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  1. #1
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    Post Engine exhausts going inside the hull.

    Hello everyone
    Putting new lift engine in the craft and before I go drilling a big hole in the top...
    What are the rules for exhausts inside the hull.
    Are they not allowed at all anymore? I herd a whisper about it and just wanted clarification
    Thanks
    George

  2. #2
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    Default Re: Engine exhausts going inside the hull.

    George

    Check your copy of the Construction Regulations!!!

    The only restriction I'm aware of is as follows, taken from HC152 - Construction Regulations for
    Racing Hovercraft:

    10. FIRE PROTECTION
    10.1 Design Safety

    A. The design of craft SHALL be such as to minimise the risk of fire occurring.

    B. Engine exhausts SHALL be designed such that no appreciable amount of exhaust gas can enter the air cushion system of a “No Flow” pressurised bag skirt. The exhaust outlet SHALL be clear of the lift fan suction area.

    10.2 Hot Parts

    A. The distance between hot parts and other components SHOULD be of sufficient space
    to prevent degradation or heat deformation; it is found that 20 mm is normally
    sufficient.

    B. If an exhaust is within 20 mm of a GRP surface, a heat reflective pad of aluminium or similar SHALL be fitted to prevent burning of the GRP surface.

    C. Hot parts SHALL have an adequate supply of cooling water or air, to maintain a steady design temperature during all normal operating conditions.

    D. Hot exhaust pipes and silencers SHOULD be protected by guards, in order to minimise possible injury to the driver or third parties in the event of an Incident.

    Hope that helps

    Kevin

  3. #3
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    Default Re: Engine exhausts going inside the hull.

    Thanks Kevin.
    I wasn't sure and just wanted to check.

  4. #4
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    Default Re: Engine exhausts going inside the hull.

    Hi Kevin

    One does read the regs but what exactly is a "No Flow" pressurised bag skirt?

    Does this mean it is therefore permissable to fit an exhaust inside the protected plenum of a finger skirt system?

    Paul

  5. #5
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    Default Re: Engine exhausts going inside the hull.

    Hi Paul

    A no flow bag skirt is exactly what it says; a bag skirt that gets pressurised but does not let air escape - and a skirt filled with exhaust fumes is potentially a fire waiting to happen with a nice mixture of hot gasses and unburned fuel. Finger skirts have lots of flow through them, so aren't a problem. The vast majority of bag skirts also have limited air flow through them, the air flow helps to lubricate them. I can only think of one French craft currently in operation that has a no flow bag skirt and even that doesn't rely on fan pressure for its inflation. With current craft and skirt design it is an unlikely scenario.

    Kevin

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