Mast and boom: Matching set for emergency dismasting

Discussion in 'Sailboats' started by JosephT, Oct 23, 2018.

  1. JosephT
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    JosephT Senior Member

    That's right James. I did some sailing in the Caribbean last spring and decided to do some research this time around on all of the islands before I departed. Below is a very good book that also discusses available trees & forests on the islands. I learned the Caribbean islands used to have VERY TALL forests with trees that would "reach to the stars". European colonists arrived, chopped them down and built ships from them. Imagine what these islands would look like today had not the early explorers been so desperate for lumber.

    Larger land masses do hold trees though. Rounding up some spare lumber is definitely a good idea even though it has to be spliced and lashed together.

    https://www.amazon.com/Wildlife-Caribbean-Princeton-Pocket-Guides/dp/0691153825/
     
  2. JamesG123
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    JamesG123 Senior Member

    Desperate for lumber, but also clear cutting to make room for plantations.
     
  3. sharpii2
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    sharpii2 Senior Member

    One problem with modern rigging cable is it is not very useful for jury-rig purposes. The stay or shroud cannot have its length adjusted because of the type of terminals used, which are used because of the type of wire cable being used, 1 x 19. I prefer a more traditional rig with a short mast and a longer boom. This way the stretch of the standing rig isn't such a critical issue. Now 7 x 49 wire cable can be used. It is flexible enough to be able to have loops at the ends instead of pressed fittings. These loops, in turn, can be held with cable clamps. These cable clamps can be loosened to adjust the length of a stay or shroud. this can be very useful in situations where a shortened mast or even a boom standing in place of a mast may have to be supported. If the boom is longer to start with, it will certainly be a better jury mast.
     
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  4. Doug Halsey
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    Doug Halsey Senior Member

    Flexible cable is definitely easier to work with, but 1 X 19 is not impossible.

    In the smaller diameters (1/8" or less), standard swaging tools & NicoPress thimbles & sleeves work just fine.

    I'm not sure about anything larger than that, though.
     
  5. sharpii2
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    sharpii2 Senior Member

    1/8" or less would be little or no help for a five to ten-ton cruising sailboat. I suppose if you had some 7 x 49 cable on board and an effective way of cutting the 1 x 19 stuff, and a good number of clamps, you could make 7 x 49 ends to your 1 x 19 cable. Enough 7 x 49 stuff and a sufficient number of clamps shouldn't take up too much space.
     
  6. JosephT
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    JosephT Senior Member

    Very good points Sharpii. You should put this in a generic specification that can be scaled up/down depending on the size of the vessel. Call it the "Emergency Jury Mast Specification", with details on the general approach, cable sizes, etc. I wonder if anyone has done that before. It would definitely come in handy for skippers who are making an offshore passage. Of course, they should know how to cut cables, install pressed fittings, etc. in advance so they know what they're doing. A spec for your typical 40ft sloop, for example, would be nice. If existing sails could be rigged up too that would be a bonus. One would think the storm sails should survive in most cases for reuse.
     
  7. gonzo
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    gonzo Senior Member

    I disagree that most dismastings occur when a boat capsizes or is hit from the side. I have observed most dismastings due to standing rigging failure, shock loads from uncontrolled jibes and poorly designed rigs. Do you have any statistics on dismastings?
     
  8. JosephT
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    JosephT Senior Member

    You have a very good point Gonzo. I apologize for the confusion. There are probably a few categories for mast failures:

    • Capsize in rough seas/storms (as primarily discussed here)
    • Poor design
    • Neglect
    You're right there is probably even a larger quantity of mast failures in the latter two categories. For the sake of this discussion we're mainly focusing on offshore bluewater boats. We're mainly focused on ways to plan for erecting an emergency mast to get back home. I wonder if there are any good books on this specific topic.
     
  9. nota
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    nota Junior Member

    LOCALLY HURRICANES #1 mostly at anchor or dock on BARE POLES or roller UN FURLING RIGS
    followed by racing idiots with too much sail in too much wind on too lite a rig

    still think a carbon lite top mast is an answer to most cases storms, seas or idiots both
     
  10. David Cooper
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    David Cooper Senior Member

    How viable would a large kite (on a string - no mast) be as a back-up propulsion method? You can't rely on being able to salvage mast parts or boom as you might have to cut them away to minimise damage.
     
  11. JosephT
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    JosephT Senior Member

    I've read about some sailors using kites for propulsion, but mainly on smaller boats. It would have to be a pretty big kite for a larger vessel. You would definitely need a winch to ease it out/in and a way to trim it. Found this chap sailing his catamaran with one. He's got it up high to catch more wind (a possible benefit with a kite). For areas with 5-15 knot steady winds I think it would be viable, like the east to west trade winds coming across from West Africa to the Caribbean. Anything beyond 15-20 knots might be vulnerable to shredding (I've witnessed that first hand with most spinnakers.). Seems 25knots is about the breaking point for most spinnaker kites.

    So yes definitely an option! If the mast were lost, you could rig it on deck, but a short makeshift mast would do it. The pic below shows a white frothy wake in the 3-5 knot range (educated guess).

    [​IMG]
     
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  12. JosephT
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    JosephT Senior Member

    Another pic of a kite with good wind.

    [​IMG]
     
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  13. sharpii2
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    sharpii2 Senior Member

    PRE-PLANNED JURRY RIG

    Now that reports of additional dis-mastings are coming in from from this stormy Golden Globe race, I have spent more time thinking about preplanned jury rigs. It is curious that I have ended up with a solution similar to the one originally posted on this thread.

    At first I thought of how superior boats with shorter rigs were in this regard. This is because of two reasons:

    The mast is shorter and, even though it may be heavier, it may be easier to some how hoist back on board the boat after it has been knocked down.

    The boom will be proportionately longer, so if the mast is lost, it will be better suited as a stand-in mast.

    The idea was to use the jib as a stand-in main by hoisting it upside down.

    But as I thought about this some more, it occurred to me that short masted boats are not that common nowadays. And it would be a much better idea to come up with a system which would work with the taller masted 7/8ths and mast head rigs.

    With solar panels and computerized auto-pilots, sloop rigs are now practical for blue water boats even with short, deep, wing like keels and spade rudders. The addition of a roller-furling jib makes them easier reef in a manner which insures proper balance. Add that to the fact that they do perform better than the long-keel, short mast, three sail types, and we have an almost certainty that these will be the dominant blue water cruising type. The long-keel, short rig types will become more and more rare (but will not completely disappear) as time marches on.

    I decided that expecting the skipper and her/his typical one person crew to wrest the broken mast back aboard during storm conditions is too much to ask. So now I'll assume the mast and all of it's stays and shrouds will probably be jettisoned.

    The problem is that the Boom on the taller masted type is usually very short, probably too short to use as a stand-in mast. Any solution I came up with would have to take this into account. The boom would probably be too short to even loft the clew of the working jib clear of the deck. It needs an extension.

    It also occurred to me that the luff of this sail would probably be too long to allow using using the original mast step, unless some kind of makeshift bowsprit is to be set up. And even if it was, the CA of this new jib-only cat rig may end up too far forward. So now I'm convinced that the stand-in mast will be stepped considerably further aft than the original, maybe as far aft as the cockpit. This would be somewhat convenient as it will be not only easier to set up there, but will be easier plan local re-enforcement for as well.

    But now the Boom needs to be even longer. The clew of this upside down jib has to clear the typical deck house now too.

    And space on board a typical cruising boat is very limited., and so is it's carrying capacity. So carrying and extra spar which will probably never be used will probably not be a popular option. But what about an extension for the original Boom?

    It could be made of the same extrusion as the boom, with maybe two bolt holes drilled through its sides. The Boom could also have two holes drilled through its sides. Sturdy aluminum plates or channel stock could be used to join the two together. Wood planks could be used for this purpose too. These joining pieces will probably need provision for lower back shrouds and maybe even lower side ones as well. The Boom will need provision for two back shrouds and and two side shrouds as well as for a fore stay. This could be done in a number of ways. One would be to provide for two simple hounds on the end that is to be on top.

    The attachment points on the boat could be strategically placed cleats. These would have to be specially designed to be used for this purpose, as well as for their usual job.

    The hull would also have to be locally reenforced to take these new vertical loads, which can be quite large.

    Pre-cut rigging wire can be stowed for this purpose, with pairs of traditional cat-heads instead of the usual rigging screws. These will allow for a greater tolerance in lengths.

    This new rig may go upwind reasonable well; but it may be a bear to get it to go down wind. Some sort of minimal drogue may be necessary to pull the stern upwind.

    Though far from perfect, this pre-planned jury rig may mean the difference between having to scuttle the boat after an expensive rescue, or being able to reach port, saving untold tens or even hundreds of thousands of dollars.

    For a 40 ft, 7.5 ton cruising sailboat, this may mean several hundred pounds of extra gear, as well as a spare working jib (which would probably be on board anyway). It may be seen as cheap insurance.
     
  14. JosephT
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    JosephT Senior Member

    Very good feedback Sharpee. Considering the likely repair conditions (lousy weather, weakened/wounded skipper) I agree these modifications should be done before departing. If not, the likelihood towards requesting a rescue becomes mandatory. I'll note your requirements below and add some additional questions or comments.

    • Sail plan: Use a jib upside down with centrally located mast (CAT rig as you describe). Mast moved aft to emergency location (hull reinforced for new mast step location).
    • Old boom: The old boom is used as a mast and requires an extension to be of any use. Comment: An aluminum extension may be difficult to store. Perhaps multiple pieces of pre-formed wood could be joined/lashed together to form the extension. May be cheaper than a custom extruded extension.
    • New boom: Q: What will you use for the new boom, or will the new mainmast fly the sail like a jib? I suspect the latter (no boom required).
    • Shroud cleats: You mention special cleats that are dual purpose (cleats or shroud attach points). Love this idea.
    • Rigging wire: Pre-cut with all hardware. Love this idea.
    I would also be temped to fly a new jib off of the existing forestay (vs mount a bowsprit). Any concept for a given vessel would need to have the sail plan math & rigging plan done in advance. You definitely don't want to depart and have to call your nautical architect on a satellite phone while underway!

    Alternate sail plan: So this really boils down to having an alternate sail plan designed in (or retrofitted) from the start. This would make the nautical architect say to him/herself: What if the vessel lost its mainmast and had nothing but a boom? What's the alternate sail plan look like? What are its performance limitations? This would be valuable for bluewater sailboats.
     

  15. JosephT
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    JosephT Senior Member

    Stumbled onto this real world example with many lessons learned. Seems cotter pins were a big headache on making progress fast! Like the old saying: The devil is in the details.

    "Tethered 20 feet above the deck, I felt that the words from Bill Seifert’s Offshore Sailing were being bounced out of my memory: “Cotter pins shouldn’t be bent open more than 10 degrees.” The cotter pins that were bent open at small angles, holding dangling rigging, were easy to slip free from the clevis pins; those bent into curlicues were taking all my effort, strength, and patience to bend straight with pliers and a small screwdriver. They were becoming a real headache, in every form."

    Ref: When the Stick Comes Down https://www.cruisingworld.com/how/when-stick-comes-down
     
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