The GH-2 is a little more complicated than the GH-1, but if you can understand the GH-2, the GH-1 is a breeze.



The GH-2 hovercraft has a lift duct in the front and a thrust duct in the back. The lift duct sends air underneath the craft where it forms a cushion of air which supports the craft. The thrust duct sends air out the back to provide thrust and send the craft forward. As the air is sent out the back, it flows past rudders which help the craft go straight.



The GH-2's thrust duct is held up by a part called an airbox.



The Goldstein Hovercraft airbox has a trick up its sleeve: a trap door. As the name suggests, the trapdoor opens and closes. When the trapdoor is closed, all of the air from the rear duct is sent out the back to provide thrust. The GH-2 is normally operated with its trapdoor closed.



When the airbox trapdoor is opened, half of the air from the rear duct is sent underneath the craft to provide lift. Since the craft is now getting lift from its airbox, the lift duct in front can be removed and used in a second hovercraft. Of course, with only one duct, the craft has only half as much lift and half as much thrust, but it also requires half as many batteries. It is nice to have a choice.

---

The GH-1 hovercraft comes with only one plastic duct, so it always operates with its airbox trapdoor open. The GH-1's cabin and hull are optimized for one duct operation by being smaller and lighter.