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Thread: Performance amphibian ultralight project

  1. #61
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    Re: Performance amphibian ultralight project

    Yes, the engine wil indeed influence the CG location. But I'm for now waiting for the engine to be shipped, should be here next week
    I'm willing so save weight of the radiators by this setup. Don't worry, there will be fine calculations and CFD simulations to check that cooling will be sufficient.

    Cyril

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    Re: Performance amphibian ultralight project

    PS : cooling from a skin is not conduction but forced convection. The macchi M72 cooled its 2800 hp engine by flowing coolant through skins on the floats. It is not particularly known for overheating. No doubt that a skin in the propeller flow will do. The concern is rather conduction from coolant to skin.

  3. #63
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    Re: Performance amphibian ultralight project

    I might be thinking of the wrong Macchi seaplane --the one they last prepared for the Schneider races had hydrofoils and a rear water prop that was intended to get the hull (and airprop) out of the water before transferring power to the airscrew --I do not know if it flew or raced but in any case the Supermarine entry took home the trophy for good. I think the Curtiss entry had surface cooling also --it would be by radiation and conduction in any case - convection requires a macroscale fluid body to work -those racers could use seawater to float conduction while taxying and only needed to work for minutes at most. Properly designed air cooling is not a great cost and far simpler.

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    Re: Performance amphibian ultralight project

    Well, the machine you're talking about is the source of my inspiration for this whole project ... It's the Piaggio-Pegna P7. It never flew for 2 reasons : the clutching system was tricky to operate once in planing mode, and the pilot's visibility was very poor because sprayed by the hydrofoils. At first, I was about to adopt the same kind of configuration, but with an electric motor for marine propulsion instead of a complex clutching system. By the way, hydrofoils are not so good for amphibians. Skis are much better. It's true that such machines weren't designed to operate for a long time. But overheating can occur very fast when the engine is WOT. Yes, there is radiation, but when the fluid is in motion, I'm positive it's convection, not conduction.

    I might go with a waved aluminium skin. This should allow coolant to flow through the whole tail assembly and as well increase the air exchange area.

  5. #65
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    Re: Performance amphibian ultralight project

    The Akoya amphib embodied some of these features also --last I looked or heard it was not being continued (maybe it was at Friedrickshaven Aero 2013 but I haven't looked ) --the use of amphibians is actually pretty restricted when it comes to it --just a wind change can 'ground' you if on a river (no run in the wind direction) and the local turbulence from riverside trees is a worry -also people like to string cables across rivers for various reasons , floating junk and unseen rocks etc are other concerns . It is not all beer and skittles to be sure. we once landed on a lake in Michigan with lots of pleasure boats and people in pedallos and water skiing etc etc --it is not easy to plan a take off run amongst such complexity (and just as we were flaring a duck popped up and took one startled look at us before heading, without delay back under water --we all burst out laughing -it was exactly like Daffy duck (the cartoon).

    You must get a quite low landing speed for a practical amphib (water is like concrete at speed ) and usually that means on oversized wing in typical amphibs which equals slow and rough ride etc . I would not just repeat the Opal nowadays but most of the layout is adaptable --mainly need an updated wing.

  6. #66
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    Re: Performance amphibian ultralight project

    Lisa Airplanes who designed the Akoya but faced major financial difficulties but were bought by chinese investors. So the Akoya might not completely vanish. The reason it did not sell is that they designed it as a sport car. Luxury and costly interior even the canopy was electrically actuated. Muuuuch too expensive for regular buyers, and no rich cheikh would buy it either because they would obviously rather get a helicopter ....
    If you ask me, amphibians are extremely scarce in France. Lakes are generally small, but the coast can be reached from anywhere considering the range of an airplane. There are 2 reasons why I want an amphibian : it will bring a lot of fun, and it's well suited for travelling. Besides, it could be used as any other land plane, so not a big deal if there's no water to operate it ... If there's no drag penalty because there or no floats / hull cusp, then there's no reason not to do it.
    You are right about takeoff speed on water, but mine will be an ultralight, meaning 65 km/h stall speed (less considering water ground effect).

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    Re: Performance amphibian ultralight project

    Forget the calculation concerning duct thrust. It was completely false since the duct is as negative AOA, it cannot be simplified that way. I will obvisouly need to proceed the CFX simulation to obtain the thrust value. The drag should be approximately true though.

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by Aircar View Post
    The Akoya amphib embodied some of these features also --last I looked or heard it was not being continued (maybe it was at Friedrickshaven Aero 2013 but I haven't looked ) --the use of amphibians is actually pretty restricted when it comes to it --just a wind change can 'ground' you if on a river (no run in the wind direction) and the local turbulence from riverside trees is a worry -also people like to string cables across rivers for various reasons , floating junk and unseen rocks etc are other concerns . It is not all beer and skittles to be sure. we once landed on a lake in Michigan with lots of pleasure boats and people in pedallos and water skiing etc etc --it is not easy to plan a take off run amongst such complexity (and just as we were flaring a duck popped up and took one startled look at us before heading, without delay back under water --we all burst out laughing -it was exactly like Daffy duck (the cartoon).

    You must get a quite low landing speed for a practical amphib (water is like concrete at speed ) and usually that means on oversized wing in typical amphibs which equals slow and rough ride etc . I would not just repeat the Opal nowadays but most of the layout is adaptable --mainly need an updated wing.
    I haven't seen Lisa/Akoya this year in Friedrichshafen but there was an interesting Italian amphibian project named Idintos with tandem wings and dual shrouded props...

    Performance amphibian ultralight project-idintos_flyer.jpg

    Water at landing speeds over 65km/h is a hard surface but wouldn't you say they could have considered to put the canard/frontwing lower and reduce the drag and weight..?

    http://www.idintos.eu/
    Last edited by DangerZone; May 25th, 2013 at 12:00 PM. Reason: added link

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by DangerZone View Post

    there was an interesting Italian amphibian project named Idintos with tandem wings and dual shrouded props...

    Attachment 24423


    Idintos
    =it is russian project \see=qxev\...

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by henryk View Post
    =it is russian project \see=qxev\...
    What makes you say that?

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by DangerZone View Post
    What makes you say that?
    Paul Weston Sea-Era

    =post 150 and ....

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    Re: Performance amphibian ultralight project

    I have seen a picture of this machine some weeks ago. Nice design, though I suspect that their shrouds have a diameter under 1m, I think they will lose some propeller efficiency for that.

    I don't get what you suggest about the front wing ?

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by henryk View Post
    Paul Weston Sea-Era

    =post 150 and ....
    Well, the idea was actually scientifically explored in the 1930s by Nenadovic and later a French guy even made a few flyable airplanes with joined wings so claiming that it was a Russian invention is a bit questionable...

    Quote Originally Posted by yellow_submarin View Post
    I have seen a picture of this machine some weeks ago. Nice design, though I suspect that their shrouds have a diameter under 1m, I think they will lose some propeller efficiency for that.

    I don't get what you suggest about the front wing ?

    There's a bunch of other issues besides efficiency, that is the least of their concerns...

    The front wing in a tandem aircraft is a canard. If an aircraft would be a three surface airplane then the canard could be used for surfing, with a slight dihedral it would be an excellent landing platform. Less drag, more stability, the canard would have a wing in ground effect, it could a more efficient design.

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by DangerZone View Post
    Well, the idea was actually scientifically explored in the 1930s by Nenadovic and later a French guy even made a few flyable airplanes with joined wings so claiming that

    it was a Russian invention is a bit questionable...

    =I was write=PROJECT,no invention...

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    Re: Performance amphibian ultralight project

    Quote Originally Posted by henryk View Post
    =I was write=PROJECT,no invention...
    Well, the Russians have a long tradition of optimizing airplanes and improvising, they often turn a good idea into a better project... Like the Beriev 103, it's origins are in a German amphibian with a single engine but the Russians successfully put twin props and lowered both the thrust line and the wing height, making one of the safest seaplanes ever.

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