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Nov 04, 2023

Don't Fall For Aerodynamic Junk Science When Shopping For Trailers (Especially For Your EV)

By Published For most people, the ultimate camper is one with as much luxury and

By

Published

For most people, the ultimate camper is one with as much luxury and as much space as possible. This often means something the size of a bus, and sometimes even bigger and taller. I get why people like that, but the cost of moving it around means you’d better have a pretty big budget for gas or diesel, or only plan for short trips. Or, when fuel prices are high, you may have to both do short trips and spend the big bucks. Ouch!

But, say you want to save money, lower your impact on the environment, etc.? Camping's a lot more fun without the cost and pollution, and if you aren't dipping into savings to afford weekend trips, you can actually afford to go use the thing! Assuming a tent doesn't work for your situation (that's probably the most efficient option), the only way to really do that is to find an efficient RV. And, this is even more important if you’re going to tow with an EV.

But, there's a dark side to the efficient RV and cargo trailer industry. Where there are some impressively efficient designs, there are many more bogus ones that are designed to look efficient while not actually delivering the goods. From well-intentioned but poorly-executed designs, to older designs that have proven to not be that great, to outright fraud, there are many ways to get taken advantage of when shopping for an efficient trailer.

Some companies (like Colorado Teardrops, whose image sits atop this article) do real engineering and come up with designs that would really work to save you fuel and/or energy. But, unlike a car, there's no EPA MPG or MPGe rating for cargo and camping trailers, so they can pretty much make whatever vague claim they want. So, there are a few things you need to know to not fall for the gimmicks and junk science.

I’m not going to spend a lot of time on weight reduction in this article. Why? Because choosing a lighter camper is easy and it's hard to lie to people about weight. The weight of a trailer can be verified easily at many truckstops and other places where a scale is available. If a trailer manufacturer misleads people or just gets the weight wildly wrong through incompetence, that's going to be noticed. So, the numbers you get from the manufacturers and dealers should be accurate as long as you understand that the dry weight doesn't include anything you put inside the trailer.

The other reason I’m not going to discuss weight is that it doesn't matter all that much in the big picture as long as it's within 80% of your towing capacity. Testing has shown time and time again that adding weight to a trailer doesn't affect fuel consumption very much unless there's a big climb along your route. But, poor aerodynamic designs can cost you a lot more than adding weight.

Here's a video showing one of the tests that proves this:

There are some fantastically light camper designs that don't perform because they’re tall and don't do anything else to make up for that, so be sure to not shop based on weight alone.

It's important to note before we get into design that properly-inflated tires, regularly greased bearings, and other maintenance items can heavily affect efficiency. If you don't take care of those things, even the most efficient trailers won't save you from expense and disaster.

The next step up from tent camping (at least in terms of driving efficiency) is probably a tiny "teardrop" trailer. They’re small, they’re light, and they give you a warm bed to sleep in. They keep the bugs out, and if you get a nicer one, there's a little kitchenette in the back. Some of the medium-sized ones even have a little bathroom. Most people want more, but we’ll get back to that in a minute. Let's take a look at one in a short video (or, just look at the image as you scroll past to get an idea of what it looks like).

These small teardrop campers are a great study in efficiency, both because they can show us the way to get it right and because they show us the way to get it completely wrong.

The real teardrops, and the ones with the best efficiency, have a fairly blunt front, a sweeping curve, a fairly long "tail", and a relatively sharp back end. They do this because that's basically the most efficient shape you can make to pull through the air. This may seem counterintuitive, to have the front of the teardrop shape be bigger than the back, but the science of aerodynamic design actually backs this.

What it all comes down to is that there are two kinds of drag that resist an object's movement through the air. First, there's the friction drag, or the resistance of the air passing along the surface of the object. Second, there's the pressure drag, or the drag of the vacuum the object leaves behind it as it goes. These two things are related to each other, but when it comes to designing trailers for maximum efficiency, the big thing to look at is that vacuum zone behind the trailer.

The teardrop shape works great because it lets the air slip along the surface of the trailer, come together neatly in the back, and make only a minimal vacuum zone behind it (if any at all). But, make the tail too stubby, make the front too flat, or otherwise depart too far from that teardrop shape, and you start introducing vacuum zones again or introducing friction drag along the surface. That teardrop shape strikes a careful balance, and you can't rebalance aerodynamic forces through wishful thinking.

And, sadly, many teardrop campers are posers that look kind of like a teardrop but just aren't. Among these teardrop missteps are the "squaredrops," cyberdrops, and other designs that try to give you a slightly more human-useful shape at the cost of introducing some drag back into the mix (or worse, introduce a lot of drag back into it). The problem with most of these shapes is that they try to substitute curved edges (which people think are aerodynamic) for actual aerodynamic engineering, which favors a more blunt front and a sharp rear to achieve the balance you’re actually looking for.

In Part 2, I’m going to discuss one more aspect of aerodynamic design, talk about how to actually optimize non-teardrop campers, and discuss some of these fake aerodynamic gimmicks in more depth.

Featured image: a screenshot from a video showing actual aerodynamic simulations of a teardrop trailer. Image from a video by Colorado Teardrops (a company that actually does some aerodynamic analysis).

Jennifer Sensiba is a long time efficient vehicle enthusiast, writer, and photographer. She grew up around a transmission shop, and has been experimenting with vehicle efficiency since she was 16 and drove a Pontiac Fiero.She likes to get off the beaten path in her "Bolt EAV" and any other EVs she can get behind the wheel or handlebars of with her wife and kids.You can find her on Twitter here,Facebook here, andYouTube here.

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