GTS225 wrote:You're right......the trailer is overkill for a teardrop. We have some folks coming in considerably under that 1000 lbs. with the teardrop fully built. (Admittedly, they are building very weight conscious, and out of foam.)
I think one of your ideas has merit. Rounded corners will help the aero, and if you build to the upper cab profile, that will also help. (Meaning 6' at mid-height, down to the 5' at the top.) The narrow upper profile will not be missed very much on the inside of the camper, but it does make it more difficult to build.
Some have experimented with a flexible "tunnel" fastened between the rear of the tow vehicle, and the front of the trailer. This would surely help smooth out the turbulence that will occur there, but it may be diminishing returns for the effort.
Something you may wish to look at and think about is the recent use on OTR trucks, of the angled "baffles" mounted to the back of trailers, and under the sides of the trailers. Those are there for a reason, and they wouldn't be there if they didn't work. They effectively break up the low pressure turbulence, thus increasing mileage, and in commercial freight transportation, that means money and a higher profit margin.
Your initial increase in economy with the rear cargo carrier shows that your thought processes are partially correct, but before I conclude anything, I should ask if you typically drive with the tonneau cover in place. "Killing" the turbulence is key here, as any vertical surfaces on the trailing side of an object will build a low pressure area, thus attempting to hold back the forward momentum of a body in an airstream. Your example of the hand held out the window will show you quite a bit, if you experiment with different angles and shapes.
Just a bit of food for thought.....Roger.
tony.latham wrote:There was a big difference when I bumped up from a four-wide to a five with my Tacoma.
I have also heard that Camp-Inn's Raindrop gets better mileage than their normal teardrop.
Tony
When you say big difference what was your MPG with out the trailer, with the 4 wide and then with the 5 wide.
aggie79 wrote:
...In the end, frontal area of the trailer is going to affect mileage mileage more than coefficient of drag. Think about height and width, and don't worry so much about shape.
aggie79 wrote:We have a 2011 F-150 with 5.0 liter V-8 and 3.55 rear end gear ratio. Without towing, we get 16 to 16-1/2 mpg at 65-70 mph. With towing our 5' wide teardrop (fenders extend another 12" on each side for a total width of 84"), we get 15 to 15-1/2 mpg at 65-70.
In the end, frontal area of the trailer is going to affect mileage mileage more than coefficient of drag. Think about height and width, and don't worry so much about shape.
aggie79 wrote:(...)
In the end, frontal area of the trailer is going to affect mileage mileage more than coefficient of drag. Think about height and width, and don't worry so much about shape.
Squigie wrote:The best way to improve the trailer's impact on mileage is to put a cap/shell on the bed of the truck. Streamlining the truck often provides a better improvement for fuel mileage than going to a trailer with a smaller frontal area.
Every vehicle-trailer combination is a bit different; but I've always gotten better mileage by streamlining truck beds, even if only a little bit - like piling gear and coolers so they're above the bed sides and sloping from front to back.
For several years, one of my brothers hung on to some old, ratty bunk bed mattresses, just for the fuel mileage gain. We'd pack his truck and mine for hunting/camping trips with the 'streamlining' method, then strap the mattress down over the top. My Ranger gained 3-4 mpg (16 mpg to 19-20). My brother's '86 F-250 (460 / 4x4 / Ext. cab / Long bed / 5-speed) would go from 11-13 mpg to 14-16 mpg. We got better mileage while hauling a 'streamlined' load than when running empty.
With my truck, there's almost no change from those numbers when pulling a sub-3,500-pound trailer with a frontal area (or rear ramp) that isn't considerably bigger than the truck.
My brother's F-250 does take a mileage hit when pulling a trailer of any kind, but he doesn't really have the right gears for towing. (I've got 4.10s, he's running 3.55s and the swapped-in 5-speed that, itself, has tall gears.)
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