Improving MPG - Page 2 - Fiberglass RV


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Old 09-30-2013, 08:46 AM   #15
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Washing and waxing nightmare + no $ savings = not a good idea.
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Old 09-30-2013, 09:52 AM   #16
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I think one of those large airfoil wings on your tow, the same you see on big trucks may help, but these little things seem worthless
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Old 09-30-2013, 11:32 AM   #17
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As Westcliffe01 pointed out, vortex generators are pretty common in the aircraft industry. You see them on the top edges of the main wings, just aft of the point where the wing's curve really starts to flatten out.

Look carefully at the water's edge in a glass. It's not flat; the water kind of creeps up the walls of the glass at the edges. That's surface tension.

Air, like water, creates surface tension and clings to surfaces when its molecules are collected and moving (or staying put) together. This is a great thing when it's cold outside, because you get a thin layer of air that warms and clings to your skin. On an aircraft wing, however, it's like having a layer of molasses sticking to the wings and creating unneeded drag. The vortex generators perterb the air, get the molecules to run in opposing spirals down the wing's surface to break the surface tension, increasing both the amount of lift the wing generates and increasing the speed and fuel efficiency of the craft.

Will it work on an RV or trailer. Absolutely . . . but.

RVs aren't like wings. They already have lots of little things sticking out, like vent covers, window trim, roof vents, air conditioners, solar panels. All these things hit the air as the trailer moves through it, kicking it up into a turbulent, non-cohesive mess. I guess it's conceivable that the turbulence might subside somewhat by the time it gets to the back of the RV, but the abrupt, non-tapered end of the RV would tend to do that anyway. I doubt this product does much in terms of drag reduction or improving gas mileage..
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Old 09-30-2013, 12:29 PM   #18
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My Nissan Pathfinder gets an easy 21 MPH on the highway but when towing the 13 foot Scamp I fight between 15/16 MPH. My Pathfinder has a wing on the rear put on by the factory which keeps the rear window clean and may have a stability function too. But I do know when towing the 13 foot trailer the truck isnt working hard to tow it but I can hear the buffeting on the front of the trailer. I can hear the window cover slapping the front window with any change in pressure. The Nissan is probably blocking about 80% of the frontal area of the trailer I always thought of a wing mounted to the roof rack to bypass the factory wing when towing and maybe help streamline the trailer when towing. But most of my tows have been relatively short making any gains hard to track. I wanted to stick on a bunch of yarn tuffts and record the action with and without the wing using my Go Pro to see the effects if any but I have been too lazy.
Anyone have a cheap source of yarn tuffts about 3 inches long? I an scareed of sticking something on then taking a month to clean up the mess.
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Old 09-30-2013, 02:47 PM   #19
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Quote:
Originally Posted by stevebaz View Post
I always thought of a wing mounted to the roof rack to bypass the factory wing when towing and maybe help streamline the trailer when towing.
I have a wing mounted on the front cross bar of my factory roof mounted bike rake. Have done some pretty long trips without the bike portion of the rack on and with it as well as without the bikes and with the bikes. Only thing I actually notice with having the wing on the rack is if I have the sun roof open it does cut down on the rack noise from over head - only a bit though. No differences in MPG at least not noticable any which way.
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Old 09-30-2013, 04:18 PM   #20
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Originally Posted by cpaharley2008 View Post
I think one of those large airfoil wings on your tow, the same you see on big trucks may help, but these little things seem worthless
The aerodynamic purpose and function of a cab-top deflector and the vortex generators are completely different; each is sized for its purpose. The deflector smoothly moves the air around the front of the trailer (so a rounded deflector has he frontal area matching the exposed trailer front, and the wing type is nearly as big); the vortex generator just break up air flow in the thin boundary layer against the trailer walls or roof, just before the air gets to the rear corners.

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I have a wing mounted on the front cross bar of my factory roof mounted bike rake...
No differences in MPG at least not noticable any which way.
I doubt this deflector would make much difference to trailer drag in any location, but I suspect that way up there (where it should be to protect the bikes) is too far from the trailer for it to matter.
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Old 09-30-2013, 04:21 PM   #21
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My Nissan Pathfinder gets an easy 21 MPH on the highway but when towing the 13 foot Scamp I fight between 15/16 MPH.
That's about one-third more fuel consumed to haul something which adds at least a third to the air drag and weighs more than one-third of the tug alone... sounds like you're doing fine. I wouldn't expect miracles from any aerodynamic aid, but even small improvements are always good.

By the way, these numbers are reasonably close to what I see with our minivan and Boler.
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Old 09-30-2013, 04:59 PM   #22
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Pretty much the same with our Mini Van and car.

25 to 30 highway solo
16 average towing the Airstream.

Note imp gal. With US gals the numbers are lower.
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