One response to “Can I Improve My RV Aerodynamics for Better Fuel Efficiency?”

1. tirod3

   August 11, 2024

   The biggest factor is frontal area, followed by speed. A square box going 55 may have better mileage than a slope nosed box at 75. If it’s still the same height and width, that is the same frontal area. Trim that down and you achieve better mileage. This all goes to compromising the amount of living space we desire vs the amount we can afford, and none of the makers will talk about towing a huge frontal area which results in huge fuel bills. It’s not good to correct a customer when they are making a mistake . . .

   You can clean up the underbelly, OTR trucks are now using side skirts that are well proven in open class endurance racing – and land speed record racers always include belly pans. What is left is to 1) control the air flow off the towing vehicle, which can be enhanced to avoid the nose of the trailer. Toppers on pickup trucks help do this. 2) Tow the trailer as close to the vehicle as possible – those who stretch the drawbar to get a door or tailgate open in “road mode” are making things worse. The limit, of course, is human failure when backing and jackknifing the trailer smack into the taillights. Our inability to see is now much better with cameras, our ability to make mistakes remains. Closing in the nose of the trailer where the “junk” box sits is another – when the air exits the towing vehicle and slams into the front of the trailer, filling the “drag void” with body work helps to stop that and also direct it more smoothly.

   3) The front of the trailer needs at least 6″ radius corners – those sharp 90s’ to maximize interior room come with a price, which is paid at the pump. Sloping the nose back, not so much, more than 30 degrees approaches the point of no further returns with loss if interior. That is the constant compromise we make, doing one trades off the other. We just choose which we will live with. 4) is having a smooth profile – not only underneath, but roof top and side. Those offroad trailers with everything strapped on outside like a traveling dry goods store work ok in that environment – except in closed in brush – because they are usually going much less than 55mph. And that is a key number, as over that speed, drag increased exponentially, which is why a horrible brick will get economy where it’s impossible to pass a filling station doing 75. 5) Lastly, the tail needs help – semi trailers are sprouting wings over the back doors, where ballistic designers simply taper the end of a bullet for a short duration then cut it off. A true teardrop camper would have a 6 foot lizard tail sticking past the frame, and one enterprising German truck designer is actually testing a blow up canvas version for the rear of box vans. Of course, said truck has a lot of frontal area – and that is where we start, how little of it can you tolerate vs interior space we demand? Hence, pop ups, slide outs and now, even a hard side elevator that resembles an artillery shell when towed, special for EV’s.

   Then DIY builders look at all the leading edge stuff, scoff at the ancientboxy cellulose framing, and get to work. The most successful compromises launch new companies.

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