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Most aerodynamic way to tow a trailer?

Discussion in 'Camping Toys' started by dannyleo, Dec 12, 2018.

  1. dannyleo

    dannyleo Been here awhile

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    My friend and I have almost identical, V-nosed, 12-foot, motorcycle trailers. With an open pickup bed, our mileage sucks big time. On my diesel with a camper shell, my mileage was about 20% better than with my truck that didn't have a camper shell, but I attribute some/much of this to the difference in gearing 3.73 vs. 4.30 read ends. He bought a camper shell to try to improve his mileage over what he was getting with a flat, bed cover on his truck. Worsened his mileage by no less than 20-40%. Tested in varying directions and wind conditions and he ended up just selling it as it not only wasn't helping, it was hurting. Then he towed two bikes in the trailer with an RT in the bed and got an amazing 20-40% INCREASE in mileage! It was like the weight didn't matter, that RT was breaking the wind as it came over the roof of the truck and providing a nice, slipstream for the trailer to 'snuggle' into. He's going to tow three bikes a thousand miles and for the return trip, he bought a canoe he's going to saw in half to replicate the 'bike-in-the-bed' aerodynamic effect.

    Any aero engineers out there with some better ideas? Or anybody found anything to increase their mileage? One of the reasons I went with the V-nose was I thought it would be an advantage, but I'm beginning to doubt the effectiveness of the V now.
    #1
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  2. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    He got 40% worse?? I heard the other day that 67% of all statistics are made up, that's up a full 2% over last year!!!:lol3

    Mileage swings of 40% in any direction is outrageous.

    My Duramax gets 16 mpg on the super slab (keeping it below 2,000 rpm). Pulling my 28' fully loaded toyhauler on the superslab at the same speed drops it down to 12 mpg which is a 25% drop. I can't imagine that aero of a little V-nosed trailer would put that much load on your truck.

    How about giving us what is being driven, how it's being driven, and the actual numbers you used to come to your conclusions?
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  3. dannyleo

    dannyleo Been here awhile

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    You sound like a troll to me. 14mpg to 10mpg sounds like 40% to me. I asked a question and you come back with a bunch of attacks. Sorry, find somebody else to troll. My question still stands for anyone with a reasonable answer or suggestion. Not here to debate, just asked a question.
    #3
  4. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    40% of 14 is 8.4 Sorry if you think I'm trolling but with so little information given all that can be done is guess as to what the problem is. Best of luck.
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  5. cheeseyboy

    cheeseyboy Been here awhile

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  6. dannyleo

    dannyleo Been here awhile

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    Dang. You’re right. My math failed due to my fatigue, and possibly some laziness too. ‘Cause I just figured it backwards and that doesn’t work with percentages. My F250 diesel gets about the same as yours under similar conditions as I also have a 28’ toyhauler. Tht’s why I was so shocked to see an 1,800 pond trailer affect my mileage about the same as my 12,000 pond trailer. air resistance seems to have a much greater impact than weight. I’m just looking for answers. My figures are based on multiple, 1,000 mile + trips back and forth between North Carolina and Missouri. Reduction of speed and therefore reduction of drag has by far the greatest impact, but there’s got to be a way to improve the aerodynamics.
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  7. dannyleo

    dannyleo Been here awhile

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    Great article. It reinforces what I’ve seen on the road with 18-wheelers and now some Mercedes vans using differing devices to control the air at the trailing edge of the vehicle. Most interesting was the trailer distance from the tow vehicle comment. So if I can figure out a way to effectively ‘smooth’ the air past that dead space, maybe that will help. The Mercedes vans were using some small, trailing edge spoilers, but they’re relatively expensive since your gluing them sided by side around the whole height and width of the trailing edge. Even the website said it would likely take 100,000 miles to break even / recover costs.
    #7
  8. MountainClimber

    MountainClimber Snipe

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    Drag goes well beyond just aerodynamics. I'd start with making sure that both the truck and trailer tires are properly inflated, trailer bearings have a fresh coat of grease, trailer axle is properly aligned. As far as operating at speed, that will be another limiting factor. For example in my Toyota, unloaded, if I run at 55-65 I can get high 18s, low 19s mpg, speed up to 75-80 and my mpgs drop to 16-17. All I'm saying is that your mileage problem goes well beyond the aerodynamic impacts of the trailer but if you wanted to focus on just the trailer what about notching the top of the v-nose down to approximately the same height as the roof of your truck?
    #8
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  9. dannyleo

    dannyleo Been here awhile

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    Repacked the bearings on the trailer just before I began my multiple trips.

    Not sure how easy notching the front of an aluminum trailer would be. Easier and something else I thought of would be a flip up spoiler on the trailing edge of the camper shell to effectively do the same thing.

    I’m always death on tire pressures, ensuring they are topped off before and during every trip. Tread on trailer doesn’t show any sign of misalignment and that would be a low likelihood event, though certainly possible.
    #9
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  10. ohgood

    ohgood Just givver tha berries !!!

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    tow slower.
    75 mph is 25% less efficient than 55mph.

    cars:
    40 mpg (55mph) " 25% loss in efficiency (75mph) = 30 mpg
    1000 mile trip at 55mph= $75 fuel
    1000 mile trip at 70mph= $100 fuel

    trucks:
    15mpg (55 mph) " 25% loss in efficiency (75mph) = 11 mpg
    1000 mile trip at 55mph= $200 fuel
    1000 mile trip at 70mph= $273 fuel

    look at modern tractor trailers, they have a lot of simple additions to reduce drag.

    aerodynamics/hydrodynamics have always interested me. watching the tractor trailer rigs get more and more slippery over the decades had been a real treat. right now i think the biggest improvements are in the closing of gaps between tractor/trailer junctions and creating teardrop shapes from the big box. look at a truck stop if you need inspiration. some wine tunnels have shown 4% drag reduction just by going from big tow mirrors to integrated cameras.
    #10
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  11. dannyleo

    dannyleo Been here awhile

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    Wow! 4% just from mirrors. Hard to believe since it seems like they're so small in comparison to what the truck is already breaking wind in. Your figures pretty much reflect what m buddy and I see with our truck and trailers. But just like the song says, "I can't drive 55!" :( So I'm looking to improve what I can get at 75. :) (It may be a losing battle, just like what folks said when I tried to improve my Harley Sportster's handling with RaceTech springs, fork brace, premium remote reservoir rear shocks, etc, etc. I never did weld up the swing arm after they told me I'd be fighting the Sportster handling forever.)
    #11
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  12. rider1150gsadv

    rider1150gsadv Long timer

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    Have you tried a tonneau cover? It is obviously lower than a camper shell but may work out to be more aerodynamic. My Chevy Avalanche got better mileage with the covers on than off but that truck was designed with the covers in mind...
    #12
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  13. HeliMark

    HeliMark Long timer Supporter

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    Many studies out that prove the tonneau covers on pick up trucks does nothing to increase the mpg.

    When I am towing, I stay at 65 mph. Not really slow, but my mileage takes a big hit going over that speed. My stock 2016 Chevy 2500HD 4x4 with the Duramax gets 22 mpg on the freeway, and 12-13 mpg towing my 25' toyhauler.
    #13
  14. kantuckid

    kantuckid Long timer

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    I'll throw this out for consideration: We owned a T@B tear drop camper for many years. They weighed them after building and the scale person wrote that weight on the sticker near the front door latch with a sharpie-sort of a sales pitch I suppose. Ours weighed in @ 1,584 lbs.. It could easily be moved around manually on a paved location. In spite of it extreme light weight, for an RV, when towed with a full sized PU truck it easily knocked the crap out of your mpg! I forget the numbers but it's enough to say it probably near half as mpg not towing. It had to be the air flow as that amount of weight alone was not enough had it been say, low in the truck bed as sand or rocks.
    Our current RV trailer, also a tow behind weighs ~ 2,900#'s and has no more effect on mpg than the T@B and it rises much higher above our truck besides the weight difference. Just looking at a T@B you'd never guess they had that much air resistance.
    #14
  15. rider1150gsadv

    rider1150gsadv Long timer

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    ^ Thats amazing really, as I too would have thought that the T@B would perform better.
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  16. RoundTrip

    RoundTrip Unintentional deerslayer Supporter

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    To the OP, I am not surprised by your mileage numbers.

    I use a 2016 F250 6.7 Diesel to tow a >13,000 5th wheel. 17mpg without, 10mpg with, uphill, downhill, with or against the wind those are the averages. If you are towing a full height trailer with a half ton gasser, those would be the results I would expect.
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  17. tzracer

    tzracer Been here awhile Supporter

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    Weight affects your mileage most in stop and go traffic, once moving on the freeway, the weight will have little affect on fuel mileage. Think inertia.

    Aerodynamic drag will have a much larger affect fo long distance freeway drives. The simplest models of drag start at proportional to v, changing over to v^2 as speed increases. The speed of the change over is very dependent on the shape of the trailer.

    Side note - trailer rated tires (ST) are speed rated to 65 mph. I rarely towed my toy hauler over 70 mph.
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  18. dannyleo

    dannyleo Been here awhile

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    Wow! Learned something again! I did not know that.
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  19. k12lts

    k12lts Been here awhile

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    I've heard from several sources that trailers with rounded corners and roof are more aerodynamic than square corners and flat roof. Airplanes don't have square corners. Square corners and flat roofs are cheaper and easier to build.

    Some say the v-nose is just a marketing technique and does not improve aerodynamics, same thing about square corners. I'm no engineer but it makes sense to me.

    As stated above, speed has more to do with gas mileage than anything.
    #19
  20. dannyleo

    dannyleo Been here awhile

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    Found the 'aero tabs' I referred to in an earlier post. They are vortex generators for the trailing edge, but at $3/ea, that runs into some $$$. Best resource I've found yet is NASA.GOV site: https://spinoff.nasa.gov/Spinoff2008/t_3.html It addresses pretty much all I was talking about. Distance, corners, vortices, etc.
    #20