For RC/UAV uses, a balsa core laminated with carbon fiber makes an ultra light construction panel with very high stiffness. While you can buy ready made panels (usually expensive), this video shows how easily you can make it yourself with no special tools.
This video does not pretend to show the best way of doing these panels. It is merely one quick and cheap way of doing it (like using a vacuum system , use rollers to spread and squeeze the excess resin out, etc)