RST Engineering wrote:
I'm going to make some offhand assumptions:

1. This is Wisconsin dirt covered with either green or brown grass quite
evenly.

2. The plywood will be 90% in contact with a supporting surface of
grass/ground

3. The airplane will weigh something on the order of 3000 pounds spread
evenly over all three wheels.

If this is true, then the plywood will have a supporting role 10% of 1000
pounds, or 100 pounds over a square foot, or a little less than 1 psi. My
best guess is that 3/8 would do, but beltandsuspenders would be half-inch.
That's what I'm bringing along.

Is that based on lessons learned in the North Fond du Lac mud two year's
ago? :-))