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What Do These Waterline Numbers Mean?

Discussion in 'Technical Discussion' started by discokachina, Oct 22, 2011.

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  1. discokachina

    discokachina Senior Member

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    What do the numbers represent on the bow in the first picture and what do the graphics along the water line in the second picture stand for?

    I would think the numbers on the bow represent draft but that does not make sense since the draft of this vessel fully loaded is a little over 8' and partially loaded is a little over 7'? :confused:

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  2. Capt J

    Capt J Senior Member

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    In the first picture, the numbers refer to the draft of the vessel at the bow. The second picture is the load line. The vessel shouldn't be loaded any heavier than that. Freighters have more markings for true fresh, fresh, salt, true salt.
  3. K1W1

    K1W1 Senior Member

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    Hi,

    Loadline explained in detail.

    Waterline - Wikipedia, the free encyclopedia

    As for the variation between loaded and empty - there are a lot of things that can have bearing on this.

    Things like the vessel being heavier on launch than calculated at design time can reduce the loaded condition by making the difference between loaded and un loaded - (with a yacht this generally refers to fuel and water) to a smaller amount while the total full load displacement remains the same.
  4. discokachina

    discokachina Senior Member

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    Thanks for the information!

    I think I understand the waterline markings, GL stands for the Germanischer Lloyd classification society and F indicates Fresh Water so in this case the boat is rated to be safely loaded up to the horizontal line in the middle of the circle when in fresh water. ;)

    I am still confused by the bow markings. :confused: If the marks indicate the distance from the bottom of the keel to the waterline at the bow that means the keel of the boat in the picture is a little more than 2' below water. In actuality she is drawing about 7.5'. The 8 mark could be correct as her max draft is a little over 8'. In reality the distance between the 2 and 8 marks is only about 2'. In this case since her keel is about 7.5' below the water shouldn't the mark be a 7 instead of a 2??

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  5. K1W1

    K1W1 Senior Member

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    Hi,

    The keel or deepest part isn't attached directly below the bow normally.

    This is the draft forward, as she loads fuel she will no doubt go down by the head more than overall so when full and that boat looks like it has been down by the head a lot she will be even on her marks.
  6. wscott52

    wscott52 Senior Member

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    Just a thought but 2 meters is 6 1/2 feet. It still doesn't seem like the "8" can be made to work if the markings are in meters.
  7. K1W1

    K1W1 Senior Member

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    Hi,

    The OP states everything in Feet so where did the Metric system come into it?

    Here is something about draft marks.

    http://en.wikipedia.org/wiki/Draft_(hull)
    Last edited: Oct 23, 2011
  8. Capt J

    Capt J Senior Member

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    There is definately 2 feet between the 4 and 6 and also 2 feet between the 6 and 8 in that picture. It is accurate, but it looks decieving in the picture.

    In the top picture the center lineof the circle is the salt load line, the line next to the F is the freshwater line.
  9. wscott52

    wscott52 Senior Member

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    I didn't see him mention anything about the draft marks being in feet. He also said they aren't right if they're in feet. It was just a guess since meters are about the only other units that would be used.
  10. Innomare

    Innomare Senior Member

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    I don't know if they do it any differently in the States, but usually the draught numbers are in dm (decimeters). So 4 would mean a draught of 40 cm.
    That also seems to be correct with your statement that there's about two feet between mark 2 and mark 8.

    That said, the numbers seem to be very low to me, because even forward, you should be referring the draught to the baseline, not to the local deepest point. That way, if you read the same numbers fore and aft, the boat is "on even keel".

    Bruno

    PS - looking at the numbers, I think there's perhaps a number 2 missing in front of each number. Numbers would then be 28, 26, 24, 22, which would represent 2.8 m, 2.6 m, 2.4 m, 2.2 m draught.
  11. discokachina

    discokachina Senior Member

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    Thanks Bruno, that makes perfect sense.

    8 = 2.8m = 9ft 2in
    6 = 2.6m = 8ft 6in
    4 = 2.4m = 7ft 10in

    Those numbers match her published min and max drafts! Mystery solved! ;)
  12. NYCAP123

    NYCAP123 Senior Member

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    I believe K1W1's explanation is on the money. If you look at the water mark it's just below the 6' mark which would be reasonable for the bow (did you happen to notice the numbers at the stern?). Loading fuel could account for why she's sitting high or that bow could be touching bottom.
  13. discokachina

    discokachina Senior Member

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    I can't see any numbers on any of the pics have of her stern. I will have to try and get some of below her swim platform.

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  14. NYCAP123

    NYCAP123 Senior Member

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    I see a reflection of something in the blue paint about 4' forward of the stern. That looks like it.
  15. discokachina

    discokachina Senior Member

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    I went back and looked at the pic again and see what you might be talking about. But, on second look I also notice what I think is a "3" about a foot to the right of where the bright blue paint turns almost black just before the side turns into transom. Would a 3 make sense? 2.3 meters = 7.5 feet which is the vessels min load draft?
  16. Yachtjocky

    Yachtjocky Senior Member

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    draft marks

    From Wiki:

    The draft aft (stern) is measured in the perpendicular of the stern.
    The draft forward (bow) is measured in the perpendicular of the bow.
    The mean draft is obtained by calculating from the averaging of the stern and bow drafts, with correction for water level variation and value of the position of F with respect to the average perpendicular.

    The draft of a ship can be affected by multiple factors, not considering the rise and fall of the ship by displacement:
    Draft variation by list
    Draft variation by water level change[clarification needed]
    Allowance of fresh water draft variation by passage from fresh to sea water or vice versa
    Heat variation in navigating shallow waters

    Draft scale

    The drafts are measured with a "banded" scale, from bow and to stern, and for some ships, the average perpendicular measurement is also used. The scale may use traditional English units or metric units. If the English system is used, the bottom of each marking is the draft in feet and markings are 6 inches high. In metric marking schemes, the bottom of each draft mark is the draft in decimeters and each mark is one decimeter high.
  17. NYCAP123

    NYCAP123 Senior Member

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    Sorry, I'm used to seeing that in feet which is what it appears to be at the bow. I also can't imagine them leaving the 2 in 2.3 meters to the imagination nor using fractions of feet or meters. Since I can't actually see it, I'm going to guess that (from what you've written) that the "3" is actually an "8" with maybe a little heavy handed painting on one side. Meaning that the stern is just under 8' draft and the bow normally (per the water stain) at just under 6' but currently just over 3'.