Guildlines for measuring boat length and width

Discussion in 'Boat Design' started by kach22i, Oct 7, 2007.

  1. kach22i
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    kach22i Architect

    I'm working on something which is hard to describe. I'll just say there are bits and pieces sticking out over the water which do not help make it float. What are the RULES for measuring the length and width of a boat?

    This might come into play when docking fees or insurance are a concern. This topic could also come into play when selling a craft or building to a customer's request.

    I'll try to list a few things which could help the debate, if you have a link please post it and save us all a lot of typing.

    1. Would you include this bow plank in the boats overall length?
    http://www.vysyachts.com/view.aspx?listingid=8
    [​IMG]

    2. Would you include this rudder in the boats overall length?
    http://www.selway-fisher.com/DoubleEnders.htm
    [​IMG]

    3. To the tip of this?
    http://www.seychelles.net/cruises/english/activities-star-sail-e.htm
    [​IMG]

    4. To the end of the sail post?
    http://www.crosswindscharters.com/packages.html
    [​IMG]

    5. Is this RIB as long as the twin stern tips or the hard hull? How about side to side?
    http://www.alibaba.com/catalog/11489199/Rib_Boat_Distributors.html
    [​IMG]

    6. I can tell you that hovercraft are often listed with hard structure measuments and when the skirt is inflated (on hover) to help avoid a little confusion.
    http://www.atlashovercraft.com/WebPages/Specs.htm

    7. You would measure to the bulbous bow (below waterline) of a ship, right?
    http://www.menkent.dk/piclexa.html
    [​IMG]
     
  2. Trevlyns
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    Trevlyns Senior Citizen/Member

    Quote – Principles of Yacht Design – Larsson & Eliasson

    Length overall – The maximum length of the hull from the forwardmost point on the stem to the extreme after end. According to common practice, spars or fittings like bowsprits, pulpits etc are not included and neither is the rudder.

    Beam - The maximum beam of the hull excluding fittings like rubbing strakes.

    Hope this gets the ball rolling!

    Best
     
  3. murdomack
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    murdomack New Member

    Most marina fees I have come across count everything that is fixed. In reality the staff seldom go to the pontoon and check, they might do after you go home. I once had a boat with a dinghy in davits on the transom. The davits were removable so I only paid for the boat's loa. I left the dinghy hanging in the davits on a few occasions and they never complained, then again I was on a six month rental

    Murdo
     
  4. kach22i
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    kach22i Architect

    I was just informed in another forum that the lod or Length of Deck might be the most relavant term. It sure seems to answer most of my question.

    By "nota":
    http://forums.pelicanparts.com/showthread.php?t=370842
    My new question:
    Would it be "proper" in the case of the RIB to list "deck length" (LOD) but on the width list the width/beam from the outermost edge of the inflatable? The "twin tails" still rattle me a little on how to handle them.
     
  5. Guillermo
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    Guillermo Ingeniero Naval

  6. DanishBagger
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    DanishBagger Never Again

    It depends – if I wanted it to be put on a trailer or in a container, I would need the real length of everything, including things that couldn't easily be taken off or drawn in.

    The same would be true if I wanted to tell whether I could squeeze into a tight spot with my huge bow sprit (or bumpkin, for that matter).

    Also, when comparing sizes, I would also go by LOD – otherwise it would be impossible to compare different types of vessels.

    Usually, though, it seems harbour masters (when they're fair) try to go by deck length, unless the bow sprit will be a nuisance to others.

    Caveat emptor, as usual, being the idjit I usually am.
     
  7. kach22i
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    kach22i Architect

    Yes, this is what it really comes down to; comparing sizes.

    On a side thought; let's say someone has a pointy dart shaped boat which holds only two people. He compares it to a square or rounded bow boat which holds 4-6 people. One would come away from a comparision thnking/knowing that the pointy shaped craft is not an efficient cargo/package carrier. The longer pointy craft in this situation looks worse on paper except perhaps when it comes to speed.
     
  8. mydauphin
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    mydauphin Senior Member

    The Answer.... Whatever you want it to be.
    That is standard.
    If your going to own boat register it as small as possible. Marinas never take out tape measure.
    If your trying to sell boat then add a couple of feet for rubrails and flags

    You laugh but I bought a 65 foot vessel, register it as 64feet. and when I measure it over the deck from bow to stern it was 72 feet. When I sell it - it will be 74. But I pay marina on 64 feet.
     
  9. DanishBagger
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    DanishBagger Never Again

    True. But you would still be able to compare the two. One parameter being size (for obvious reasons), another being shape - for purposes of speed, seekeeping and not forgetting load capacity.

    LOD will never be "the one and only" parameter, of course there will be others too, even if LOD is important. Yet another parameter is fuel efficiency. How many NM can you go per litre/gallon? To some, that is more important than LOD, and that parameter can easily dictate other parameters such as LOD, width, weight, shape (both under water and above) –*you name it, basically everything else.


    Take, say, a Grand Banks 36 and a plank-on-edge sailboat the same length. It's obvious that one can't use LOD as the only parameter. Say you want to compare how much space is inside? Then you'd have to have more LOD. to go by. But LOD will enter into the equation at some point: Imagine (got tired of "say") your client wants "two heads, an airy owners stateroom, yadda, yadda", you could get him a GB36 (he's well off, but not wealthy), or you could get him a much longer plank-on-edge sailboat, a somewhat longer, slimmer modern electric cruiser, and so forth.

    Length, and in this context: LOD, seems to be only one of the parameters, albeit an important one, especially since you pay per foot at most places.

    Me? I'd rather have the longer, skinnier one, even if it meant I "had to" lie to an anchor more than I otherwise would would. I like long and skinny, rather than short and tubby – but I'm not a speed boat driver, and form should follow function. :)

    ______________

    Rereading this post, it looks to me like it can be interpreted as I'm patronizing at some places, but I am not. My english skills just seems to fluctuate depending on what day it is, and what time of day it is. Sorry about that.
     
  10. kach22i
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    kach22i Architect

    I wonder if there is an "index rating" which at a glance informs one of the length to width ratio and other factors.

    For example they now list automobiles with a yearly fuel use index in barrels as well as the city/highway mpg ratings.
     
  11. mydauphin
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    mydauphin Senior Member

    The narrower the boat, the longer the boat the better. Even in rough water a narrow long boat seems to do better. But CG has to be low. It is amazing but a WW1 destroyer hull is still a very efficient hull. So are ocean liners like SS Normandy, Even a supercarrrier that is very wide is narrowed compared to length.

    Obliviously, a wider boat is more comfortable for people spaces. But increase beam, increase engine size, increase fuel usage, more pounding, more drag.
     
  12. Hotel Lima
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    Hotel Lima Junior Member

    I've allways heard people ask for the LOA, LWL is somewhat irrelevant because you cannot park another boat of the same size in that difference of length. So you pay for what you occupy, which is best represented by LOA.
     
  13. DanishBagger
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    DanishBagger Never Again

    Yes, people do ask for LOA, but usually they mean LOD, not LOA – at least in my experience. People ask me how long (LOA) my boat is, and when I reply, they always, without except (if they have seen it), go "and what if you count the bowsprit?". They are really asing about hull-length, not how far there is from the end of the boom to the very tip of the sprit.

    IMO, it all boil down to how people conceive boat-sizes in their mind. And that usually revolves around hull-length (most times even discounting sugar scoops at the stern, unless massive.
     
  14. Man Overboard
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    Man Overboard Tom Fugate

    Does LOD include raked transom's in the measurement?
     

  15. DanishBagger
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    DanishBagger Never Again

    Good question. I think it depends how raked it is, and how massive it is. Unfortunately, there doesn't seem to be any "LAH" - Length along hull - measurement. (Edit: to my knowledge).

    In the end, I would use the LOD-method, but no method is flawless, so one has to use good judgement on top of that. Otherwise we will have all sorts of ridiculous attempts to circumvent rules, simply because rules in itself are rigid, unless we're talking "rules-of-thumbs" …

    Hell, you could make a box-rule, asking people "how long and wide box could you squeeze your boat into without damaging it?" Only, people would still come up with this and that retractable, sugar scoops and bows that come off etc. Heck, folding dinghys for that matter.
     
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