I read through most of the posts and you have a lot of helpful advice. The only reason that I write is because I have towed a lot of different types and sizes of trailers over the years. I have the most experience towing a small utility trailer. That is because I often have left it hooked up to my van for days or even weeks at a time. My current little utility trailer is only rated for 1,200 pounds but I have carefully hauled over twice that amount on occasion.
I also started out hang gliding nearly thirty years ago, moved on to a homebuilt ultralight aircraft and eventually purchased a general aviation aircraft about 20 years ago. So I have a bit of familiarization with aerodynamics.
I think that you are overthinking your problem. There basically is almost no chance that your pop-up camper would be capable of developing enough lift to get its wheels to break ground. As others have said... behind your SUV a 3ft high trailer is going to be almost completely sheltered from the wind. The wind shadow behind your SUV is only going to increase as your airspeed increases. IN this shadow the air is going to be turbulent and unable to develop lift even if the trailer formed a very effective airfoil with an optimal angle of attack.
Surprisingly one of the greatest hazards that you are going to face with your short little trailer is forgetting that it is behind you after first getting into your vehicle. Try not to park where the first thing you will be doing is backing up. I can almost guarantee you will eventually get distracted take a quick glance in your rear view mirror and forget that the trailer is there. Unlike a larger trailer... it literally takes only a few feet and your trailer will jack knife and you will have damage to both the back of your SUV and to your trailer. Unfortunately, this is the voice of experience talking. This is one of the reasons I normally leave tall plywood sides on it. What I am hauling can’t fly out or be easily seen in a store parking lot but it also is easily seen in the mirrors.
I do like to get the proper adapters to level my trailers out. They just look stupid when they are tilting one way or the other and also water will get in and be trapped in low spots. I also have replaced the ball couplers on all of our small trailers so that they all take 2” balls. It is just much more convenient for us. Harbor Freight may have one that will fit your pop-up trailer.
As far as trailer brakes on a little pop-up trailer... if the trailer has them already installed by all means get a controller. If the trailer doesn’t already have brakes depending on the size of your tow vehicle they are probably overkill. I have had to hit the brakes on the freeway so hard that the trailer has actually come off the ground. Always leave extra following distance when you are towing a trailer because it will take longer to stop whether or not you have trailer brakes.
Thanks for the info. That’s probably more useful than a simplified formula of some sort, esp. since you know something of the aerodynamics.
Now, granted, the top of the pop-up is actually 51” off the ground (in the front), and it is significantly wider than the SUV (at ~62” (effective width?) for the SUV.) But, still, your point about lack of lift should be right — at least as long as air isn’t actually compressed under the pop-up. The “tilt” may not be enough to accomplish much compression. Still, 90 mph is a lot of energy. (Think of it as more like “hydroplaning” on air, than actual “lift”, perhaps.)
Just for fun, assuming one could generate 1 psi, taken over the bottom surface of the trailer we’d have 1030 lbs. of lift. The pop-up would not “fly” with that assumption — it’ll be between 2 and 2.5 k lbs. depending on how much we put in it. Whether there’d be any control issues, I don’t know.
As for backing up, since I have only, oh, maybe 100 hrs. of towing experience, I try to avoid backing up situations like the plague, though I do sometimes run into them with our utility trailer, and, of course, the boat. The pop-up is wider than the SUV, so it’s hard to miss in the side mirrors - in fact, I’m considering adding mirrors that set further out, so I can see around the popup! As for the rear view mirror - hmm, you’ve maybe given me reason to add a mount for a US flag! :-)
No prob. on the ball adaptors other than the “not enough drop available in a Class II adaptor from anyone” problem. We have Tractor Supply, Rural King, Lowes, Wal Mart, Menards, and Harbor Freight, all within a reasonable distance, and for anything they don’t have, if it’s made, etrailer.com is a couple mouse clicks away...
Appearance? Yeah, “that too”: The pop-up DOES look a little stupid with even a 1 deg. tilt.
The (proportional) controller arrived yesterday & I have 10 and 12 ga. wire, connectors, etc., so we should be set there. I didn’t have it for a couple “trial runs” or bringing the trailer “home” (~400 miles) using my Dad’s pickup truck: We were fine — just made sure to drive conservatively and think ahead. The truck handled the one hard stop that did occur anyway, well, but I also was convinced by that stop that if we use our Outback for short camping trips with the pop-up, the controller would be a very good idea.
There are also insurance & legal considerations. Most common (and “here”) is a legal requirement to have electric brakes on any trailer of 3000 lbs. or more, so we’d be a little under, but if (IF) we went to NY, any trailer over 1000 lbs. is required to have brakes. (What the heck - do New Yorkers try pulling 1500 lb. trailers with “Smart” cars, or something?)
Good link here: http://www.towshop.com/trailer_supplemental_braking_laws.htm
Anyway, thanks again!