aerodynamics

[campingguy62]

Would the Forest River Flagstaff Micro Lite 21 FBRS be considered to have good, fair or poor aerodynamics?

[Francesca_Knowl]

PawPaw_n_Gram wrote:

facory wrote:
Wow!! Have never seen a trailer like that. Looks like it came our of Star Wars.

It's from "A long time ago in a state far, far away......."

Yeah...California in the 1930's! :B

Here's a link to the video the pic came from.

[PawPaw_n_Gram]

facory wrote:
Wow!! Have never seen a trailer like that. Looks like it came our of Star Wars.

It's from "A long time ago in a state far, far away......."

[facory]

Wow!! Have never seen a trailer like that. Looks like it came our of Star Wars.

[69_Avion]

The Airstreams, Avions, etc. do make a big difference in the way they tow. It isn't all measured by mpg, but by the way they handle. The low center of gravity and decent aerodynamics make them stable, even at higher speeds. They don't sway as much in cross winds and tend not to be affected as much by passing semi trucks. I have towed plenty of trailers and the rounded aluminum trailers seem to tow the best and the higher the speeds, the more noticeable to difference is.

[Francesca_Knowl]

sushidog wrote:
Aerodynamics is a simple formula. CdA which is its drag coefficient times its frontal area. Both matter. My Aliner is basically a proverbial brick, so it has a poor Cd, but it has a small frontal area. In the other direction an Airstream has an excellent Cd, but a large frontal area. Most TTs are the worst of both worlds. Even those with a rounded front end have a barn door flat rear end creating lots of drag. Adding Air Tabs helps, as will a tail cone. But reducing the frontal area, like a HiLo or a Trailmanor is even better. A pop-up teardrop would be the best solution if anyone would build one.

Here's a scalable concept I drew up years ago.




Chip

[sushidog]

Aerodynamics is a simple formula. CdA which is its drag coefficient times its frontal area. Both matter. My Aliner is basically a proverbial brick, so it has a poor Cd, but it has a small frontal area. In the other direction an Airstream has an excellent Cd, but a large frontal area. Most TTs are the worst of both worlds. Even those with a rounded front end have a barn door flat rear end creating lots of drag. Adding Air Tabs helps, as will a tail cone. But reducing the frontal area, like a HiLo or a Trailmanor is even better. A pop-up teardrop would be the best solution if anyone would build one.

Here's a scalable concept I drew up years ago.



The aerodynamics of the TV also make a difference. Here's my idea of a pop-up wind deflector for a pick-up bed topper - to direct air flow over a boxy TT. Triangular side walls will also pop-up. I plan on building this one for full-timing use.


Chip

[PawPaw_n_Gram]

If you can improve mileage by 1 mph - that's a 12.5 to 10 % increase for most folks.

Truckers would kill for 10%.

Some very scientific studies have been done on automobile windshield shape. 30 degree slope reduces resistance on the windshield about 25%. The winds shield still have to move all of air pressure out of the way at that speed.

The way we tow, and the speeds we drive have a greater impact. Changing your cruise speed from 70 to 62 will normally gain you more mileage increase than aerodynamics. It takes approx. 27% more power to go 70 mph than 60 mph because of the resistance of the air being moved out of the way.

Weight does have an impact - very small unless you are in mountains with a lot of uphill driving.

Smarter driving is the best thing most of us can do to improve fuel mileage.

[Andy_F]

aftermath wrote:
The aerodynamics of a trailer really does make a difference. I can't quote actual numbers here like others will since I don't know if you save 2 or 3 mpg or not. But I can tell you of my experience. I used to pull a 21 foot hybrid with my current truck. I changed to a 25 (actually 26) foot Airstream. Using the same truck, going the same places, packing the same equipment and traveling the same speed I found that my mileage did not change. Even though our current trailer is 5 ft longer and 2000 pounds heavier, we get the same mileage. The only other variable here was the shape of the trailer.

Some people question what a few hundred extra pounds will do to their mileage. The extra weight of the water or equipment is a minor issue when compared to the size and design of the frontal area of your trailer.

x 2 based on our experience. We towed a 23 foot Rockwood hybrid shaped mostly like a brick. We went to a 30 foot TT with some aerodynamics to it and it tows much better. The wide stance axles also make a difference but I'm convinced shape does matter.

[facory]

IMHO: More importantly is the protection built into the front of the trailer. So many new trailers have the fiberglass shell unprotected from road debris. It only takes one rock, or something else left on the roadway, to punch a hole through or crack the fiberglass shell. What I look for is the diamond plate protection. I have it and can tell you it has saved my trailer from serious damage on more than one occasion. I would not purchase a trailer without this protection. Period! Aerodynamics is a non issue with today's trailers.

[W_E_BGood]

An interesting article from RVlifestyle from several years ago.

And while this discussion is about semi trailer aerodynamics, I would think a lot of the principles still apply to travel trailers.

And one more technical (read: scientific, not opinion) discussion on semi and trailer aerodynamics with an imbedded youtube video of the Dassault System's computer program.

Hope this helps. Regards, BGood

[thomasmnile]

Traded an 10000 lb. plus fifth wheel for a Jayco WhiteHawk that weighs about half as much. Took the WhiteHawk on an extended trip for the first time last month (320 mile trip to Fl. Panhandle mostly on Interstates). I was shocked the fuel mileage I was getting (3500 Ram diesel) was no better/slightly worse than towing the fifth wheel. Apparently the airflow over the truck cab, through the bed, and into the sloped nose of the TT produces quite a bit more drag. Fuel mileage to the Panhandle 10.6 mpg, trip home 11.6 mpg (driving on cruise @ 60mph except for about 60 miles driving on secondary roads both legs of the trip). So yes, a towable RV possesses the aero properties of a brick.

[aftermath]

The aerodynamics of a trailer really does make a difference. I can't quote actual numbers here like others will since I don't know if you save 2 or 3 mpg or not. But I can tell you of my experience. I used to pull a 21 foot hybrid with my current truck. I changed to a 25 (actually 26) foot Airstream. Using the same truck, going the same places, packing the same equipment and traveling the same speed I found that my mileage did not change. Even though our current trailer is 5 ft longer and 2000 pounds heavier, we get the same mileage. The only other variable here was the shape of the trailer.

Some people question what a few hundred extra pounds will do to their mileage. The extra weight of the water or equipment is a minor issue when compared to the size and design of the frontal area of your trailer.

[Francesca_Knowl]

ROBERTSUNRUS wrote:

beemerphile1 wrote:
A little better than towing a barn behind you. :B Good aerodynamics and RVs don't really fit well in the same sentence.

🙂 Hi, some do!

:R

Yeah...popups!

[ROBERTSUNRUS]

beemerphile1 wrote:
A little better than towing a barn behind you. :B Good aerodynamics and RVs don't really fit well in the same sentence.

🙂 Hi, some do!