ideas needed for a large sliding roof hatch grp boat

Discussion in 'Boat Design' started by janner, Nov 23, 2013.

  1. janner
    Joined: Apr 2012
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: uk

    janner New Member

    At Southampton boat show I looked at a very impressive high tec sliding roof hatch , but it came with a 2000 pound price tag , so only option is to self build GRP, could really do with some insparation, design ideas and advise on sliding mechanisms etc, The hatch size is 3ft x 4ft
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 470, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    You're talking about a huge hole in the top of a boat, which generally isn't a good idea. As to mechanisms, well keep it simple, as the fancy high tech stuff often works just fine, until it gets balled up with dirt, salt and other grime and jams open or closed, with no hope of freeing it short of a fire ax. Think about self lubricating parts and naturally "containing" assemblies.
     
  3. rwatson
    Joined: Aug 2007
    Posts: 5,821
    Likes: 270, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Sanded fibreglass is pretty slippery, especially when wet.

    However, you can buy strips of Polyethylene ( the stuff that plastic cutting boards are made of ), that make heavy things slide easily.

    3ft x 4 ft isnt that big, and a properly designed glass hatch would have no trouble behaving itself on metal slides.
     

    Attached Files:

  4. janner
    Joined: Apr 2012
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: uk

    janner New Member

    hi rwatson and PAR, Thankyou for your advice, any Idea where I can buy the right sort of sliders /mechanisms, I am in the proccess of trying to design and build a mould for the roof 10ft by 15ft, I need to lower an engine up to 250hp in through the roof hatch and through the engine room hatch,
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 470, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Typically, there are a few approaches to this, the most common is a fully bonded in section, that's designed to be cut out, removed and bonded back in when a repower is performed. This is the water tight way to do it and structurally, much stiffer. Another way is exactly the same thing, except it's precut for you and typically bolted down, over bedding on a flange. This is simply a molded hatch cover, screwed or bolted down to a flanged opening and only removed during a repower. Lastly is a dedicated hatch, which can have hinges, struts, slides, parallelogram arms, etc. These are the weakest, most likely to leak, most likely to rattle, etc. They often are set into a drip rail/flange sort of thing to help shed water and stiffen things up. Which you employ is up to you, but generally this approach (hinged) isn't necessary, unless you're getting something else by doing it, such as more headroom or easy access to the engine for maintenance.

    Usually, when you have to pull and engine through a salon or pilothouse, after snatching it up through the sole, deck or engine room hatch, it's a two stage process, unless you have an articulated arm/hoist. An example is one I did this summer, where I used a standard boom style engine hoist on the deck, hoisted the engine up, then rolled the hoist, with the engine dangling, through the pilothouse hatch, out onto the cockpit sole. From there I used a gantry to hoist the engine out of the cockpit. I placed some 3/4" plywood down on the pilothouse and cockpit soles, to protect things as I rolled the hoist around and to help spread loads, without damage.

    What boat do you wan to do this to (year, make and model)?
     
  6. janner
    Joined: Apr 2012
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: uk

    janner New Member

    hi PAR
    I have built the boat myself over the past three and a half years , I was given an old hull mold, was told the mold was a sea-lion possibly 30 years or more old ,no top ,I build a new hull molding then have had to design the rest, built and assembled it like a jigsaw ,I have aimed for a classic design rather than power boat look, so far she looks good , I am on the last leg , just need to design the rest of the wheelhouse from the waist up and roof, the idea was engine access and a sun roof as an added bonus , however I'm not a designer and value all info offered.
     
  7. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 145, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Look at kitchen drawers for ideas. The cheap ones have a plastic strip screwed on each side, resting on wood or an aluminum profile. They do slide as long as they are empty and have a lot of play.
    The ones that move without effort have metal guides and a set of small wheels, so they don't slide but roll. For a large hatch I would use aluminum U-profiles, fixed to the wheelhouse with countersunk screws and a number of small stainless ball bearings on short stubs attached to the hatch.
     

  8. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    could really do with some insparation, design ideas and advise on sliding mechanisms etc,

    Look in any old boat building book and copy a companion way slide.

    Sparkman and Stephens has on line files as a start..

    The best do not leak even when a wave crashes aboard , so should work fine on top of a boat.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.