Minimizing Aerodynamic Effect for Trailer Towing

[ennored]

The second picture does seem to show the front vertical edges are rounded a bit? The corners only need a small radius, 4% of the width, like 3", to get smooth flow.

Looks like it could use some rounding on the top though.

Something like this:


Is shrinking the gap something you'd consider? Shortening the tongue might make it harder to maneuver, but might help. Phil has posted some graphics about the gap distance.

Found one:

[Hersbird]

Originally Posted by freebeard

Two posts 12 minutes apart? If no-one else has posted, just click Edit and add to the first one.



I was hoping someone else would chime in, but since you ask I made the effort. Searching on 'trailer front edge radius' for instance didn't work. Searching on the picture title turned up zero (doesn't search inside HTML tags?) Believe it or not, I finally hit pay dirt with 'Wurlitzer juke box'.


http://ecomodder.com/forum/showthrea...tml#post481517

If you can't sort out the details, PM Hersbird, it's his trailer.

That's actually hilarious on the jukebox part. I also have taped up and added some aluminum straps to the Styrofoam domes. I don't have good before and after testing, especially on just one part of the mods I did. I do know the last trip home with the camper I got over 16 mpg. That's with a tow vehicle I have a hard time getting 20 without towing. I loaned it out for a month and the family using it averaged 12 mpg! Probably 100% city with lots of prewarming as they have a newborn and no garage.

[Hersbird]

Here is what the front looks like today, and the rear.

[ByDesign]

Thank you, everyone. The above info and photos (especially the camp trailer corners) are cool. Yes, I agree, the top edge needs something for sure.
_____

OK, on with the project. Violated my own requirement for aestetics because I couldn't resist testing the concept. Yea, Yea, YKYAEM if .....

Mods:
1) put on the 8" drop receiver (lowering the front of the trailer "sail" another 3"). It is now slightly tilted down forward on level ground -- not sure if that's better or worse for aerodynamics. Maybe I'll just need to buy a 6" drop.

2) filled the void between vehicle and trailer as much as practical. Drempt this up and just had to try it.

3) used the cap rear window as a deflector. Not sure how much this helps, but it sits down nicely against the tarp at speeds over 40 mph. Makes a slight deflector over the tubes and introduction of the trailer.

The problem with most fillers between the tow vehicle and the trailer is they don't accommodate turning. I loved the spandex idea used with the VW towing the trike trailer, but they also had an issue with turning and took it off when exiting the highway.

So, stacked 5 truck tire inner tubes on the tongue. They fit pretty close against the truck, but "move" when turning. I then wrapped it with a tarp and taped it to the trailer sides for better streamlining to the trailer. It looks totally red-neck.





Amazingly, the way I tied the inner tubes at the back keeps them in place beautifully. So well, in fact, it is hard to move them enough to access the hitch -- and impossible to use the tongue jack. Had to lift in on and off via strong back.

Anyway, I'm jazzed to try it. Any bets?

[Frank Lee]

I like your stack o' tubes as long as the tarp doesn't flap in the wind.

[freebeard]

Drempt this up and just had to try it... It looks totally red-neck.

This beats any of our suggestions. I understand there was only a 2.2mpg difference, so even if you gain back half that it might be hard to measure.

I agree with Frank Lee on the tarp (as most things). It would be interesting to see it without, if only to see the lashings. Perhaps fins of coroplast on piano hinges the front corners, with the front halves of the inner tubes exposed? For questions on the excessive hitch drop, I'd PM slowmover. Or just go to his profile and search out everything he's written.

One thing I'd wondered about: Does it need vinyl signage to represent at events, or will it be blank to keep it on the down low out on the highways. The blue tarp doesn't help either case.

Originally Posted by Google

Showing results for Dreamt
Search instead for Drempt

I like looking things up. Thanks.

[aerohead]

[Xist]

It looks like the window sticks up too high; maybe you could design something smaller that attaches to the hinges.

[Ecky]

[ByDesign]

Second trip. 166.2 miles. Without even looking at the fuel numbers, I could tell it made a difference. On trip #1 I had a hard time holding speed, and 80 mph was pushing it. With this (except going up a few of the hills) I was able to cruise at 75 mph. I sped up to test it at one point and did 90 on the flat without much trouble.

The tape held on the way there, but came undone at the bottom on the trip back (some loss of effect for sure). This photo, taken out the back window driving at dusk shows the tarp being pulled by the wind (note the lower corner where the black trailer is visible). Interesting, because it's the wind from below causing much of the turbulence -- more perhaps than from the sides.



This photo shows the trailer the next morning with the tarp loose.



Final fuel numbers gave minus 1.5 MPG for the trip over normal driving without the trailer -- 0.7 MPG improvement over the trailer by itself. Interesting mod, but not very practical (limited access to the truck, really hard to use the tongue jack) though nice for security since the hitch and tongue jack are near impossible to access and popping a tube would make a huge noise! Anyway the Ghetto look has to go and I need the functionality.

The fuel economy numbers are not scientific. Conditions were similar, but not exact. Secondly, we traveled faster (7 mph faster average) on trip #2 than on trip #1 (because we could), so that distorts the values.

The take away: substantially filling much of the void changed fuel use ~5%. I'd guess if the top of the tubes had been covered, including a proper slope up to the trailer top along with better accommodation near the bottom, (and real tests at the same speed) that number would rise to something closer to 7 or 8% -- in line with the numbers Aerohead has posted from books about tractor-trailer combos. Cool.

By the Way, Thanks to Aerohead for the above images. Most of them I've seen posted in other threads, but a couple were new to me. Thanks for posting.

Another interesting point -- not one comment or question from any observers about it. I can't believe it looks normal, but .... I didn't have a black tarp, and the blue is obnoxious. I was ready for criticism and weird questions.

Finally, it will get decals. I've been slow, but got some quotes. It's more fun to mod than to decorate.