Expert: Paul Soderman - 3/8/2010

Question
Hello Paul,my 2nd attempt! I am a trade qualified metal fabricator. I have two unused 505 HP Chevrolet 2006 LS7 crate engines which i will be installing on a 7-10 metre aluminium
WIG (ground effect- sorry ) marine craft fabricated by myself in a twin pusher, twin alum ducted fan configuration. Imagine the letter H with the motor/fans thrusting rearward at the bottom of the H with the direction of travel towards the top of the H with the long sections being twin hulls and the cross piece being the wing with a chord of 5-10 metres, with possibly fold down short wing sections being in the shape of the letter U when looked at in an end view when in folded position.
I was researching airfoil design/section points for propellers,construction methods etcetera.
Maximum manufacturers engine RPM is 7000 and HP is 505 each,Direct drive off rear of crankshaft preferably to save weight and cost of gearbox. Could you please provide any tips or information about diameter (hopefully about 36 inch) blade width, airfoil sections at set points from center of rotation, balancing???? I have MIG %26 TIG welders, large lathe, pedestal drill and will fabricate the blades by TIG welding the two longitudinal halves together (after pressing an airfoilshape into one side) and machine the centre hub from a 10 inch by 36 inch alum bar, TIG (heliarc) welding blade sections to machined hub.
I think that about that about covers it, sorry about the long question!

Answer
Gregg

You haven't given me enough information to design a propeller.  I don't know what your machine looks like, what the control system would be, and what the performance goals are. But you can design a propeller yourself - go to http://www.mh-aerotools.de/airfoils/javaprop.htm and try the design code.  Some typical propeller airfoil shapes are also listed on the page.

Paul