Hi again... thanks VERY much to everyone who helped with my questions on the below thread:
https://singletrackworld.com/forum/topic/building-dirt-jumps-putting-dirt-over-brick-piles/
After checking out my friends garden it seems the ground is pretty nice...but a bit soggy, think thick grass on clay soil...ground is a bit bobbly/tussocky and it's pretty dang soggy when wet.
Do folks just ride a trail into the ground and just stick to when it's dry...or would we be better doing something to the ground like gravel or whatnot? Once again we're rank novices and any tips would be greatly appreciated, especially ideas that are cheap. We've almost got enough old palettes to do a boardwalky kind of thing in between the jumps, but then we want kids to be able to crash on it safely. Ta again!
You need to dig out all the topsoil down to the clay. Then use the clay to build the trail/jumps.
Topsoil will
a) turn to mud as soon as it gets wet
b) erode quickly
c) not set hard like clay.
If you build it properly from clay and let it dry out it will set almost like concrete and last a very long time as long as people don't roll or case the jumps or ride in the wet. In an ideal world, you'd cover the jumps in pond liner between sessions to keep them dry, then put a few watering cans over them before use to stop the surface from breaking up.
You'll also need to sort out drainage, make sure each section slopes somewhere so you don't end up with puddles. So if the trails run downhill, make sure it's not just creating puddles at the foot of each take-off.