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Raising Boom for Bimini

Discussion in 'Ask All Sailors' started by 76Oday20, Jan 21, 2019. Add this thread to a FAQ

  1. Meriachee

    Meriachee

    Joined Aug 1, 2011
    3,049 posts, 976 likes
    Catalina 270
    CA Wabamun - on the orange ball
    Raising the boom requires cutting a sail. Hopefully, it’s not cutting THE sail, unless there’s a NEW sail and you’re cutting the original sail.
    (I hope that makes sense)
    Cutting the sail would normally entail cutting X from the foot, and that’s the biggest bulk of the sail area/material. So yes, you’re making the sail smaller, but you’re doing it somewhat exponentially, and actually reducing the forces on the mast and rig proportionally.
     


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  2. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,164 posts, 2,110 likes
    O'Day 19
    US Littleton, NH
    By "higher", it would be geographically higher, not quantitatively higher. This means, more of the force applied to the mast would be higher above the righting force (percentage). But, overall, there is less sail area, so less force.
    If you kept the same boom, would it interfere with the backstay?
    If you kept the same sail and cut off the bottom, that is less sail area than if you had a new main cut to fit. A custom cut sail would have the same foot length as the original to fit the boom. The clew would come out to the same place as on the original sail. The cut down sail would also have a shorter foot, as well as a shorter luff. Of course, if you have a lot of roach as you might with a full batten main, the foot length would remain pretty close to the original foot.

    -Will (Dragonfly)
     


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  3. Ron20324

    Ron20324

    Joined Jan 22, 2008
    6,707 posts, 798 likes
    Beneteau 323
    US Annapolis MD
    WHY NOT TAKE ONE FOOT OFF THE TOP, NOT THE BOTTOM.
     


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  4. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,164 posts, 2,110 likes
    O'Day 19
    US Littleton, NH
    What happens to your battens and the roach and the backstay?

    -Will (Dragonfly)
     


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  5. mm2347

    mm2347

    Joined Oct 21, 2008
    225 posts, 24 likes
    oday 222
    US niagara
    What a great excuse to get a new, custom cut mainsail!! "Sweetheart, we will never have to buy sunscreen again. A new sail will save us money." Gene: your upgrades and workmanship have been super, but this one is over the top.
     


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  6. daviddp

    daviddp

    Joined Aug 7, 2018
    24 posts, 9 likes
    o'Day 34
    113 us NY
    I recently had my sail recut on my O'day 34 to raise the outboard end of the boom by 4" down to zero @ the mast. Head room. The cost was $200 to cut the sail and redo the clew. The tack did not change, the sailmaker suggested the idea to allow clearance for a new dodger and reduced the loss of sail area by 1/2 of what it would have been had it been cut 4" at both ends of the boom. The boom stays where it was in my application. You could do the same if you don't want to raise the mast end of the boom, just raise the cockpit end. As to added stress on the mast from raising the boom upward I have to believe that the boat was not originally engineered to such exacting standards as to allow for a slight variance in the location of the boom.
     


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  7. Meriachee

    Meriachee

    Joined Aug 1, 2011
    3,049 posts, 976 likes
    Catalina 270
    CA Wabamun - on the orange ball
    Taking one foot off the top completely alters the forces applied to the leech, unless you are prepared to install a solid top cap to spread the load.
     


  8. 76Oday20

    76Oday20

    Joined Jan 6, 2018
    14 posts, 2 likes
    Oday 20
    ? US Hilton Head
    Hi Gene, I purchased a thumb screw from Rudy at D&R Marine that slides in my mast track. This can be placed below the boom to prevent the boom from slipping out of the hole. I have also seen someone make a metal plate to cover that hole. I believe it was on the Stingy Sailors blog.
     


  9. 76Oday20

    76Oday20

    Joined Jan 6, 2018
    14 posts, 2 likes
    Oday 20
    ? US Hilton Head
    Thanks Will, you bring up some good points. I also wondered if the boom would need to be shorter. I am going to order a new boom and the earlier year model of this boat had a shorter boom, that might work? Thank you!!
     


  10. 76Oday20

    76Oday20

    Joined Jan 6, 2018
    14 posts, 2 likes
    Oday 20
    ? US Hilton Head
    Thank you Daviddp, I am going to step the mast and play around with this idea too.
     


  11. DrJudyB

    DrJudyB

    Joined Jun 25, 2004
    243 posts, 159 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA
    You'd have to trim the roach and move the top two battens, as well as replace the headboard. If you don't trim the roach, it will overlap the backstay too much probably

    We built many sails for boats and we raised the boom a few inches. It has never caused any problems. There is one important limitation: You can't raise the boom if doing so would make it impossible to use the mast feeder. Usually there is a way to modify the gooseneck to make it practical.

    If you're modifying the mainsail, it would be far more practical to cut the foot in terms of the amount of work. As already mentioned, You can probably cut the clew to raise the foot so the boom meets the mast at an 86 degree angle. Raise the aft grommet for the reef as well. If

    If you make the angle more acute than about 86 degrees, the slides may bind a few inches above the gooseneck and prevent it from lowering all the way.

    I personally would never recommend putting the boom above the mast feeder.

    Judy B
    Semi retired loft owner.
     


    Last edited: Jan 24, 2019
    76Oday20 likes this.
  12. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    4,164 posts, 2,110 likes
    O'Day 19
    US Littleton, NH
    SEMI RETIRED? What the #€||?!?! My sail maker can't retire!

    -Will (Dragonfly)
     


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  13. 76Oday20

    76Oday20

    Joined Jan 6, 2018
    14 posts, 2 likes
    Oday 20
    ? US Hilton Head
    Thank you for your expertise Judy B
     



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