Removable Aerodynamic Fairing?

[RICHARD FURROW]

I'm very much in the lurking, planning, ok, trying to find the funds stage. Anyway, I am a firm believer in aerodynamics. With this in mind, and still trying to keep the classic shape of a TD, why not have a vinyl fairing that snaps to a frame on the trailer tongue. It extend and snap to the sides and roof of the TD. If you were looking down on your TD from above, it would appears as a "V", with the small of it on the frame, and the big part of the "V" on the trailer sides. If you look at your TD from the side, the fairing would slope up to, and snap on the roof. It would somewhat resemble the fairing on the top of a semi. It would also double as a bra for TD frontal protection as well. When you get to your destination, take it off. I'm not an aerodynamics major or anything, but I do believe it would better divert the air around the trailer. It also would not damage the tow vehicle in a "jack knife" parking situation gone bad. What do you think?

Ricky

[asianflava]

Various aerodynamic aids have been discussed before. The consensus is that the tow vehicle would disrupt the airflow. The best would be to keep the trailer within the frontal shadow of the tow vehicle.

It would be something to try though. At the very least, it could serve as a rock guard for the front of the trailer like you mentioned.

[M B Hamilton]

Airflow behind the typical tow vehicle is pretty dirty, that can represent a problem for an aero-aid that is less than rigid. Anything flapping around in the breeze costs you and it seems likely to me that a soft vinyl add-on is likely to do just that in the turbulent air behind such a tow vehicle.

E.G. - think of the new swimsuits the U.S. Swim Team is taking to the Olympics. It features compression panels to create smooth, rigid surfaces over the bodies of "professional" athletes who are probably in the best physical shape they will ever achieve. Does it work? Well, swimmers using the new suits are faster than they have been in the past. I realize that aerodynamics and hydrodynamics are not identical, but in this case I think the example is appropriate.

Just my impression.

Mark

[RICHARD FURROW]

I was encouraged to think of this after seeing the way the verticle corners of Arne's Aero 1's were rounded off. (Beautiful trailer Arne. I love your green interior and design.) I don't really have the skills to do this, plus I want a Woodie. I thought this would be a way to obtain similar aerodynamic results from my skill level, and still keep the classic shape so that it could be built as a woodie.
As far as the material flapping issue, I guess that if it were flapping, it would prove that there is some nasty air back there! I have thought about some stragetically placed, stretched, bungie cords that fit through loops on the underside of the vinyl. Maybe PVC pipes where you need the edges. The vinyl does need to be taught.
Anyway, thanks for the input. I am a long ways from putting a fairing on a trailer anyway. I was wondering if anyone had tried it, or thought it had enough merit to try it, they could.

[QuietOutdoorsman]

The air directly behind any vehicle is very disturbed, basically rolling in a three dimensional vortex with a stagnant air zone up next to the vehicle. The larger the vehicle, the larger the wake zone. With something small, like a Toyota Corolla, the wake zone is very small, barely extending off the trunk. A Mini would have only a slightly larger wake than the Corolla due to the abrupt back wall of the vehicle. Something like a Suburban could easily generate a wake zone of 5-6 feet behind the vehicle.

If you have a larger vehicle, try to keep the trailer a little smaller than the tow vehicle and keep the trailer tongue as short as practicle. This will give you the best practical aerodynamic solution. If you have a small vehicle and like to drive fast.... Only a truly ridgid fairing will work. You could do a canvas on wood or pvc frame as long as the canvas is stretched tight so it won't flap at all. If the canvas was flapping it would create more drag than if it wasn't there.

Dirk

[M B Hamilton]

There is also information on how the terminal velocity of a naked sky-diver is higher than that of one clothed in the typical loose fitting jump suit (':oops:'). And that's really all I'm go to say on that.

But the lesson we can take for all that is Think Smooth. Smooth sides, smooth roof. Radius edges. That and keeping within the slip stream of the tow vehicle will get you the most bang for your buck (oh man, maybe I shouldn't use the word bang after mentioning naked sky-divers (':?'). Keeping the gap between the tow vehicle and the trailer as short as possible also helps, but it still needs to be long enough to avoid contact with the tow vehicle when maneuvering.

[sushidog]

How about a Styrofoam nose and tail cone (for those heretic TTTer's like myself). Foam can be easily formed with a hot wire to the perfect shape for your individual situation. To protect the foam, it could be covered in a thin layer of fiberglass (of epoxy/cloth composition) or possibly coated with a rubberized bed liner type material.

I was thinking of building a nosecone for my Aliner out of the corrugated plastic material like they make signs out of. It would be very light weight, hinged from the top for filling my propane tank, and would serve as rock/weather protection as previously mentioned. The cowling would feature a smooth rounded curve top-to-bottom, teardropesque, with radiused sides, curving towards the hitch (ogive shape for those rocketeers,) for turning clearance.

The only think holding me back is figuring out a way of attaching the plastic to itself. Glue? flush fitting pop-rivets using a piece of plastic, angled molding? I would use wooden ribs inside to help it hold its shape in the buffeting of my TV's airstream. It protrudes quite a bit outside the slipstream of my little Cobalt TV, so I think both a nose-cone and a tail-cone would help my little 4cyl car's mileage quite a bit.

Right now, my gas mileage drops from mid-upper 30's to low 20's MPG towing at 60-65mph (the slowest I dare on the interstate)- a pretty big hit percentage wise. I think it could do better if it were a little more aerodynamic, as gas mileage goes back up to around 30mpg at 45mph.

[M B Hamilton]

There is (or was) an Expedition version of the Aliner. Part of the package was a tongue box with rounded corners and a downward sloping lid. Maybe you could pattern a front extension on their tongue box design. Or, purchase their box and fit it to the front of your Aliner.... and pick up an extra bit of storage space as well.

[angib]

I think Arne's got it just right - what matters, I believe, is rounded corners on both the sides and top of the body - and Arne will explain just how much work that was to achieve.

A V-shape is such a poor second that I wouldn't bother with it. I know a V looks like it should "cut through the air" and that's what the advertising blurb always says, but it simply ain't true - you don't see V-noses on aircraft, at least not until they're supersonic and you ain't gonna tow that fast, are yer?

Andrew

[brian_bp]

Aside from the issue of whether a simple vee shape would be effective (probably not) or whether any nose cone would be very effective, I wonder why it would need to be removable? Why not just make the front of the trailer the desired shape?

Perhaps the plan is to have traditional appearance while parked and good aerodynamics while towing. If so, I wouldn't go through the hassle of removing the fairing for appearance.

[brian_bp]

...I was thinking of building a nosecone for my Aliner out of the corrugated plastic material like they make signs out of...

Ah, Coroplast(or similar), the duct tape of lightweight sheet goods. From buildings to vehicle bodies, just about everthing but floors seems to get made from this stuff. I don't know how tightly you can bend this (in the easy-to-bend direction) before it buckles.

From the Coroplast FAQ:

Q: Is it possible to bond or glue two pieces of Coroplast® together?

A: Polypropylene is great for many uses due to the fact that it is resistant to chemicals; unfortunately the same properties make it difficult to bond using chemical bonding agents. However, several products have been developed recently by companies such as 3M that are designed to bond polypropylene structurally. Coroplast has not yet tested these products fully. 3M's Scotch-Weld™ Structural Plastic Adhesive DP-8005 is available from Grainger and other distributors for industrial use.

Heat welding with proper tools is an excellent method to bond two sheets of Coroplast®.

[sushidog]

Thanks Brian,

Now that I know it's glueable, I'll have to buy some and experiment with various bonding methods. I don't think I'll need too tight of a radius bend. Maybe if I heat it and bend it slowly it will take the bend better.

I'll let you guys know how it turns out.

[angib]

sushidog, for reducing the drag of your trailer, I believe its not the overall shape that matters (much), but the details. Look at your car and you'll see a pretty rectangular box (OK, the windscreen slopes, but that's about it) but with ever-so-carefully crafted corners and edges.

To keep my modelling task easier, let's pretend you've got a rectangular trailer:



A fancy shape in the wake of your car won't do much - what I think you need is to round off those sharp corners sticking out. One fairly easy way of doing that would be to add half-round pipe pieces along the edges:



8" diameter plastic vent ducting would be a good choice for this, though cutting along its axis wouldn't be easy. You could then stick the half-rounds onto some flat sheets and stick the flat sheets on with double-sided sticky tape or even with Velcro if you wanted to be able to get them off easily.

Cutting half-rounds out of foam with a hot wire would work as well.

To make this work, the edges of the half-rounds need to be perfectly aligned with the sides behind them, or inset by no more than 1/4" - definitely not 'outset'.

From the look of it, your trailer sticks out either side of your car, so it's the half-rounds on the sides would do the most good, but the one across the top might be a benefit - in truth the one along the bottom is unlikely to do much.

Of course Sod's law says it would be the sides that need it most, because you would actually need three half-rounds each side to follow the complex shape of your trailer.

Andrew

[sushidog]

Thanks for the help.

Of course the thing to do would be buy a model Chevy Cobalt and build a scale model Aliner mock-up for wind tunnel testing. Get out a small yet accurate spring scale and get to work with modeling clay.

The underside if the Aliner is pretty rough aerodynamically with lots of protruding pipes, frame members, etc. Do you think a rubber air-dam on the front of the trailer would help?

[RICHARD FURROW]

Why don't the big semi truckers use this instead of the big fiberglass fairings that they do? I really do appreciate the discussion. Best ay to learn is listen, then ask questions later!

Ricky