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Boat Balls, how to get an 80' mast under a 65' bridge

Discussion in 'General Sailing Discussion' started by Norseman, Sep 17, 2011.

  1. Norseman

    Norseman Senior Member

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  2. PropBet

    PropBet Senior Member

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    I wouldn't do it on mine, but I've seen them before. At first in awe, and then in slight awe the second or third time.
  3. CaptTom

    CaptTom Senior Member

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    I think it takes a really big pair of balls...boat balls that is, to even consider trying that. Just watch out for the guy on shore with the rifle who shoots the ball right when you are under midspan. Then you'll be left holding your balls...not the boat ones. :cool:
  4. lobo

    lobo Senior Member

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  5. brunick

    brunick Senior Member

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  6. Kevin

    Kevin YF Moderator

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    I seem to recall one of the Volvo Ocean Race boats doing that a few eyars ago without using weights... they just canted the keel.
  7. Fireman431

    Fireman431 Senior Member

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    I wonder how much the mast loves that 4000 lbs being suspended from the tip?
  8. K1W1

    K1W1 Senior Member

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    Hi,

    Have you thought how much load would be on it when running a spinnaker in a good breeze?
  9. PropBet

    PropBet Senior Member

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    You could hang 4X that if needed.
    There's a semi complex mathematical formula to figure it out based on wind speed, angel of attack, total sheet(s) surface area, ballast, etc. etc.
  10. Fireman431

    Fireman431 Senior Member

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    Amazing. I had no idea masts were that strong.
  11. PropBet

    PropBet Senior Member

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    Google Wind Load Calculator for more reading.
    Basically Load in Pounds = Sail Area * (Wind Speed )2 * 0.00431

    So mt Father's boat has roughly 1800 feet of mainsail, which at 20 kts of wind is 3100 lbs of force. Now add a headsail, jib, sock, etc.

    My comment earlier (the mast can support 4X that) was perhaps a slight exaggeration in that I'm not going to attempt to hang 16,000 lbs off the top of the mast, but I'm confident in their strength and are build to endure great amounts of pressure.
  12. Kevin

    Kevin YF Moderator

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    I've found some actual load numbers from the VOR70 and ACv5 yachts:

    Volvo 70
    Forestay: 17 tons
    Runners: 13 tons
    Windward Shroud: 25 tons
    Mast Compression: 62 tons

    ACv5
    Forestay: 20 tons
    Runners: 12 tons
    Windward Shroud: 35 tons
    Mast Compression: 70 tons

    Albeit, these are race boats built far stronger than the average cruiser... but if they can sustain a load of 50-70 thousand pounds on the windward shroud then 4000 pounds isn't much at all.
  13. AnotherKen

    AnotherKen Member

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    Get the owner of the Maltese Falcon to show you how they do it, no balls required!
  14. dieseldan

    dieseldan New Member

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    There is a way to heel a boat sufficiently for the mast to pass under a bridge with no balls required!

    Line the deck on one side with empty barrels and fill them with water until the mast is sufficiently heeled.

    To gauge the amount of heeling a weighted line a foot or two shorter than the bridge clearance height is attached to the mast head.
    As the mast heels this line hangs like a plumb line over the water. When the weight of the barrels causes the weight to touch the water,
    the mast will clear the bridge.

    This technique is used at the Port Myakka 49' horizontal lift railroad bridge on the Okeechobee Waterway in South Florida.

  15. dieseldan

    dieseldan New Member

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    More Boat Balls
  16. Capt Ralph

    Capt Ralph Senior Member

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    I used to help push botes thru that bridge in the 90s. A bunch of kids would come out from Indaintown Marina and load the boom. One mast we pulled over from a work boat, Just made it.
    The funny thing, we would come back out to clear the keel the same way.
    SFBs.
  17. Pauline

    Pauline New Member

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    Maybe I am retarded asking this but at low tide wouldn't you have more clearance than at high tide so is there any dates that where there are minus low tide I am very ignorant in knowledge and would be interested to know more about that
    Last edited by a moderator: Mar 26, 2019
  18. Capt Ralph

    Capt Ralph Senior Member

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    The Okeechobee Waterway levels are controlled by drought and its canal locks that try to keep the water level up.
    There is no lunar tide here.
    Hope this helps.