Calculating ballast for a motorsailer

Discussion in 'Motorsailers' started by Annode, Sep 22, 2019.

  1. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    That's a no then.

    See i thought you wished to engage and learn. And it seems even the classic 'know your audience' evades you - like the entire subject matter at hand.
    You prefer to obfuscate and misdirect and deflect...rather than answer questions from those that you seek answers, to enable your understanding.
    Most odd behaviour...
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Annode, people ARE trying to help you - I and others are still waiting patiently for answers to questions we have asked previously.
     
    Last edited: Oct 15, 2019
  3. Annode

    Annode Previous Member

    Yes, I am just a little bored with the invective that must be stowed to pursue this here.

    This boat is just about identical but a little shorter and lighter. The keel they gave it extends below the bottom of the rudder line on this boat. I assume that is all their naval architect deemed necessary.
    http://pacificmarine.org/blog/donat...-shipyard-motorsailer-1968-94-seattle-wa-2-2/

    Thanks to those that made constructive suggestions.
     
  4. BlueBell
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    BlueBell . . . . .

    Yes.
     
  5. bajansailor
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    bajansailor Marine Surveyor

    Brilliant! Thank you Annode for the link above. This helps a lot.
    For those who haven't opened the link, here are a few drawings of the vessel.
    The WR155 photo is of the original vessel in the 60's before she was converted to a yacht.
    I think that I could generally say that if you followed the same path re your vessel conversion you cannot go wrong - Vripack is a very respected naval architecture group in the Netherlands, and if they thought that the simple welded on keel was all that was needed, I wouldn't doubt their wisdom..
    If your hull is basically similar but longer, I am sure that you could weld on an extra keel in the same fashion.
    Could you post a photo of your hull for comparison please?
     

    Attached Files:

  6. TANSL
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    TANSL Senior Member

    @Annode, I guess you will not like my answer at all but with the information provided it is not possible to make any calculation. If you want a serious response, you must show how your ship's shapes are. Otherwise, you weld ballast on the outside of the keel until the result seems satisfactory to you. I'm sorry, others see it very simple and should explain to you how to do it, but for now, I don't see it as possible.
     
  7. Ad Hoc
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    Ad Hoc Naval Architect

    I wouldn't be so quick to jump the gun here.

    The dwg of the bits added to keel to me looks much more like they wanted a more firm landing area for slipping and to avoid damaging the prop, and bearing support for the now bigger rudder. Not so easy to slip if the keel flat is narrow, and not necessarily designed to be on the hard stand for weeks or more, on said keel (technically this is now a skeg). Also converting into a motor cruiser means an engine with more power than when she sailed. This means a bigger prop is required. Ergo, they dropped the keel/skeg line so the prop is not exposed below the keel.

    Therefore, it looks like a classic "docking keel" and prop protection only. Thus i would conclude it is bit of a stretch to assume the small increase in keel is for any stability reasons when there does not appear to be any reference to it.

    EDIT
    In addition it states this:

    "...He undertook her lengthy planning and conversion to a motorsailer. This was designed by the Vripack International naval architects of Sneek in the Netherlands,.."

    Ergo, it is safe to assume being competent NA, the did a complete weight and centres and stability review...and the fact she has sailed endlessly safely since, is proof of that.
    So, what else needs to be discussed...
     
    Last edited: Oct 15, 2019
    DogCavalry and bajansailor like this.

  8. The Wing Guy
    Joined: Mar 2022
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    The Wing Guy Junior Member

    No, that is the norm. Virtually every monohull (other than dinghy) will recover from a mast-in-the-water knockdown.

    In order to sail, a trawler would also need a leeway resisting means. The keel in a sailboat has two principal functions: stability and resisting leeway. Converting a trawler into a sailboat would be far far more expensive than simply buying a sailboat. To convert a trawler into a sailboat that would perform moderately well, you would also want to replace the entire hull with one better shaped for sailing.
     
    DogCavalry likes this.
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