What is the difference between a hovercraft lift fan and a hovercraft propulsion fan?

 I'm researching to build a hovercraft, and I am not sure what the difference is between a propulsion fan and lift fan.  I can find a hovercraft propulsion fan that requires 19 hp, but an engine like that is too expensive. The hovercraft lift fan only requires 11.9 hp, and I can afford an engine like that. So I was wondering if I could just use the lift fan as a propulsion fan, if I ever decide to build a hovercraft. I understand the difference in the fans' functions, but what is the difference in the fan itself?
is it a different size, pitch or shape?
...All I really want to know is if I could replace the 'propulsion fan' with the 'lift fan'

sort by: active | newest | oldest
jscandrett6 years ago
None of your answers really answer the question. Thrust fans are designed to move the air at high speed with low pressure, where as a lift fan is designed to move the air at a slower speed with higher pressure. Using a thrust fan for lift only will likely cause the fan to stall due to the extreme blade angle. Combined Thrust / Lift fans are used for this purpose to satisfy both conditions in the beach craft.
frankenboom (author) 7 years ago
 i understand that the lift fan pushes air under the craft and the propulsion fan pushes it forward, but what is the difference in the fan itself?
 is it something with the pitch, or the size?
because there is a website that calls the fans lift fans and thrust fans, but they look the same...i was wondering if i could use one that says "lift fan" as a propulsion fan. 
heres the link

www.hoverhawk.com
(9th one down is a lift fan, but could i use it as propulsion?)
acidbass7 years ago
lift fan is for getting the skirt filled propulsion fan is for moving
Bartboy7 years ago
The lift fan fills the skirt with air, but the propulsion fan faces backwards and moves the hovercraft.

I was actually looking into building one, (A big one, that would have enough room for 5 people) but I  found that I could buy one for cheaper if it were used.
frollard7 years ago
Some designs use a single fan which dual-functions as both propulsion and lift. 

Small-beachcraft size ones like this have the functionality of working like a jet-ski (sea-doo).  When you idle the fan spins down and the craft slumps down and sits on its own belly.  When the fan spins up it both lifts the craft, and propels it forward.  This design is made possibly by a duct that takes some rear-thrust from the engine and forces it into the bladder underneath.
Burf7 years ago
Well, your question actually answers itself.
The propulsion fan propels the craft forward and the lift fan lifts the craft on a cushion of air.
I would say that the lift fan is going to be the critical part. If it is powerful enough to lift the craft, then the propulsion fan only needs to be powerful enough to overcome the craft's inertia and get it moving. More power than than that is for regulating the speed you want the craft to move forward.