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Travel Trailer Nose Cone Aerodynamics: How to Create a Wind Deflector and Make Your Trailer Go Into the Wind with Ease
John P. Bridge (4-14-07)
© 2007 by John P. Bridge
In January of 2006 I "retard." That's Texan for retired. Actually, I only semi-retired, because I still do tile work part of the year. I specialize in building and tiling Kerdi showers. In the summers my wife Patti and I travel. Last year we spent three months on the road covering the western part of the United States in a used travel trailer, a 28-foot Jayco Qwest, I bought on Ebay. We wanted to make sure we liked the lifestyle before we splurged on a new RV. We traveled 9,000 miles and liked the RV lifestyle a lot.
2000 Jayco Qwest. 28 feet long, dry weight 5,600 lbs.
The best mileage I was ever able to get with the Jayco was about 8.5 miles per gallon of gasoline. As you can see, the front of the trailer is not designed with aerodynamics in mind, and that is true of most trailers produced in the U.S. The Jayco's front measures about 56 square feet, just a little less than the area of two 4X8 sheets of plywood, and the "angle of attack" (into the wind) is nearly flat.
We loved the Jayco, but it had a serious leak problem that I was not able to solve, so I sold it (on Ebay) to a fellow who is going to fix it and park it on vacation property. In December, 2006, we bought a brand new Puma by Forest River.
The Puma is 32 feet in length, 4 feet longer than the Jayco. Its dry weight is 6,600 lbs., 1,000 more than the Jayco. Additionally, it is a full foot taller. Its front measures 64 square feet, exactly the size of two 4X8 sheets of plywood. The angle of attack is about that of the Jayco.
We took the Puma on three trips down the Texas Coast, each about 400 miles in length. The best fuel performance I was able to achieve was 7 miles per gallon of gasoline. I had considered the 8 mpg of the Jayco to be atrocious, and the Puma mileage was unbearable. I calculated the miles we intend to travel this summer (2007) against the probable cost of gas and came up with a projected fuel bill of between $6,000 and $7,000. And that's if gas peaks at about $3 per gallon. It will probably go higher, judging from the spring prices now. Something had to be done to improve the situation.
I began searching the Internet for information on trailer aerodynamics. I wanted to purchase something, anything, that would make my trailer go more easily into the wind. I learned from other travelers that wind "drag" is the number one cause of poor fuel economy. Weight is a factor, but not much of one unless going up hill. Wind, on the other hand, plays havoc with a travel trailer in any terrain, especially at speeds above 50 miles per hour. I like to drive 65-70 out on the Interstate. Being able to cruise in over-drive is essential to decent fuel economy.
I researched wind deflectors that mount on top of the tow vehicle, but from reading of the experiences of others I determined that truck mounted wind defectors are not very efficient. For one thing, they are much too far forward of the trailer's front end, the two sheets of plywood you are trying to drag flat through the wind. And a number of veteran RVers have observed that truck mounted wind deflectors might even cause more air turbulence than they eliminate. And they look ugly.
So I checked out plastic "bubbles" that can be attached to the front of the trailer just like the ones you sometimes see on the fronts of commercial "box vans." But while these are somewhat more efficient than truck mounted deflectors, they are very expensive. One large enough for the front of the Puma would run around $2,000, which would more than gobble up any savings that would accrue during the course of the summer and the next summer, too. We will be traveling up the West Coast to Alaska., across Canada to the East Coast, down through the Carolinas and finally back to Texas, a distance of about 15,000 miles when you factor in side trips. Fuel efficiency increases seven to fifteen percent with the bubble.
I looked around at truck outfitters hoping to find a fiberglass cab deflector like the ones that most over-the-road commercial haulers use nowadays. I hoped I might be able to buy something reasonable, cut it down and adapt it to the front of the trailer, but nothing I saw even came close to what I needed.
At last I decided I would have to design and build my own apparatus. I would have to modify the front of the Puma to make it much more aerodynamic, and at the same time maintain the new "factory" look of the trailer. I did not want to ruin what aesthetic quality the trailer might claim, nor did I want to lower its value and accelerate the depreciation it will accrue soon enough without any unsightly modifications. But what in the world could a person do?
An aircraft type fiberglass reinforced plastic nose came to mind, but I determined it would be too costly to build "one-off." You would first have to construct a plug from which a mold could be cast and then finally cast the finished product. I didn't even bother to compute what that would cost in time, energy and money.
I decided that whatever I built would have to consist of flat panels that would be arranged in the most aerodynamic structure possible. Hard corners, instead of curved ones, are not as efficient, but anything would be an improvement over the two flat sheets of plywood. I thought about aluminum tubing or angles with sheet aluminum for the covering panels. But I doubted I could form aluminum into a workmanlike product. Sheet steel likewise.
I considered steel electrical conduit. The thin wall version is fairly cheap and easily bent with a bending tool that is not expensive, but steel framing would add quite a bit of weight to the front of the trailer. I decided on lightweight sheet metal studs, the type used in interior commercial construction. I could frame the structure from metal studs and cover them with some sort of panel. "Tile board," the paneling that is used around tub showers in mobile homes and other residences, might do the job. I could coat the undersides of the panels with paint to make them a bit more weather worthy. It was beginning to sound like a workable plan.
Sketches were drawn on paper, on book covers, on napkins, and various angles of attack were plotted. I did a bathroom remodel for an aerospace engineer at NASA, and he helped and encouraged me, drawing sketches of his own. Over the course of several weeks the plan materialized on paper and was improved in bits and pieces.
A time came when I had a free week, and I headed into a local home center to buy materials. As I headed toward the lumber area to find the metal studs I noticed the racks of white Schedule 40 PVC pipe in the plumbing department, and a giant light bulb went off in my head. PVC. Why not? Schedule 40 pipe is fairly rigid, and what rigidity it lacked could be compensated by the stiffness of the panels that would be attached to the structure. In the space of five minutes my metal stud framing plan went out the window, and a new plastic pipe one replaced it.
I bought several lengths of 1-1/4 inch pipe, and headed toward the paneling area to find the tile board. There were two types of tile board available, one with score lines in it to make it resemble tiles, and another that was flat and plain white on its surface. As I reached for the plain one my eyes shifted to the shelf below. There rested some bright white fiberglass reinforced plastic panels that cost almost three times as much as the tile board, but they would not have to be painted on the underside, and they would certainly last longer. Light bulb number two exploded in my head -- wow, a completely plastic nose structure. What could be better?
So here it comes from start to finish. I'll post a few pictures and briefly explain the process that evolved as I went along, for by that time what was left of the original plan was not significant at all.
The bulk of the structure is complete. The junctures of the pipes are secured with galvanized plumbing strap and self tapping screws. The end cuts of the pipe segments were achieved by trial and error.
The first panel is applied using washer head self-tapping screws. Fitting and bending this panel to conform to the framing took two tries. I mis-cut the first panel and had to recycle it into a later cut.
All the panels have been installed except for the triangular piece at the front.
Completed nose. I used a couple tubes of silicone making sure the connection to the trailer won't leak. The area left open down below accommodates the back of the truck when jack-knifed and also allows open access to the batteries and propane tanks.
The angle of the triangular panel at the front matches that of the back door of the truck topper. The gas bottles and the open space surrounding them are completely blocked by the truck and topper. You can appreciate the improved "angle of attack" here. The distance between the nose and the back of the truck was determined by the swing of the topper door. I want to be able to open it while the trailer and truck are hitched. The new nose added about 150 lbs. to the tongue of the trailer, but that can be easily transferred to the front truck wheels with load leveling gear.
This is what the wind saw before my modification.
And this is what the wind sees now.
Patti and I road tested the rig before the final caulking and trimming was done. We drove 40 miles in two directions, 20 with the wind behind us and 20 into the wind. About 30 miles were comprised of Interstate driving and 10 of city street driving (starting and stopping). We fueled the truck before starting out and again when we completed the run (at the same service station). I computed the fuel efficiency at 9.1 miles per gallon, a 2.1 mpg improvement (a 30+ percent gain). I will of course test further, but I think I will achieve about 10 mpg on straight Interstate driving. That means that even though much of our summer driving will be through the tallest mountain ranges of North America, I should be able to average 9 mpg overall. Folks, this is huge!
Now in the history of aerodynamics, my invention would fit in during the very early 1900s, but the planes of early aviation history did fly, and my nose structure does go through the oncoming wind better than anything the travel trailer industry has marketed to date, save maybe the Airstream trailers, which cost three to four times the price of the Puma. In my research I learned that aerodynamics is not "intuitive," but it really is, at least up to a point. Most folks can figure out that something pointy will go into the wind better than something blunt.
Blunt fronts aren't the only problems travel trailers incur. There are non-aerodynamic appendages hanging out of the sides, top and underbelly of the vehicles, things that a nicely shaped nose structure won't contain. The Puma is typical, and it has a rolled up awning on the right side, an air conditioner, a skylight, a TV antenna and a sewer vent on the roof. And under the trailer there are three holding tanks, a folding stairway, axels and stabilizer jacks. There is a slide out room on the left side, and it doesn't close quite flush with the side of the trailer.
Additionally, the rear of a travel trailer is usually straight up and down and flat, not rounded at all. And when a person learns about aerodynamics he learns there is a suction behind the trailer as it goes down the road, and this suction contributes to "drag." That is why jet liners have pointy tails. I've thought about creating a more aerodynamic rear for the Puma, but I don't think the traveling public is quite ready for that. What I will do is remove the spare tire that is mounted on the back bumper (along with the bit of turbulence it causes) and stow it inside the trailer.
I will be thinking about all of the things I've just mentioned with a view to the future. It's not that the RV industry is unaware of the bluntness and square aspects of the products it puts out. It's just that the industry can't improve aerodynamically without raising prices considerably, and that's always tough to do in any industry. It'll happen when fuel prices rise even higher, but I don't have time to wait.
Happy RV-ing, y'all.