Improving aerodynamics

Discussion in 'Tow Vehicles, Hitch & Towing' started by aust, Jan 12, 2018.

  1. aust

    aust New Member

    Jan 12, 2018
    I tow my Aliner Expedition (~2300 lb) with a Volvo S70 sedan, and while it is a capable enough TV for the job (190hp/199lbft light turbo 5 cylinder is able to just barely keep highway speeds up steep grades) I was hoping for better fuel economy. It gets 27-29mpg hwy on its own and only 17mpg while towing 60-65mph on flats. This jumps up to 23mpg when drafting a big rig. I suspect that a TV with a larger front profile might perform better since pups are so boxy, and ultimately it's a choice between the TV or the pup punching that hole through the air, and TVs tend to be smoother lines. It also struck me that the sedan shape is probably pretty inefficient since it leaves a lot of empty space between the vehicles.

    Has anybody experimented with adding on any kind of fairing to their rig? My understanding is that the main places to focus are 1) between the TV and the trailer, 2) under trailer skirts, and 3) in the rear of the trailer.

    For (3) I see that a product called airtabs exist, and truckers tend to have these rear fairings that look pretty simple to replicate DIY, just 4 flaps that fold into a roughly tapered shape.
    And (2) seems like a poor choice because it costs ground clearance
    But (1) seems particularly interesting since I suspect it would have the most impact on my particular rig. I got thinking how articulating busses have those accordion connectors, think I could do something like that between the back of my car and the front of my trailer?

    And yes, I know 17mpg isn't too bad in the grand scheme of things, but I was hoping that I could get to the 20-25 range by using a somewhat underpowered vehicle.
  2. Byrd_Huntr

    Byrd_Huntr Well-Known Member

    Jan 27, 2013
    I don't have numbers, but when I was towing a TT with my Chev sedan many years ago, I found that I got better mileage when I strapped an inverted Coleman canoe on the roof of the car when towing.
    jumpoff likes this.
  3. SteveP

    SteveP Active Member

    May 21, 2015
    Seems like a V shaped fairing following the lines of the A frame to the trailer body and also covering the top of the propane tank(s) might do some good. You actually used to see these on some of the upper level campers in the 70's. But you have to consider, if they worked why aren't they still available? For the back, a simple deflector wing like they used to put on the old station wagons, should help to break up the low pressure pocket, but I doubt that gas savings would be hardly more than noticeable.

    Then again, cars are more slippery than they were back then so there might actually be some benefit. The only way to know for sure is to try.
  4. Lumbergodd

    Lumbergodd Member

    May 20, 2016
    We had a '72 VW Beetle that got better highway mileage with our 17' Grumman on top.[:D]
    jnc likes this.
  5. jnc

    jnc Welcome from New Hampshire

    When I tow the pup with my F350 it do not affect my mpg even with my 4wheeler in the bed. Newer TT are rounded in the front to help with the drag of the front wall. a bet a fin on the rear of the TV would help deflect the wind over the aliner.
  6. 1380ken

    1380ken Well-Known Member

    Nov 7, 2013
    You must have some complex fuel usage measurement system to determine this. The easiest way to get better mileage is to drive slower. Your aerodynamic drag is a square function of speed.
    xxxapache likes this.
  7. Rusty2192

    Rusty2192 Active Member

    Jul 30, 2014
    Now that you bring it up, it is kind of surprising the people that make the trailer tails for semis haven’t made a smaller version for RVs and enclosed trailers. If you wanted to try building one, coroplast would work great for it. I’d think about trying it myself, but the kayak and bikes I usually carry on the roof of the TV aren’t very conducive to aerodynamics.

    If only you could turn your sedan into a wagon [:D]
  8. aust

    aust New Member

    Jan 12, 2018
    Thanks for the tip on coroplast, that does seem like the right material. Any recommendations for a non-permanent but secure way to attach it to a vehicle?
  9. Yak

    Yak Well-Known Member

    Apr 18, 2009
    Had one of these for the race trailer years ago, didn't do squat


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