Wind tunnel / road

[Ron Dickey]

I think I know what the answer is but for the sake of those who will answer it here it goes.
when pulling your trailer does the type of front end shape make a difference with wind and gas milage as you pull it down the road.

All I have pulled are Uhauls.

George T. made one with a flat front, the weekender is semi round, teardrops are round, airstreamers are like bullits

Ron D.

[David Grason]

I have an 1971 Chevy ¾ton C20 Camper Special. It's getting restored right now. But when I first bought it, it came with a huge 11ft slide in truck camper. It had a big section that extended over the cab so that we could sleep up there. It was a neat camper and all but the first camping trip we took in it was to Fall Creek Falls here in Tennessee. It's about 120 miles from Nashville. My truck has 2 gas tanks on it and left with both tanks completely full. We emptied one tank getting there and the other tank getting back and I ran out of gas on the way to the gas station Monday morning when I headed for work.

Without that camper though, that truck has alwasy gotten 10-12 MPG. For reference's sake, it has a 350 smallblock with a TH350 tranny. I wasn't running the air conditioning that trip either because it was early in the season and the weather was nice.

Yes, I could tell that the camper was catching a LOT of wind running down the road. Even with the truck being a ¾ton, the 18-wheelers were pushing me all over the place. It never felt stable.

[Arne]

I'm going to do a test this afternoon. Shirley will drive, I'll be sitting in a 55 gallon plastic drum on top of her car. She will accelerate slowly and record the speed at which she hears the 'thump' of me falling off the top of the car onto the road.

Next, I'm going to cut a piece of 3/4" ply with the same 'wind shadow as the drum) and attach 2 handles. Again, I'll be atop her car holding the ply square to the wind and she will accelerate slowly until she hears the thump of me falling off.

We have to do the drum test first, because I plan on cutting two pieces from the drum to duct tape to my sneakers so the coefficient of friction will be the same.

The tricky part is I think drag increases as the square of the velocity, so the drag at 20 mph is 4 times the drag at 10 mph, but I'll figure that out and report here as soon as we get back from the hospital.....

I want to settle this debate once and for all time.... in the interest of science, of course.

[JunkMan]

My vote is just a guess, but I think the curve makes a difference. A lot of newer cars are getting better mileage by removing rain gutters, and having flush mounted windows.

I pull a 35' 5th wheel that grosses 10,000 pounds with my pick-up, and get the same mileage with it in tow as I do when I have a 10' pop-up pick up camper in the back. The pop-up probably weighs 1000 pounds, but the shape of it really kills my fuel mileage. I'd hate to see what my mileage would be if the camper wasn't a pop-up!

I used to pull a 6' tall, 10' long enclosed motorcycle trailer with a Suburban. It got worse mileage empty, then I got with 4 Harleys loaded on a 16" open car trailer. The shape definatly makes a difference!

[An Ol Timer]

Most of your scenarios are refering to a camper in open air. Take a Nascar race car with a damaged front end. If it is open to the air and running by itself the spped will be significantly slower than if it is tight behind an undamaged car and in it's draft. I guess that it might make a difference if you are going to have your camper beside the tow vehichle or behind it. Personally I prefer to tow it rather than out run it.

[BobR]

Aerodynamics and coefficient of drag are wonderful topics for engineers. Most tears builders can't afford to have both the tow vehicle and trailer put in a wind tunnel for testing. All I know is I get much better gas mileage towing my teardrop than my 19' Fleetwood. 5,000 lb. bricks aren't real aerodynamic.

In either case I don't care...as long as the beer is cold at the end of the ride

[Woody]

I have to agree with BobR as long as the beer is cold when I get there, who cares. With the double radius in front and at Highway speeds in the rain, I have seen the way my teardrop cuts the wind. Next time driving in the rain you will see the air peel away from the front to the back, there is not a large amout of turbulance behind the trailer with the misting from the roadway. There is more from the tow vehicle than the trailer

[angib]

I'm interested in road vehicle aerodynamics and there is only a limited amount of work that has been done on travel trailers/caravans - lots on truck trailers, but little of that transfers to travel trailers.

Here's an illustration from a European test on roof deflectors for trailers:


However, none of this reading is as interesting as Arne's practical experiments. Arne, I do hope you you are going to video your experiments - then when the staff in the hospital say "How did you get these injuries?", you can just replay it for them!

Andrew

[SteveH]

Should probably stay out of this thread, but sometimes I can't keep my mouth, or fingers quiet.

I've never done any testing of course, but I do have a lot of experience pulling trailers. I've pulled many differnt kinds of boats, many different types of pull behind travel trailers, box utility trailers, and flat utility trailers. It is my opinion that shape is very important in the aerodynamics of pulling trailers. I've had two relatively square travel trailers, a Holiday Rambler 24', and a Mobil Scout, 19', and they were horrible to pull. I also had a 20' Argosy, a 23' Avion, a 24' Argosy, and a 23' Airstream, with the 20' Argosy being a single axle and by far the easiest to pull.

The rounded trailers were by far easier to pull than a square trailer. So much in fact, that I would not in any circumstances, own a square travel trailer ever again.

However, an interesting observation that I would add, is that the angle of the wind can have more effect on the tow vehicle and trailer than the shape. Of course a tail wind is the best having a pushing effect. The worst, contrary to what some folks would think, is the quartering wind from the front. A wind that hits you from 45 degrees off head on will give you more problems with drag and tubulence/buffeting than a head on wind.

[Ron Dickey]

I'm going to do a test this afternoon. Shirley will drive, I'll be sitting in a 55 gallon plastic drum on top of her car. She will accelerate slowly and record the speed at which she hears the 'thump' of me falling off the top of the car onto the road.

Next, I'm going to cut a piece of 3/4" ply with the same 'wind shadow as the drum) and attach 2 handles. Again, I'll be atop her car holding the ply square to the wind and she will accelerate slowly until she hears the thump of me falling off.

We have to do the drum test first, because I plan on cutting two pieces from the drum to duct tape to my sneakers so the coefficient of friction will be the same.

The tricky part is I think drag increases as the square of the velocity, so the drag at 20 mph is 4 times the drag at 10 mph, but I'll figure that out and report here as soon as we get back from the hospital.....

I want to settle this debate once and for all time.... in the interest of science, of course.

whow wait a second. time out!!

take a househould fan get a stick set it ablaze get some simple toy cars and trucks and blocks of different hights and balles of different sizes and put them behind the small cars and trucks and after the stick is on fire awhile spay it with some water so it smocks set it infont of the fan and see what you get ... lot cheaper then the hospital.

and let us know what you get.
we want you sleeping comfortable in your teardrop.

Ron D.

[campadk]

The curve of the tear is better for towing since it looks better on the road

[Jolly Roger]

I drive an Aztek and if any of you have seen one you understand the strange slope of the back end. It results in the wind slamming right into the center of the front of my teardrop. I can certainly feel it. I'd like to find a spoiler for the Aztek.