Boat tail mod to my enclosed trailer

[Braebyrn]

Originally Posted by Cd

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

Thanks. Plates?

[Braebyrn]

Originally Posted by 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.

Any suggestions to make it better would be happily received.

Thanks,
Rick

[Frank Lee]

Just like with the rounded tail, I don't see how this one could work at actually reducing drag- looks like it tapers in too quickly to have attached flow. But you really got that much mpg improvement? For sure? Better run a few more tanks through before sticking with that claim...

[Varn]

Excellent fuel economy increase. Swing away design. Good engineering. Makes me think that I might use my trailer hitch receiver as a mount for something similar. What did you cover your frame with?

[Braebyrn]

Originally Posted by Frank Lee

Just like with the rounded tail, I don't see how this one could work at actually reducing drag- looks like it tapers in too quickly to have attached flow. But you really got that much mpg improvement? For sure? Better run a few more tanks through before sticking with that claim...

I saw an study done by NASA a few years back with the boat tail design. I adapted that study to my trailer setup. Although I don't have the full aero mods done yet to see the full potential of the boat tail design, that is coming. If you look it up on the web, you can see the study and see that it has a trunciated design and a full boat tail. Pretty impressive results.

I have drove for two days with this setup and put on over 1145 miles to this point.
101 miles 7.11 gallons, 14.20 mpg. Going up and over mt. pass 60 mph.
228 miles 20.83 gallons, 10.945 mpg. 60 mph
162 miles 13.93 gallons, 11.665 mpg., 60 mph
229 miles 20.07 gallons, 11.41 mpg. 60 mph
169 miles 14.86 gallons, 11.37 mpg. 60 mph
257 miles 21.75 gallons, 11.77 mpg. 60 mph

11.89 average. Before I had any mods, I drove around 10,000 miles and I was lucky to get 9mpg.

This next tank I am on, I bumped up the speed and am showing another mile per gallon increase, but will see when I get the tank full.

[Frank Lee]

Perhaps it's just the angle of the pic that makes it appear too steep?

[KamperBob]

Here's the pic embedded for convenience.


Would it be possible to quantify the final taper angles for top, bottom and sides? Inquiring minds want to know.

Execution of the mod looks great!

Cheers
KB

[JasonG]

Originally Posted by Braebyrn

Thanks. Plates?

Yeah, they seem to be missing. Lights look cool.

Originally Posted by Varn

Excellent fuel economy increase. Swing away design. Good engineering. Makes me think that I might use my trailer hitch receiver as a mount for something similar. What did you cover your frame with?

If you dont put up lots of pictures here with a detailed build thread, DOT will never let you drive that thing. Blueprints with dimensions are required as well.
Its the only thing that saves Basjoos.

I'm sooooo jealous.

[Braebyrn]

Since last post
183 miles, 14.968 gallons, 12.22 mpg, at 60 mph.
217 miles, 13.852 gallons, 15.66 mpg, at 60 mph. on flat and level.

Here are some more pictures. The license plate is on the side at the rear of the trailer. Didn't want to loose it if the coroplast decided to give way. The frame was made with 3/4" thin wall tubing. Its sturdy as heck, but will probably add some angles there. I am going to set up a string test and camera's when I get a chance to see the flow pattern.

[Braebyrn]

Originally Posted by KamperBob

Would it be possible to quantify the final taper angles for top, bottom and sides? Inquiring minds want to know.

Execution of the mod looks great!

Cheers
KB

The top angle is because of the angle of the trailer design. The length of the tail is 6 ft. and a few inches. In the NASA study somewhere I read that the ideal length is around 2 meters.

If it was a flat roof on the trailer, I would have came down differently, but it is not. I ran out of steel to do any more mods on the design and had to use what I had (mostly donated). I can't pasted the photos of the design that I used, but here is the link to the pdf file.... http://www.nasa.gov/centers/dryden/p...ain_H-2283.pdf

The next tank, I am going to take off the square piece on the end and run it open and see if that changes anything.