Aerodynamics of the front end of a travel trailer

[GSP9]

I noticed a lot of companies advertise some of their trailers as fuel efficient models because they have a sleeker front end such as the Keystone Passport/Bullet or Dutchman Kodiak. Is there any advantage in fuel savings with these models? In the grand scheme of things, are they really any better than some of the more traditional campers? And if so, how much better?

[Tin_Pusher]

Let's face it, they are designed to be occupied first, towed second, and manufactured at the lowest possible cost.

I think the belly pans are a help, although a headache for DIY types. Glad I don't have one:)

Based on what I see going on in the PU bed when towing the FW I think a cab-top deflector would be helpful. A ton of turbulence back there. PITA the rest of the time.

It all depends on what you do, if the extra manufactured expense vs the extra fuel mileage is a plus. For me, generally it is not.

[msmith1199]

beemerphile1 wrote:
Sleeker designs can save some fuel but consider that some RVs are a barn door going down the road and others are a slightly curved barn door. :B

It has always seemed to me like getting rid of some items on the roof would be low hanging fruit in terms of aerodynamics.

All those air conditioners and vent lids sticking up into the airstream have to be detrimental. There are a few RVs that put the air conditioner/heat pump inside a cabinet rather than on the roof. The vents, antennas, and other items could also be streamlined.

Look at the trucking industry. I don't know what all they call these things, but on the top of the tractors you see wind deflectors that are adjustable so they can be stored when the truck isn't pulling a trailer. Or you'll see the box trailers with a fiberglass looking bubble on the front of them at the top where the air would hit them coming over the tractor. You also see things under the trailers now designed to keep the wind flow out from under the trailer. Not to mention the tractors themselves getting more aerodynamic. What if all these things on those trucks was able to save 1 mile per gallon? Do the math. That could be thousands of a dollars a year per savings per truck. Millions of dollars for large fleets. It all adds up.

[msmith1199]

Kayaks are pretty aerodynamic unless you put them on the roof sideways.

[beemerphile1]

Sleeker designs can save some fuel but consider that some RVs are a barn door going down the road and others are a slightly curved barn door. :B

It has always seemed to me like getting rid of some items on the roof would be low hanging fruit in terms of aerodynamics.

All those air conditioners and vent lids sticking up into the airstream have to be detrimental. There are a few RVs that put the air conditioner/heat pump inside a cabinet rather than on the roof. The vents, antennas, and other items could also be streamlined.

[wanderingbob]

Well , get your trailer perfect aerodynamically and then throw a square front pickup with two kayaks and seven bikes on top !
Actually it improves my mileage when I put kayaks on top of my truck ! Maybe I should try a rowboat !

[msmith1199]

bradyk wrote:
Buddy of mine who works with the high tech eco cars tells me they should spend more time shaping the rear than the fronts. Look at airplanes and the super high eco test cars. They have aero fronts but rear shape to match. Maybe the trailer designers are missing something.

I was about to say the same thing. A flat rear end :W causes a vortex which creates suction. You'll see on some semi-trucks they have these weird looking fold out things on the back of the trailer that helps to reduce the vortex created in the back. As somebody below pointed out, it's the same reason airplanes start with a point and end with a point.

[Road_Ruler]

bradyk wrote:
Buddy of mine who works with the high tech eco cars tells me they should spend more time shaping the rear than the fronts. Look at airplanes and the super high eco test cars. They have aero fronts but rear shape to match. Maybe the trailer designers are missing something.

Not all trailer designers are missing something.

[mavapa]

Total aerodynamic drag for any object is a product of the drag coefficient and the frontal area. You can reduce drag by reducing frontal area or by lowering the drag coefficient. Once long, long ago Car & Driver magazine tested aerodynamic drag for a Pinto (remember those?) by letting it coast down a hill and measuring the distance it went. Then they modified it to reduce the drag coefficient (thinks like putting a fairing over the headlights and taping up hood and door joints), and they got a significant increase in the distance it would coast. So, they kept the frontal area the same but reduced the drag coefficient, and it moved through the air easier.

So, the short answer is that making the front end more aerodynamically smooth will decrease the total drag and the amount of fuel needed to move the trailer through the air. Unfortunately there are plenty of other sources of drag, like awnings, vents, and the cluttered underside of the trailer itself.

[bradyk]

Buddy of mine who works with the high tech eco cars tells me they should spend more time shaping the rear than the fronts. Look at airplanes and the super high eco test cars. They have aero fronts but rear shape to match. Maybe the trailer designers are missing something.

[rockhillmanor]

Not an RV but same scenario. I had a flat front end horse trailer and bought the new V nose ones. Here to tell you.....WHAT a DIFFERENCE!

All TT's are like dragging a 4 x 8 sheet of plywood behind you. Even the ones with kinda round corners doesn't make a bit of diff in gas mileage. Like mentioned about making the front aerodynamic takes a big chunk out of the floor plan inside. Something that most if not everyone does not want to give up.

I do think adding one of those air deflectors on top of the TV does help. It made a big difference on towing the flat front horse trailer. Not sure why this is not promoted more for the RV'er.

[Dick_B]

Yes but by how much is the bigger question. A corollary question is the change in the inside layout for the better mileage acceptable?

[Road_Ruler]

GSP9 wrote:
I noticed a lot of companies advertise some of their trailers as fuel efficient models because they have a sleeker front end such as the Keystone Passport/Bullet or Dutchman Kodiak. Is there any advantage in fuel savings with these models? In the grand scheme of things, are they really any better than some of the more traditional campers? And if so, how much better?

You are correct. Aerodynamics can make a huge difference in fuel savings and towability.

This towing review/test really addresses your questions.....

Towing a white box or aerodynamic trailer

[Camreal]

Same here, I went from a 24 ft flat front to a 28 ft Keystone aerodynamic front and get 1.5 mpg better.

[mileshuff]

As stated, wind drag has far more to do with MPG than weight. I recently moved from a 5,000lb TT to a 9000lb 5'er. I get the same MPG towing either. The 5'er has a shaped front cap while the TT was flat.