Wolf Creek 850 roll over story

BradW wrote:

Redsky wrote:
I did a rough calculation of the wind force side load on my 845 camper and with a 50 MPH gust the force is about 844 lbs., which is not all that much and countered largely by the weight of the camper. But with a 70 MPH gust the side load nearly doubles to 1660 lbs. of force. It's the gusts that will get you.

The problem is that all that force needs to be resisted by the two windward hold downs on the camper. The turnbuckles are designed to provide 300 lbs. of holding force or 600 lbs. per side so even a 45 MPH gust could overwhelm them.

Just so no one is confused, 1,660 lbs side force does NOT translate into 1,660 lbs of force on the tie downs. The force on the tie downs would be MUCH less. I assume your calcs are based on the wind being exactly perpendicular to the camper side? What are the odds of that?

Also, if there had been 70 mph wind gusts, you would have seen a LOT more dust blowing around in those photos.

Brad

Yep. Consider the lower left edge if the camper as it sits in the truck bed the pivot point. Multiply the wind force times the average height of the wall above that point (so maybe 1660 x 5 feet?). That's the rotational force hurting you. Now subtract off the weight of the camper pushing down at it's side-to-side center. I'll use a conservative (3000 x 2 feet).

1660 x 5 - 3000 x 2 = 2300 ft-lbs. This means a wind like that could start to tip over an unsecured camper.

Figuring the tiedowns in, they are about 6 feet horizontakly away from the left edge. That means even with only one tiedown, it need only hold 384 lbs to stop 2300 ft-lbs.

The truck was either tilted, bouncing or that tiedown was already compromised before the wind hit or some combination of these.