Teardrops: Does shape affect MPG?

[TFin04]

I'm curious if the rounded shape of a traditional teardrop makes any difference in MPG's vs some of the newer boxier style "teardrops."

Does the trailer roof line being slightly above the vehicle roof line make any difference, or does the tow vehicle create enough of a draft space for it not to matter?

 

[SWITAWI]

I would think weight would be just as big a factor, unless the trailer's front is wider/taller than the rear of the tow vehicle.

When I towed a friend's M101A3 (on the military 37in run-flats) we did need to take down the canvas top to prevent it feeling like I was towing a parachute. But after that the wind resistance felt pretty nil and my FJC got 12.5mpg with the trailer loaded up (maybe 3000-3200lbs combined trailer and load?) as opposed to my normal 18-19mpg.

I don't see the aerodynamics of a 'Tearbox' like a Hiker/Lead Dog or IntechRV being hugely affecting behind a similarly boxy vehicle like a Wrangler/4Runner/Xterra. Maybe it would be catching some frontal drag over the tailgate of a pickup.

I'd be interested to see what MPG this guy is getting versus the car by itself, but he's also got a kayak up top so... - http://forum.expeditionportal.com/threads/164573-Intech-RV?p=2321345#post2321345

 

[PhulesAU]

Yes it does.

 

[summerprophet]

Large teardrops like the R-pod series, actually negatively affect fuel economy. The gap created between the trailer and the tow vehicle actually creates a turbulent area not found on more boxy style of trailer.

As the teardrop height and width is reduced, obviously the effect is also reduced.

 

[Kmrtnsn]

The vast majority of aerodynamic drag generated by a trailer comes from underneath.

 

[TFin04]

Large teardrops like the R-pod series, actually negatively affect fuel economy. The gap created between the trailer and the tow vehicle actually creates a turbulent area not found on more boxy style of trailer.

As the teardrop height and width is reduced, obviously the effect is also reduced.

Are you saying a boxier front end of the trailer is more efficient?

I know we drive lot of heavy and boxy trucks, I'm not trying to nitpick MPG's. I'm planning on building a trailer so I can do either template and I'm wondering how much, if any, it matters. I might also tow it with our 4cyl Outback from time to time and keeping that a long range cruiser would be nice.

 

[ottsville]

Large teardrops like the R-pod series, actually negatively affect fuel economy. The gap created between the trailer and the tow vehicle actually creates a turbulent area not found on more boxy style of trailer.

As the teardrop height and width is reduced, obviously the effect is also reduced.

I've often wondered why more trailers aren't built with and enclosed space over the front triangle. This would lessen that dead space and although crosswinds might be more of an issue, I would think that MPG would be improved.

 

[independent]

I've often wondered why more trailers aren't built with and enclosed space over the front triangle. This would lessen that dead space and although crosswinds might be more of an issue, I would think that MPG would be improved.

Weight and aerodynamics are the mitigating factors, along with speed at which you tow. I have an AT Tear drop, which weighs 1500 lbs dry. At 60 to 65 mph I can get 16 mpg with a Rubicon Unlimited.
I recently purchased a Bowlus travel trailer (my wife wanted a real bathroom,sort of) and at 2300 lbs dry. 24 feet long and traveling at 60 mph I was able to achieve 16.5 mpg in the same vehicle.

 

[Capercrew02]

It really depends on the tow vehicle. A classic teardrop behind a Honda Civic, vs a boxy one, might have a difference. A lifted off-road body teardrop vs a socal teardrop, behind a lifted inneffecient vehicle, almost Nill of a difference. My mpgs are more effected by my highway speed than even if I do or don't have my hiker trailer behind my jeep. 80 without trailer, vs 70 with trailer, that's right, better mpg with trailer at the slower speed. 70 vs 70, almost exact same.

 

[panoel]

We just took a trip from Oroville, CA to Summerville, SC. We rented a Hiker Trailer 5x8 in Las Vegas, Nevada and completed our journey towing with a Subaru Outback 2.5. Without trailer and on the highway we would get 33 MPG with the trailer the best we achieved was 18 and as low as 15 with strong side winds. Fuel may make a difference as well as CA fuel is formulated specifically for CA but the trailer made a noticeable difference in fuel economy.

 

[ex m38a1er]

@ SWITAWI
According to physics (aerodynamics) his trailer should have the square end in front and the rounded in the back.

 

[Midnightsun]

@ SWITAWI
According to physics (aerodynamics) his trailer should have the square end in front and the rounded in the back.

That is exactly right. Good information is rare these days

 

[rruff]

According to physics (aerodynamics) his trailer should have the square end in front and the rounded in the back.

Rounded front corners (sides and top) and kammtail would be best I think.

 

[Jeffer949]

My friend who is a aerodynamics professor helped a friend design his home built teardrop. He agreed with the above statement. He had a radius that was pretty small like 10-12 inches that he said it didn't matter if you went over this.

 

[SoCal Tom]

My Teardrop had the Benroy shape, and the top of the TD pretty much matches the height of my JK. When I drive in the rain without the TD, the back window gets wet, when I drive with the TD in the rain the back window stays dry. The Benroy front curve, is a 19inch radius. The sloping back of a teardrop reduces the vacuum created as you drive through the air, so yes, I believe the tail end shape does matter.
Tom