RE: Vintage ducted fan (1975)
Thomas- i agree with everything you have said.
you probably know that for ICDF the trick is to match the engine's power/torque curve to the load of the fan at all rpm- or at least to the point where the engine is making maximum torque and/or power.
This limits engine selection to very few types- especially back then.
the housing etc was very poor indeed. The rotors too heavy and too soft. (they expanded at high rpm and ended up slipping on the shaft).
Still- as they were for IC engines, they were/are agressively pitched and bladed (edit: well, they were setup for lower rpm than E RCers are used to) and although we're seeing such things now due to the newer cells and motors, its been a long time coming.
For sure his production methods let him down big time. I would suggest that it wasnt just his theory, but the R&D also.
One of the things that really gets under engineer's skin is when people who test things to death only to confirm the testing/theory already done- or perhaps contradict it out of context. They then make statements like "you're just a book worm", or "have you tested?", or "ive tested these fans over and over".
For some reason people think that engineers get paid big bux to read out of a book and not apply anything in real life- when the whole purpose is to solve a real life problem with controlled test- then use that info to advantage.
im probably preaching to the converted, but the amount of times it comes up in RC forums is amazing. I always use the analogy that we dont build bridges then put weight on them to see if they work, or when they break. Why?- because we already know what it can do as we've got the data.
same applies to DFs.