Is a walkway around a deckhouse always necessary?

Discussion in 'Boat Design' started by JohnGB, Sep 30, 2022.

  1. JohnGB
    Joined: Feb 2021
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    JohnGB Junior Member

    I've gotten interested in boat design but I'm not an experienced sailor. I am however an engineer and I've been trying to assess many of the norms from first principles - as I would with other engineering projects. From my engineering experience often decisions are made because of the available technology, but sometimes when the technology changes the designs originally constrained by the older technology remain out of tradition. So (for my own interest) I've been working through some of the technologies that have changed are are changing and thinking through which common design elements may be freed up by those technology changes.

    The question that I'm currently stuck on is the walkway on the deck around the deckhouse (if there's a specific name for it, please let me know). Every reasonably large (>30ft) sailing boat (whether a mono or multihull) that I've come across has walking access around the full deckhouse, which I understand is necessary for sail handling and running rigging handling. My question isn't whether there should be good access to the sails and rigging, but rather whether that access needs to be around the deckhouse. Or to put it another way, is there a reason other than sail and rigging access to have a wide path around the deckhouse?
     
  2. tlouth7
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    tlouth7 Senior Member

    This is an interesting question. I think there are elements of tradition, elements of construction technology, elements of aesthetics.

    Firstly we should make a distinction between a trunk (over much of the length of the boat, with a coachroof making the top), deckhouse (higher, over a shorter section) and pilothouse (taller version of a deckhouse, likely with more controls inside, walk directly onto the deck). None of these would typically span the full beam, though there are examples of generally smaller yachts with a full width trunk.

    Construction: modern GRP boats are primarily built of two mouldings: the hull and the deck/trunk/deckhouse/cockpit. The shear line forms the join between these - typically a big flange and lots of sealant and bolts. Having this as a continuous surface without sudden changes of direction to go up the sides of a cabin makes it easier to mould and assemble.

    Aesthetics: this shearline is key to the look of a vessel. People expect to see it in a certain form, and aesthetic balance dictates a certain distribution of the volume above and below. Having volumes above set back towards the centreline reduces their visual weight.

    Tradition: boats were typically decked, with individual openings. These openings might be covered by deckhouses, doghouses, skylights etc. The expectation is that there is a continuous deck with the cabin protruding through it, rather than the inverse.

    These are just my musings. Have a look at the latest generations of IMOCA 60 to see how the standard layout can be deviated from.
     
  3. Tiny Turnip
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    Tiny Turnip Senior Member

    I used to have one of these little sweeties. Only 15ft, but a two part grp moulding, with access fully across the cabin roof. And rather well resolved aesthetics, I thought:

    [​IMG]
     
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  4. Blueknarr
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    Blueknarr Senior Member

    Sailing vessels need access to running rigging on both tacks.
    So either side decks or flush decks.

    One should also be able to dock both sail and power boats on either side. Unfortunately many vessel designs have reduced the available space to perform docking assistance from the deck.
     
  5. Will Gilmore
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    Will Gilmore Senior Member

    There will always be a reason to have access to the foredeck, even if the rig can be worked by automation from the cockpit. When things go wrong on a sailboat, it will be at the worst time. However, there is no reason that access has to be around the outside of the deck house. Many North Sea fishing trawlers extended the house to the bull works to either side.

    The narrow access around the bridge of a boat is often called the catwalk.
     
  6. zstine
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    zstine Senior Member

    The Macgregor 26 is a very popular boat with no side decks. Obviously not over 30ft. With small boats there is more of a need to push the deckhouse out to the gunwales for interior space. Above 30ft the needs below for this is less and the disadvantage of having to climb over the deckhouse are greater. Side decks are safer/prefered because the deckhouse typically provides a hand hold and you are lower and more easily able to duck under the boom.
     
  7. JohnGB
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    JohnGB Junior Member

    My current rough plan is to have easy access to the fore and aft decks through the house rather than around it. The only time I can see possibly needing to have access to the sides of the boat is during docking, and then the sails would be put away so it would be possible to access from the house if needed.

    Thanks, that's useful to know.
     
  8. JohnGB
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    JohnGB Junior Member

    Thanks, I wasn't aware of the term.

    Lots of interesting design ideas for monohulls there. Thanks.
     
  9. JohnGB
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    JohnGB Junior Member

    If there is no standing rigging (unstayed mast), and all running rigging is on the foredeck (which would have access), those criteria would be satisfied.

    If docking I presume that all sails would be stowed / reefed, and so access to the sides via the roof of the house (if designed for this) should then suffice, unless I'm missing something.
     
  10. Blueknarr
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    Blueknarr Senior Member

    Flush decks are a traditional way to increase interior volume while maintaining service decks.
     
  11. Rumars
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    Rumars Senior Member

    This has nothing to do with engineering, it's an ergonomy problem related to the intended use. There have always been boats without side-decks, either with full flush decks, or with full width cabins with a step to the foredeck. Cockpits are also optional, there are boats without them. All of this configurations have proven unpopular in the long term, but they resurface regularly.

    If you want a boat without side decks it's ok, you just have to know the compromises you make. For example the hatches have to be big enough to pass a chair since there isn't anything on deck you can sit on. There are plenty of other such things to consider, if the owner is ok with the results then the boat is viable.
     
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  12. jehardiman
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    jehardiman Senior Member

    One thing that hasn't been mentioned is natural light in the habitability spaces. I've sailed on flush deck racing boats and it is dark and dank below even with deadlights. While there is a modern trend to put windows in the hull sides, I don't feel that is a healthy design compromise. Many coachdeck boats of the 1960's and 70's (looking at you Cal 25) had tumblehome above the effective maximum beam specifically to avoid the issue.
     
  13. Alan Cattelliot
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    Alan Cattelliot Senior Member

    In your deck arrangements, do not forget that companionway openings should have a sill. Your aft companionway shall have one. Your fore companionway shall also have one. The If the deck in way of your fore opening is not self draining, ie in case you make a recess, an appropriate drainage of the recess should also be made.
     
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  14. rangebowdrie
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    rangebowdrie Senior Member

    When, (not if,) the weather "goes south" a companionway on the foredeck is an excellent way to flood the boat.
    In an ocean-going sailboat the idea of a foredeck with a companionway and self-draining cockpit is likewise a fool's errand.
    Having to scramble back-an-forth thru a cabin, perhaps with driving rain and dripping foul weather gear, not to mention having to haul needed gear in a storm is a recipe for a miserable boat in rough weather, or maybe a disaster.
    Many, (if not most,) of today's "modern boats", in the quest for a "spacious interior" have ridiculously small/narrow side decks, often severely cambered, that are further impeded by inboard rigging and heavily inboard sloped cabin sides.
    In mine own experience, when things go bad one needs to be able to walk. (or crawl,) along a side deck that has decent width with handrails on the cabin top and a good height toe rail/bulwark to keep you and gear aboard.
    There are reasons that certain things about boats have stood the test of time, some call it "Tradition", others realize that the sea hasn't gotten any more peaceful just because some "designer" has some idealist notions of "modern thinking".
     
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  15. JohnGB
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    JohnGB Junior Member

    Tradition was that a yacht didn't have a motor and docked by sail or rowing power. That has clearly changed with technology. The context of my question is not for a monohull with a lower companionway out front, but something more in line with a Chris White catamaran with a forward cockpit. If you feel that Chris White has an "idealist notion of modern thinking", then I would disagree with you. Traditional boats have been constrained by standing rigging for example. If one were to not have any standing rigging (which is perfectly doable with modern building materials), then why maintain the "traditional" aspects of boat design that were limited by the needs of standing rigging? If fundamental characteristics change, then it's reasonable that other connected characteristics would also change, is it not?
     
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