That $100 is fuel only - add in the additional load on the engine and
transmission and the cost goes up. How much depends on what you drive.

Adam wrote:
On Apr 9, 2:19 pm, Adam wrote:
More trailer-talk....

I have a Minden-Fab / Scheder-style trailer and tow with a 200hp V6
station wagon. The front "barndoor" of the trailer is about 1.5 to 2
feet higher than the roofline of the car. The whole setup feels draggy
on the road. 65 mph is about the limit before I feel like I am abusing
things. I get about 17 mpg with the trailer, 26mpg without. I plan on
a 3000 mile round trip this summer and with gas where it is, a few
more mpg would be nice.

I was wondering if it would be worth fitting a deflector to my luggage
rails near the back of the wagon to reduce the drag and increase my
mpg a few points (and my L/D would also go up too!).

I will can fabricate something from stainless sheetmetal that would
mount to my Thule rack. Any tips or guidelines on the form of such a
deflector are appreciated. Or is this a bad idea?

Thanks,
Adam

I am running on mostly flat roads. The rig feels just as draggy with
no glider in the trailer. Of course in the hills everything changes.

I ran a bunch of quick "what ifs" through my CFD program. What I find
is that a roof-mounted deflector reduces the drag about 12%. One
problem is that the deflector itself creates some drag so the total
net gain is not so great.

I then tried added a full round quarter-sphere to the leading edge of
the trailer, with no deflector on the roof. This made a bigger
difference in the LE drag, dropping 30%.

In total, the air drag reduction with this type of device could be
20-25% at 65 mph. My mileage could raise from 18 to 22 mpg best case,
saving me around 30 gallons or $100 over the 3000 miles. Probably not
worth it as Steve pointed out.

/Adam