Fore-stay Loads

Discussion in 'Boat Design' started by Jay Thompson, Mar 25, 2018.

  1. Jay Thompson
    Joined: Mar 2018
    Posts: 4
    Likes: 1, Points: 13
    Location: Etel, France

    Jay Thompson Junior Member

    I am currently building a foiling offshore racing prototype. We have a mast engineer who is specking the mast. My sailmaker is very busy so I looking for somebody or recombination of software that can calculate headstay loads of various sails using the Righting Moments.
     
  2. TANSL
    Joined: Sep 2011
    Posts: 5,926
    Likes: 239, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

  3. Blueknarr
    Joined: Aug 2017
    Posts: 743
    Likes: 131, Points: 43
    Location: Colorado

    Blueknarr Senior Member

    Why isn't your mast guy doing the nessicary calculations?
     
  4. Joakim
    Joined: Apr 2004
    Posts: 892
    Likes: 52, Points: 28, Legacy Rep: 422
    Location: Finland

    Joakim Senior Member

  5. Jay Thompson
    Joined: Mar 2018
    Posts: 4
    Likes: 1, Points: 13
    Location: Etel, France

    Jay Thompson Junior Member

    Thanks I will check into these various options.
     
  6. Jay Thompson
    Joined: Mar 2018
    Posts: 4
    Likes: 1, Points: 13
    Location: Etel, France

    Jay Thompson Junior Member

    The reason is that he is a mast engineer and does not have the sail design software to appropriately check the head stay loads for various sails. Normally it is the sailmaker that can do this but mine is busy. The mast guy is ready to start so it is a question of workflow.
     
  7. Blueknarr
    Joined: Aug 2017
    Posts: 743
    Likes: 131, Points: 43
    Location: Colorado

    Blueknarr Senior Member

    I would put serious consideration into replacing both sailmaker and rigger, as both are bulxxxtting you. It takes longer to explain his reluctance to perform calculations than to actually do them. My experience running rigs is that the greatest load placed on forstay is from flexing mast with backstay. Forstay load and backstay loads must balance each other or the rig will topple towards the greater.
     
  8. TANSL
    Joined: Sep 2011
    Posts: 5,926
    Likes: 239, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    and, according to your experience, how would loads be calculated on the forestay and backstay?.
     
  9. Jay Thompson
    Joined: Mar 2018
    Posts: 4
    Likes: 1, Points: 13
    Location: Etel, France

    Jay Thompson Junior Member

    The Rigger I can't replace because he is me. We are building a mast not rigging it, yet. This is not a strait forward as it seems, foils changes everything, and everything is dynamic and a function of speed. Your example is somewhat correct that buffering on the mast is one of the biggest consideration when designing a mast. In this case it is different because as you reach greatest RM the buffering becomes less because you are foiling at this point. If you create a mast that can "withstand" the RM that the foils create by calculating in the normal way, you will end up with a mast that is too heavy. Thus in this case you would calculate a mast to withstand the RM then reduce safety factors to create a light mast. Here is where you need the most information possible, so to have a sailmaker create a sail virtually and give us headstay loads for a given RM would really help.
     
  10. gonzo
    Joined: Aug 2002
    Posts: 13,953
    Likes: 486, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    It is irrelevant where the righting moment (RM) comes from. The forces on the mast are what you need to calculate. Safety factors are not the best way of designing. You should analyze each component separately for stresses; particularly if you are looking for minimal weight. Safety factors, if used, are added later at the end of the design. It is incorrect to design with safety factors and then take them away.
     
  11. TANSL
    Joined: Sep 2011
    Posts: 5,926
    Likes: 239, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    In the calculation of any structure, a safety factor is always used. That is why it is calculated so that the stress in any element does not exceed the "maximum admissible stress", which is much lower than the maximum stress that the element could withstand before failing.
    In the rigging calculation, for example, the NBS method clearly establishes the applicable minimum safety factors.
     

  12. CT249
    Joined: May 2003
    Posts: 1,228
    Likes: 66, Points: 48, Legacy Rep: 215
    Location: Sydney Australia

    CT249 Senior Member

    In foilers isn't the greatest load created by the rig loading up when the boat crashes off the foils?
     
    philSweet likes this.
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.