Originally Posted by Hersbird
Just curious how the by the book, engineers need to be 100% trusted, the letter of the law towing guide needs to be followed, crowd get past the Ford F150-F450 60 sq ft frontal area limit for bumper pulled trailers? The trailer the OP posted about is at least 72 sq ft, and I bet most of the 5ers around here are over the 75 sq ft limit as well for those. I agree engineers need to be trusted but I don't believe engineers are the only folk involved in what number Ford puts out.
I'm an engineer for one of the biggest defense contractors in the world. We build stuff with limits or "do not exceed" for a reason. Why? Because people will die if it's not used as intended, expected, or beyond limitations. We've tested it and engineered safety margins in to it. We know that the safety margin drops dramatically if you go beyond a certain point. The laws of physics cannot be broken casually like a 55 mph speed limit! They are real and when you try to mess with them, the wheels fall off quicker than a Chinese motorcycle.
I'm not familiar with those frontal area numbers, but I would imagine it has to do with wind load at speed. Does it mean from frame rails upward to where the front starts sloping back? Or is it from the top of the tailgate of the tow vehicle to top of the trailer since this is realistically where most forces are applied? If you go with full frontal, that's probably 8 x 8 ish and at the 60sq ft mark. I would imagine most travel trailers would fall into this limit these days given the sloped fronts, etc.
As far as the forces applied, think of it this way. Ever carry a piece of sheetrock or plywood? I can carry 2 sheets at a time. And then on days with a breeze, carrying one sheet is an adventure! If its a 12 foot piece, you better get 2 people. My point is that the slightest amount of wind load influences a flat surface more than you can imagine.
Same goes for the frontal area of the trailer. Get it up to 60mph and that is a LOT of wind load pushing on the tongue and influencing the back end of the tow vehicle. Have too big a "sail" area and you end up with the tail wagging the dog. When you increase the frontal size, you increase the forces exponentially and you can go fast enough where that force is exceeding the influence the tow vehicle has to keep the trailer on track.
In the end, physics and the math behind it are constants since the days Newton put them to paper. Calling BS, ignoring them, or using "gut feeling" does not make them go away. If the manufacturer says "don't do this", as an engineer I would tend to agree.
I respectively say, do what YOU think is best for YOU and YOUR equipment. Safe travels everyone!