Boat tail mod to my enclosed trailer

[KamperBob]

Originally Posted by Braebyrn

Well about the only thing to fill in the gap on my setup is to put a flexiable connection between the truck and the trailer. Something that is on springs or maybe surgical tubing imbedded in a vinyl wrap. That way there is no drag behind the truck.

I tend to drive 64 at the most even when the speed limit is 75. Seems to get the best right around 60-64 now with the new parts I put on the truck.

Funny thing is when just driving the truck, I am getting around 21mpg on the highway at 60. Thats with the air dam, side skirts and mods on the bumper and grill area.

A hit from 21 w/o trailer to 12 w/ is a LOT of loss. Are you in a hurry? If not there should by all rights be further room for improvement w/ driving habits alone. Combine those with aero mods for the ultimate. :thumb

Good luck!
KB

[Braebyrn]

Originally Posted by KamperBob

A hit from 21 w/o trailer to 12 w/ is a LOT of loss. Are you in a hurry? If not there should by all rights be further room for improvement w/ driving habits alone. Combine those with aero mods for the ultimate. :thumb

Good luck!
KB

I have always pulled with a open trailer until recently and got around 15 at 60 to 65mph. Hook up the enclosed and its really like pulling a brick wall! I am going to bring the trailer in to the mfg to check for the wheel alignment, dragging brakes, etc.

The truck has just had a front end alignment and the brakes checked for draging which was fine. Also, since it gets the best fuel mileage now ever without the trailer, I tend to think now its got to be the trailer.

I just drove from Seattle to Austin, TX and back and was not in a hurry. This is without the nosecone, but with the airdam , side skirts and mods to the grill opening area.

From Texas to WA
11.4 mpg 60mph
9.9 mpg 60 mph
8.9 mpg 60 mph
9.8 mpg 55 mph and into headwind
11. mpg 60 mph
9.9 mpg 60 mph
10.2 mpg 60 mph
9.3 mpg 60 mph
10.3 mpg 60mph and into headwind
8.7 mpg 60 mph and into headwind
9.3 mpg 60 mph and into headwind
8.6 mpg 60 mph
9.1 mpg 60 mph
9.6 mpg 60 mph
8.2 mpg 60 mph


9.6 average mpg. No nose cone, no boat tail, only airdam, side skirts and mods to the front bumper area. It seems to me that with the mods only to the truck, the aero drag got worse in the back? Does that make sense?

[KamperBob]

Dropping from 21 w/o trailer to 15 w/ seems like a big hit to me, especially for an open trailer. I'd still obsess over driving habits. Set the ScanGauge on Current MPG mode. Then it's a game. Go for high score. If it's not possible to improve, maybe the truck isn't a "great" tug. (shrug)

Good luck!
KB

[Frank Lee]

21 to 15 towing sounds about right. My F150 goes from 18-19 to 13 or so pulling a big heavy flatbed. It does take more fuel to do more work.

[JasonG]

Keep it simple.
Add a deflector wing on top of the truck.
They work better on 5ths but can help on TTs.
The good ones / homebrews fold flat when the trailer is off.
I am working on one that goes negative for a sort of kamm effect.

[Braebyrn]

Well a friend and I made a new boat tail setup. It has a welded frame and pivots on hinges. I tested it for about 25 miles and came up with 3 to 4 mpg increase, but the long drive is coming up for the real test. I'll post some pictures in the next couple of days.

[KamperBob]

Looking forward to the new tail and report.
KB

[Braebyrn]

Ok, I put 550 miles on since it was built. Driving 60 mph, I am getting a solid 2.5 miles per gallon increase. I havent yet been able to drive on level ground, but that is coming today.

[Cd]

Beautiful !
( I can't see any plates though. )

[Cd]

Hey Phil, what's your opinion on adding some small trip strips along the sides of the tail where it has excessive curvature ? I'm guessing that due to the excess curvature on the sides, the flow is separating and going turbulent. If trip strips were added, it would keep the flow nice and tidy, but by still leaving the tail the length that it is, much of the wake could be filled in.