Hi cran, just my opinion for the litle it is worth...
ENGINE:
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People often suggest using modern automotive engines, with their high level of technology and apparent reliability.
>>>> now most of the common jap engines (even small ones) can get over 200 000 km without any big problem.
Another option is the use of a surplus APU or de-rated surplus turbo-shaft engines. Nonsense, not even going to discuss that!
>>>> apu are available and quite cheap, who is going to overhaul them ? COSTY operators. cheap parts ? no, available "old series" parts ? no, unless you can really operate a recent apu, i would forget that. btw gearing is heavy and costy and R&D hungry.
Modern 2-stroke Engines; light, cheap...but unreliable.
>>>> a FAA certified 2 stroke, could be as reliable as a lyco, but 2 strokes are nor FAA aproved, because no one would certify a such endless gas pit.
Motorcycle engines? Again you would need to thrash them, so reliability and longevity is a problem.
>>>> wrong, the suzuki bandit is well known for its reliability and availability, you told about using automotive parts ? it is a good example.
Modern aero-diesels? None of an appropriate size, generally heavier, very expensive to buy and unproven reliability.
>>> the dieselis i heavier, but lowers the costs in a significant way over time, not for recreationnal local flights, BTW it has a huge torque.
How about a VW-derivative as used by drag/street racers and fixed wing guys? Possible and definitely cheap, but I have serious reservations about the reliability.
>>>> cheap if bare ! costy and unreliable if custom prepared.
How about a radial engine made out of VW-parts? Again proving the reliability is the issue.
>>>> R&D it..
FUSELAGE CONSTRUCTION:
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i agree for composites, but not single skin hulls > heavier and costy than tubes, but nicer.
why didnt anyone had the idea of cheap honeycomb ? light, stiff, easy to assemble.
ROTOR SYSTEM(S):
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When you said rigid, did you really mean rigid or articulated or really rigid like the BO-105?
>>>> th BO105 is called rigid but behaves like a semi-rigid. the blades endure bending.
3-bladed articulated hub but in my mind it is not the way to go.
But what about the substantial additional cost, weight and complexity.
>>> i disagree, the ecureil proved the 3 bladed design can be 40 % lighter, 40 % cheaper and 40 % simpler
What about ground resonance?
>>> the same as in an articulated, with less risk due to semi-rigid setup.
SEATING CONFIGURATION:
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I'm glad you like the tandem concept as there are some serious technical benefits for a two seater in this configuration!
>>> i love this config but instructors will stay away from this as thay like to have their students aside, that would mean double instruments panel.
GENERAL REMARKS:
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classicism vs innovation is a bad struggle.
accordding to ones, nothing can be done better than existing...
and others just dump everything old going in fully-rigid-innovating-over-engineering-thinking.
i m not an engineer, just giving an arrogant opinion
thanks