Aerodynamics - One Hundred Years of Missed Opportunities

[Pmullen503]

Very interesting.

[twisted lines]

Take a look at what one company that is focusing on aerodynamics is doing - Polydrops. Their page on aerodynamics makes it easy to understand why a well-designed "boxy" camper can massively outperform traditional designs in this respect.



Incredibly, 5x more aerodynamic than a standard teardrop!

Very interesting Indeed;
I am just finishing the top two rear pieces today, have the walls cut straight.
Tapering the rear down now; was easy

[kd8cgo]

I don't like that trailer for some other reasons too, like the door placement, lack of the integrated galley, size/features I'd like to have (and of course the $$$) - but they are showing some nice ability to step outside the normal and get some practical results, which is laudable! It's basically just a foamie with a laminated aluminum skin from what I can tell. They have some kitchen module that hooks on the back hitch instead of an internal galley on that one model, a kind of chuck box arrangement I guess. A cool proposition and pretty creative overall build nonetheless!

[Pmullen503]

An interesting result was that a tongue box and their kitchen pod on the back reduces drag significantly.

[kd8cgo]

I saw that too, this is of course possible; filling the space up between the vehicles is supposed to help, but it also partially block that strange front tunnel they've created, which is a unique thing I'd not seen tried before. Adding stuff to the back could help or hurt, I guess they shaped it so it would help, at least according to the CFD output... These results from the page are also just CFD analysis, which is to say it's StatisticalWildA$$Guessing, with extra steps and better graphics. They've done two little videos on YT with some short trip, <55 mph testing that looked somewhat promising, but that's all the real world experimentation I've personally seen from them. Take with grain of sand, add salt to taste. I hope to see some more detailed owner reviews of these some day.

[twisted lines]

Now the warnings
I was cutting my side walls down while you posted that!
2" in 8'
Ill be ok I am going for the tapered rear as well as a top drop the last 12"-13"
My deal on #2 was mileage; drop with #1

[kd8cgo]

Oh my! Well we can't bake any cakes without breaking a few eggs! I think it will turn out

[StaceyK36]

Has anyone seen this Safari Alto A2124? They’re saying the shape reduces drag by 15% (47% of their other models) and the shape looks like it might be a little easier to replicate…sort of! They changed the frame so that it’s smooth underneath….





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[kd8cgo]

First I've seen that model, but I know that other Alto models have some really nice design elements. It looks like it follows many recommendations for aerodynamic improvements, I like it! I've seen their teardrop-shaped pop up roof Safari Condo model before, also cool!

[Rustic313]

Just kicking this around, and looking at the shape plus the polydrop...

Rather than a rather difficult to build curved shape, I think you could probably just use straight angles and get 80% of the way there. Keeping everything straight opens up the use of easy to source and work with construction materials too like sheet plywood, aluminum panels, roof panels, etc.

DESIGN ONE (SIMPLEST)
- Front: Straight vertical up until you get to the window height of the tow vehicle, then a slanted piece at approximately a 45 degree angle to get to the roof peak of the trailer.
- Slightly sloped long roof back to the vertical line marked "15 degrees."
- Rear: Chop it off straight down at that point. "Kammback."

That is basically what the polydrop does with their smaller trailer, except instead of going straight up at the front and back they have a slope. For a DIY home build "KISS" seems to just call for going straight up and down.

This is pretty simple: You have two straight vertical walls, and a roof with two different angles on it. Water runoff is not an issue.

Eyeballing it with the help of a CAD sketch of a basic steel trailer on the ecomodder tool, if you are 4' high at the peak of your interior box space (4x8 sheet of plywood... and keeping the total height shorter than a sedan or CUV height), I think you can go about 10' long if you chop it down at the 15 degree mark. If you're 52" high at the peak of your interior box space, it looks like you can go about 14' long.

DESIGN TWO (HARDER)
For a longer trailer you could put a "bend" in the roof piece, effectively having a fairly long gently sloping roof, and then a bend to a steeper roof segment towards the back. Exact placement depends on the length of the trailer vs. the airfoil template, but the slope clearly gets steeper the further back you go.

Looking at the CAD drawing of the steel trailer, I think I'd probably go with a gently sloping roof to the fourth line (between those marked 25 and 15 degrees -- can't quite read it), then a steeper roof to the 22 degree mark. This lets your design be about a third longer.

This is remarkably similar to what Polydrops does with their longer trailer.

Depending on how you do this you could also have that second "bend" be hinged for a kitchen space. From a practical point of view, honestly most of the space aft of the line marked 15 degrees seems pretty marginal in utility. The headroom is getting really quite short. And as interesting as having the rear galley is, adding that hinge adds more water intrusion problems (just google "teardrop galley leaking" -- seems a common issue).

I guess it could also be useful if you had something with extremely low height, but I can't imagine going much shorter than 4' tall.

I also honestly don't know how practical this is. I would certainly consider building a 5x10 DIY trailer, but a 5x20 seems like a lot.