If anyone is remotely interested in this topic I am scraping it off the bottom of the vegetable storage compartment in a sharehouse fridge, so the search function on Key brings it up. Postwar it seems there was some consternation between UK airscrew concerns – Rotol, Fairey and dH- in respect of design calculation for the purpose of competing for Air Ministry tenders. So the SBAC came up with a design guide to unify propellor theory in the immediate postwar. Surprisingly a copy was recently found in Israel and has been delivered by camel to my desk. It seems even the original designers had an incomplete grasp of the dark art of propellor design and much was learned in continuing wind tunnel work. I am starting to grow away from aluminium props from the simple realization of how difficult it is to contemplate forging blanks, and how limited the demand for obscure LH and RH tractor types will ever be. With some understanding of blade design it is still possible to plunge into the remains of the great US commercial airline legacy, and make remaining blades work at a fraction of their original efficiency for display aircraft operated within a small fraction of their original design capacity. No one will really notice. A point of wisdom raised by a certain Canadian restorer is that a timber blade, in a nose over, will sacrifice in preference to an unobtanium engine crankshaft, and this seems very sensible indeed. So its almost like designing a rotol -Jablo type ‘socket’ to fit into a HS hub arrangement is one pathway to provide a solution for unique profiles and tractor arrangements for the next 50 years, if original blades finally run out. Apparently the HS profiles made in the Czech Republic are machined from billet, and modern vacuum smelted alloys can seemingly allow this. You still need upset forging at the base of the blade, but this is a common step to any profile. A funny thought is that with electric propulsion, everything old is new again, as blades are the only way to convert electric torque into getting to a destination. Perhaps, with infinitely variable RPM, modern sensing technology and computing power, old blades that constantly, individually, and as a team, adjust their pitch and RPM offer a whole new field of development in the dark art.
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