When finishing the Atomatic 5, I carved suitable propellers.
It's not a difficult task - laying out the blank is the important part, and good work-holding a close second. Tools used were a small block plane to trim things up after sawing, a chisel, wood rasp, big half round file and some 60 and 80 grit abrasive paper wrapped around a piece of 25mm dowel.
The pitch defines the angles required at the tip and the inner station and once worked out the blank can be cut. This should have been approx 60.0mm wide at the tips but the material to hand was only 40.0mm so due allowance was made.
Two blanks and the initial template:
The blanks marked out on the face and the taper marked on the sides:
Rough sawn ready to shape the rear face:
With one blade clamped to the bench and a dowel pin through the centre the rear faces are cut flat across at a slowly twisting angle from low edge to top edge - making sure it's the correct way, otherwise you make a pusher prop.
First stage done and the helical twist created:
The prop shape is marked on the face biasing the blade to one side to give more thickness on the leading edge (the thinner side just created).
Bandsawn to the line ready to carve the front face:
Clamped as before but using tapered packing the blade is carved to an approximate airfoil section.
After rough sanding the true shape begins to materialise for final sanding.
A couple of discs to match front and rear diameters were used with a 6mm dowel to locate them. The hub was sanded to the discs just like filing buttons.
A balancing pin was turned up (6mm silver steel) with 60 degree points on each end and used as a pivot. This is a simple but effective way of balancing for props used at the lower end of the RPM bands - more than adequate. Balancing is achieved by sanding the thickness/reshaping slightly the heavier blade. Due to that thick hub they do look a bit heavier than they actually feel. Wouldn't want to make the blades much thinner.
It is important to allow sufficient to sand to a smooth finish - this one didn't quite reach the mark and only showed up on oiling.
And ready to use. Finish is just a couple of coats of Danish Oil rubbed in.
