Strut Keel Design and Engineering Grounding Forces

Discussion in 'Boat Design' started by an2reir, Apr 21, 2020.

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

    Sound plan, good stuff.

    Quite possibly.
    BUT... if you wish to account for such a load case, the strength of the keel/skeg will be so large, it will be draggy and also affect flow into the prop.
    Whilst this is a "nice" to do... there is only so much you can account for.

    I had a similar problem designing P-brackets on our patrol boat. I just took a load case if one blade is damaged and then the prop spinning unbalanced and eccentrically, the forces it creates became the load case.
    I designed the palm to suit - and touch wood, hasn't broken yet after many years of service.

    Try not to over think this...

  2. an2reir
    Joined: Sep 2001
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    an2reir fifty boat designs

    Hi Ad Hoc thank you for your very friendly and useful feedback. I will absolutely follow your advice. I am thinking of the situation a friend of mine senior engineer Bob Bradfield in the Royal National Lifeboat Institute marine Design and Engineering Department told me one day about a mission one of the RNLI boats had to go try save some kinds that were stranded in a cave somewhere on Dorset coast. The lifeboat could not go too near that cave. I think I saw a video of a canadian Coast Guard boat attempting to do the same namely approach people stranded on rocks near the shore on stormy weather and powerful swells. That situation may be considered somehow close to this video of coast guard assisting

    The idea is to keep the manoeuvering capability even when hitting rock. I myself have ran aground twice on sailing yacht but was able to tow myself off the rock. I think the ideal will be if the boat keel can take the chrages of hitting rock without distorting in such way as to block propeller, as well protect propeller - but keep power to motor off ; and in the case of a massive load situation break clean so does not block propeller. Very likely the solution seems to be that of bolts that are designed to be the weak link
    Last edited: May 16, 2020
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