Please visit our home site at www.TRILOBOATS.com.

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.

Please feel free to browse the archives, leave comments where you will and write, and I'll respond as I can.

Fair winds!

Dave and Anke
triloboats swirl gmail daughter com

Saturday, November 9, 2013

Mast Overboard!

 
Scene o' the Crime


Now the LIZA JANE got a new foretruck,
Good stick o' wood but it wouldn't stay stuck -
Got a breeze one day from the nor'northwest
Doggone thing come down with the rest.
Hi diddle di and a breeze from the west
You'd a' thunk the truck wouldn't stuck with the rest.

  -From words attributed to J.B. Connolly by Gordon Bok, 

      who put them to music as LIZA JANE


If ants were called elephants,
  and elephants ants,
I could SQUAAAAASH
  an elephant!
   -- Danny Kaye


MAST OVERBOARD!

In a previous post (this one), I recounted the tale of our first dismasting which I attributed to a willawaw (micro-burst of wind), under-sized mast and low quality wood (widely spaced annular rings). We've now doubled our 'experience' in this regard, but with none of the excuses.

We'd been visiting my Brother's family in Northern Lynn canal, and it was time to head south. It had been blowing SE6 (of course) for weeks. We can claw against that, but it's slow, uncomfortable going. [Here's a great graphical chart of the Beaufort Scale for wind strength.]

But that day, it was forecast to drop to SE4, and we make pretty good time in that.

So we set out with the tide, about an hour before dawn, pulling our two anchors and beating out in flukey, gusty wind. We could tell by white-capped waves that the forecast was understated... here, at least, it was back up to SE6. 

We were doing well, however, and hoped that, once we cleared the Chilkat Peninsula it'd drop down (S winds get squeezed, N of that point). If not, there are anchorages in the Chilkat Islands off its tip.

By first light, we'd cleared our little bay, and were tacking across the tip of the minor peninsula that forms it.

A bit of a gust, and, without much ado, our foremast and sail calmly take a jump to the right and overboard!

What, again???

Quick assessment: Canted into the wind on the port tack, held up by our mizzen. The blunt end of the peninsula is a lee shore. Ranges show we're don't have a chance to clear back into the Bay. 

We back rudder and mizzen, attempting to 'tack', but no go... too much drag to bring the bow across the wind. Anchoring may be possible, but it's deep, here, and by the time it shoals up, it will be our last option.

Okay. If Mohammed won't go to the mountain... 

We're free-standing junk rig, which means the sails can be run forward of the beam. And a barge looks pretty much the same, one end and the other.

So we declare a proa-like reversal - the bow is now aft and the stern forward (ants are now elaphants).  

We fix a dock line to the end of the mizzen boom, and lead it aft. Sheet in, reverse steering from the bow on s'brd tack, slightly broad of a beam reach. Check ranges? Clearing!

Once clear of land, we anchor altong shore on the Lynn Canal side and haul the sails and mast aboard. This was challenging, as they'd spent a while, tossed and tangled in the waves. But we managed.

Next trick-in-a-row was to get ourselves into a lee. The next reasonable choice was Portage Bay (Haines), about eight miles north. Without the drag of the mast and sail, we were able to steer the (true) bow off, so we squared away and ran off under the mizzen alone - more or less like normal folks.

NOTE: Sailing off with an after sail gives about 90deg of solid freedom, from broad reach to broad reach. Some hulls can come up even higher, even to a beam reach... but this can depend on wind and sea state.

By afternoon we'd arrived, anchored, shortened the mast and rerigged. Beer-thirty at the most excellent Haines Brewing Company!

*****

What did we learn, this time?

The autopsy showed that onset rot had made deep intrusions into one side, along big stretches of its length. Oddly, none of this showed (usually the edges of longitudinal stress cracks start first), nor sounded (when thumped like a watermelon). 

The areas with rot were still pretty solid, just robbed of strength. Maybe that's why I couldn't hear it? Or maybe I need to better train my ear!

We had felled this tree for Andy Stoner's MARY ELIZABETH a mere eight years earlier (already??). It never got installed, but sat on the dock, waiting. When the Harbor folk wanted it out of there, Andy offered it to us and we jumped at the chance. But top down, fresh water had taken its toll.

LESSON: Make sure that lumber has been well-treated... take its full history into consideration.

Another point is that Anke and I have used a rule-of-thumb for when to reef, being when the leeboard guard goes awash (about 15deg). We're reassessing this, however, especially in gusty weather. And especially given the... ah... funky nature of our trip.

A big virtue of the box barge is its extremely high form stability. It resists heeling in direct proportion to heeling moment. But all that force has to go somewhere. It is distributed around the boat and rig. In a free standing rig, a good dollop accumulates just above the mast partners (in our case, the tabernacle hinges). This is just where both breaks have occurred. 

LESSON: Reef a little earlier, Simpletons! The whole point of junk rig is to make that easy!

*****

We found a beautiful, new mast, and she's withstood her sea-trials in blustery autumnal gales. We've rescheduled the mizzen for early replacement, and are considering up-grading to foremast size. That would allow exchanging, should it ever become necessary (knock on sound wood!). And we're thinking about running backstays for tough going. Can't hurt.

So we sail on, a little delayed but wiser.


PS. Anke thinks the Ants/Elephants allusion is typically opaque and unnecessary. I love it as an early prod toward thinking out of the box... reframe the problem and squash it (not that I want to squash any elephants!).

6 comments:

  1. Only a temporary delay, no-one hurt, that's the main thing.

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    Replies
    1. Hi Joel,

      You SAID it! Reading back over the post, I see I neglected to mention the shaky knees and cotton mouth.

      There are times and places this event would have been very bad, indeed. Losing a mast is no inconsiderable accident. The domino effect could take that all the way to catastrophic.

      In emergencies, it's important to remain calm, alert and flexible. Panic lurks around the corners. It's a fine line between down-playing the real dangers (mis-assessing the situation), and losing one's self in them.

      But all's well that ends well... and hopefully we learned something that'll help us avoid another one!

      Dave Z

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    2. Oh indeed! It's easy to sound brave after the event. When my boat decided to move down and sideways (only a couple of inches) the other day when I was lowering it, it nevertheless made a great thumping noise...I went weak at the knees, even though I was nowhere too close for danger. So yes, I learned something else at that moment... I hope I'll remember it. Don't tell my wife though... :)

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  2. One of the things this episode illustrates is the benefits of the fail-safer rule-of-thumb.

    Free standing rig may have gone down a bit sooner, in these instances, than stayed rig, but this one was an accident-in-wait. Sooner or later (unless the rot began to show itself), it was going down.

    A (fully) stayed rig would have gone down harder, and likely on-board (dangerous). Response would have been much harder, both initially, for 'jury rig' (loss of only one panel's sail area) and replacement. We sailed about another 100n.miles, upwind and down, blow high blow low under jury before replacing (admittedly reefing quite a bit early to spare the suspect mast)!

    Free standing rig also allowed the aft sail to be used as a foresail. We were able to work slightly to windward (close reach) under it. Though that ability wasn't crucial in this situation, it's fine to know that it's in the bag of tricks!

    Split rig (sails set on two masts) affords the redundancy that let us sail off the wind WITHOUT a jury rig. This kept us off a lee shore, and even allowed us to relocate to a calm anchorage for jury rigging.

    Off-centerboards (leeboard-like) help keep our underwater shape nearly symmetrical (vs say, a 3/4, deep keel). This makes it relatively easy to reverse sail, and even abetted that close reach I mentioned.

    Our kick-up rudder and yuloh didn't play a part this time, but when sailing reversed, one could pull up the rudder and move the yuloh 'aft' to the true bow... using a corner post for a fulcrum, one could steer from there.

    If we'd not managed to clear the shore, shoal draft keeps the bottom clear longer (increasing chances of hooking a shoaling bottom without grounding). In case of contact, our copper plate bottom holds damage at bay, to some extent. In a worst case, we're likely able to jump or wade ashore, rather than swim.

    All these features contribute to a fail-safer approach that increases options and confidence in times of trouble.

    Dave Z

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    Replies
    1. (Conversation with JOHN):

      Hi John,

      J: I'm trying to understand how you sailed SLACKTIDE backwards using just the mizzen sail. Did you twist the sail around the mast such that the luff was again the leading edge of the sail (with the stern now the bow)?

      D: Yes, this is the way we did it. The extra line (single) was lead to the the end of the boom as a sheet, since the real sheets would have taken too long to shift. As we sailed deep reefed, we didn't need the extra purchase.

      If we would have had to 'jibe', we would have let it stream down wind (normal position, and back around the 'forward' side of the mast. If we jibed normally (relative to our 'bow'), we'd end up wraping the haulyard tight around the mast, going the wrong way.



      J: Or did you attach a (single?) line to the lowest batten at the luff end, and call the previous luff edge the new leech?

      D: This wouldn't work out... the proportion of sail on each side of the mast is very unequal (85%/15%, in our case). Off the wind you'd have to sheet the larger portion, or it would stream downwind, levering the other upwind (against the sheet, which goes slack in compression).

      If one were sailing ON the wind, it would be possible, but inadvisable. The sheet would be working in tension, but the leverage of the unsheeted portion would set up large stresses in the battens.


      J: How did you control the sheet in the new location? Threaded through blocks to winches?

      D: We just lead it straight aft and tied off on one of the tabernacle struts. It didn't take any tending until we were clear. Then we fooled around a little bit, experimenting, but with the mast and sail still dragging, it was hard to tell what worked well. May try it again, down the road, under more controlled circumstances!


      J: Some say that a free-standing mast on a catamaran needs to be stronger than a free-standing mast on a monohull, because a catamaran won't heel (very much) and spill hard wind gusts like a monohull will. Since your Triloboats (and maybe LUNA too) are initially stiffer than many monohulls do you think that SLACKTIDE needs a stronger mast than a similarly-sized round-bilged keeled monohull?

      D: Definitely yes, though Van Loan's formula for calculating mast diameter factors in beam. In otherwords, both types would use the same formula, but generate different numbers.

      Still, with any rule-of-thumb, debriefing is important in the attempt to learn how that rule applies to specific situations.

      The rule seems to have been adequate so long as the mast is in good condition.

      In both our dismastings, there were problems with the masts. The first was undersized (didn't comply with the rules) and had poor annular ring pattern (wide spacing = lowered strength). The second had rot.

      Nevertheless, both had sailed stoutly through many heavy blows, despite our tendency to reef late. I believe this confirms the rule.

      Going heavier would grant an extra margin of safety, but would be heavier and stiffer (less able to flex before a gust). Masts in good condition, sized according to a successful formula would still be my choice.


      Continued below...

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    2. (Conversation with JOHN, continued):

      J: A counter argument to catamarans needing stronger masts was made by Pete Hill, who has now made two junk-rigged catamarans. He noted that monohulls are just as stiff fore-and-aft as catamarans are stiff amidships, so if a free-standing monohull mast can withstand a wind blast from astern, then certainly that same mast will be sufficient on a similarly-sized catamaran. The only question I had to that argument was the fact that both cats and monos are made to slide forwards relatively easily (and thus may relieve some of the wind pressure), but only monos can easily heel to relieve wind pressure. So it still may be true that cats need stronger free-standing masts than monos?

      D: Interesting hypothesis from Pete (who has vastly more experience than I), but I'd agree with your analysis.

      Anything that 'gives' before a force absorbs some of it. Quite a lot of it, actually. A boxer who merely ticks his opponent's glove on it's way in has robbed it of its heavy hitting power.

      It's one of the main arguments for free standing rig that it can absorb so much energy by flexing. A stayed rig transmits nearly the full force to much more localized points (e.g., chainplates and mast-step).

      So I'd think that accelerating the boat forward would be quite a cushion, whereas heeling mounts tremendous righting arm in opposition.

      Dave Z

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