Sunday, October 23, 2016

Dehumidifier vs. Desicant

Four years ago, in the fall, I noticed something I had not seen before; the dreaded black spots, this time on cabin carpeting. Clearly, better humidity control was in order for the cooler season.

A large compressor unit would be a beast on a small boat. Though I have a 30-pint unit at home, the downsides are major:
  • A lot of amps on the shore power cord.
  • A back injury waiting to happen; the unit is huge and awkward.
  • In the way.
  • Loud.
  •  More capacity than I needed.
So I looked around and found the Eva-Dry 2200. The no-compressor  principle is elegant, the only moving part being a small fan. The over simplified explanation is that of a thermocouple, but in reverse. Instead of a temperature difference creating a small electric current, the current is forced in the reverse direction through a whole stack of thermocouples, creating a cold plate. Water condenses on the cold plate and runs into a tank.

The size and weight (just a few pounds) are appropriate; when not in use it's easy to swing it into a cabinet for storage, although for day sailing I just put it in the sink to keep it from falling. They are prone to icing in temperatures below about 45F, but deicing by controlling the run cycle with a light timer is simple; 8 hours on at night and 6 hours off during the day. Even in the depths of the winter, the interior of the boat warms above freezing during the day due to solar heating.

I modified the tank by drilling a hole and tapping in a 1/4 NPT x 3/16" ID hose barb. The hose runs to the sink so that it never fills and to prevent freezing and breaking in the winter.

 So far--four years--the unit has just  purred along, removing 2-8 ounces per day, keeping the relative humidity at 45-65% at temperatures from below freezing to 95F. The boat is always dry, the bedding fresh, and interior corrosion issue non-existent.Just like home.
 Cold plate thawed

Cold plate frozen

The only real alternative is calcium chloride descant. I did an article about these for Practical Sailor  magazine and still had a few left over. I held a race several years ago, the Eva-Dry in the port cabin and a large absorbant bag on starboard. It wasn't even close. It would take ten 5-pound buckets of CaCl2 to do what this unit will do over 3-4 month winter season.

I also tested a cheaper version from Perfect Home. It lasted about 8 months, just like the reviews said it would. The Eva-Dry 2200, run almost continuously, dropped on the floor repeatedly, and frozen nightly through the winter, is still purring four years later.

Monday, October 17, 2016

Hate the New CARB Spounts on Jerry Cans?

The solution is a Shaker Siphon. Just a few quick up-and-down pulses and it goes nearly as fast as pouring from a can (I timed it), but without spilling a drop or straining your back.

I promise, you will never lift a can again. Even good under way.

  1. The farther you stuff the hose down the filler, the faster it runs. 
  2. Remember that you lift the suction end to stop. Stop a few ounces early so that you can empty the hose into the tank and clear the hose.
  3. Tip the can and place the hose in the corner and you will get every drop.

[I still use a 1-gallon non-carb can to fill the integral tanks on the dinghy outboard. Easier to control when only adding a pint or so.]

PDQ 36 Swim Platform

Several years ago I extended the transoms of my PDQ 32 both to improve performance and, more importantly, improve boarding from the dinghy. The molding was more work than many would care to take on, and estimates were the price of a good used car. During the planning phase, several people suggested I should just ad a swim platform, something that could fold out of the way.

This PDQ 36 owner did just that.

It's not the way I would do it. I'm concerned that...
  • the extension would actually add turbulence
  • No buoyancy at low speeds
  • Could be weird backing
  • More trouble to clean
  • Not strong when I back into something (I back into my slip every time)
  • Not as strong if someone jumps of falls down on it.
Weight and materials cost are actually similar, I think: I was able to build with lighter materials.  But it would be easier and faster, without question. I think I would have hinged it at the step and the back edge and had it swing down against the transom, leaving it up underway. I would only do one side. Or they could be molded and held down with some manner of latch, like the Firebird cats... but then why not fix them.

Many possibilities.

Tuesday, October 11, 2016

Let There be Heat!

The Problem. The delivery trip of Shoal Survivor, from Deltaville, VA to Deale, MD took place between Christmas and New Year's (2008-2009); while it was actually quite comfortable at the helm during the day, protected behind the windscreen, it was decidedly chilly watching movies at night, and my daughter and I vowed that we would install heat before the first frost visited us in the next winter.  

The Solution. I belabored the different types of heaters at length. We already had propane, and a spare propane tap existed. The boat was equipped with propane leak detectors and a solenoid valve, further simplifying the decision.  I had a fair idea of the BTU requirement, having spent a few nights on the boat last winter when the temperature dropped into the 20s. I learned that a single 1500 watt space heater didn't quite do it at all and two were just about right. I learned that a vented heater was an absolute requirement, as even cooking with propane in a sealed cabin brought on a slight headache; I'm not certain whether it was lack of oxygen or carbon monoxide.  Applying an appropriate conversion factor (about 3.3 BTUs/watt) and estimating the thermal efficiency at 85%),  5,800 BTUs seem to be the minimum requirement, and perhaps 10,000 BTUs would serve better. The Sig Marine / Dixon P-9000 (5500-7500 BTU output) seemed a reasonable choice and was also the most we really have room for.  A 10 pound bottle of propane should last 50-70 hours, depending on the rate, or most of a season for a $12 refill.

  I  taped a cardboard of the approximate sized to the wall and we lived with it all summer to prove that it was not in the way.

Note on photo: there is a short gap above the heater, between the heater and the air intake pipe. Installation was not finished yet and this was later sealed with a metal band.

Our Experience.

Note 2-19-2010. Winter experience has proven the above numbers. We burned through 20 pounds in 14 very cold December - February days and nights on the boat. I except when on the hook, I have turned the gas off at night and used dock power to run a single 1500 watt space heater. On one very windy 22F night I had to run the heater on low and 2 x 1500 watt heaters in order to keep the entire boat over 70F. I turned the gas off to sleep.

Note 3-24-2013. 3-day cold weather trip (27F-46F). Heater ran most of the time (sometimes on low), plus cooking, and burned about 2-3 pounds each 24 hours. It was off when we left the boat, generally for about 3-6 hours per day.

Installation. While not overly difficult, gas always require meticulous attention to detail. There are Reasoner that on dry land, most jurisdictions no longer allow gas repair and installation parts to be sold to unlicensed individuals. Please be careful, and read-up on the code.

  • The gas line must run through a vapor-tight fitting from the propane locker into the cabin. This is a standard item through West Marine, Defender Marine, or Sig / Dickson. The hose is typically pre-assembled with 3/8" flare fittings on each end, so it is a bit fat. The vapor-tight fitting will accommodate this.
  • 12 volt electric is required for the fan.  The unit will run without it, but the heat output will be somewhat less and it will not be as well distributed. This is another reason we chose this over the Cozy Cabin Heater. The shut-off safety is not dependent on electricity.
  • Installation side clearances are actually quite small for this unit, because the fan circulates cold air around the firebox.  Additionally, the combustion air is drawn through the deck, and around the flu via a double wall pipe. Thus, smokestack never really gets hot on the outside.  The required clearance around the firebox is only 2 inches, and a little bit more around the smokestack. The smoke stack is almost cool enough to hold in your hand by the time it reaches the deck, so no special insulation is needed. The back of the stove and surfaces only a few inches away stay quite cool and no discernible heat is transferred to the bulkhead.
  • Mounting. I suppose I could have simply placed screws in the wall, but it's rather heavy and I decided through bolting made more sense.  The backside ( visible inside the head) fold heads are covered with decorative caps matching those used throughout the boat, and I used acorn nuts and on the heater side of the bolts. The holes were over-drilled, filled with epoxy, and re-drilled. ahead is a shower compartment as well and thus is quite wet.  The bulkhead is foam cored.
  • Through-deck hole for the smokestack. This was the most stressful step, I assure you.  Boring a 3 1/2-inch, gaping hole through the deck and through the salon roof and extremely visible place - not relaxing at all the first time you commit this sort of surgery on the new boat. It went smoothly enough. After drilling the core was removed extending about 1/2-inch back from the edges and the space filled with epoxy thickened with Cabosil (fumed silica) to a peanut butter consistency. The small holes for the mounting screws were also over drilled and, epoxy-filled, and then re-drilled as well. The smokestack comes with a very thick rubber gasket that is not drilled for the mounting screws; the screws drill their own holes through the rubber and make a very tight fit.
  • Heat and epoxy. It is perfectly acceptable to use moderate heat to encourage epoxy to cure more quickly in cool weather. However, there are some caveats: Do not apply significant heat before the epoxy reaches a gel state, as it will become very runny; do not heat thick layers until you are certain they will not exotherm and get hot on their own; it is better to warm the substrate than either the epoxy or the curing mixture after it has gelled.
  • Passing the electric wires and gas lines through the bulkhead near the heater was quite simple. I purchased an assortment set of rubber grommets from Home Depot; the largest and second largest nested fit the gas line, and the smallest one accommodated the 2 x 16 gauge wires.
  • There is a gap in the flue in the picture - that was covered by a collar, not yet installed, that allows for deck movement.Remember that distance between the heater and the roof changes as you go through waves and as people walk on the deck There is also thermal expansion to consider. Provide for some movement.
  • I checked for gas leaks with diluted dish washing liquid and a brush. I have added a simple carbon monoxide detector.  

Note: as of 1-13-2010 the CO monitor has never chirped. There is no odor, moisture, or other side effect. Just like my home gas furnace, in miniature.

  • The optional stack heat shield seems unnecessary. The stack stays pretty cool (maximum175 F with infrared thermometer - hurts, but would not burn very quickly). Also, the guard will only fit if the stack is straight.

  • The deck guard is necessary; the stack (deck cap, included with the heaters and pictured to the left) is a VERY effective sheet grabber and will foul your sheets on every tack. I built a similar custom guard from 1/8" x 3/4" aluminum strap that stands 5" high by 12" across, since the custom guard from Dickson was not streamlined enough to effectively shed sheets.
  •  Distributing the heat. We direct a small pre-existing fan (at first a Hella Turbo, now a Camaro Bora), set on low, at the stack and heater, blowing downwards. It increases the heater out-put by cooling the pipe and exterior, and helps spread the heat evenly throughout the cabin, floor to ceiling, without producing an objectionable draft. I'm sure location is critical, so experiment with your geometry.

About five hours of labor, overall.  The only hideous step was drilling the hole into the propane locker.  That involved boat yoga, worming into one of the under seat lockers in the saloon, which is obviously not designed for human habitation.

Although the heater doesn't get hot on the outside, thanks to the fan and jacket configuration, the glass front gets hot enough to take some paint off your hand. My daughter has also determined that with the door open and the flame set on low, it can be used for somores!

I'm now actually looking forward to our first overnight trip in true winter weather. I like winter: in the summer, there is a limit as to how many clothes you can take off; in the winter it is a simple matter to layer up with modern fleece and stretch products, enough to be comfortable in anything. My other joy is ice climbing; watch me enjoying a New Hampshire icefall at ~ -10F... and loving every moment. There is no swimming in the winter. The wind can howl and often does. Beach combing is different. Many Bay area businesses close for the season. But it is still beautiful.

Experience note, 1-13-2010: operation at the dock and underway has been flawless. Spray and moderate wind have caused no ill effects. Wind gusts of 25 knots apparent have caused flame-outs, but the unit interrupted the gas flow quickly. The heat generally stays in the salon, leaving the cabins quite cool, and so thick blankets are required. I like it that way. At dock, we use small electric space heaters on low in the cabins.

Note on thermal efficiency. The exhaust gases go through a double-pipe heat exchanger, giving up heat to the incoming combustion air. The draft is controlled (there is not too much excess air, as the gas flame is yellow) and waste up the stack is reduced (the maximum stack temperature is only about 285 F by IR thermometer). Thus, depending on the assumptions, the of the heater is about 85% efficient , as good as you will find short of a high-efficiency condensing heater, not available for boats. Most marine heaters are 70-80% efficient and have much higher exhaust temperatures.

10-22-2011: I just returned from another cool weather trip; still working well. As it is a vented heater, it warms the boat without humidity increase, CO or CO2 risk, and is without odor. 

3-24-2013: Some continuing problems with flame blowing out if sailing with wind on beam above 20 knots. I need to upgrade the deflector. No problems at anchor, only with wind on beam. 

A simple. dependable solution, without the complications of forced air heat. Not what I would do if I lived aboard, but just fine for the occasional year-round cruiser.

Thursday, October 6, 2016

Something Lazy, Something Free

Free is always good, except this is not quite free.

Or rather, it is free if you use any sort of holding tank treatment chemical.

 I've done all sorts of holding tank stuff for Practical Sailor Mag. Chemicals, hoses, vent filters. Fun stuff. And in the process, in addition to learning all sorts subtleties, I solved all of my own odor problems, save one; odor from the bowl itself. If I flush with seawater and leave it a few days, there's some stink; sulfate in seawater is converted to hydrogen sulfide by millions of wee bacteria. If I flush with fresh water, it's better, but not zero; I guess something sneaks back down the waste hose, or perhaps up the feed hose. And either way, the bowl tends to get ratty, as marine flush volumes are limited and the water isn't chlorinated. I hate scrubbing.

Place a 20% solution of holding tank treatment in a spray bottle and mist the bowl down with each use, or at least each day, or and certainly whenever you'll be leaving the boat for a while. This cleans the bowl, treats the water in the bowl, and treats the water in the waste hose, preventing stink. And since it's the same treatment you would be using anyway, just subtract this from the usual dosage.

 I haven't scrubbed in months; the treatment eats the waste off. Very lazy.

However, not all treatments work.
Camco TST 4 oz. Orange Power RV Toilet Treatment

  • Pick an scent you like, preferably very mild. I like Forespar Refresh and Raritan CP, but Camco TST Ultra-concentrate is our favorite. These are compatible with any type of holding tank treatment, including bacterial treatments.

    • No blue sterilizing treatments, containing with formaldehyde and the like. Toxic, smelly, stain-prone, and well... gross. Too much like a portable toilet. Very tough on joker valves. Formaldahyde is listed as a human carcinigen. I don't understand why they still make these. Ban them from your boat.
    • No bacterial treatments, like Bactank T3 or Happy Camper. They grow in the bottle and get gross. They are quite effective in the tank, just not for this.
    Less work. Less money.

    Wednesday, September 28, 2016

    Got Questions or Testing Ideas?

    Ask them here! Or rather leave a comment below and we'll have a discussion.

    I'm continuously searching for ideas to research and write about. Perhaps something I wrote only raised more questions. Perhaps you read something studied elsewhere and don't feel they answered critical questions. Maybe it's just a seemingly dumb problem you have; really, most likely you aren't the only one, which makes it worth researching and writing about!

    Fire away!

    Testing snubber loads. Part of an up-coming e-book? Perhaps. 

    So if my 35-pound Manson Supreme is secured in the background, what's holding the boat? A 2-pound dingy anchor I'm testing, of course.

    Tuesday, September 27, 2016

    Line Selection--Is Low Stretch More Myth Than Function?

    Clutching a bit of frayed line in our fist, we trudged to the back of the chandler, where we are met by a wall of multicolored rope spools, ranging from working-class polyester double braid to the most exotic low stretch line with a trademarked name. Some are expensive, and some are breathlessly expensive. I'm not a Luddite. I like Dyneema for soft shackles. But I'm also not convinced that vendors--the folks that are competing for your hard-earned money--are always the best source of information regarding what you actually need.

    At the heart of the question is deciding when low stretch is better, and when low stretch is worse. Define the benefit. I've recently been involved in a testing program reviewing jibe force reduction devices. One clear lesson has been that low stretch is not always better.

    Jibe Force Reduction Devices. [I'll be reporting on these more later.]
    • Nylon traveler line (8 mm dynamic climbing rope)
    • Nylon rope (sheets and pendants)
    • Gybe Tamer (shock absorber for the mainsheet tackle)
    • Boom brakes (a climber's figure-8 and several other devices)

    [From West Marine. Other vendors have similar recommendations--I'm not picking on anyone in particular]

    Line Type                            Stretch at 20% Breaking Strength
    Nylon dynamic climbing rope                    14 %
    Nylon double braid                                   8.5 %
    Polyester double braid                               2.5 %
    Dyneema and other high modulus              less than 0.6%

    Halyards. Reduced weight aloft, reduce chafe, improved sail shape are strong arguments in favor of high modulus halyards. Laminates and other low stretch sail materials demand low stretch halyards. Polyester working sails, on the other hand, are less demanding and can be served by polyester halyards. Spinnakers don't require low stretch halyards for shape maintenance, but spinnaker halyards are notorious for chafe caused by halyard pumping under load. Thus if you have polyester sails you're probably fine with polyester halyards, but laminate sail demand high modulus halyards and high modulus spinnaker halyards will experience less chafe.

    Replacing a wire halyard with fiber is a great application for high-modulus line. I replaced the wire main halyard on my Stiletto 27 with a 2:1 Kevlar rope halyard very successfully. Although Kevlar has been largely replaced by other fibers because of its tenancy to fail from bending fatigue, main and jib halyards were always a good applications, because flexing is limited, sheaves are typically large (they were sized for wire, which also requires large sheaves), and it neither stretches nor creeps. Do be careful to de-burr the sheaves; I skipped this step and ended up chafing a spot near the end.

    Traveler. Several years ago I found myself with a tattered polyester traveler line and a bit of surplus Spectra line of exactly the right size, a leftover from a testing project. I installed it without giving it much thought, assuming it would be a nice upgrade. Wrong. In fact, no matter how careful I was in my mainsheet management, it was exactly like jibing against a brick. I then read about Evans Starzinger's use of climbing rope for traveler line. He had sailed halfway around the world and was quite satisfied with both sale shape in the reduction in shock loading. I replaced my traveler line with 8 mm nylon dynamic climbing rope and have been extremely satisfied with the result. Because traveler lines are nearly always controlled by a tackle, the line load, even to windward is not very high. Stretch after the strongest gusts is only about an inch. On the other hand, during a rough jibe the traveler remove as much as 3-4 inches to leeward, absorbing damaging impact force.

    I wrote about dynamic travelers here.

    Practical Sailor reported on climbing rope for travelers, a good practical application.

    Climbing rope is optimized for impact loads.

    >Vang. Next in importance to the traveler line, in terms of absorbing shock and a rough jibe, is the vang. The mainsheet is typically a multipart tackle and cannot be expected to stretch much. On the other hand, stretch in the vang can allow the boom to rise just a few inches, absorbing critical impact force. Under normal sailing conditions, little stretch in the Vang may allow the boom to lift just a tick in a gust, perhaps a desirable thing. Thus, polyester double braid, again, seems the rational choice. The wrong choice, is to pair high modulus line in both the vang and the traveler; surefire recipe for a mangled gooseneck.

    I think it's funny that mainsheet and genoa sheet are typically placed in the same classification. Because sheet tension largely defines genoa draft, any stretch compromises sail shape. Mainsail draft is largely controlled by cut and outhaul tension. Mainsail sheet loads are typically 2-3 times lower, and typically this is a tackle, reducing line tension another 3-8 times. A mainsheet is shock loaded during jibes, but the genoa sheet is not. Very different.

    Mainsheet. Because main sail shape is less affected by sheet tension than a genoa (the boom provides outhaul tension) it is more tolerant of stretch. It would also seem that because the mainsheet is typically controlled by a tackle that stretch would matter less, but this is not true. <0 .6="" nbsp="" p="">Stretch is always proportional to length. If you move a clutch farther from the load, the line will stretch more. If you add a tackle the line is also longer. Stretch is proportional to load. The same load carried by a tackle will carry less load per strand and thus stretch less for a given length of line, but about the same amount overall, because the ratio of length/purchase is unchanged. This may be counter intuitive, but it is the reason that nylon is unacceptable even in multi-part purchases. Polyester double braid seems a rational choice choice because of the slight shock absorption it provides in jibes. High modulous line makes sense for racer, for the increased control it provides, but it should always be paired with either nylon (better) or polyester traveler line.

    Genoa sheet. My boat has two genoa sheets; one inside the shroud for close hauled work, and one outside the shroud for reaching work. I use Dyneema core line for the inside sheet and polyester double braid for the outside line. While it is critical that genoa sheets not stretch at very high load, the reality is that typically there is only 5-10 feet of line between the clew and winch, allowing little space for stretch. On the other hand, just a few inches of stretch can significantly increase the draft of a genoa during a gust, which is exactly what you don't want. Bottom line: this can go either way, depending on your budget and sailing style.

    Avoid Kevlar blends. They are subject to failure due to fatigue. I had a massively over strength genoa sheet rupture in light winds, the result of years of flogging at the clew.

    This sheet was cow hitched to the genoa clew. The failure was at the not exit, where it was subject to flexing. Somehow, the sunburn polyester cover held together even after the core had failed completely.

    Spinnaker sheets. Stretch is not a problem, at least not the small amount a polyester sheet will give. A little give actually improves sail stability in lumpy conditions. What does matter is weight on the clew. Thus, always down size sheets; if the genoa sheet is 1/2-inch, the spinnaker sheet should be no more than 3/8-inch and perhaps 5/16-inch, depending on how much wind you like to carry the chute in. Lighter line is good. Soft shackles can also save important ounces on asymmetric chutes, also reducing snags, metal flying about, and accidental opening risk (if you are using a squeezer or furler, as most cruisers do, there is no need for quick release).

    I'm not a big fan of Sta-Set X. Although it is a good value in terms of stretch versus cost, it's an abomination to coil and is prone to kinking if used as a sheet or even as a Hilliard when a sail is dropped quickly. Some folks like it, I don't.

    Likewise, I dislike single braid for running rigging. The cover tends to be loose and I find it tends to snag on rigging and hardware. It doesn't always like cam cleats or line clutches very well. Some folks like it, I don't.


    What lasts the longest? You pay your money, you make your choices. Curiously, high-tech line often does NOT last as long as polyester, because the determining factor is most often the polyester cover. Because the cover will slip against the slick core and bear much of the load, covers on high modulus lines generally do not last nearly as long as those on straight polyester line. Time and again, I've had the cover tear loose from the core of Dyneema line. If your racer, maybe you don't care about replacing lines every few years. . As a cruiser, I bet you do. I like to go fast, but I also like to go reliably and economically.

    This feels a bit like a rant because of the way I've departed from conventional wisdom. On the other hand, I've sailed a lot of miles and, to the best of my knowledge, this is the truth about running rigging for 30- to 40-foot boats.

    Sunday, September 25, 2016

    The Science of Sloppy Sailing

    (First posted January, 2012, it seemed worth re-posting, to me. I guess the first cool breezes of fall help me relax.)

    It doesn't come easily to me. Sloppy dress--easy. Sloppy appearance--haven't shaved in a week. Sloppy topsides--easy. I've learned to like substantial rub rails and dock rash, and can ignore seagull poop, at least in moderation. Sloppy marinas-- my favorite ones, since properness for appearance sake rubs me all wrong. But sloppiness in functional things also rubs at me, even on my laziest day. Perhaps even in this, I need to learn to change gears.

    Being an engineer works against me. I like things to work correctly and efficiently. There's also my active nature; my wife thinks I just can't sit still.  She says I should relax more when cruising, not understanding that tinkering and adjusting and generally fooling with things is at the heart of messing about in boats. Just sitting--if for too long--is torture. Give something to fix--not something unpleasant, preferably something rewarding--and I'm much happier.

    Sloppy sail trim. I just can't do it.  I've owned too many performance boats, where speed was everything.  Why would I buy a high performance boat, suffer all of the compromises that accompany that choice, only to sail slowly and poorly? As a cruiser I still see poorly trimmed sales as just plain ugly. I don't grind and trim all day long, but I spend a few minutes getting very close to right and then leave the autopilot to stay close. But I hate the look of a wrinkled sail, over trim, or an uncontrolled twist that would better suit an Annette Funicello movie.

    Sloppy anchoring. I loath doing something twice that I could have done once, had I paid more attention. I enjoy doing something efficiently, easily, and with the minimum number of steps. I can't just drop a pile of chain on top of the anchor and hope for the best. I can't just drop a second anchor, some place or other, because I'm too lazy to set the first one properly and I worry. If a second is needed, it will be placed rationally and the rodes connected rationally. I'll spend a few moments gauging what the tide will do and how I will swing. I'll pay attention to the feel of the ground when the anchor takes hold, estimating what the bottom must be like and how the anchor will like it. I like to spend the afternoon securely parked and the night sleeping peacefully. Sloppy anchoring would give me more exercise. Mid-night excitement too.

    Sloppy navigation. Well, perhaps I am guilty of this.  I've spent too much time with shallow draft boats. I tend to glance at the chart in the morning, memorize what I think I need to (where I'm going and places the bottom might be shallow and rocky), and then just sail.  I watch the GPS in a general way, but not the details.  I've sniffed the bottom a few more times than was strictly necessary, entering an unmarked creek while distracted by daydreams of what the afternoon at anchor might bring.  But I don't think I'm sloppy when it counts.  Grounding on a coastal sandbar to be deadly. If the Chesapeake had rocks I'd be more attentive. I've piloted many miles of hazardous coastline; I'm only sloppy when it's safe to be.

    Sloppy docking. Nope, just too embarrassing. If getting sloppy means putting other boats at risk, it's not acceptable. Now, when it comes time to flemish the dock lines, scrub the deck, and hide all of my "cruisers stuff", I'm sloppy and loving it . I don't have a problem with leaving a beer bottle by the helm. I've sailed off with fenders hanging more than once; I swear some of those were intentional-- a short move--and the rest.... well, at least I'm not sloppy when it comes to trying  fenders in place. Of course, I did leave a rather nice spring line in Cape Charles, nicely coiled on the dock.  It occurred to me when I reached Cape May.

    I'm too cheap to be sloppy with sail covers or window covers. But I don't mind a kayak lashed to the side decks and a jerry can lashed to the stern quarter rail, if they serve a good purpose. I don't mind fishing from the dock or leaving some cut bait on a board, so long as we are still fishing.

    Sloppy planning. I've made progress. When I first started distance planning, I made a list. Now I leave more on the boat and sometimes untie the lines without any firm notion of where I'm going, the desitination determined by the wind forecast. A float plan? Pretty funny.

    Unfortunately, the reality is the opposite. Somewhere in my subconscious, as I motor out the channel, I'm considering the forecast I read, considering the waves I see on the horizon, factoring my mood, and making a very informed decision. Sloppy and rash planning is just plain difficult for us old farts; we've made or seen a lot of mistakes and just can't aim ourselves  toward a grand epic without real effort. Descending from a grand snow and ice climb in the Tetons with a long-time partner, we questioned why, in all the years of climbing together we had never experienced a real epic, not in thousands of climbs. Although we had cut it a bit thin a few of times, we knew the line between epic and dead is thin, and we maintained a safety margin. We had stayed just within our abilities.

    Sloppy maintenance. I'm not sloppy when it comes to quality of work. I keep my boats a long time, really try to make every fix or modification and honest improvement, and then sell them for more than I paid. I keep my work area neat when on the hard; basic courtesy to the yard and my neighbors. But if we're talking winterizing and spring clean-up... well, I've covered that before. I'm not above used parts, dumpster diving, and re-purposing, but only if I can match or improve upon original quality.


    Maybe there is hope for me. I have a few sloppy traits--the megayacht group  in Cape May pointed them out--a foundation I can build upon. I could learn to like the curve of a stalled sail. I can try catching fish with the spinnaker. I suppose, so long as I am becoming old and physically decrepit, I need to encourage decay of my mental faculties without further delay.

    Saturday, September 24, 2016

    Can Nylon Rope Melt Due to Load Cycling --- Myth Semi-Busted

    The Problem. There have been reports of nylon sea anchor and ground anchor ropes failing due to heat build-up when repeatedly cycled to a high percentage of rated breaking strength. True? Let's try a few reasonableness checks. We'll start with climbing ropes, since these are tested for energy absorption and the results are well known.

    In a UIAA (the governing authority for climbing gear) test fall 2.5 meters of rope arrests an 80 kg object falling about 5.6 meters, stretch included. This is an impact so severe that the rope is only expected to survive 5-15 cycles; I doubt any anchor rope would do as well, so this is very conservative. if we convert this to US units:

    Energy = 176 pounds * 18.3 feet fall/8.2 feet rope = 393 ft-pounds/foot of rope

    Expressed as heat. However, only energy dissipated by hysteresis (it takes more energy to stretch a rope than it returns--it is not a perfect spring) is converted into heat. After all, a metal spring does not heat, true? Hysterisis with nylon rope is about generally about 10-20%. We'll assume the worst.

    0.20 x 392 ft-pounds/ft = 0.10 BTU/ft

    How much heat needs to be lost? If the rope is cycling at more than 50% of this load it won't last long for many reasons, so I will assume 0.05 BTU-cycle as the limit, which corresponds to 25% of the breaking strength and 200% of the safe working load (SWL), which is normally taken as about 12% BS for nylon. 

    How many cycles? Assuming we are taking about storm waves, 20 second period seems reasonable, or 180 cycles per hour.

    Heat = 180 cycles/hour * 0.05 BTU/cycle = 9 BTU/hr*ft

    How much strength does a hot rope lose (PA66 is nylon 6/6)?

    About 18% weakening by 80C (176F). There is a reason clothes don't fall apart in the drier! Long-term, there are oxidation effects, but these take months.

    How fast can a dry rope loose heat? Assuming strong winds, about 6-8 BTU/ft2-F, depending on the reference. Assuming there is some spray in the air, we will use the higher number. A wet rope will cool more quickly due to evaporation and better heat conduction within the rope.

    Heat loss = 0.11ft2 area/ft * 8 BTU/ft2 * (90-80) = 9 BTU

    Clearly the rope won't get that hot. In fact it will top out at about 10F above ambient. Noticeably warm, but not in any danger.

    What if the rope were larger (3/4-inch is what the Dashew's reported failing), of a less efficient construction (3-strand), and operated at a higher load factor (30%?)? The surface area to core ratios is greater, the heat generation per cycle is double, and the rope generates about 20% more heat due to the construction difference. What if the boat were tied to a dock and the period was much shorter? The core temperature gain can reach about 140For 60C--still not in the danger zone. Isolated fiber bundles could get hotter, if the load is not evenly carried or if there is significant friction between the fibers in that location.

     Note: I've greatly over-simplified the engineering. Insulation from the rope fibers and the cylindrical coordinates need to be considered. However, the result was similar, about 20% higher. On the other hand, we've assumed that no spray is striking the rope (it remains dry) which seems VERY unlikely in storm conditions.

     Observation 1: Lines smaller than 1-inch do not heat significant under cyclic loading unless they are significantly undersized, in which case they would fail anyway.

    Below 3/4-inch rope heating due to cycling is probably not an important factor, even in the worst hurricane docking situation; failure will be due to something else. Beginning at 1-inch moving upwards, it can be important, since the larger rope cannot cool as easily. Large Barge tow lines can heat. Thus, the myth seems plausible, but not in sea anchor applications; the period is too low. The rope would need to be ~ 2 inches in diameter to provide sufficient insulation.

    So why did the rope break? First, lets look at the load. Several investigators have found the wind load to be about 1/4 the ABYC estimates (these are based on anchoring with all-chain) and the load on a nylon rode to be about 1/2 the estimate. For a 50-foot boat, that would be about 2400 pounds. The SWL of 3/4-rope is about 2000 pounds. But that is before we include weakening due to wear and water. Dynamic tests by UIAA (climbing standards group) shows as much as 50% strength loss for wet rope in impact conditions. The SWL in practice is probably closer to 1400 pounds. In short, the rope failed predictably at 20%  BS after some time in the storm (probably higher due to a larger wave) with predictably melted ends. It was simply under speced due to a misunderstanding of SWL.

    Second, we should do some forensic thinking. What does nylon rope look like when it breaks under load? In fact, it always looks melted, the result of the enormous energy release at the moment of rupture. If the rope was slightly warm from cycling the effect would perhaps be slightly greater, but it would not be the cause. The larger the rope sample broken in the lab, the more noticeable the melting.

     This is very load speed break testing, yet the ends are melted. I think folks just don't understand what they are looking at when they claim mysterious heating. One sailor reported a false observation and it became internet fact.

    Observation 2: Nylon ropes always appear melted when broken at high load.

    What about heating under chafing gear? Yes, there can be some heating, as calculated above. Covering the rope will make it worse.
    • If the gear is waterproof, that prevents both water cooling and reduces the internal lubrication that water provides. Bad.
    • The gear provides insulation, like an over coat on the line. Thus, a 1/2-inch line is going to heat like a 3/4-inch line, and a 3/4-inch line like a 1 1/4-inch line. Bad.
    • If there is motion under load, there will be friction and some resultant heating. Permiable gear that allows the rope to stay wet will help, since that reduced friction.
    • Chafing gear should be made of low-friction materials. I like nylon tubular webbing, because nylon-on-nylon friction is very low. It has done very well both in practice and in chafe machine testing.
    • High friction chafe gear (rubber and vinyl hose) is bad. 
    • Motion at chafe points must be reduced. Chocks should be close to cleats. Using non-stretch line in chocks areas can be smart.
    Thus, any chafing gear that keep the line dry will weaken a line subject to hard cycling for a long period, such as a hurricane or nor'easter.. Only permeable gear is acceptable. But that said, the weakening will be only a small percentage. Even without heating, the gear will break under the gear because it is probably over an edge. So just because we see rope broken under chafe gear with melted ends, we should not believe heating was the culprit. The rope was simply too short to absorb the energy and was under engineered. Nylon rope looks melted even when broken at very low speeds and cycles; it is an artifact of the enormous energy release at the moment of failure.

    Observation 3: If the rope breaks under the chafing gear, don't leap to line heating as an explanation. The rope was just too small and too short.

    Bottom Line: Lines don't heat up, but users often underestimate the load, over estimate the SWL, and sometimes use docklines and snubbers that are too short to absorb energy safely. 


    An exhaustive report by the US Coast Guard goes deeply into synthetic moorings. It's a big deal for deep water ATNs. 

    Thursday, September 22, 2016

    Jamaican Stew Fish

    I picked this one up during a business trip to Kingstown. It seems the only used oil recycling going on in Jamaica at that time (about 1990) was a couple of septic tank service guys that had a pit in the ground they could pour it in. The inter-modal terminal in Kingstown is one of the largest in the world, conveniently located for shifting boxes before or after transiting the Panama Canal. Shipping companies were obviously uncomfortable with pouring their oil in a hole in the ground, inconvenienced by having to haul oily bilge water and used oil to their next port of call, and my company was being encouraged to build a recycling plant. That project never happened, and the boys wondered how used oil is recycled in Jamaica today.

    But that stories got nothing to do with good eats!

    Jamaican Stew Fish
    Makes any fish island style.  Serves two very hungry sailors.
    ·                     1 pound fish (spot, croaker, flounder, or rockfish. Pork and chicken also work well).  If all you caught were little fish, add more vegetables!
    ·                     1/2 medium onion , sliced
    ·                     1–2 cups baby carrots, sliced in half lengthwise
    ·                     Salt & pepper
    ·                     0–1/4 teaspoon ground red pepper, according to taste
    ·                     1–2 tablespoon soy sauce
    ·                     1/2 teaspoon ginger, thinly sliced
    ·                     Several sprigs of thyme
    ·                     1 teaspoon butter
    ·                     1/4 teaspoon cumin, 1/4 teaspoon curry powder, according to taste
    ·                     Water
    ·                     Oil for frying
    ·                     1 lime
    ·                     1 cup rice
    1.                  Clean the fish (fillet or whole), dry, and rub with lime.  I like it with the skin on.  Allow to soak for 10 minutes.  Butter both sides.
    2.                  Brown fish lightly in preheated oil.   Need not be fully cooked at this time.  Set aside to drain.
    3.                  Sauté sliced vegetables, ginger, and seasonings on a high flame for five minutes, using the oil from the fish.
    4.                  Reduce heat. Add soy sauce and water to not quite cover.  Stew vegetables for 10 minutes until brown. Salt & pepper to taste.
    5.                  Add fish, covering with stewed vegetables.  Stew covered for another 10 minutes, until fish flakes apart easily.
    6.                  Prepare rice separately.  Serve over rice.

    Jessica's first catfish, caught on croaker guts in the C & D Canal; catfish aren't fussy. [circa 2012]