HDU is awesome to work with. It comes in various weight ratings, from 10 pounds per cubic foot to 90 pounds per cubic foot. It is a foam, but FAR more dense, and it has none of the characteristics of wood. Imagine carving a frozen stick of butter, or a large bar of soap. It is like that. HDU is closed cell foam, so it will not be saturated with water in rain. It will not crack or warp. It can be cut, glued, shaped, painted, etc. It is fantastic stuff for these types of projects!
The trade name is "Sign Foam" but it is sold under different names. HDU (High Density Urethane) is the way to go for CNC routing and carving.
Last edited by The Hobbyist; 12-20-2019 at 11:09 PM.