wind resistance

[Ron Dickey]

When I first built my trailer it was to be pulled by a truck with a cap.

My trailer is only bowed in the front at the top.

I am now pulling it with my Carolla and I can feel the wind as I pull it down the road.

on Man suggested I put a cargo holder in the front the shape of the curve on the front. He felt I should put what is in the trunk there reducing weight in the trunk and I realized this would cut my wind resistance as well.

The other idea I had was to put bars over the roof of the car and put a air foil or scup to push the air up.

Any thoughts on this??

[Trackstriper]

No suggestions as such, but how much difference did you notice with and without the trailer behind the PU with the cap, was it anything noticiable?

[Ron Dickey]

I don't know if you have ever pulled any of those little Uhauls but it is much like that you feel it kinda tuging behind you as the breeze catches be hind and then lets go.

Behind the truck although I did not drive it as far nor as fast I wall un aware that it was back there. Which is what most of the folks that have real Teardrops say.

Behind the Carolla which it shorter then the truck, though it does have a spoiler on the trunk the air did like it did with the Uhaul. the car is a foot shourter then the truck, and no cap so in the rear it drops another 2 feet. the spoiler might deflect some of that air but not much. which is why I thought of putting a rack on top with a Yakama carrior on top.

[Ron Dickey]

would not be to hard to make I have Yakima bars that will fit my car.
but luggage carrier would be more usefull.

or a over cab tent for guests to sleep in.

ron

[Alphacarina]

It's important to know what's going to be pulling it before you build and to design with that in mind - Still, with small cars you can easily be surprised when you get it done

I have a Mazda Protege 5 with the 2.0 engine in it and I've been pulling all sorts of trailers with it ever since we bought it 5 years ago. I've pulled flatbed trailers with machinery or motorcycles on them up to about a gross 1500 pounds and had very good results with surprisingly decent gas mileage

When it became evident that I was going to be pulling my classic CBX across the country a couple times per year, I really wanted an enclosed trailer for the job . . . . and I knew it needed to be kept as small as possible because windage has a much greater effect on my mileage than gross weight does

I bought a HF 1740 trailer and chopped it to 6 feet in length and then added a 2 foot Vee nose to it. Only 4 feet wide, 8 feet long (including the nose) and only 5 feet high from the trailer deck. I mounted the axle upside down to keep it as low to the ground as possible and the trailer weighed in right at 700 pounds when I was done

Since I've towed twice that weight across the country before with pretty good mileage, I was really shocked when I towed the empty trailer about 900 miles to go pick up the bike - The windage is absolutely terrible . . . . even with the Vee nose. I got about 4 or 5 mpg less towing this 700 pound trailer than I've got towing twice the weight on a flatbed trailer . . . . and the faster I go the worse it gets. slowing to 60 mph gets me about 2 mpg better, but it's still TERRIBLE . . . . and it'a all due to the windage. Only about the top 18 inches of the Vee nose sticks up above the roof of the little station wagon, but it's enough to really cause extra drag. The only 'good news' was that the mileage didn't hardly change at all on the return trip, despite the fact that the trailer was 600 pounds heavier (1300 total) with the bike in it . . . . and the guys with the pickup trucks said I should quit bitching about my 22 mpg, since they were all getting about half that

So . . . . if you have a small car and you are designing a teardrop to pull behind it, try to keep the top of the trailer about as high as the top of the car, if at all possible and round or Vee everything you can - Especially if you have a 4 cylinder car and you're concerned about mileage



Don

[Steve_Cox]

Ron,

I don't think the air foil on top of the car will help, because it wouldn't be close enough to the front of the trailer. Dale, the guy that built the Squiget made an air foil/spoiler and if I remember correctly it made a little difference but not much.

[Johno]

One way to see how the wind currents are working with your particular setup is to attach a few streamers that are long enough to go from the front of your car to at least the front of the trailer. Then you can drive down the road with someone else beside you, and take a few pictures of the effects of the streamers in the wind. Drive at different speeds and note the differences. The results of this can help you figure out what (if) anything can be done to improve the situation. This is usually best done early Sunday morning when there is little or no other traffic on the road.

- John -

[bobbruso]

Have you ever seen the curved (bubble-style) clear plastic covers for basement window wells? (I'd include a pic or link, but can't find the darned things on the web)

How about using one of those mounted on its side on the trunk of a sedan (like the above one, only more curved)?

Anyway, back to reality.

[KevinS]

I've noticed (being a newbie and not knowing how a tear is supposed to look) that few trailers have any streamlining on the underside of the tear, with all kinds of supports, etc., sticking out.

Does it not matter on the underside?

[caseydog]

There are a lot of things you could try, but I don't think anything is going to make a difference.

You are still going to punch the same size hole in the air, no mater what. You are still going to have the same horsepower available to punch that hole.

It may feel strange to you now, since it is a new experience, but as long as the TD doesn't hurt the car, you are probably best off to just live with it as it is. I'd hate to see you throw a bunch of time and money at this and not get much, if any, results.

Remember, as you go faster, the effects of wind resistance go up exponentially. With this car, you may discover what most Europeans who tow with small cars already know, that you just need to keep your speeds to 55 mph or close to it.

CD

[Sparksalot]

[quote}



Don[/quote]

Are you any relation to this guy?

[dcbrewmeister]

I don't think you are going to "fix" the issue by changing the wind. I don't know what kind of truck you had, but a truck is almost always more "qualified" to tow compared to a car. I haul a very heavy duty utility trailer (10,000lb capacity) with my truck, and it "feels" like I am dragging bricks on a rope. The sides and front is all open and just has a frame that is about 3' high, so wind resistance is nearly nil.

Unless your Corolla has a towing package, you're at the limits of what the can tow in the first place, so you feel like you dragging bricks on a rope and any breeze/wind will make it even worse.

Don't throw any money at the problem that you aren't going to be able fix.

[KevinS]

Have you ever seen the curved (bubble-style) clear plastic covers for basement window wells? (I'd include a pic or link, but can't find the darned things on the web)

How about using one of those mounted on its side on the trunk of a sedan (like the above one, only more curved)?

Anyway, back to reality.

http://www.windowbubble.com/metal.htm

Looks like $$$$$.

[Arne]

It's not that fact that you are punching the same size hole, it is how you punch the hole.... a flat surface to the wind is the worst... any type of improvement over that just gets better.

[dcbrewmeister]

It's not that fact that you are punching the same size hole, it is how you punch the hole.... a flat surface to the wind is the worst... any type of improvement over that just gets better.

True, but if the vehicle you are doing it with is at the limits of what it can do in the first place. The towing capacity of a corolla is ~1500lbs... how much does your TD weigh? I'm gonna guess you are somewhere around half to two thirds it's MAX rated, so performance is going to suffer exponentially, add people and supplies, and it just keeps getting worse.

A tow vehicle a Corolla does not make. It will do it, just don't expect a lot out of it, you are simply out of horsepower and torque, wind resistance is only one part of the whole equation.