2009-03-05

What a difference a PROP makes !

http://www.eaa.org/experimenter/articles/2009-02_elippse.asp

90 % efficiency obtained by Ellipse prop !

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It is funny but for ten years no as I have been designing aeroplanes I have always drawn it close to that kinda prop which has a wide root almost parallel to fuse and thinner at tip by instinct. I get good vibes about it...strong and efficient at the same time..no bad vibes during the flight.

Unfortunately i think I have to design my own prop for the Max III, since no one makes 820-880 mm dia 4 bladers...nor 2 or 3 blabers for pushers. How hard can it be ?

16 comments:

  1. This comment has been removed by a blog administrator.

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  2. And who is the throll in here ?

    I have a strong feeling that you are a throll.

    Better stop that tone here.

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  3. Toivotan tervetulleeksi kaikki Ilmailuliiton saitilta tänne visiitille tulleet ilmailijat. Sana on vapaa kunhan sävy pysyy sallitussa rajoissa.

    Rakentavat kommentit otetaan vastaan kernaasti ja yhteistyötarjoukset erittäin lämpimästi.

    Moderaattorina täällä toimin minä.

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  4. Prop clearance?

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  5. You have a point...dislayed prop is 880mm dia. Intention is to use 820mm dia with 185 mm clearance. Smaller prop allows direct drive with flexidyne shaft and ball bearings..and energy will be lost from engine to prop...also less moving parts.

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  6. ...I meant to say no energy will be lost more than 2-3 %.

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  7. Okei !

    Now there is the intented smaller 820 mmm dia fan.

    You gotta screw up the landing pretty badly in order to brake the prop.

    rgds,

    Juke

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  8. How about dust&debris getting into the prop, still quite small clearance. Undercarriage may also spreand some nasty stuff nto the prop. And I think it's a propeller. Fan is enclosed.

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  9. Dust and debris is a problem..this plane cannot take off ( and land ? ) from a remote dust covered airstrips without being in danger of loosing the prop. Very thin titanium prop could be the answer on small rocks, but even that material could not handle thumb size rocks. Another answer is to make a wooden prop with steel enforced leading egde and suffer to some extent the bumbs an srcathes on the prop and buy new one little more often than in a tractor configuration ( if you wish to operate the plane from dust covered airfields ). This might also need to look after the last bearing in powertrain to be such way that there is some sorta dampening to allow the small rocks hitting the system without braking anything important. Or even developing a 5-7 blader fan that would still be able to fly even if large portion of one prop blade is missing ( if you need that to reassure that flight is possible after a rock hit )and return to the field is possible when plane is shaking.

    rgds,

    Juke

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  10. Fly with a prop portion missing, wake up, earth calling? Have you ever seen what happens when propeller is not in balance? Even in moden planes?

    Small rocks, size less than quarten on an inch is very bads to propeller, wears it quite much even in normal ac:s with clearance about a one ft.

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  11. Normal physics do not limit this design at all. Imaginary debris doesn't harm imaginary propeller. And even if it does, it still doesn't create such an unbalance what couldn't be countered with good imaginary materials and design.

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  12. I do allow sarcasm to some extent.

    Mr. Lars Giertz lost a 4 inch portion of his VmaxProbe wooden prop leading edge while taxiing it on a his airfield..that is why I suggested the steel reinforcement on the leading edge.

    Like I said not for dirt airfields..but same fields where jets operate can be plausible.

    If you scroll back I havedesigned also ski and float version...no rocks on those take off fields.

    I do know very well what a portion of a prop can cause..but if you have more blades like 7 tha little piece missing will do less damage in small dia fan than a same piece in larger two blade prop. Do some maths and physics for gods sake befor you expose yourself being throughbreed "you know what".

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  13. Water also eats propellers. Even metal ones.

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  14. Definitely..therefore the prop has to be protected by the design that does not allow splashes to go into the fan and certainly not into the tips of the fan blades which rotate faster.

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  15. What is also good news is that more blades at lower rpms will allow to fly with prop efficiency.

    See the EEA article on Ellipse props.

    Thanks for the comments. I understand the rear mounted axial prop designs with all known advatages are surrouded by lotsa suspicion and not without a reason. We see very little working solutions...Bede-5b with 150 built specimen ( 5000 ordered ) being the best example yet and Moltor Taylor Mini-Imp.

    Recent ( 1997 ) crash of Lars Giertz and massive setback in LF 2100 projects ( 260 orders and FAA did not certify the plane ) had made people to turn away from this kinda setup.

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  16. Ok I miss the word BETTER ...prop efficiency...from above.

    Here are Micro-Imp specs with 25 hp engine ( dimesions almost like in Sierra Sue 2-seater 80 hp plane ).

    http://en.wikipedia.org/wiki/Aerocar_Micro-IMP

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