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Topic: V-Nose Towing Theory

Posted By: Gorky on 07/19/16 10:58am

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!


Posted By: jmtandem on 07/19/16 11:10am

Quote:

Hi everyone! Any additional thoughts welcome!


I think you did a pretty good job of delineating the issues of a V nose trailer. Two things I would add. How much compromise inside the trailer will the V nose create and can you live with it? And, where I live the wind blows all the time (almost) and to tow with a V nose there will almost always be a frontal area that the wind is hitting unless the wind is from the rear. So, for me a V nose is not in the cards.

In a no wind situation rolling resistance is more important than wind resistance up to around 40-45 miles per hour. The time spent over 40-45 mph is when wind resistance becomes important. So, the nose shape is not that much of an issue under 40-45 mph.


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Posted By: BarneyS on 07/19/16 11:11am

I agree with your last two sentences. [emoticon]
"DON'T choose a V-nose to get better mpg. They're designed to have more cargo space, not better aerodynamics."

Good analysis.
Barney


2004 Sunnybrook Titan 30FKS TT
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Not towing now.
Former tow vehicles were 2016 Ram 2500 CTD, 2002 Ford F250, 7.3 PSD



Posted By: Chuck_thehammer on 07/19/16 11:40am

have you looked at the newer stuff hanging off the rear of semi-truck/trailers... panels attached to the rear/back of 40/48 foot box trailers...

similar to the engine covers used on the space shuttle when attached to there 747 aircraft to return to Florida...

its the Flat back ends of trailers that adds lots of drag. like all trailers.
trying to PULL air behind trailer.. need to break the vacuum/backdraft or whatever they call it.

keeping under 60 mph helps a lot with gas mileage..


Posted By: Bumpyroad on 07/19/16 02:29pm

when I bought my cargo trailer, they had a rounded bull nose type of jobby that mounted on the top half of the front that was supposed to improve aerodynamics. don't know if it did anything however. I remember there was a TT that tapered slightly with the rear a lilttle wider than the front.
bumpy






Posted By: SoCalDesertRider on 07/19/16 03:45pm

Let's face it. Practically all box cargo and RV travel trailers have the aerdynamic charistics of a giant cardboard box going down the road. Small modifications to the shape are not going to make massive differences in mpg or how they tow. Pick the trailer you like, pick a truck with more than enough balls to tow it, and be happy.


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Posted By: ACZL on 07/20/16 02:25am

To look at this another way. Cabover semi or slope nose conventional semi? Don't see many cabovers anymore from any mfr. Everything is conventional via very sloped nose. Most long haul semis try to close the gap as much as possible between cab and trailer. If not, cab is equipped with big 'ol air fairings and on some trailers a "bubble" on the front to aid in reducing wind resistance.

Not being scientific here, but seems to me a "V" would be more aero than a flat front or even a angled flat front.

In response to the post about the "wings" on back of semis. they are called "Trailer Tails". Supposed to do just as you said in reducing the drag or draft effect coming of rear of trailer. Have no idea how much they cut down on drag VS cost, but if going cross country, then I could see it saving money. If local, not so much. Another product one could try (have seen a few RV's w/'em) is "Air Tabs". They adhere to flat sides of a truck or trailer. They to are supposed to reduce drag at end of unit.


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Posted By: LarryJM on 07/20/16 04:55am

SoCalDesertRider wrote:

Let's face it. Practically all box cargo and RV travel trailers have the aerdynamic charistics of a giant cardboard box going down the road. Small modifications to the shape are not going to make massive differences in mpg or how they tow. Pick the trailer you like, pick a truck with more than enough balls to tow it, and be happy.


IMO that's a pretty good analysis and outlook on all this. Biggest mpg gains will be in the TV engine/drivetrain efficiency mainly gas vs diesel and rear end ratio and tow speed. All the rest will be down in the weeds so to speak.

AFAIK about the only aerodynamic improvement might be the use of "air tabs" as mentioned by ACZL in the post above, especially on the rear, but I haven't seen enough documented facts to even WAG at a payoff of long term costs.

Larry


2001 standard box 7.3L E-350 PSD Van with 4.10 rear and 2007 Holiday Rambler Aluma-Lite 8306S Been RV'ing since 1974.
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Posted By: bradyk on 07/20/16 07:08am

I talked to some engineer types at one of those high tech one man cars as we have some of the top in the world here. I asked about that and they told me that they are almost doing it backwards. The biggest gains would be had with the shaping at the back rather than the front. Flat front doesn't help but the flat at the back is even worse. As mentioned that is why you see semis not with the extra piece on the bottom of the trailer.


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Posted By: mkirsch on 07/20/16 08:02am

I agree that the REAR is where you can make the most gains as far as aerodynamic drag.

If I were building this trailer, I would definitely go V-nose for the extra space. I would also look into adding the rear fairings similar to what you're seeing on some 18-wheelers these days, or some other aerodynamic aid.

Take a look at a product called "AIRTAB." I don't know if they work but they sure do talk a good game.


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Posted By: proxim2020 on 07/20/16 08:29am

ACZL wrote:

To look at this another way. Cabover semi or slope nose conventional semi? Don't see many cabovers anymore from any mfr. Everything is conventional via very sloped nose.


Back in the day cabovers had horrible aerodynamic, but these days there's not much of a difference between modern cabovers and a conventional. Cabovers still lag a little behind in the aero department, but the gap isn't nearly as big as it once was. Since they're typically lighter, it helps them bridge that efficiency gap. Cabovers just break wind once while conventionals break wind twice. Aerodynamics was a very small reason why you don't see them here anymore.

The real reason why you don't see cabovers any more is because drivers hated the old ones and refused to buy them when they were no longer required to. The ride was terrible, you had to sit next to a loud and hot doghouse, they were harder to get in and out, they had a tiny sleeper, maintenance could be a real pain, all your stuff goes flying when you tilt the cab, etc. After the length limits got removed in the US, everyone jumped back to conventionals as soon as they could.

Low production numbers is what really killed them off. Freightliner actually made a pretty nice one for North America up until 2005. A lot of drivers didn't really notice a huge difference between that truck and a conventional. A lot of the annoyances of the old have been fixed in modern cabover trucks, but our drivers refuse to get back in them. Too many bad memories lol. Freightliner, MAN, Scania, and Volvo all make some pretty nice and efficient cabovers for the rest of the world.


Posted By: myredracer on 07/20/16 08:41am

Can't see a V-nose helping either.

Perhaps a deturbulator on top of a tow vehicle like on a semi truck might work. Removing your side view mirrors, AC unit(s) and roof vent covers ought to help. How 'bout side pods or spoiler on a trailer? Maybe pickup trucks for towing need a major rethink. Imagine what a Ford travel trailer of the future would look like coupled to a Ford truck like in the photo.) I'm sure there's much to be researched when it comes to towing TTs. [emoticon]

[image][image][image]






Posted By: OH48Lt on 07/20/16 08:44am

Regular or V-nose, the fuel mileage will not be affected in any noticeable way. Theoretically, the V-nose will do better, but in a practical sense, its not going to impact your gas credit card much. What you gain with a V-nose is that space up front that extends over the hitch frame, which a flat nose regular trailer does not have.


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Posted By: 2012Coleman on 07/20/16 08:53am

If your focus is purely on gas mileage, and you are staying with a V6, then your best bet is to buy a used pop-up.


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Posted By: Gorky on 07/20/16 10:03am

I was pulling a little 13-foot Serro Scotty (9-foot interior space) with 3.4 V6 and getting 13-14 mpg fully loaded with 2 kids and enough food and camping gear for a month of boondocking. We kept track of almost every tank on a 7000 mile trip, pretty consistent mpg but elevation made a noticeable difference over 4000 feet. The one time we found Ethanol-free non-premium gas we were getting 14.5 or so.

Granted the trailer supposedly only weighed 900 lbs dry, it did have the frontal profile of a typical old aluminum trailer and from everything I've read, aerodynamics plays a bigger role than weight in towing-ability so long as the vehicle is comfortably within spec and you're not going uphill. So if I end up with a cargo trailer, if I can squeeze better drag coefficient out of it I would expect better tow ability even if it weighs 500 - 1000 pounds more.

The trailer tails on semis get 5.5% better fuel economy at 65mph. Sounds great but I don't know if they make anything for a cargo trailer since that's where the tailgate drops down.

I'm pretty sure a smooth bump like NoseCone placed where the front of the trailer rises above the TV would squeeze better mpg. 5th wheel towers seem to have surprisingly good mpg for their weight and for how gigantic the frontal area is. I think it's because their's no gap between TV and trailer and the trailer itself is slippery and round.

I usually have a roof box on the TV for extra cargo. I'm thinking of getting a full-width one and modding it with something like the Airtabs mentioned by another poster to help deflect air over the trailer.

Popup camper not an option, bears, winters, and serious durability concerns. I'll go buy a diesel first. I remember winters in Texas in a popup; when we were waking up to find ice on the interior of our camper we upgraded to a 50s era canned ham, which was probably cheaper actually. Still no heater but with 6 warm bodies and a sliver of insulation it kept us pretty warm.


Posted By: Gorky on 07/20/16 10:32am

jmtandem wrote:


I think you did a pretty good job of delineating the issues of a V nose trailer. Two things I would add. How much compromise inside the trailer will the V nose create and can you live with it? And, where I live the wind blows all the time (almost) and to tow with a V nose there will almost always be a frontal area that the wind is hitting unless the wind is from the rear. So, for me a V nose is not in the cards.

In a no wind situation rolling resistance is more important than wind resistance up to around 40-45 miles per hour. The time spent over 40-45 mph is when wind resistance becomes important. So, the nose shape is not that much of an issue under 40-45 mph.


Thanks! A V-nose would be a compromise if it prevented a back-hatch from opening, but otherwise it actually increases cargo space a bit and one could probably find another vented spot for propane / batteries on a custom camper build.

I don't think wind and wind direction is any factor for the V-nose trailer. From what I've read of real world experience, it's easier to tow in windy places regardless of wind direction. Not sure if that's legit but I could conjecture that because the forward-moving trailer is more evenly splitting the air in front due to the V, there will be a more consistent equally-pressured air on both sides of the trailer. Whereas a flat-fronted trailer is blasting the air out of the way, air doesn't adhere as much to the sides of the trailer, and a crosswind of any angle can switch pressurized air streams from one side of the trailer to the other and cause wobbling.

Either way, if wind hits the front of your flat trailer at a 45-degree angle it's going to push on that surface pretty equally to if it hits the side of a V at a 90-degree angle. Wind force doesn't drop away that much with angle change. Hence if you're making wind turbines there is not a huge difference between a 60-degree and a 30-degree blade angle; more important is the overall surface area the wind will affect and spinning stability since mechanical wobbling drastically reduces energy efficiency.


Posted By: Bumpyroad on 07/20/16 11:55am

this thread about trailer efficiency reminds me I saw a Hi-Lo being towed this am. too bad they bit the dust.
bumpy


Posted By: Drbolasky on 07/20/16 02:22pm

Bumpyroad wrote:

I remember there was a TT that tapered slightly with the rear a lilttle wider than the front.
bumpy

That would have been the "Advancer" model from Sunline, built just down the road in Denver, PA. They hit the market shortly before Sunline went under due to inept management. Don't know how many they made before the doors closed and have never seen one on the road. In any event the corporate claim was less about gas mileage and more about subduing trailer sway.


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Posted By: SoCalDesertRider on 07/20/16 02:45pm

Airstreams, Avions and Silver Streaks are fairly aerodynamic.


Posted By: trail-explorer on 07/22/16 11:35am

Gorky wrote:

2. Cargo trailer sales people say a V-nose tows better but should not be expected to noticeably increase mpg.


They are pretty much correct.
MPG increase will barely be noticeable on a trailer built out with living quarters due to the weight of said living quarters.


Bob


Posted By: Grit dog on 07/24/16 10:37am

SoCalDesertRider wrote:

Let's face it. Practically all box cargo and RV travel trailers have the aerdynamic charistics of a giant cardboard box going down the road. Small modifications to the shape are not going to make massive differences in mpg or how they tow. Pick the trailer you like, pick a truck with more than enough balls to tow it, and be happy.


Couldn't have said it better!
Unless your V6 SUV is an Ecoboost Expedition or your cargo trailer is of the 6x12 variety.....
Otherwise 20kmi a year in Montana and surrounding states will eat your lunch regardless of the shape of the trailer!


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Posted By: LVJJJ on 07/27/16 04:14pm

I built an air deflector for the back of my flat back TT that takes the air coming off of the roof and directs it down the flat back to break up the vacuum which helps it release from the air flow. Works good. I got the design off of the internet after googling "flat back vehicles" or something like that. The back of the TT stays cleaner too since the dirt doesn't curl back and stick onto the back siding. Years ago I used an air deflector on the back of the TV, don't think it did as much as my rear deflector on the TT. The TT also tows much more stable without the turbulence going on behind it.

Notice that airplanes are fat in front and taper to a point in back.


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