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truckersnuts - n/a
10-Dec-07, 04:10 AM
hi.

Whats best for larger craft 1 thrust fan or 2?

ie. 1 bigger unit or 2 smaller ones

Can you run 2 fan units with 1 engine?

Hornet - n/a
10-Dec-07, 05:08 AM
1 Larger fan would be more efficient and is also simpler. Two fans means two belts, three pullies, two ducts more frame work and more weight.

Ian Brooks - n/a
10-Dec-07, 09:19 PM
The most efficient set-up is one large fan/prop for thrust, and a separate lift fan - either driven from a single engine (smaller craft), or twin engine (larger craft). The single engine type is far easier to operate!



Ian

jon_curtis - n/a
11-Dec-07, 05:39 PM
werent older craft fitted with two thrust ducts, due to only small fans being available and small ducts also?



you might think two small ducts would equate to one large one,(with the same hp thru) but thats not the case. the two smaller ducts will be less effiecent as one big one, you have more drag and more loss thru the drive train. smaller ducts generally have faster spinning fans compared to larger ducts, there is more noise etc etc



now when you say larger craft are you talking around the 12ft, 16ft, then an axial lift fan and prop for thrust would be the most effective setup, in my opinion! however if your talking about a craft bigger than this? then the use of a centrifugal lift fan is more effective than an axial fan. centrifugal fans are available around the 1m + diameter and would give tonnes of lift.



A good example are the old hoverhawks, dispite the funky look of these things (which i like), they had a centrifugal lift fan and therefore nice amount of lift, however they had two very small thrust fans, and the engines were very close to the duct inlet, ergo they had pretty c**ppy thrust!