Saturday, October 15, 2011

How Quickly Things Can Change...

I've been following the adventures of SV Footprint for some time... since I first started looking for a cruising cat. Just a few days ago, after crossing oceans and cruising for years, they made a gamble on an exposed anchorage that turned out badly. Fortunately, no one was injured and the insurance company came through like a champion. The expereince would leave me in shock. They are looking inward, I'm sure, wondering where life will or should point next.

The blog of SV Footprint

In a nutshell, the cove turned into a shore break, the anchor somehow failed, and the boat was lost. I believe they had a Spade 80 (33 pounds), all 1/4-inch G43 chain rode, and a bridle, but I'm working from memory and a cursory search or older blog posts. If we consider the case of a catamaran on an all-chain rode in exposed conditions (based upon the this calculation) we must quickly conclude that there was simply no way the anchor could hold--the strain peaks at 7,550 pounds, well over the breaking rating of 1/4-inch G43 chain. This is before the effect of breaking waves is considered. Any veteran of ocean beaches has felt the difference between the gentle vertical undulations of a wave in deep water and sharp impact of a breaker, which would throw the boat up and backwards with a force exceeding the displacement of the boat.

They might have survived this on a combination rode--20 feet of chain plus 1/2-inch nylon 3-strand--for much the same reason a big fish can't escape light tackle in open water--he can't get a good solid snatch on the line, it just keeps stretching. But we can't truly know.

 I've just converted to an all-chain rode, for reasons of convenience--the windlass handles it more easily--but now will need to find a solution for this scenario, should I (...when I...) face it. One solution would be a 50- to 100-foot snubber secured to the chain with a prusik knot or locking chain hook... but how would it be deployed in quickly worsening conditions? It couldn't. Would it be more practical to lengthen the bridle with extensions made of softer stuff, perhaps 7/16-inch nylon, perhaps 70 feet long, capable of stretching 4-6 feet in extreme conditions? I carry a retired climbing rope meeting just these requirement, designed to absorb climbing fall energies in exactly this range. Yup, I think that's the plan.

What can we take away from this expereince, and this discussion?
  • Shallow anchorages are very bad when waves move in. There may have been no effective mooring solution in the waves they saw.
  • All-chain may be a mistake in some circumstances. We all need to consider a way to ease the impact load.
  • They had a bridle and it didn't matter. Two 15-foot lengths of 5/8-inch nylon simply don't stretch enough to change the math. Longer, undersize bridle lines would help, but most sailors over-size them for better durability. Unless they were 75 feet long and more slender, I doubt the outcome would have been any different.
  • Jackline Insurance gets top marks.

And by all means read their blog. They've had some wonderful adventures and tell the story well.

Strengths of all-chain rodes:
  • Excellent chafe resistance, where rocks and coral are present.
  • Quiets the motion of the boat in shifting winds. Thus, better holding in moderate conditions.
  • Matches the swing to other boats on chain.
  • Can help the anchor re-set on a shift by slowing the rate at which the direction of pull changes (the chain has to pull across the bottom and through the mud if deeply set, making the change more gradual and allowing the anchor to slowly redeploy to face the new strain).
  • Easier to handle with a windlass.
  • Generally longer life, though this is only true in areas with abrasive bottoms. In the Chesapeake, corrosion often destroys the chain of  the weekend or occasional sailor before abrasion gets the rope. The rope-to-chain splice should be remade every year or two, depending on chafe.
Weaknesses of all chain rode:
  • Greater surge forces in gusts than a mixed rode--about double.
  • Greater surge forces in waves--about four times--if combined with strong winds, which serve to straighten the chain and eliminate the shock absorbing potential of the catenary. The chain itself cannot absorb the surge as it has no stretch, and thus, has reduced holding in extreme conditions.
  • Expensive. Not really important, in the grand scheme of things.
  • Harder to handle without windlass. Need a chain stopper or equivalent, in addition to bow cleats.
  • Harder to handle as kedge or secondary rode.

Another detailed treatment of anchor rode loading, by Don Dodds, author of Modern Cruising Under Sail. This is rather long and convoluted, but arrives at very similar conclusions; anchoring in shallows on all-chain rodes is fatal if the waves pick up.
 Don Dodds Anchor Rode Calculations Part I
Don Dodds Anchor Rode Calculations Part III

      And a summary of some on-line discussion:
      Compuserve Group Anchor Discussion

      Saturday, October 8, 2011

      My favorite Bottom Cleaning Tools

      My last paint job, I used Micron 66. It lasted 2 years, in spite of dire warnings that it would peal in brackish water.. It didn't. I spoke with the factory and they repeated the tale, but I spoke with a rep at the boat show in Annapolis and he explained that it was winter haul-outs that caused the trouble. He also said that if you use the bottom paint up, running for 2 years, scrub a few times, and sand a little before repainting, it's all gone and that reduces the  trouble. I used Micron Extra this time, which I've used before but found slightly less effective. I may go back to Micron 66 next time, unless the new Micron 77 is out, which is brackish compatible. But this is all off-topic.

      Notice that the scraper blade is curved; it quickly wears to match the average curve of the hull, making the scraping action both more efficient and more gentle on the paint.

      I do end up scrubbing 2-3 times before I consider paint spent. You need a scraper that...
      • gives leverage for hard growth and enough handle for 2 hands. I have sore hands.
      • is soft enough not the remove paint.
      • floats.
      Mine is made from 1/8-inch polyethylene sheet and closet rod split with a saw curf. A screw secures the blade. My first version used a Home Depot plastic paint scraper with the handles removed, which was OK but perhaps a bit too aggressive. The polyethylene sheet is better (I generally get it from work, but we have used the heavy dividers that show up in some binders). There is no need to sharpen the sheet; it will wear to something of an edge very quickly. I use the same scraper to clean off my spiffy new Manson anchor; there's just enough handle and it stashes easily in one of the winch handle holders on the bow. I keep a few on the boat, in case I can get helpers--not often, really.

      Of course, use the scraper as little as possible. Try to clean before there is hard growth. Even then, use an easy hand, and only where you must.

      The best pads for removing soft growth are...
      • easy to hold.
      • self-cleaning.
      • have enough loops to pull off small barnacles.
      • don't remove soft paint.
      • 5 inches square seems a good compromise of coverage vs. scrubbing pressure. The one in the picture is smaller, which can be better when some of the growth is hard.
      • floats, at least for a while.
      Mine are berber carpet squares, not pile carpet--that will just smear things around. You need the irregular loop pattern. I got the idea from a professional hull cleaner and I like them to be both very gentle and effective; far better than the 3M pads generally recommended.  Because they are carpet, they conform to the curves of the hull. They work very well in combination with Atlas Fit gloves, which keep them from sliding out of your hand.

      And they are free (I have cut-offs from our rec-room carpet installation)!


      rev. 6-10-2013. Yup, the Micron CSC was less effective than the Micron 66. Some hard growth starting at 20 months, though not too bad. But more than Micron 66. Switched to West Marine PCA Gold (great price on sale).

      rev. 8-31-2015.  To my surprise, the West Marine PCA Gold is performing just as well as the Micron 66, and for 1/2 the price, and better than Micron Extra. I'm going to try tho stretch it to 2 1/2 years and do it in the spring. It is basically gone now, but it's always good to wear off more paint and the growth will slow when the water cools.

      Just me and My Wife

      A mid-week cruise, to celebrate our webbing anniversary. Few days of nothing planned and no commitments.

      We went to the boat the night before. No morning rush to pack things away and get away from the dock. It got a bit cold, below 50F at night I think, but that's outside, the heat works, and so does close company.

      The wind was working in the morning, a nice broad reach with a 10-15 knot breeze and a brilliant sun. In spite of perfect traveling conditions, we weren't headed far. The goal was to have an afternoon in a quiet place with nothing to do.

      There's an an un-named creek off Harris Creek, off the Choptank River, between Briary Cove and Cummings Creek, one of the nicest little anchorages in the area, with no mention in any guide. Perhaps the shallow entrance--about 6 feet over a narrow bar during exceptionally low tides--is enough to disqualify it for inclusion, but it's deeper inside, 7-10 feet over most of it's area. If you chose to visit, stay close to the south side of the remains of a blind located in the center of the mouth of the creek-- that is the deepest spot, and it is quite shallow on the north side. Most of the creeks in this area are heavily gentrified. We passed the ever-popular Dunn Cove on the way in, always crowded; I supose folk feel some safety in numbers. Perhaps being in front of a mansion or two makes them feel secure or perhaps they hope something will rub off if they stare at money long enough. Our cove has only a few old houses, well screened by trees, a few blinds, and a few working farms.

      We took the dingy and explored the margins, in no hurry. Even in October the water is warm enough for wading, and with the reduced algae population, the water becomes clear. We read books and told stories and listened.

      See the decoys in the woods, waiting for the gunning season to open?

      Morning found us homeward bound. Though the forecast had suggested no wind, we got 10 knots just behind on the beam and slid across the Bay in no time. The Annapolis Sail Boat Show was starting and I had a press pass waiting with my name on it.



      A press pass is, first and foremost, an invitation for every two-bit gadget maker to grab your sleeve and pitch his latest must-have-you-can't-survive-without-this-and-mine-is-better doo dad. It gets you more attention when you wander on boats costing more than your house and that would require your entire family and all of your friends to crew. And it's free.

      The reason for the visit was practical, a working day to shop for article ideas, for myself and for other reviewers. There is so much, but any thick catalog will convey that. But what things make sense to test, side by side? Many things--clothing, kitchen stuff--boil down more to personal preferences than quantifiable differences. Most of what I write centers on fuels and chemistry, my area of expertise, and that narrows things further.

      A boat fell on my head. I was talking with a salesman about a small catamaran that looked particularly fast, when a small gust of wind came up. They had placed several performance dingies up on stands, 3 feet tall, with full sail set perpendicular to the wind and trimmed in tight, on the most windward dock of the show. Fortunately it was a small dingy and the event caused nothing more than apologies and excitement. Pretty dumb, though.

      What I should have spent more time doing, was to sit on the edge of the dock and simply listen to the banter. To the comments folks make upon leaving a boat. To people on the boats trying to impress each other or the salesman with some sophomoric display. Lots of mature people, simply enjoying the spectacle, the weather, and boat shopping. Interesting people to meet; Lin Pardey called out to me from her booth--she has a new book out--wondering who else from Practical Sailor was there. We talked a bit about sailing without and engine and writing.

      But my wife was waiting, hanging out in Annapolis and shopping, but mostly enjoying a perfect day. We sat at a table and exchanged stories.