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Anke and I are building our next boat, and writing about it at ABargeInTheMaking.blogspot.com. Access to the net comes and goes, so I'll be writing in fits and spurts.

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Fair winds!

Dave and Anke
triloboats swirl gmail daughter com

Saturday, August 1, 2020

Off-Center Masts for Off-Center Sailors

Don't get more off-center than this!Bolger BRICK, TETARD

One does not walk into the forest and accuse the trees of being off-center,

Nor visit the shore and call the waves imperfect.
-- from the Tao te Ching

Think off-center.
-- George Carlin


Off-Center Masts for Off-Center Sailors

When we were building ZOON (ex Bolger LONG MICRO), we stood the aft mast in place, off-center, to see how it stood. A visitor to the project took three wordless passes around, humming and clucking at such unusual features as the square sections and bow transom. Finally, he draws himself up with hands on hips and exclaims, "NO. That off-center mizzen is just too much."

But that off- center sail was perfect. Squared off across the stern, we could run down the off-wind quadrant in a gale of wind with balanced power and a clear view ahead.

Since then, every boat has had at least one mast off-center for one reason or another. Masts at the aft transom are offset to clear the rudder and sculling oar. Those at the companionway are offset to allow center-line openings which, in a knock-down, remain furthest from the water and least likely to flood.

We've never been able to observe a sailing difference between tacks in our larger, relatively heavy cruiser size vessels. We will wing out the offset sail to its near side when running... from there, they overlap the foresail less and behave much better. Otherwise, it appears a draw.

But this one time...

I wrote this account in a previous post:
A friend of ours had built a Bolger BRICK (shaped about as it sounds). He brought it out to Tenakee for a Mess-About. All day, he and his daughter sailed circles around the rest of us (including respected designs of similar size by Devlin, Hess and a TORO!).
Circles, in fact, barely describes the figure 8s and jaunts across the inlet and back while our fleet trudged along in comparison.

I was wowed by this and have mused lo these many years upon it. Now I venture a theory...

The BRICK has its mast stepped along one hull wall, and very near the bow. The crew is live ballast, but in practice needn't move much around (according to its skipper). When I first saw the arrangement, I felt sure it would capsize mast-side at the first gust. But no.

Here's my thinking, taking the BRICK pictured above as example:

On the port tack (wind blowing from port across the hull to the lee-side sail) it acts as a proa. Windward hull lift is opposed by crew weight.

On the starboard tack (wind blowing into the wind-side sail, then across the hull) it acts like a normal hull (center mast). Leeward hull depression is opposed by outboard displacement.

Setting the mast at a point of maximum beam, in effect, doubles the beam! That dinky li'l x4ft punt has the equivalent lever arm at the mast as our x8ft WAYWARD. Whether sailing as a 'double wide' monohull or proa, the righting arm is twice what one can expect with a centered mast.

With such a doubling, one can fly twice the sail area or sail a normal amount twice as aggressively (which appears to be the case).

Somethin' to ponder on!


Picture this mast position as center-line!





5 comments:

  1. Our first Loose Moose (a Bolger Jessie Cooper) sported two off-center masts as well as an off-center dagger board. They worked just fine.

    That said, the off-centeredness of our boat drove folks nuts and we were often forced to listen to long-winded lectures about how the boat could not work as designed in spite of the fact that we were obviously sailing and for us to be sailing the boat had to sail.

    So it does go...

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    1. Hi RLW,

      Amazing, innit? Doing the impossible since way on back.

      So... once again, you are the voice of experience on this matter...

      Did you find your JESSIE COOPER to be noticeably able to stand up to her sail plan for longer/harder (or alternatively, that it was surprisingly large for the boat?

      And if so, were you able to maintain a noticeably higher fraction of her hullspeed?

      Dave Z

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  2. Nice illuminating of the directly downwind advantages of a offset mizzen mast. Makes sense likewise for the main to lessen undue force on a self steering gear? Shemayas "Auklet" was pictured running due downwind with the Reddish geomtery lugsail squared off like a big square sail on the boats centerline. With a offset mast a Van Loan or Hasler sail might do basically the same thing. What a great experiment this would make.

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  3. Hi Roberto,

    Yes, bringing that CE inboard running before high winds eases round-up tendencies to the point of cakewalk!

    Some experienced, ocean-going, soon to be friends saw us sailing that gale (in our 20ft boat) from a state ferry. They later told us they thought we were totally insane.

    Totally green was more like it. We were under such good control, we thought nothing of this (though it was, like, totally awesome under snow-blown Chilkoot mountains.

    Knowing better these days, I deem it safer than it looked, but still not exactly advisable!

    Dave Z

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    Replies
    1. PS... I think one of the under-mentioned problems of an uncontrolled jibe is that sails balanced when running wing and wong jibe into sudden and radically unbalanced mode (all one side).

      Aside from any danger to shrouds and other gear, this imbalance riskes round-up and broach before following seas.

      DZ

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