Newbie intro and aerodynamics questions.

[pete c]

Hi. I am new here. This is a great forum and I have spent hours reading.

I don't currently own a tiny trailer. I actually own a tiny C class (Toyota Sunrader). If you are not familiar with it, think old toyota pickup with a Scamp on its back.

Anyway, a few things have me considering going the triple T route.

First off, the Toy C Classes, especially the Sunrader seem to actually be appreciating. Mine is very low miles, 40K and runs like new. If I get a few things sorted and put a coat of wax on it, I think it might bring pretty damn good money.

2nd, I am the new owner of one of the outlaw TDIs. 2011 Jetta Sportwagen. I absolutely love diving this thing. And while it won't win many drag races, it is an absolute beast on long highway grades. There is a reason every large truck on the planet is a turbodiesel. They love pulling things. Even the little ones.

My Sunrader on a good day makes 17, maybe 18 mpg. Pretty good for a C Class. But I have read that tdi owners pulling Scamps can do 30 mpg at 55 mph.

The Scamp is a cool little trailer, but I think there are big aero gains to be had.

One of these gains, that I don't recall seeing anywhere, including this site, is to clean up the aero of the tow vehicle.

Teardrops appear to be quite aerodynamic, on their own, but I think a better idea is to view the TV and the TT as a single aero unit. Think modern tractor trailers.

Do TT manufacturers try to make the lead edge of the trailer aero?

No.

They make the tractor aero and leave the front of the trailer as flat as a board. It doesn't matter because it is sitting in still air.

I have an idea floating around in my gord of a scamp sized TT with a flat front that sits as close to my car as possible and a tractor trailer type fairing mounted to my roof rack. I would boattail the TT, sort of like a tear drop, but turned 90 degrees. This would create a much cleaner airflow and that rear boat tail would be a great place to store a few bikes out of the weather.

I have some Paint sketches I will put up when I figure out how to do so.

[pete c]

Just noticed I titled this aero questions, then didn't really ask any.

I guess my biggest question would be where are examples of this already done. I can't be the first guy to want to put into practice an idea we all see everyday on the highway by semis.

[tony.latham]

You might try the search function. There are threads on this. Here's two:

http://www.tnttt.com/viewtopic.php?f=62&t=70977&p=1238390&hilit=aerodynamic#p1238390

http://www.tnttt.com/viewtopic.php?f=67&t=70301&p=1228398&hilit=aerodynamic#p1228398

I noticed a difference when I went from a 4-wide 'drop to a 5-wide drop with my Tacoma.

T

[lfhoward]

Thinking about the TV and trailer as a single unit is a good idea. If the trailer is the same height as the tow vehicle, the loss of mpg should mostly be due to extra weight and not so much increased wind resistance. Boat tailing the trailer would certainly help as well.

For mine I built my trailer taller than my TV, but planned the design so that the 45° inclined front would start at the same height as my Jeep’s roof. I figured this would be better than a straight up box type design for wind resistance. My trailer doesn’t win any awards for aerodynamics but it pulls well and if I keep it at 62 mph or below I get much better mpg’s than at 70 mph. (Same is true for the Jeep all by itself.)

[working on it]

Thinking about the TV and trailer as a single unit is a good idea. If the trailer is the same height as the tow vehicle, the loss of mpg should mostly be due to extra weight and not so much increased wind resistance. Boat tailing the trailer would certainly help as well.

For mine I built my trailer taller than my TV, but planned the design so that the 45° inclined front would start at the same height as my Jeep’s roof. I figured this would be better than a straight up box type design for wind resistance. My trailer doesn’t win any awards for aerodynamics but it pulls well and if I keep it at 62 mph or below I get much better mpg’s than at 70 mph. (Same is true for the Jeep all by itself.)

* I was thinking along those lines, when I started my trailer build. And then, because I had built too heavy for my originally planned tow vehicles, I threw aero out the window, and relied on the brute strength of my pickup to tow it with (it doesn't matter what it weighs, the mpg's stay the same). The airflow over the tailgate pretty well matches the spot where the trailer's front slope begins.

* from another thread http://www.tnttt.com/viewtopic.php?f=2&t=67589

My original concept was to make it simple, strong,and with a 45 degree front slope for aerodynamics (since I couldn't bend 3/4" ply). The Kammback was also in the original plan, though I used a semi-rigid piece of conveyor belting to create the Kamm effect. Aerodynamics was always a factor of the design, because I had intended it to be towed in the air shadow of either my wife's Cobalt (@55.5 inches roof height, and roughly 40 inches at the trunk), or my HHR Panel (@63 inches roof height), while the trailer's front began sloping back @ 40 inches, rising to the roof @70).

* But, it ended up way too heavy to be towed by either (1600+ lbs, way over their tow limits of 1000 lbs each). Ended up towing with my HD truck, so the aero is not a factor, nor the weight. The trailer doesn't affect mpg at all; truck doesn't even notice it there. That's ok, though, since I started out wanting it to be semi-off-road capable, despite the Cobalt or HHR not beng capable of off-roading in the least, so weight be damned, I was able to keep adding more features (+weight) and a stronger undercarriage (3500lb axle, heavy-duty springs) to make it more off-road capable.

* Since then, the trailer weight grew to 2150+ lbs, and I built racks on the front/top (and now sides) to carry all the gear, so the aero is even worse. I did clean-up the open-bed of my truck recently, and covered it with hard panels, so it probably counteracts some of the negative aspects of the trailer's shape & exterior cargo. Another thing that possibly helps: the raised conveyor belting on the rear top edge of the trailer (it covers the gap when the hatch is opened) breaks up the linear flow over the top, and reduces the suction/partial vacuum at the rear.

stiff conveyor belting used to cover hatch "gap" when opened (shields gap, breaks up laminar airflow to decrease suction effect behind trailer)

top deck airfoil.JPG (109.08 KiB) Viewed 769 times

[pete c]

I have done a search and found a lot about aero, but not much about putting fairings on the TV to clean up airflow.