Too many non linear variables for the heavy duty math required. It will look like a log table when done for actual loads given wind speed.
That was my first thought too... But I want to get to the ROM point of how much is too much.
My driveway setup is a lot like the HD picture I posted in the beginning. So I dont want a lot of stuff out to the side, blocking access of the other door, etc. And I dont really care for a ton of concrete filled buckets or bags or cinderblocks. If it goes to that pount, aesthetics matter more to me, and Ill spend a few thousand dollars to get a legit carport engineered and built (probably the best scenario anyway).
So I really just want to get a grasp of if I need 100 lbs or 1000 lbs to keep it down in a reasonable breeze (say a gust of 45MPH.
My FIL has a similar structure to keep one of his boats under, and he is in a very windy area. He removes the tarps for a hurricane, but theyre up otherwise and it holds up fine. The difference is he has a concrete pad and has some bigger anchors holding the whole thing down. I have asphalt in that part of my driveway, and so Im not sure if anchors would work, or if they have to be really large to hold properly underneath.
My ideal is a half cinderblock (Lowes sells these near me), on each leg, and the plastic "foot" (which keeps the metal leg 1/8" off the ground) and leg through-bolted to the cinderblock.
This would make the foot only ~12x12, very low profile, and easily moved if I wanted to move it (I do want to be able to temporarily remove one middle leg to maneuver cars through it.
Thing is, six half cinderblocks at 14# each is only 84 lbs...
So if I use the uber-simple calculation, where P = 0.00256 x V2, where V is the speed of the wind in miles per hour (mph) and P is in pounds per square foot (PSF), and the tarp is 10x18' or 180ft2, then,
@ 25 MPH P=1.6psf x 180sf = 288lbs
@45 MPH P=5.2psf x 180sf = 933lbs
But that would only be appropriate if the whole thing was perpendicular to the wind. The wind was (is) turbulent, and parallel (approximately) to it.
Seems high, though my child said they saw it lift up towards the clouds, and I did find it many feet over in my yard, flipped over...
So, using the NASA tool with a geometry approximately of the carport...
Camber as percentage of chord was handy once I found this... It is 20% in my case, barring more thought or better measurements of the carport tomorrow...
Yikes!!! 1952 lbs of lift?!???! So maybe 1000 lbs isnt so far off for a non-horizontal wind... But regardless, attaching cinderblocks (or even concrete buckets) to the bottom will just result in an additional 84+ lbs of more damaging mass flying up and down...
But wind probably isnt purely horizontal either... So....?