Help me choose a trailer

[KamperBob]

It's hard to tell from that angle

but suppose the front and rear slopes are oriented so that surface normal vectors point toward the axle. Then any pressure drag -- positive in front, negative in rear -- lacks any fulcrum leverage to apply "pitching moment" going down the road. Tongue weight then does not change with speed so a trailer balanced at rest stays balanced at highway speed cleverly avoiding potential for speed-induced sway which characterizes and plagues so many enclosed trailers on the road. European campers seem to apply this lesson regularly, perhaps due to smaller, lighter tow vehicles (compacts and subcompacts), and also indicated by typically aiming for 7 rather than 10 percent tongue weight as a minimum. In the US where heavy trucks and SUVs dominate, as reflected to some extent in fuel prices (ie, demand) few trailer designs seems to heed this design knowledge. But some do and this Montrose seems like a possible example. It may not be aero for FE but aero for safety is a very good thing that deserves attention.

[slowmover]

With a cubic foot capacity needing statement, plus needing to know how "hard" is the 6'6" interior height requirement (a standard enclosed cargo trailer spec), the best candidate from among production trailers might be chosen.

As I wrote (I believe on this forum) once before:

"Were I in a position to spec a cargo trailer I would do my best to keep height and width to a minimum, about 6'H and 6'W for purposes of fuel economy. It wouldn't be higher than my truck and certainly not wider. I would rather have an extra ten feet in length (well, five feet plus) than another one foot in heighth or width. An 8'H x 8'W x 20'L trailer could be 6'H x 7'W x 30'L if cubic capacity had to be identical. (Which I doubt). Here are the words of an expert:

Andrew Thomson, Can Am RV

". . weight is highly overrated as a factor when towing. Aerodynamic drag, balance and suspension are all far more important than weight. I would rather tow a trailer that is 6 feet longer and 2000 lbs. heavier than one-foot taller."

The difference between the two trailers above is 64 sq/ft frontal area versus 42 sq/ft frontal area; a reduction of one-third (conventional-hitch trailer).

All corners and edges should be greatly radiused. My nine-and-half-foot tall 34' travel trailer had such, and wind just rolled off of it, instead of piling up against -- and pushing against -- the trailer walls.

I haven't found the source, but have seen quoted numerous times that a square box versus a rounded/aero trailer had road horsepower differences for the same speed of 50HP and 30HP respectively. AIRSTREAM maintains that their trailers take 20% less fuel to tow, all other things the same. Obviously, an enclosed undercarriage."

Radius edges may not be possible (short of affixing a Don-Bur style roof DIY).

I am most impressed by ALUM LINE trailers, specifically GNA-8B, photo #25 of 27 in GN "Enclosed Automotive" cargo trailers as per the earlier discussion and drawings above. These aluminum trailers appear to be of the highest quality with a long list of options (and, likely a price to match).

I believe some extra length may be worthwhile, as:

With 3k miles per week postulated the possible addition of living quarters could save what one Truck LTL forum estimates is $16k annually on motel expenses. Some customization and reasonable living quarters could be a real money saver on (the killer of) road expenses. A "wet bath" with composting toilet and small grey water tank plus fresh water tank, small stove and fridge (all electric I'm thinking) plus a bunkbed and LG Split HVAC system. A generator could be mounted on the truck in a toolbox that also houses an additional fuel tank. (And, while it isn't "aero" an attached roll-up awning would be good for those long weekends at truckstops. And the ubiquitous trucker charcoal grill.) Plus a good WiFi antenna system for the Kindle, movie downloads, etc.

Load balance may require that some freight occasionally ride in the living quarters, so adequate floor space and e-track should be provided.

If a GN is the suitable choice, then an aero rear could be added that would not be troublesome come loading/unloading I believe (and had I the DIY fab skills to make that a worthwhile statement). A TrailerTail is said to be worth 6.6% on one aftermarket company's site. (And a Euro university said 7.5%.)

I've found at least a half-dozen other owners of Airstream type trailers such as my own where, (all 2nd & 3rd Gen) DODGE Cummins engined trucks were achieving 13-16 mpg on 28' to 34' TT's weighing from 7k to 11k at speeds reported from 55 to nearly 65 mph. I saw 13-15 in my barely less aero Silver Streak at 63-mph (backroads vs. Interstate).

A GM DuraDud ought to be able to inch it's way near there. (Ha!)

.

[ecomodded]

A pop up trailer would provide the best aerodynamics and be one of the lightest choices,I think.
This next model is 29' 11" feet long when its extended.

Trailmanor 3326

[da_dt]

Originally Posted by wyatt

This is how I understand your requirements. I am guessing that the relatively long rounding on the front will make a bowed roof less effective. The orange on the tail could be a kit you add on, like the Trailer Tail that is seen on semi trailers. If you did one of the steel or aluminum trailers from your link, and just skin the sides of it with something, round up the front edges, add on the "cab topper" (orange thing) and maybe a tonneau cover on the bed, you would be in good shape. It would be best if you can also shield the tires on the trailer (and truck) to the max extent possible, and throw some smooth wheel covers on everything while you are at it. I show the wheels inside the trailer's outer walls, but I understand that may not be possible. The goal is to minimize the volume between the lead vehicle and the trailer, but not have everything smashing into each other. Also, the trailer should be "hidden" from the oncoming air to the maximum extent possible by trying to not make it any larger than the lead vehicle than necessary. The tail should have a maximum of 15 degrees inward slope. Hope this helps.
OH, and throw a smooth underbody on it why don't you? You can put one on the truck too, just be careful to let lots of air through the engine compartment, since we don't want to blow a transmission...

Thanks for a great post.
Is that setup going to be much better than an aerodynamic bed cap pushing the air over a bumper pull trailer?

I will kamback, belly pan, and fair the fenders on any configuration I get.

[da_dt]

Thanks, everyone! Took me a while to read through it all.

Yes, it is a cubic feet requirement. That is why I specced a 6' x 20' as opposed to the more common 7' wide sizes. The ability to stand inside without hitting my head led me to the 6'6" height.

My biggest problem will be economic--I've been looking at $20k quotes to get what I want. That's not an option.

[da_dt]

Thanks Slowmover. Lots of good info!

Believe it or not, I don't stay anywhere. I do 650 mi/night returning home in the morning.

I hope trailer tails will become available in the smaller widths/heights I'm looking at--it would save me from having to build my own. Otherwise I have plans for a polycarbonate version.

I actually found a decent deal on a used Airstream and was trying to figure a way to make it work. Don't think I can though--I need ramp access for ease of loading.

[slowmover]

Understood about the "regional driving" as I guess you may call it. The suggestion I had made I've further read upon and found that a horse trailer with living quarters converted to a "toyhauler" might be the way to go for those interested in that. But cargo weight/size will determine if it would work. Not cheap, but highly rugged (compared to a conventional toyhauler).

The GN configuration trailer will do better than most trailers since you have that interior height requirement. It would be my choice if one could mod the rig as shown in that fantastic drawing above.

A custom trailer is beaucoup money, unfortunately. Maybe a used 3-4 horse trailer could be adapted? If those are all too tall, then maybe other, lower, stock trailers.

.

[wyatt]

Originally Posted by da_dt

Thanks for a great post.
Is that setup going to be much better than an aerodynamic bed cap pushing the air over a bumper pull trailer?

I will kamback, belly pan, and fair the fenders on any configuration I get.

Gooseneck trailers have several advantages. In addition to allowing you easier backing and putting the weight directly onto your truck's rear axle, it will also allow you to fill in the gap between truck tan trailer much more. The less the gap, the better for aerodynamics. Standard truck-trailer gaps for bumper pull trailers is on the order of 4 feet, I am guessing you could do 2 feet or less with a gooseneck. Be sure that no matter what configuration you choose, you round the front edges to help reduce drag.
I am assuming that the bed cap you are talking about has a high rear end to help move air up and over the trailer. My guess is that it would be better to use a "standard height" truck cap and fill in some of the gap between lead vehicle and trailer with a rounded sloping trailer front. Get as close as is practical to doing a full V front. 2 feet between the back of the tow vehicle and the front of the trailer is enough room for movement when hooking up and unhooking a trailer (as long as the trailer jack fits in there and operates), but you will have to make sure you are able to back the thing when needed.
I understand the economy side of things, so whatever you find that works, I would be more than happy to give pointers on how to make it more aerodynamic. I think the airstream trailer would work, but you would have to be able to open the rear and fold down a ramp (may not be practical). A trailer like this would be nice because of it's nicely rounded front end, but Hucho (one of THE aerodynamics authorities, and by far the most quoted in this forum) says that rounding the edges and adding a splitter (vertical fin on the front of the trailer) is almost as good as sealing the gap between, so a really big radius shouldn't be necessary.