New member, old question. Is it easier to tow a V-Nose or Flat Nose trailer?
In context, I'm planning on a custom travel trailer made out of the hull of a cargo trailer and I probably will have to decide between a V-Nose or a Flat-fronted cargo trailers. Since my tow vehicle is tentatively a 6-cyl SUV, and since I plan to live in the trailer and tow it 20000+ miles per year, ease of towing is important not only for the gas savings but for the longevity of my engine and tranny (I.e, big $$).
As such, I've been reading everywhere (including here) the various resources ranging from aerodynamics in theory, 2nd-hand observations, marketing materials, actual towing experience, etc. So here is kind-of my summation of the topic to cover the bases and submit it for the review of all the minds here.
1. Shape of trailer's front-end is only a small portion of the total trailer tow-ability equation. Other considerations include: good tires, running gear, and well-balanced load so the trailer doesn't bounce, wag, and provides least rolling resistance. Smooth sides, bottom, and top. Drag-reduction at the rear end. Size of mirrors. Weight. Etc. Road speed is the biggest determining factor, but we can't expect to go 45 mph everywhere. Speed limits on some 2-lane roads here in Montana are 75-80mph, slow gets dangerous.
2. Cargo trailer sales people say a V-nose tows better but should not be expected to noticeably increase mpg. Other people say arrows and knives cut better than bricks, so V of course will cut air better than U.
3. In a wind tunnel, a V-fronted trailer allegedly performs the same or worse than a flat trailer of the same size. The V in front does split the air instead of pushing it, but the split air adheres to the larger frontal area of the V itself, the sides of the trailer, and creates more drag at the square back-end, so the overall friction and drag is the same or slightly worse. I assume the test was done without any TV in front of the trailer but I haven't been able to find any info from the actual testers, just hearing 2nd-hand from other posters.
4. At highway speeds, the size/shape of the TV and the amount of gap between a trailer and TV has more impact than the shape of the trailer's nose. Turbulence coming off the back of the TV will obviously have no impact on the front of the trailer if there is no gap between, and increases the wider the gap until it's virtually the same as if the trailer were stacked on top of the TV instead of behind it.
5. Aerodynamics can be counter-intuitive. A TV with a rounded rear has less drag. A trailer with a rounded front has less wind resistance, on its own in a wind tunnel. But, a TV with a rounded rear towing a trailer with a rounded front means the air will sweep down the back edges of the TV and hit the trailer's full frontal area instead of being deflected over it. That's why lots of folks are disappointed by the mpg they get pulling a lightweight R-Pod vs. a longer and heavier Airstream; the sloping "tear-drop" front of the R-Pod just increases the gap (and therefore turbulence) between the rear ceiling of the TV and the front ceiling of the R-Pod. A cargo van pulling a square cargo trailer actually has less overall wind resistance, although drag at the back of a flat-backed trailer may negate most of it.
6. The gap between a trailer and TV means the air flowing off the back of the TV may try to go all the way across the front of a trailer, increasing resistance and friction. That's why some aerodynamic modifications (especially of big rigs) include a cross flow plate; vertical plate along the tongue between TV and trailer, or a series of smaller vertical fins that discourage air from crossing horizontally front of the trailer.
7. The nose of the V-fronted trailer is usually advanced into the tongue area between TV and trailer. In other words, a flat front is not chopped off at angles to make the V; instead a V is added onto the front of a the flat so the overall interior length at trailer center increases; the gap between middle of TV and nose of V is less than that of a flat trailer.
Therefore, I would expect that a V-nose pulled behind a big squarish TV would perform very slightly better (as advertised) than a flat-front trailer with the same length of tongue. The V nose slightly reduces the gap between trailer and TV (at-least at the centerline) and the V will act like a weak cross flow prevention plate, reducing turbulent air flow across the front of the trailer. Since a V-nose by itself does badly in a wind tunnel, the less drag you expect from your tow vehicle (i.e, sloped back end) or the shorter it is comparatively, the more air will hit the V-nose and the worse its affect will be for aerodynamics overall compared to a flat-front.
But if you must have a minimum distance between TV and front of trailer, to be able to open a rear hatch for instance, it would be much better to have a flat-front at the same distance from the TV as the tip of the V-nose.
Since tongue distance, TV shape, and driving speed are variables determined more by utilitarian necessities (i.e, if you need to turn sharply or can't afford a different tow vehicle) and these will all determine if the V-nose will help or hurt, I would agree with what trailer sales are saying: DON'T choose a V-nose to get better mpg. They're designed to have more cargo space, not better aerodynamics.
Hi everyone! Any additional thoughts welcome!
