Trailer and tow aerodynamics

[DrivingDan]

An all EV RV will be challenging, no doubt we'll get there, but I wouldn't think we'd have density and cost to the point where that makes sense until the 2030's (once you add in the RV it gets really expensive). Meanwhile I think that what RV OEM's should focus on first is making them more aerodynamic.

Here's a good one

SWAPPING FUEL FOR MORE BEER ON YOUR NEXT CARAVAN HOLIDAY

An analysis shows the low hanging fruit



Trailer-TV different heights


Same height


So turns out even without the OEMs we can do quite a bit ourselves

• Slow down
• Slow down some more
• Put a fairing on top of your truck (maybe in the bed) to raise to the height of your trailer.

[DrivingDan]

Recently Airstream did some wind tunnel and CFD

Airstream Aerodynamics Put to the Test

They found the low hanging fruit to be the dead air eddy between the TV and trailer. this is why the Tesla semi has such a close fairing fitting to the trailer.

[DrivingDan]

Replying to a post by @radar on another thread, with a truck it should be possible to achieve same height balance between the TV and trailer

Putting a shell of the proper height should give equivalent performance - you would think at least. And has the added advantage of covered storage.

• 6' 4" Chevy 1500 Silverado height approximately
• 2' 1500 bed height
• 5' Bed rail height?
• 9' Airstream height w/out AC approximately

This is the Century T-Class shell, specs appear to be that the back is 31', which might be enough to gently lift the airflow up towards the top of the Airstream. Additionally it looks cool. That's 31' on top of maybe a 5' bed rail height, which is short of the 9' trailer by a foot and a half, but maybe because it's graduated that would just 'lift' the top flow to the trailer which lifts it another foot and a half without too much turbulence.

[George Schweikle]

A neat article. Way back before CFD (Computational Fluid Dynamics) the University of Michigan did a wind tunnel study of motorhome aerodynamics and concluded the only improvement was to round the corners of the "box". As seen by the additions to over the road trucks, aero changes can be cost effective over long mileages but I wonder if the sometimes used roof flaps do anything to mitigate the drag of the popular tall 5th wheel trailers.

Originally Posted by DrivingDan

An all EV RV will be challenging, no doubt we'll get there, but I wouldn't think we'd have density and cost to the point where that makes sense until the 2030's (once you add in the RV it gets really expensive). Meanwhile I think that what RV OEM's should focus on first is making them more aerodynamic.

Here's a good one

SWAPPING FUEL FOR MORE BEER ON YOUR NEXT CARAVAN HOLIDAY

An analysis shows the low hanging fruit



Trailer-TV different heights


Same height


So turns out even without the OEMs we can do quite a bit ourselves

• Slow down
• Slow down some more
• Put a fairing on top of your truck (maybe in the bed) to raise to the height of your trailer.

[kdauto]

I'd say aerodynamics are often the greatest factor in fuel economy in most cases when talking travel trailers.

We had a 26' Dutchmen TT (bumper pull) weighing 6000-6500lb loaded and ready. Behind the old 1994 Suburban, we were guzzling 35l-40l per 100km on average. TERRIBLE! In 2013,upgraded the truck to a 2011 Sierra 3500HD Gas engine, now only guzzling 28l/100km.

In 2014, replaced that 6500lb, 10.5' tall TT with a 29' 12'-8" 5th wheel weighing 13000lbs loaded and ready. Guess what? The 5th wheel doesn't suck any more fuel than when hauling the smaller and lower TT on the same truck. Checked this over thousands of km and conditions.

The buffeting between a large SUV and a TT is terrible! We tried a large whale tail at the back of the Suburban's roof and it was no help. It did create some very weird aerodynamic issues where the propane tank cover got sucked about 50' in the air the 1st outing. We had to tie it down after that.

Buffeting between a pickup (no canopy) and a TT is bad, but not as terrible as with an SUV. I suspect a canopy will cause the same issues as it mimics an SUV shape.

The underside of the TT was insulated but the crossbeams and such were not covered. The entire underpinnings of the 5th wheel are covered in corroplast and the spare tire is recessed. The rear cap has an aerodynamic recess whereas the TT had a square,flat boxy rear cap. The front cap shapes and aerodynamics are both similar and not streamlined. I feel way less buffeting and slowdown with the bigger 5th than the TT, and that's in headwinds, crosswinds, anything. I attribute it to being closer to the cab with less buffeting.