Thoughts on a rig please???

Discussion in 'Sailboats' started by john.G, Apr 24, 2009.

  1. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    Here is a drawing of a gaff headed yawl rig for a 20 x 5ft boat with an extreme shallow draft. The boat is too small to have both a usable cabin and a cockpit, so the design goal is to work the rig from below. Strategicly placed hatches should facilitate this.

    Another requirement of this design was to have the masts stepped either at the bulkheads (5 ft from each end), on deck, or off center. This is why the Gaff mainsail is bigger than usual.

    Here is an essay I wrote about this rig:

    GAFF HEADED YAWL

    This rig may be the best of all that have been considered. It boasts a modest top hamper along with the lowest Center of Area Vertical (CAV). With its three sails and two masts it is the most versatile as well as the most complex. The Main Mast is held up with a fore stay and an upper (1.) and a lower (2.) shrouds. This is to improve survivability as well as to permit a lighter spar.
    The Gaff is on a gooseneck (3.) which rides up the mast on a car so it can get past the spreaders.
    A pair of Running Backstays (4.) holds the Jib luff tight. These have to be tightened and loosened on each tack, if the Mainsail is still up. Otherwise, they can be left tight on both sides for easier tacking.
    To reef, The Mainsail is lowered and is caught in the lazy jacks (5.). Or the Jib is hauled down with a down haul (6.) and the mizzen is furled by slacking the out haul (not shown) and by pulling in its Brail Line (7.) until the sail is bound against its mast. The Mainsail can also be reefed (probably with the Jib and Mizzen still up). It is easy to reach from two hatches, so it has the old fashioned Reef Ties (8.). Once that has been done, the Jib and Mizzen can be struck, leaving only the shortened main, about 50 SF, to drive the boat.
    The versatility of this rig helps recommend it. Its complexity somewhat condemns it. Rig (E)y, the Gaff headed Cat yawl, is just about the same except the jib is eliminated and the Main sail has been increased by lengthening the hoist with a taller Main Mast. No more need for Running Backstays or a Jib Downhaul or Jib Sheets. But the CAV goes way up forcing one to add ballast, carry slightly less Sail Area (about 10%), or do a combination of the two.
     
  2. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    Looks like my attachment didn't load. I'll try again.

    Here, again, is my essay:

    GAFF HEADED YAWL


    This rig may be the best of all that have been considered. It boasts a modest top hamper along with the lowest Center of Area Vertical (CAV). With its three sails and two masts it is the most versatile as well as the most complex. The Main Mast is held up with a fore stay and an upper (1.) and a lower (2.) shrouds. This is to improve survivability as well as to permit a lighter spar.
    The Gaff is on a gooseneck (3.) which rides up the mast on a car so it can get past the spreaders.
    A pair of Running Backstays (4.) holds the Jib luff tight. These have to be tightened and loosened on each tack, if the Mainsail is still up. Otherwise, they can be left tight on both sides for easier tacking.
    To reef, The Mainsail is lowered and is caught in the lazy jacks (5.). Or the Jib is hauled down with a down haul (6.) and the mizzen is furled by slacking the out haul (not shown) and by pulling in its Brail Line (7.) until the sail is bound against its mast. The Mainsail can also be reefed (probably with the Jib and Mizzen still up). It is easy to reach from two hatches, so it has the old fashioned Reef Ties (8.). Once that has been done, the Jib and Mizzen can be struck, leaving only the shortened main, about 50 SF, to drive the boat.
    The versatility of this rig helps recommend it. Its complexity somewhat condemns it. Rig (E)y, the Gaff headed Cat yawl, is just about the same except the jib is eliminated and the Main sail has been increased by lengthening the hoist with a taller Main Mast. No more need for Running Backstays or a Jib Downhaul or Jib Sheets. But the CAV goes way up forcing one to add ballast, carry slightly less Sail Area (about 10%), or do a combination of the two.
     

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  3. Timothy
    Joined: Oct 2004
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    Location: canada

    Timothy Senior Member

    sharpii I have been considering a similar rig for my boat . I have struggled with and discarded many incarnations as unworkable or to complex. I will have freestanding masts so a jib is impracticable as head stay sag would be significant. You might consider that if you went with the less complex jibless yawl rig although the center of effort would rise the main could be higher aspect for better windward performance and the mizzen smaller and further aft in better air . Perhaps these efficiencies might allow for less sail area and the center of effort need not rise that much. The open unshaded deck between sails could come in handy for a bimini made from a sanyo awning 215 watt solar panel to charge the agm batteries you might need for ballast to componsate for the higher center of effort.
     
  4. old_sailor
    Joined: Aug 2009
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    Location: Virginia

    old_sailor amateur boatbuilder

    Since you don'rt want to go to windward, and I don't blame you. I would agree with you and KISS. I would go with a cutter rig so that you can have a large roller furling jib and a relatively small main. In addition, I would definitely go with twin engines. If you are counting on the sails as auxillary, then you need a backup for your primary propulsion. Being a sailor, I count on my sails, storm sails, etc. for my primary, and with jury rigging if necessary, have a built in back up. The engine is auxillary. I know that is a big budget item, but it seems that you feel a lot more comfortable under power than under sail. CYA.
     
  5. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    I have decided to forego a stayless mast if the mast is tall.

    My main concern is the survivability of the rig in extreme conditions. A stayed mast is more likely to be still in the boat when the boat recovers from a capsize. Especially when carbon fiber spars are not used.

    The masts in my design are to be good old fashioned wood. This is to keep costs down and to ease replacement when necessary.

    In your case, carbon seems to be the best option. A great deal of strength is possible without adding a great deal of weight. Making such a mast could be a challenge, but even I have thought of schemes to simplify the construction.

    I agree with you that the taller main would be better for windward work, but there is no hiding the loss of sail area due to going that route. I haven't carefully done the numbers, but it seems that if you do not forego about a 10% decrease in Sail Area or an increase of draft, you will have to go with a 12% increase in ballast. It may seem laughable, but it actually appears you're better off cutting sail area than adding ballast.

    This is because, when increasing Sail Area vertically, You have to square the increase, because the sail area is increased, but so is the Center of Area Vertical. So a 10% increase in area ends up being a 21% increase in heeling moment (1.10 * SA * 1.10 * CAV = 1.21 * HM)

    I found this to be true with the top hamper of masts. A shorter mast may have less top hamper than a tall one even though it is heavier.

    And you wonder why modern sailboats usually have deep fin keels.
     
    Last edited: Aug 11, 2009
  6. sharpii2
    Joined: May 2004
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    Location: Michigan, USA

    sharpii2 Senior Member

    It's not that I don't want to go to windward, but that I consider the fact that most deep water voyaging (even in races) is down wind. Sailing upwind is useful when trying to claw off a lee shore or to get into and out of a harbor. For this, adequate windward performance is necessary, not stellar.

    Sails will be the primary propulsion system of my design. An outboard engine and its fuel will be stored in a specially designed compartment aft the aft bulkhead.

    I have considered and still am considering a cutter rig.

    I feel it is less likely to be wrecked in a capsize, but harder to repair, as all sails depend on just one mast. It also, when conventionally designed, usually requires a pair of running back stays.

    I drew one (see attachment) that eliminates the running back stays by having both the jib and staysail attach to a common tang at the mast head.
    I also eliminated the battens in the mainsail by running the boom almost all the way back to the backstay and securing it with an unadjustable super vang.

    Both of these moves will slightly decrease the efficiency of the rig, but simplify its use.
     

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  7. old_sailor
    Joined: Aug 2009
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    Location: Virginia

    old_sailor amateur boatbuilder

    Sorry Sharpii,

    I am new to forums and got confused. I didn't check the date and was responding to the original post of this thread.

    Oops!
     

  8. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    No oops... You did right :)
     
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