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cbjroms - n/a
19-Oct-08, 04:03 PM
My son & I are building a hovercraft as a 'bonding' project. We are just fitting the duct to the hull and are about to fit a set of flow straighteners.



My questions are:



a) One end of the flow straightener is virtually straight whilst the other has more of an aerofoil curve and is longer. Am I correct in thinking that the shorter, straight end goes into the stator/cone and the longer, end with the aerofoil goes into the duct?



b) What is the optimum seperation between the rear edge of the fan blades and front edge of the flow straighteners?



c) Am I correct in thinking that rear edge of the straighteners should be at 90 degrees to the duct?



Thanks in anticipation.



Chris

Bob Beech - n/a
19-Oct-08, 07:32 PM
Chris - You might find it useful to go to the home page and click on the downloads button in the left hand menu.



There is a very good article by John Bucknall on Stators - flow straighteners.

Keith Oakley - n/a
19-Oct-08, 07:50 PM
To reduce noise generation the optimum separation between the fan tip and the leading edge of the flow straightner is 100mm+

nickyd - n/a
20-Oct-08, 07:41 AM
Chris, andwers to your questions:



a) yes, from your description that sounds right. Although you should have specified which way your blades will be turning when you ordered the straightners. Therefore there will be only one way round for them to go. Does that makes sense?



b) as Keith said. apparently moving the straightners away from the fan does not reduce performance but does reduce noise.



c) yes, well all the ones I have seen or fitted are. a picture tells a thousand words. Could you post a pic?



Good luck with it all





Nick

cbjroms - n/a
20-Oct-08, 10:11 AM
Thank you for the replies. The help is much appreciated.



I had read John Bucknall's excellent article which helped alot but still left me with the basic questions.



Having received the replies I am now confident to start cutting and sticking.



Thanks again.



Chris

Jamie Lewendon - n/a
20-Oct-08, 10:04 PM
You should also think about the scrutineering requirements. You should not be able to get a 300mm disc any closer than 250mm to the rear of the blades. This effectively means that the back edge of your flow straighteners are 250mm from the rear edge of the fanblades. Unless your rudders/elevators leave no gap bigger than 300mm diameter.



Jamie