're on the right track with the camper shell and some fender extensions to cover the tires up a bit.

[MetroMPG]

Sounds like the right cap plust some kind of aft treatment on the trailer might be getting you up towards ~10% savings. Nothing to sneeze at.

Here's what I was looking for:



From FuelSaver by ATS™

[5.0 Junkie]

This is the type of topper I'm looking at. They are $1200, so I don't want to mod one too bad. They are also fiberglass and painted to match.

Those "balloons" wouldn't be bad. I could deflate them when I let the door down. Heck, I'm guessing on 2mpg which would be a 25% increase. I think that will be the best bang for the buck now and I'll start on the sides/rear of the trailer then start on the front of the truck.

[Christ]

That's the cap I was talking about originally, that has a step up that might match up closely w/ the trailer.

Is the trailer wider than the truck? If you can find some way to trip the flow off the sides of the truck outward, making it rejoin as close to the corner of the trailer as possible, that will be in your best interest, so that the air doesn't get stuck in the vacuum between the truck and trailer as it comes off the corner of the truck. To that end, some spats at the rear of the bed/cap down both sides, just enough to kick out the flow a bit, might help.

If you can take a pic of your rig, a clean pic from about 20 feet back of the front of your truck w/ the trailer attached would be perfect for a reference view.

[aerohead]

Sorry,just joining the party.
Hucho has a whole section on commercial vehicles.The shots of the rig will help to see if there's something in the public domain you can borrow from.
I'm guessing it's a tongue-pull seeing that your going to do a topper.
Getting the trailer to "draft" behind is the key.Match tow rig back with frontal area of trailer front.
The gap between the truck and trailer can be 20% of the drag.Filling that in will pay you back.
If the trailer fenders protrude out into the airstream,they could be streamlined fore and aft.
Will wait to see pics.

[MetroMPG]

Food for thought:



Source: Platform for Aerodynamic Road Transport

'Boat tail' decreases fuel consumption trucks by 7.5 percent

A boat tail, a tapering protrusion mounted on the rear of a truck, leads to fuel savings of 7.5 percent. This is due to dramatically-improved aerodynamics, as shown by road tests conducted by the PART (Platform for Aerodynamic Road Transport) public-private partnership platform.

Source: TU Delft

[Christ]

Looks like they found that rear side panel accounts for the largest reduction in drag... I wonder how that scales down to our sizes?

If it can be scaled accurately, it seems to say that covering your rear wheels and installing side skirts to effectively lower the vehicle's lowest body point will prove very profitable in fuel savings. If the picture is any accurate representation, the skirts may be best situated at the lower lip of the wheel rim?

[5.0 Junkie]

I was trying to think of a way to put the "wings" on the back of the trailer. If they were hinged and folded out of the way, it could work. Likely have to spend a bunch on plexiglass as they would cover up the lights.

On the wheels, will just a flat skirt on them suffice, or do I need some moon caps too?

I'm likely going to break down and buy one of the extended height camper shells to help there.

Any big things on the truck to try? Skirts on the trailer?

[zman]

Has anyone tested the effect of the air deflectors some SUVs and Vans have at their rear window. Would that help dissipate the low preasssure area behind a trailer such as one we are talking about.

[botsapper]

My aero mods on the trailer package. Must first address the truck fairing. There is a retractable hinged top to serve as a bow fairing. Many truck cab designs use this retracting fairing combination. To seal off as much gap between the trailer & fairing, there is another cone fairing/storage on the top front on the trailer. An adaptation of Don-Bur teardrop profile is added on top of the flat trailer top. And at the end there are hinged foldaway panels that extend the trailer for your on road long-tail configuration. Front & rear spats for the bogeys, and wheel covers compliment the whole package.

Take your pick or add all of the aero treatments.

(Conceptual ideas only)