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    Less than 10 posts so far! USER IS NOT AVAILABLE
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    Default Almost finished hovercraft but....big problem!

    Hello All,



    Thanks for your help over these last years, I have finally finished, excluding cosmetics, my hovercraft.

    One big problem....

    It don’t work 

    Why?

    Well this is what I hope you could shed some light on.

    Apologies for this lengthy email but it should contain most of the information you need.

    My craft is based on a challenger; it has various mods that are not recommended in the constructors guide:

    • Adjustable splitter plate

    • Correction for duct circularity(by strengthening cord around duct)

    • As by the advice, pressure seggies at the front, open’s at the side and drag flap/chip bags at the back.

    • Sequentially larger holes as you get closer to the front: 34mm at back, 64 at side and 72 at the front.

    The specs of the craft are as follows:

    • Engine- RD250LC 1980, 35BHP @ 8500RPM

    • Fan- 6 Blade multiwing in 9 blade hub, 2up configuration, attack angle 45degs.

    • Gearing, 22 @ engine to 48 @ fan

    When I designed the skirt I changed it subtly to have the following:

    • Folded up corners to form loops instead of tabs.

    • Much longer tabs so they could join the top of the aluminium edging see figure 1 below.

    • Designed the “hull edge” part of the skirt so it is designed to actually hold against the hull rather than having a gap, see figure 2.

    I have also uploaded a video on YouTube of the event to help further, see:



    http://uk.youtube.com/watch?v=OPvoaPFfG9Y



    The few observations I have made is that by decreasing the blade angle I get a lot more static pressure and therefore lift which makes the craft easier to pull along but not enough thrust to push me along.



    There is a hell of a lot of drag at the back, i cannot even push it backwards at full power, but forwards it can easily be pulled.



    A lot of air is escaping from the top part of the skirt segment where it has the long tab, it forms a triangle shape where air freely escapes from. Does the skirt/hull need to be as air leak free as possible for crafts to work?



    I hope I have given you enough information to have a guess at the problems....



    Really hope you can help get me ready for next race season.



    Thanks Nick

    [img]index.php?t=getfile&id=1857&private=0[/img][img]index.php?t=getfile&id=1858&private=0[/img]
    Attached Images Attached Images

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