Hatch Design

Discussion in 'Boatbuilding' started by Charly, Aug 14, 2011.

  1. Charly
    Joined: Dec 2009
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    Location: st simons island ga

    Charly Senior Member

    I am looking for ideas on the best way to design and build my own flush deck hatches for my 36' beachcat.


    I want to end up with something that is

    1 weathertight,
    2 tamper proof,
    3 accessable from outside,
    4 flush deck,
    5 affordable,
    6 Simple,

    7 AND I don't want to excite the coasties if I decide to get a COI, sometime down the road.

    I once had an old wooden sloop that I re-did. When I rebuilt the deck I put a simple coaming and built a lid out of plywood to cover it. The underside of the lid I glued a strip of neoprene (from a wet-suit) as a gasket. Then I attached a couple of pad-eyes to the center part of the underside of the lid, and hooked a bungee cord to that, that was also hooked to a pad eye underneath the deck. this was enough to hold the thing down and compress the gasket. Then I had a heavier pad eye with a short length of chain and a padlock on it. The idea was you could raise the hatch enough to get your hand inside and unlock the padlock, enough to then gain entry, by unhooking the bungee cord. It worked fine, though I never was in a hurricane with it.

    This may be all I need to do again with my new build, though I probably would want to add some feature to allow "battening down" (where did that saying come from anyway?) for a real storm.

    The plans show enough detail to build a flush deck style hatch with a drain channel into a tube and overboard, so that part seems easy enough.

    Any ideas? Thanks
     
  2. CatBuilder

    CatBuilder Previous Member

    Charly: I don't have an answer to your question, but sure would love to see pictures of your hulls and beams and whatever else is complete. Asking about hatches should mean there is a pretty cool looking boat to show us. :)
     
  3. Charly
    Joined: Dec 2009
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    Location: st simons island ga

    Charly Senior Member

    Thanks CatBuilder. I will update the build thread soon. Right now there is not much new to show. I do have the second hull decked, and ready to move out into the yard with the other one, and then I will start building the beams. They should go together fairly quickly. I am thinking more and more now about such details as hardware placement, hatches, thru hulls, paint, etc., and will have many more questions I am sure.
     
  4. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    Sorry not much help but also looking for hatch plans...... Surely there must be something between the commercial hatches and the sandard DIY hatch
     
  5. Charly
    Joined: Dec 2009
    Posts: 429
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    Location: st simons island ga

    Charly Senior Member

    Just wanted to bump this thread.

    I have now roughed- in the companionway hatches for each hull. They are hinged, and at right angles to the hulls, per the design (KHSD 36 Beachcat). The design features watertight bulkheads at each of the crossbeams, so when thinking about ventilation issues it gets complicated. I had hoped to avoid the clunky style dorade boxes and cowls If possible. The solar vents have a sleeker profile... anyone have recommendations?

    I am still leaning towards the homeade flush deck hatches with channel drains led overboard, for an uncluttered deck, and omnidirectional opening, and to save money. These would be made up from the cut-out deck material, so the deck camber would be uninterrupted. Tied off from below, with four bungees, or small line, the opening could be manipulated by loosening the side you wanted to open and slipping in a wooden wedge or something, that way you could open to (or opposite) any point of wind. This should be real nice, especially in the head. One downside to this style is that without a coaming to stop a driving rain or spray, the hatch would take on water when opened, unless there was some kind of canvas dodger over it that could somehow be tied down to the deck tight enough to stop the water from running under it and then slooshing down. Comments?
     
  6. cookiesa
    Joined: Mar 2007
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    Location: Launceston, Tasmania

    cookiesa Senior Member

    Would love to make a flush deck hatch for the anchor well, thought about cutting the deck hatch out of the deck then using some oregon and the router to make a flush drop in hatch with the same profile as the deck...... Being self draining taking on a little water isn't an issue as it would drain out, different if it was in the foredeck above the v berth of course! Lol
     
  7. sean-nós
    Joined: May 2010
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    Location: Dublin,Ireland

    sean-nós Senior Member

    1 person likes this.

  8. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It seems you want your cake and eat it too.

    Hatch design, with the usual assumptions in place, boils down to opening flange design and hinge design.

    The flange typically has a few roles to play, addressing each with the desired safety margin, is a reasonably simple set of engineering problems. The hinge also has to receive some thought, though generally an "over center" offset style, is the way to go on a flush hatch. This lets the hatch ride a bigger radius, so it doesn't foul the flange on the way up.

    As to the engineering aspect for something cheap, easy, tamper proof, etc., well you could look through some of the stock plans at S&S and see if they have something that might work or could be modified to suit.

    http://sparkmanstephens.com/yachtdesign/design_typeplans/typeplans_D12.php
    http://sparkmanstephens.com/yachtdesign/design_typeplans/

    If you don't want to "excite the coasties" then you'll need someone to sign off or make it so clean, that they'll think it's a manufactured unit.
     
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