Transforming my trailer via "the template"

[Varn]

Good job on the trailer.

I thought that I had a pic of Steve Delaire's aero trailer. His was 2D shaped much like this car.


Teardrop shaped when viewed from above. I recall that it was about the same height and max width as his vehicle.

He used it to haul his bicycle streamliner. Told me that it improved his fuel mileage 3mpg when towing with his van.

He shaped the main structure (1" square tubing) by screwing appropriate wood blocks onto the deck behind his home. Then he pulled the tubing around the blocks making 4 equally curved shapes and spaced them with straight sections. The door was on one trailing panel. That had a piano hinge with the clasp at the point at the back.

[Hersbird]

Varn, I was curious if the trailer shape you describe would be prone to sway problems. That shape would be better for a stand up camper then the traditional teardrop style but I'm worried it will wag like a happy golden retriever.

[Varn]

IYO hersbird, who do you think it to be unstable? The way Steve described it to me it sounded win/win. Particularly considering the lightweight quick build. I am pretty sure I took a pic.

Back to the topic....

[Hersbird]

I don't know, I'm just asking. Most aircraft need a vertical stabilizer. I just wonder as you start to get slippery upright especially if there is a slight difference in manufacturing side to side or a cross wind if it wouldn't start to load and unload and just keep getting worse.

[aerohead]

Originally Posted by Hersbird

Varn, I was curious if the trailer shape you describe would be prone to sway problems. That shape would be better for a stand up camper then the traditional teardrop style but I'm worried it will wag like a happy golden retriever.

I've no data for trailers,but VW had a 'drop' form body,created by Rolf Buchheim and his associates in 1981 which is shaped like Varn's description of Delaire's trailer.
This 'car' had around Cd 0.16-0.15.Nothing is mentioned about directional stability in Hucho's book.
In Hucho's section on trailers he does mention that leading edge radii can impact yawing moments.
This trailer body type would make for a nice graduate,scale model wind tunnel study.

[Varn]

Delaires bike is in the background. His trailer is opened up, the rear right side is opened forward exposing the inner panel of left side. It is difficult to visualize the shape but you can get an idea of its size.

[freebeard]

Originally Posted by Hersbird

Varn, I was curious if the trailer shape you describe would be prone to sway problems. That shape would be better for a stand up camper then the traditional teardrop style but I'm worried it will wag like a happy golden retriever.

It sounds like your concern is with a vortex street. You'd get that with too low a fineness ratio.

[Hersbird]

Is that what brought the Tacoma Narrows bridge down?

After reading the wiki article it says Aeroelasticity is what brought the Narrows down.
Yes this is the kind of thing I would worry about. In a car or bike with wheels at each end there shouldn't be a problem but on a single axle trailer already potentially with sway a problem, I just was wondering why we haven't seen boattail trailers since the earliest days.

[freebeard]

Ummm, we have....
http://www.tincantourists.com/wiki/doku.php?id=bowlus#.U7Q3Ver-mkI

[aerohead]

Originally Posted by Hersbird

Is that what brought the Tacoma Narrows bridge down?

After reading the wiki article it says Aeroelasticity is what brought the Narrows down.
Yes this is the kind of thing I would worry about. In a car or bike with wheels at each end there shouldn't be a problem but on a single axle trailer already potentially with sway a problem, I just was wondering why we haven't seen boattail trailers since the earliest days.

My single-wheeled trailer went across Texas,New Mexico,and Colorado at speeds up 80-mph and I experienced nothing unusual in handling.
She is a 'pumpkin seed' design,rather that a section/strut,so I can't vouch for those,but a 'classical' half-body is rock solid on the road.
Goro Tamai of MIT reported in his 'The Leading Edge' that these flattened torpedos are very stable,including crosswind gust.