Double ender designs slow

Discussion in 'Boat Design' started by adam stevens, Sep 10, 2020.

  1. adam stevens
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    adam stevens New Member

    I am specifically speaking about Colin Archer designed pilot boats from late 1800's to early 1900's. I hear complaints of these designs (as well as other CA inspired double enders) being extremely slow. They are heavy and full keeled but are double ender designs inherently slow for other reasons? English pilot cutter designs are also heavy and full keeled but seem to not get as bad of a reputation as the Norwegian double enders in terms of speed. Obviously they are all slow compared to light weight modern day designs and construction materials but I am wondering about comparisons between the English and Norwegian pilot cutter designs. Thanks
  2. bajansailor
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    bajansailor Marine Surveyor

    Welcome to the Forum Adam.

    I think the main reason why they are considered to be 'slow' (relatively) is that they are very beamy (low L/B ratio), very heavy (high displacement / length ratio), with conservative sail area / displacement ratios while being pretty 'full' in the midships section.
    I have sailed on a ferro cement Colin Archer derivative many moons ago - 39' on deck and 19 tons displacement. Yes, she was 'slow' - in winds less than say 15 knots. But she could easily carry full sail in 20 knots, and she would stomp along happily when other boats would be reefing.
    I think that maybe the English pilot cutter are not so extreme in their hull form, with finer ends.
    Last edited: Sep 10, 2020
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  3. BlueBell
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    BlueBell . . . . .

    Welcome Adam S.

    Slow, maybe, but they used them for a reason.
    I don't care how slow a boat is if it gets me home in a storm.
    Seaworthy is a word that comes to mind.

    Edit: Sorry, I didn't answer your question.
    No, double enders are not typically or inherently slow.
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  4. Will Gilmore
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    Will Gilmore Senior Member

    I have always known double endeders to be particularly easy sailers. At or bellow displacement speeds, the stern moves the water very easily off for less turbulent release.

    They can have other problems from slightly reduced aft flotation that can allow for squatting near or above hull speed and they naturally have more rocker than a square transom, but a well trimmed and balanced double-ender can sail extremely well.

    -Will (Dragonfly)
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  5. fastwave
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    fastwave Senior Member

  6. Dolfiman
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    Dolfiman Senior Member

    Double-ender option should not automatically associated with heavy blue water designs, Ray Hunt explored a lot the double-ender option for light racing sailboats with its 201, 401 and 501 designs , competitive in those days :
    C. Raymond Hunt International 210 - Classic Sailboats
    C. Raymond Hunt International 410 - Classic Sailboats
    C. Raymond Hunt International 510 - Classic Sailboats

    The Sliver quoted above by Fastwave is in line with these light fast double-enders,
  7. Waterwitch
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    Waterwitch Senior Member

  8. gonzo
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    gonzo Senior Member

    If you want to compare a Colin Archer to faster designs that can actually sail upwind, check designs by German Frers (senior) and Manuel Campos.
  9. philSweet
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    philSweet Senior Member

    See also the designs of Albert Strange for a look at boats contemporary with Archer's
  10. sharpii2
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    sharpii2 Senior Member

    I don't see why a double-ender would have more rocker than a transom-stern boat. I would think it would be the other way around.

    A transom stern boat needs to carry its transom above the WL. A double-ender has no such requirement. One I designed has its stern-post about three inches under water. This is intended to discourage broaching, and also to limit the rocker of the keel son.

    One design I played with would have the top of the stern post higher than the top of the bow one, as this design would be sailing down wind much of the time.

    I think the double-ended is best for slower boats, which are likely to be menaced by following seas. But the stern-post had better be high.

    A disadvantage of a double-ender is that it needs a fuller bow to get the same amount of sail carrying ability as a transom-stern boat with the same beam and same ballast placement. All the more reason to pick this plan-form for a boat designed to sail at hull-speed or less.

    It will typically have less deck area and less room down below than a more modern transom stern boat.
  11. Will Gilmore
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    Will Gilmore Senior Member

    Good point.

    I was looking at it from a pitching point of view. Even with the stem below the waterline, there is less flair to increase floatation as it sinks, where a square transom has lots of submerged flotation once it begins to pitch. Of course, the fullness and shape can be manipulated in the design. It doesn't have to be a fine stern to be a double-ender. [​IMG]

    -Will (Dragonfly)
    Last edited: Sep 13, 2020

  12. Velsia
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    Velsia Floater

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