gutter extrusion ? water management -Hatch cover

Discussion in 'Boat Design' started by marcbeaudry, Jun 17, 2015.

  1. Kevin Morin
    Joined: May 2013
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    Location: Kenai, AK

    Kevin Morin Junior Member

    extruded hatch gutter

    marc,
    While aluminum is great in extruded forms, I'm not aware of a cross section that would lend itself to your hatch gutter/drain/coaming.

    In order to get a special shape made, the cost is truly prohibitive unless you're planning a product line (!) as there are costs for the die design, the machining of that extrusion die and a minimum mill run of the final product. This means, unless you locate an existing aluminum shape that fits your needs- forget extruded solutions to your question.

    Next, aluminum is not all that well behaved around wood. The level of effort to protect it from crevice corrosion often associated with wood boat installations is pretty extensive, and since this assembly would be screw fastened or bolted (not welded in) the metal perforations implied further this sealing work and reduce the likelihood of success.

    If you do plan to use aluminum (? not the best choice when other metals are less susceptible to corrosion in this application) press forming the shape, or shapes, you need is the only economical method of obtaining sheet metal converted to the cross sections you'll need.

    I'd suggest copper alloys first, SS next and aluminum alloys last in my choice of metals working in a wood boat? Even encapsulated with epoxy, the interface can retain a thin film of water and initiate crevice corrosion in all but the copper alloys.... so they're not the best choice for this application.

    cheers,
    Kevin Morin
    Kenai, AK
     
  2. marcbeaudry
    Joined: Jun 2015
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    Location: Toronto Ontario

    marcbeaudry Junior Member

    Hi Kevin
    after a great deal of research for suitable pre-existing extrusions - i can confirm that you're correct - finding one is unlikely and custom is cost prohibitive- that said i made an assembly using some flat, some angle and channel to create the end profile i was looking for - tig'ed together over it's length to provide a water tight seam -
    subsequently any fastening will be below the level of the gutter to avoid presenting a penetration for water ingress - i could have used stainless - copper would not have been a choice I would have made though- perhaps on another project - at the finished thickness of 3/16'' in the thinest areas - I suspect i'll be a long time off of this world before crevice corrosion becomes a concern though although it's something i'll keep an eye out for - thanks for the comments
     
  3. viking north
    Joined: Dec 2010
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    Location: Newfoundland & Nova Scotia

    viking north VINLAND

    After speed reading the thread if not already suggested why not simply fasten a run of wood stripping around the inside of the present opening of such width that they stand proud of the deck say about 1 1/2 in. Run a bead of 5200 around the seam they make with the deck of the original opening. Modify your present hatch to serve as a male mold or a plug and glass up a nice drop over and latch down lid type hatch and solve your deck hatch leaks forever. To make it hurricane proof install a self sticking foam rubber gasket around either the hatch lid lip or where it makes contact on the deck. Seems much easier than cutting bending and forming gutters not to mention the hassle of installation and drainage.
     

  4. marcbeaudry
    Joined: Jun 2015
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    Location: Toronto Ontario

    marcbeaudry Junior Member

    water management - hatch cover

    [/ATTACH]
    not certain if that pic was attached or not -
    in the end - aluminum channel mitred cut to fit the hatch opening and tig welded together - then i turned some aluminum spigots and welded them into place in each aft corner - tied the plumbing into the scupper drains with some turned up pvc plastic fittings - the strip of wood idea had crossed my mind - but it's a big hatch - large enough to take the tanks out of - so i didnt want to stress the gutter
    with a heavy trap - and i certainly didnt want to worry about the fat lady falling through the hatch !
     
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