Teardrops n Tiny Travel Trailers

I've been trying to come up with a profile I like for the Compact. I really like the Cabin Car but I like the interior room of the Compact. Sooo, I crudely had my way with Andrew's drawing of the Cabin Car.

I copied the front bottom curve for the back top curve. The last 5' of the top, up to where it slopes down, will pop up. The door in the back will be hard to build but not any more so than the dreaded hatch. Oh, and it will be 6.5' wide so the bed can go from side-to-side. So what does everyone think? Is this too ugly to pursue or is there hope for it?
Bruce

Bruce...I like it...but I'm confused on how the the back pops up...really a practical trailer, plenty of room...windows in the front too? Starting this winter? Doug

No hatch in the back, just a door to get inside, like a truck camper. It would be tricky to build because it will need to follow the curve up and its probably prone to leaks. I think the front foot or so will be a closet, like the Road Titan, so no window in the front. I've been buying parts on the sly so I can put together a mock up of whatever design I go with. I might get started this winter, depends if I can get enough done around the house before hand.
Bruce

Making a side-hinged door in a curved surface isn't actually impossible, but it is incredibly difficult. Top-hinging it solves most of the problems, except now it's a narrow hatch, not a door! A practical solution is to make the door a conventional flat rectangular shape, mounted in a projection from the curved body, as shown by the brown line:



If the projection looks too square for your tatse, you can slope its 'roof' downwards, on a curve if you wish, like the red line.

Andrew

Well, part of my goal in this project is to simplify the construction so I think I'll just change the profile instead. A small radius at the back top corner should fix it, say about 2" maybe? I'll have to check and see what the minimum bending radius of Filon is.

Oh, and I changed the window to the one shown in the compact.
Bruce

ach, 'twas better before!

What cad system did you draw tht up in?

Andrew, what about the aerodyamics of a flat back?

I can't recall if it is good or bad?.... or indifferent.

Laredo wrote:ach, 'twas better before!

What cad system did you draw tht up in?

I used TurboCad. I downloaded it for free from somewhere, didn't save a link.

I fixed the window, I like this better...

Bruce

Arne wrote:Andrew, what about the aerodyamics of a flat back?

I can't recall if it is good or bad?.... or indifferent.

Bad, about as bad as it geats. But, I'm trying to maximize interior room so I'll have to live with the increased drag.
Bruce

Sorry to spoil the teardrop-is-good story but a square back is just as aerodynamic as a teardrop - the air does not flow over the back of the teardrop, it breaks away from the roof at the galley hinge at the latest (or a hatch, if fitted), so that sloping back is purely for looks and serves no functional purpose.

The most aerodynamic shape would be a very gentle slope (no more than about 15 degrees off horizontal) to a square back - in other words, John Blewitt's Boxter:



But if the teardrop is in the wake of the tow vehicle (ie, every teardrop, unless towed by a Miata), I find it difficult to believe the shape matters much.

Andrew

Andrew,

I can say that the milage towing the escape hatch this weekend was terrible.

I'm sure that a/c on top didn't help much. Probably neigher did the flat vertical surface on the front.

I might have to get the saw out and do some chopping... and get rid of that durn a/c.

Mike...

Or build a fairing...

Andrew,

Yeah, you're right again. I went back and looked at the NASA paper you posted awhile back and a full boat tail rear was barely better than a flat one. I have to figure out a way to integrate the popup roof and solar panel so that they don't cause a bunch of drag. Maybe a fairing on the front of the solar panel since it will be closer to the front than the pop-up. I sloped the rear of the Boxcar at a guessed at 15 degrees. I'll refine it a bit as my CAD skills progress. I also plan on experimenting with vortex generators across the top of the back.
Bruce

When you are using a 3/4 ton Diesel to tow it with, aerodynamics doesn't matter matter that much.

I get 18mpg going 65 and 16mpg going 75 or 80. Doesn't seem to matter that much if there are hills. The new design will be increasing the frontal area by over 50% so I figure it won't hurt to try and throw in some easy aero fixes. Besides, I don't want to lower my top end.
Bruce