Trailer Mod Drawing to Scale

[aerostealth]

The small house issue is a red herring. Obviously they would not fall into the RV class.

As for hersbird comments they are spot on. I have the same problem with wanting to use out camping trailer more often then we do because of cost. In point of fact we never use it for just one day of camping but alway stay two days to justify the work it takes just to hook up and then set up. The goal is in fact to save cost over what a motel would cost us. A week long trip to L.A. is a good example as total cost was reduced by about $500 for our vacation over motels.

[Hersbird]

I won't go out for less then 2 nights. I need one day sun up to sun down not having to do any driving or setup.
I agree the tiny house is not a big number but a big reason they are built on wheels and not just skids is so they count as an RV and are difficult to ban from most city ordinances in driveways, back yards, etc.

[aerostealth]

I see a lot of strange things out there. Last week I seen a Prius at the post office with a cargo carrier on the roof. I thought to myself "Are there no laws, are the prisons full?". I seen a home built three wheel motorcycle with the back half of a Camero body for a rear body once. A more perfect motorized parachute could not be designed by anyone. It had a V-8 engine and it needed it I am sure. Seen a semi truck towing three other tractor rigs once piggy backed on each other and being towed backwards. No problem here until you consider there all had high aero farings and he was towing parachutes. Best thing I ever seen was a shrink wrapped boat that made for a beautiful aerodynamic aft body. Probably unknown to the hauling company however.

[aerostealth]

Been going over the boat tail numbers today. Looks like the total frontal area including the AC and the tires is 62 sq ft. A 3 ft boat tail reduces that to 42 sq ft. A 4 ft boat tail reduces that to 34 sq ft. That is a 32% and a 45% reduction in wake area respectivrly. The AC unit looks easy to shroud. Under belly paneling looks not hard to do either.

[slowmover]

By shroud do you mean more a tailpiece than anything else?

[aerostealth]

No, I actually mean both a front and tail piece. Thinking a plastic wheel barrow for a front shroud if I can find one 30 inches wide. The tail would be built out of fiberglass panels.

I have been googling rv mpg forums this morning and I do not find much out there in the way of awareness about the problems at hand. In the first place there is no real discussion of modifications other then a deflector.

Frontal area come up in some discussions but there seems to be no appreciation of wake area V frontal area at all. I did see mention of 5th wheels having less of a gap from the tow vehicle and cleaner under bellies. But they are usually taller, longer, and heavier.

[aerohead]

This inflatable nose is purported to add around 26% fuel economy.That would require a 52% drag reduction.
A 'typical' travel trailer combination @ Cd 0.53 (as measured by the frontal area of the trailer) would drop to Cd 0.254 if true.
Definitely a good target for mods.

[aerohead]

This box truck depicts a Cd 0.80+ drag due to the sharp leading edges on the 'trailer.'

An 'optimized' radius will help with separation control

Increasing the single radius may not reduce overall drag

Adding radii to all leading edges really helps



Airstream covers these bases

NASA's research recommends that we use the bulbous pathway to loft the air onto the T.T. roof and around the sides,as AeroStealth is approximating with the up-coming mods.

As to the boat tail,here you can see the 3-dimensional vortex pattern which is part of the drag reduction.

According to Bearman et al' research of 1982,
*the initial 25-degree top angle causes a 14.7% drag increase due to vorticity.,Cd 0.3005.
*the 10-degree diffuser added in creates a 16.8% overall drag reduction,Cd 0.233.
*when the sides are boat-tailed in at 10-degrees,the overall drag reduction rises to 32.8%, Cd 0.176.
*if all the panel intersections are chamfered,the overall drag reduction is 36.6%, Cd 0.166.
Altering any parameter throws the drag right into an unknown quantity.
And,anything we can do to murder the wake will pay deep dividends into the future

[aerostealth]

We took the tractor into town today to have some work done on it. I was pleasantly surprised to see in the mid 16 mpg range towing it. Once I dropped the tractor off we took the interstate home. I was seeing 21 mpg at 55 mph, 19mpg at 65 mph and 18 mpg at 70 mph. Shortening the sides and the fact that the trailer hides behind the truck more is why we see better mpg towing this trailer over using a 4 Runner to tow it.

[aerostealth]

Took the trailer to town yesterday to pick up my tractor after having some work done on it. Got some interesting MPG figures on this rig in the process. On the way to town traveling empty with the trailer I seen 22 MPG at 55 MPH. At 40 MPH I seen 30 MPG. These numbers really show the power of aerodynamics. At 40 MPH drag is much less a proportion of the forces loading the engine and I was only paying a 2 MPG penalty. At 55 MPH I was paying a 5 MPG penalty.

On the way home it was a entirely different matter. I was looking at 18 MPG at 40 MPH and only 14.5 MPG at 55 MPH. I find this interesting because in some respects it models towing the Apex trailer. The weight is within a couple hundred lbs of what I would be if I were towing Apex, but without the frontal area. The air does not like the irregular shapes of the tractor sticking up, including the roll bar and roof, however it does not have the frontal area of 62 sq ft that Apex has. This results tell me that 14.5 MPG is certainly possible towing Apex possibly 15 MPG is a reasonable expectation.

Next week we are removing the Aerolid for open bed test of towing Apex in order to acquire a baseline MPG figure for the truck and trailer. I hope to acquire a baseline with a bed cover also. I am interested in 55, 60, and 65 MPH specifically.