Hi
There's not a lot of information on them, they're a bit vintage these days. The Hovercraft Museum did have an operational one and might be worth talking to, especially about the skirt, they may have some information or even patterns. Otherwise we can try and help from first principles.
First a few questions:
When was it last working well?
Has there been any changes recently, such as a new fan, belt, pulleys etc?
How many blades are in the fan?
What engine?
You mention the skirt, have you a reason to think it's in poor condition?
Ian