Compairing Viking Boat stability to modern vessels

Discussion in 'Stability' started by Olie_b, Mar 10, 2009.

  1. Olie_b
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    Olie_b New Member

    Sorry for the abstract post, as you may be guessing already I am a student. My dissertation is on reconstructing anceint ships from archeologial data which has now lead me to this point.

    What would be good for me would be to compair some results from (very simple) tests I have subjected my model to so I can write up how this boat would perform and discuss if it would be sailed, rowed, used for long journeys, carrying produce etc etc

    I have found info on the STIX stability of loads of craft but would be really good if there was some straight forward Righting Moment charts I could easily access. I know the ISO code for STIX stability but cannot access that (yet) and also my model really is a much simplified... well - model.

    If anyone knows of a site/ book that I could look up to access righting moment data for a range of craft that would be a great help.

    Thanks Olie
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    You are a student of ...er......what is it you are studying..???

    This enables anyone reading this, to know how best to advise.
     
  3. rwatson
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    rwatson Senior Member

    Interesting study subject - I always wondered if those ships had some sort of ballast as a matter of course - probably plenty in the form of loot coming back, probably plenty in the way of stores going out.

    I wonder if there are any historical references on the loading and and usage of these boats ?

    This would have a profound effect on any calculations.

    ps - there have been a number of full scale reproduction craft built and sailed - they would have doen those calculations I am sure - just for insurance reasons.
     
  4. Tcubed
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    Tcubed Boat Designer

    The viking ships used beach stone as ballast, preferably smooth rounded granite stones, which are dense and not too harsh on the boat as well as plentiful around the shores they most frequently frequented.

    Being free and plentiful they would never hesitate to dump ballast to lighten ship, for extended rowing or to compensate for extra cargo, or for portaging etc.

    A large amount of flare was worked in to improve rowing performance, help throw spray down and provide extra buoyancy to leeward when nearing the heel limit.

    The ballast would be expeditiously thrown out leeward if the boat was overpowered in a gust. Without ballast the hull would float.

    I remember reading an account of a rescue in the descendant form of the viking ship; the femboering. These are essentially unchanged apart from a squaring off of the forefoot and heel to improve performance to windward.

    In the account one femboering was capsized with the two men on the keel. Another femboering sailed right at and over the capsized one, and the survivors latched on, one on each side, to clamber aboard.

    They also had an ingenious system to be able to lower the mast even when at sea (normal tabernacles get broken when you try to use it in a seaway due to the mast wracking forces) and the shrouds were tightened up with a long lever held in place with a piece of twine. This meant the shrouds could be released in seconds. Whenever rowing for any length of time against a stiff breeze they would lower the mast to reduce wwindage as much as possible.

    There is plenty of information to be found in the written sagas.

    If you have maxsurf you can quickly draw up a hull and run the stability program which will quantify the righting moments.

    The Oslo museum may even be able to provide you with some lines plans.
     
  5. Olie_b
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    Olie_b New Member

    Im studying a MEng in Mechanical Engineering,

    Yea im expecting there to be ballast in the base of these boats of some description. Im closely studying the Sutton Hoo Ship, as ive managed to access lots of information on this one! Its an Anglo Saxon ship rater than a strict Viking so there are some differences but things like construction and building materials etc are very similar. When it was buried it looks like almost everything was removed from the boat including any decking and the mastfish (bit that secures the mast???) due to it being dragged inland a fair distance. So im starting to investigate whether it would have been sailed or rowed (there are all ribs complete and present in the mid section and no evidence of a mast ever being positioned) (I say present, but actually there is no remailns left, only imprints in the sand!)

    Ive not come accross maxsurf, is this a industry standard programme or something I can use for free? (Also will it accept a CAD file? That would make my life much easier)

    Just to reitterate, im looking to compair the righting moments I have come up with against those from other boats - otherwise I will have nothing to discuss at the end of my report! And I forgot (again) to see if I can access the iso standard for the STIX stability from the uni library so I can see if I can calculate that.

    Thanks for your interest

    Regards

    Olie
     
  6. Tcubed
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    Tcubed Boat Designer

    The Sutton Hoo ship did indeed have plenty enough differences to not justify grouping it with the Nordic ships.

    As far as i understand the Anglo Saxon ships were less optimised for rowing, in other words they were mostly sailed.

    Maxsurf is not free, will exchange files with CAD and of course there are many programs which will do the same calcs, just that i've found Maxsurf to be one of the most user friendly and therefore fast to learn.

    The 'mastfish' is what i was referring to as part of a broader system for mast lowering in adverse conditions.
     
  7. safewalrus
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    safewalrus Ancient Marriner

    Olie son, get ye to the Shetlands, see some of the real things in action, tis nearer than Norway
     

  8. apex1

    apex1 Guest

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