Sun tarp picture

Sun cover

I built this to keep sun off the boat while it is in storage.  I built it without measurements from the actual boat.  I used drawings from the sail plan and my own photos to determine the design.  I made a mock-up of paper to make sure my geometry was correct.  It turned out beyond what I expected.

Sail dynamics

Well-trimmed sails

I am very interested in the science of how our boats interact with natural forces, both wind and water.  I sail partially for the connection with nature and feel more connected when I understand it.  I have found a person, Paul Exner out of Tortola, British Virgin Islands, who can explain these concepts at a high level while putting them into practice on a boat. These are my thoughts on an afternoon we spent together.

The properly set sails of a boat cut through the wind like a blade.  The rounded shape of this blade bends the wind just like a river bends around a rock, we just don’t see the wind bend. And the forces created are different when a gas is bent.  Bending the wind creates relatively lower air pressure on the convex side of the sail which pulls the sail forward.  To harness this force we are able to shape and position the sail.  This triangular piece of fabric has curve built into it which we can shape by varying the tension on each of its three edges.   Likewise,  we can change the angle at which we present the sail to the wind.  The shape we create and where we position the sail vary based on the force and direction of the wind.  Ideally we position the leading edge of the sail so that it evenly splits flow of wind to each side and as the force of the wind gets stronger, we decrease the curve in the sail. As the boat moves, the speed and direction of the wind relative to the sail changes.  Getting it all right is as much art as science. 

The elements of sail shape on which we focused were draft and twist.  Draft is the depth of the curve in the sail and we can change both the amount of depth and its location. Deeper draft bends the wind more, maximizing the lower air pressure that pulls the sail forward. But there are limits to the benefits we can get with draft because the wind needs to flow smoothly across the back of the sail, bending with the sail, to create the low pressure which causes the suction. In light air the wind cannot follow the sharp curve associated with deep draft and it will spin off, forming eddies like on the side of a river, effectively unwinding its energy into the eddy rather than drawing the sail forward. In higher winds, the sideways forces associated with a deep draft can be too much and will cause the boat to lean over to the point that the hull does not move well through the water.

Apparent wind is the sum of the wind due to
boat speed plus the actual wind.  Higher
winds make the apparent wind
come more from the side

The twist of a sail is often unrecognized. To appreciate twist, see it in the picture which accompanies this post.  At the base of the sail the trailing edge points nearly straight back while at the top it is released off to the side.  The sail is twisted from bottom to top along a vertical axis. The angle of the sail relative to the boat is wider at the top than it is at the bottom. This feature is useful in light air because the wind will blow harder at the top of the mast than at the surface.  This occurs because the wind near the water’s surface is slowed due to friction.  The apparent wind (see diagram) at the top of the sail is more to the side so that section of the sail can be set wider to match the wind at that elevation. We can allow more or less twist so as to match this deviation of the apparent wind and keep the sail working through its entire height.  Of course while all this theory is good, sometimes sailing with less twist so that the sail is trimmed theoretically too tight at the top results in faster boat speed, possibly due to hydrodynamic considerations. 

In higher winds there is less change in wind speed caused by friction with the water.  Twist can still be used instrumentally because we might not want the entire sail to be working and we can twist off the top of the sail where it would have the most leverage to create heel. We can sometimes get the top of the sail to luff while it is working lower down.

Twist can do funny things when a boat is going downwind with the sail all the way  out. If we allow twist with the sail in this position, the trailing edge of the upper part of the sail can actually be pointed forward. A strong puff in this setting will heel the boat to windward — the boat rolls away from the side that the boom is on, opposite what one normally expects.  This can induce uncomfortable and potentially dangerous rolling.

Wind bends before it
meets the sail

The two sails of a boat like mine, a sloop, work together rather than as individual units.  Each sail changes the airflow over the other.  A cool thing to understand is that the wind begins to bend even before it reaches the sail in the same way that a river begins bending upstream of a rock.  The wrinkle in the wind created by a sail begins upwind of the sail! They figured this out observing the flow of smoke over a sail. Now consider the wind that is about to go over the mainsail. It is changing its course before it meets the mast, coming now slightly more from the side. This local wind shift is occurring right where the jib is operating and helps he jib work better. It creates a local apparent wind which is at a wider angle to the boat than the true wind so the jib experiences a lift -- the wind is slightly less opposed to our direction of travel. Unfortunately the jib does not return the favor to the mainsail. The jib causes the wind that flows over the mainsail to be more forward of the sail, so the main experiences the opposite of a lift, a header.  The advantage to the jib outweighs the disadvantage to he main.

The space between the sails is referred to as the slot. I do not find consensus about what is going on within the slot. There does seem to be agreement that he slot should be even, so that the sail shape and position of he two sails should be similar.  The slot would not be pinched or become wider further aft.

The shape of a sail is modified via the tension on each of its three edges — the leech (trailing edge), the luff (forward edge) and the foot — and, for the mainsail, our sail trim devices allow us to tension each edge individually. Tension of the leech by pulling the back corner of the sail down removes twist.  Leech tension, with the boom in close, is created by the mainsheet because with the boom over the deck the mainsheet pulls more down than in.  People tend to think of the mainsheet as moving the boom in and out, but it pulls down, too. Once the boom is far enough out that the mainsheet pulls more in than down, then leech tension is achieved with the boom vang. 

Tension on the foot reduces draft in the bottom of the sail while tension is the luff also reduces draft at the same time that it pulls the draft forward.  Luff tension is typically created by a downhaul, or Cunningham, however my boat is not set up with one.   We found that I could create good luff tension with the halyard, probably because the Harken Battcar system eliminates friction between the mast and the sail so the tension from the halyard goes evenly to the luff.  We also found halyard tension would change the twist.  This makes sense because pulling the head of the sail pulls only slightly less on the leech than the luff. 

When the sail is trimmed close the the boat and the mainsail is pulling more down than in, the traveler is the best tool to position the sail.  Some guy walking the docks told me I was wasting my time redesigning my traveler, but I find it an essential tool when close-hauled. Trying to use the mainsheet to bring the main in tighter at this point does more to change its shape than its position. The traveler, which controls where the mainsheet pulls from, will change the angle of the sail to the wind without changing its shape. As the sail moves further outboard the mainsheet takes on its commonly perceived role of positioning the sail in and out.

In contrast to the main, the jib only has one point, the clew, from which it is typically controlled.  We can control luff tension, and therefore draft, with the halyard but with furling gear and headstay foils, not many people are going to do that. We can, however, pull the clew in different directions to affect jib shape. Most boats have a track by which the jib fairlead (the pulley that the jib sheet goes through before it is led back to a winch) can be moved foreword or aft. Moving the fairlead foreword causes the jib sheet to pull the clew more down than back so the leech is is tensioned relatively more than the foot. Move the fairlead back and the foot gets tensioned more than the leech.  The center position for the fairlead is found empirically and is that point at which the entire length of the jib’s luff breaks at once (or all the tell tales lift together) as you head into the wind. Partially rolling up the jib changes that center. 

The jib sheet can also be redirected so that it pulls more from a position further outboard through the use of a barber hauler. This device can simply be a block attached to the rail through which the jib sheet passes before it is led to the fairlead. Paul figured out that on my Morris Justine, when sailing on beam and broad reaches, the sail had a more powerful shape with the clew further outboard.  We began with the straight forward system of a block (pulley) attached at the widest part of the boat. Over the course of the afternoon we invented a system in which we could vary the height of that block. We did this by putting the block on a line that could be controlled by a winch.  If you enlarge the picture attached to this post you can see this setup.  The jib sheet is led via the aft corner to its winch and the barber hauler is going through the midship hawse pipe, through the genoa fairlead, then to a winch

An important aspect of any headsail trim is holding the clew steady. If the clew is allowed to move around, the flow of wind across the sail can detach and the suction is broken.  The more stable the clew the better and thus the benefit of fixing it with a pole or building rigid sails like the America's Cup boats.

I have deliberately not discussed the hydrodynamic issues which include the forces generated as the keel moves through water.  The keel acts like a foil, creating forces which help the boat go upwind, similar to the sail.  There is interplay between the aerodynamic and the hydrodynamic forces.  I will write about that as I understand it better.

We had the picture of our handiwork taken by a guy standing in an inflatable, one hand on a throttle extension and the other holding a camera.  He is the boating equivalent of the guys who position themselves on popular ski runs and try to sell you a picture. He came along just as we were getting things dialed in. Good timing to sell me a picture. An excellent souvenir for a sailing dork’s vacation.

References:

Sail Power by Wallace Ross
Seaworthiness, The Forgotten Factor by C.J. Marchaj

Bulwark Cap Rail Covers

The Caribbean sun is doing a number on the teak.  Before I start varnishing I want to at least know that it will be protected when I am not there.  Here are photos of the covers I constructed.

At home, where I had the sewing machine, I created the basic foundation for my covers.  For each side I made 7-inch wide strips, double-hemmed on each side, 42 feet long.  For the stern, the strip was 9 inches wide and only 10 feet long.  I used Sunbrella fabric and V-92 thread.  For sewing the double hems I spooled the fabric off a broom (as shown in picture).  The spool kept the double hem folded and allowed it to easily feed into the machine.  I used Sailrite advice and videos from their website and was inspired to buy a Sailrite machine after struggling through this project with a less suitable machine.

The cap rail is interrupted by three stanchions on each side and two in the stern.  I cut openings for each stanchion, but had to do that at the boat. I had pre-made the velcro pads at home on the machine but at the boat I had to hand-sew them in place.  Each one took me about an hour to hand sew.  I did them at anchor with a cocktail after the kids had gone to bed.  (My new Sailrite will come with the Monster Wheel for hand cranking).  This picture also shows some of the creative ways I found to attach the covers to the boat so that I could limit the number of snaps.  There is a loop of webbing around the mooring post and a tie through the hawse pipe.

I was able to limit the use of snaps to four on each side and two on the stern.  The reason to limit snaps is that the sockets are screwed into the fiberglass, are not as pretty and will corrode.  This picture shows my how I hung the water bottles directly opposite the snaps to avoid pulling the cover off.  The snaps are positioned to put slight tension on the fabric.

I cut slits for the ladder attachment points.  I tried to do most cuts with the hot knife. but found that cutting with scissors and singeing with a lighter also worked.  Here again I can attach the cover with a tie through the hawse pipe.

I avoided snaps in the back by tying the corners together (Kate's idea).

When I made mistakes I kept going.  Here I cut the opening for the back stay in the wrong spot and just patched it

I hung bottles filled with seawater on outside so that I did not need hardware on the outside hull (thanks to Tom from Nomad for that idea).  I used a constrictor knot around the neck of the bottles and tied them to the grommet with two strands.  The line through the grommet should prevent the grommets from hitting the paint in the wind.

More bottles hanging.  I used one bottle for the corner.

I thought it was clever to use one bottle in the corner.   

Meditative sailing videos from the passage

These two videos were contributed by my crew member Adam from his watch during the 

Caribbean 1500

Traveler redesign

A more technical post in which I describe the problems with the original traveler and how I improved it.

Some people scoff at the idea that the sail trim afforded by a traveler is significant for a cruising boat. But I simply enjoy being a geek about sail shape.  It is more than the practical consideration of being able to get the sails trimmed just right so that we are able to sail home rather than motor home.  It is more a matter of understanding how the sails work and how to get the most out of them.  And when the boat is going just right you can feel it.  So I was not going to deprive myself of a fundamental tool for achieving sail trim.

Original traveler set-up showing the line coming forward
through a bullet block and then back to cockpit

The original traveler on the Morris Justine was difficult to operate because the line chafed on the block that led it forward and the line did not go smoothly through the bullet block.  I have labeled the first chafe point in the overview picture and show a detail of it below.

Close-up of chafe point

This stacked cheek block would only allow the line to be turned straight forward or in-board but the line is led to a bullet block which is outobard of it and it chafes on the cheek bloc where the curved arrow it.  Then the line does not go smoothly through the bullet block which leads it back to the cockpit.  The system was nearly impossible to move under load and it is not something I would pull with a winch.  So instead  I would go up on deck and pull the traveler line straight forward.  My son would remain in the cockpit and pull the slack through the bullet block.

I also did not want a block in the location of the bullet block because I planned to be up there while we were sailing and I wanted to eliminate tripping hazards.

Redesigned traveller

My redesign uses a cheek block on the traveler support bar to divert the line downward rather than forward.  The key to placement of this block is to put the first hole as far into the corner of the support beam as possible while still leaving enough room to get a nut behind it (I actually had to file down my nut to get it on the bolt). On the deck I used a stand up block (I ended up not using the spring that makes it stand up) to lead the line back to the cockpit.  The key to placement of the pad eye securing the stand-up block is to determine how the block will be angled when the line is under tension.

The deck had wood core in the location where I wanted my new pad eyes.  I over-sized my holes, removed core with a bent nail in a drill, filled these holes with epoxy and then redrilled holes the proper size for my bolts.  The interior cabin picture shows duct tape holding the epoxy in the holes.  I just used washers to back up the pad eyes as there is not much pressure on these blocks.

These headliners may make the boat look pretty, but they make every project more difficult.  Getting them back in is much worse than getting them out.

Unanticipated issue

One flaw in my design is that the line lays on the companionway cover when the traveller car is all the way to one side.  I have thought about putting a piece of teak or SS quarter-round to lift up the line, but so far it is not leaving a mark.

I was in the early stages of this project at the Morris dock in Northeast Harbor, Maine when some older guy walking the dock started to tell me how many oceans he had crossed and that I was wasting my time on a traveler and that I had many other insufficiencies on my boat that I should be worrying about.  I was already having a hard enough day without the right tools on a Sunday and finally told him I needed to make my own mistakes.  I've since been advised to do projects out of public view.

Undefended

I needed to have the goal of the trip when I bought the boat.  The “trip” was the sailing trip from Maine to the Virgin Islands, with pit stops in Annapolis and Portsmouth, Virginia, then joining the Caribbean 1500 rally for the last leg.  The boat is a 1993 Morris Justine 36’ sailboat, not my first sailboat, but certainly my first ocean-worthy boat. The trip was what made me focus.  The prospect of sailing 400 miles from land in a boat that is new to me served to focus my attention, daily for six months before departure, on my lists of proactive maintenance and system improvements.  Despite intense focus I was not able to learn what I needed for the trip until I did the trip.  It might seem I would feel a sense of accomplishment having made it to my destination.  I do acknowledge the accomplishment but feel more a sense of being humbled than a sense of mastery. 

While the learning curve was steep in the months before the trip, it became even steeper once we left the dock.  The intimate understanding of the boat that is necessary to prepare her seemed to come to me following situations in which things were not working correctly.  I read as many books as anyone and I would ask questions until I feared that I had become a pest.  Still I needed to go out there and have parts or systems fail and then fix them before I understood them sufficiently to go offshore with them.  The way I would prepare for going offshore was by getting beat up offshore. 

Tangle of wires

For example, there is a tangle of wires behind the companionway ladder concealed by a panel which takes some determination to remove.  I did not appreciate what was going on in there until after the autopilot and GPS quit working early into the Gulf Stream crossing.  We were given a clue to the source of the failure by an accessory display for wind and navigation data that read "insufficient voltage." We asked, using our satellite phone email program, for advice in deciphering the clue and Morris Yachts Service suggested we use our multimeter (“I’m assuming you’ve got a multi meter on board?”) to track down a presumed short circuit. By the time we found the short we had tracked most of the wires in that tangle to all over the boat.  You could say I prepared for the GPS failure by having a handheld GPS and buying a new fuse for the multimeter before we left, but I only began to understand that system once I had to fix it.

My system for spare parts storage had consisted of several garbage bags gradually getting ripped apart by their contents.  On the trip I accessed these so often that by end of the trip I had them organized into bins repurposed from my children’s on board toy collection.  Among those spares were several extra fuel filters the chief mechanic at Morris had thrust into my hand at departure which I had been meaning to change already. When the engine quit and we saw what looked like phlegm in through the filter glass, I pulled out the books and figured out how to change a filter.

My understanding of what to do in high winds followed a similar pattern.  Not until I was out in them did I become convinced of what I needed.  The serene waters of Maine that we had seen most of the summer, gunkholing between Northeast Harbor and Camden, had lulled me into a sense of security with my current sail control systems.   A sled ride from Annapolis to Portsmouth, by myself in 35 knot winds, moved a few things up on my list.  I had debated running backstays all summer.  Deploying the stay sail in those winds showed me how the mast can pump when a force pulling at its midpoint is unsupported by running backs.  At least I learned while I was still in Chesapeake Bay. 

Before those high winds I figured I could get by with “work-arounds” rather than secondary winches.  Work-arounds are fine until shit hits the fan and you need all the mechanical help you can get.  I realized I cannot afford to save the money when I was up on the bow trying to manage the disaster created by failed work-arounds.  I had to turn down wind to keep the headsail blanketed by the main sail but had little sea-room so not enough time to set up the clunky preventer system and I watched the boat jibe.  Nothing I can do but hold on.   I needed the ability to control lines with enough redundancy to manage multiple things at once.  A situation might start with just one thing going wrong, but can become several things very quickly if things are not brought under control.

Ocean Marine Yacht Center
Portsmouth, Virginia

Upgrades continued to occur right up to departure, possibly to the point that they compromised overall management of the campaign.  I had the boat hauled out of the water in Portsmouth to inspect and repair the keel because I had hit a couple rocks hard on the way down.   We launched as soon as I returned and I was back to my lists.  The biggest job was installing those secondary winches and I thought I had everything set to go until people started telling me I needed backing plates, making the project more complicated to the point it almost did not get done.  Boat projects always seem to have complications and extra considerations that make them take longer.  I was blessed with a crew member who could take on projects independently and I took full advantage of that.  The safety inspection found some deficiencies we had to address, I needed charts and we had to provision the boat with food for twice the length of our anticipated trip.  I was determined not to leave the dock with projects we still needed to do, having been convinced to leave Maine in such condition.

Mechanically I suppose things worked out alright.  We got our autopilot back once we figured that the short was in the GPS antenna cable, and all we had to do was disconnect it, and we felt pretty smart.  But now we were tired.  For a full day we had rotated one man always at the wheel, with waves the size of the sledding hills at home in Minneapolis, while the other two tried to get multimeter readings in inconvenient places. A couple days later we found the actual frayed spot on the antenna cable, which could only be seen using a mirror and a flashlight, and bypassed it so we could use our computerized navigation again.  We were on a roll.  We got the engine running when it quit and I learned how to bleed the fuel lines while wedged in a corner to keep from being thrown around. I kept devising various rigging experiments like my continual perfection of the preventer system. Until the boom broke we had been able to fix most things, and even then we had fuel in jerry cans which enabled us to motor-sail the rest of the way to Nanny Cay without a main sail.

But the challenges go beyond figuring out how to control the boat and keep it going.  I needed to also manage a crew.  I did not appreciate early on how important it is to clearly communicate the way in which I wanted things done and maintained.  Lines on the boat have specific uses which sometimes need to be employed immediately and I do not want those lines used for random jobs.  Equipment storage is tight and moving one thing can create a domino effect of other things being moved.  The set up of a sailboat is part science, but part art, too and this blend of art and science creates a system.  Well-meaning deviations from that system by new crew can have repercussions that break down the system.

Before I had a chance to even consider those issues I was having a hard time just finding crew.  Without crew I would not be able to sleep, so I required at least one person to sail with me and had decided I needed two in case someone got sick or hurt.  By October four people had backed out and another turned out not to be a good fit.  Each time I was down a person I was left slightly panicked about who else I could find. I was asking people to take a three-week trip out on the ocean with a captain new to ocean sailing and with a new boat.  My list of friends to call was getting short.

I could certainly tell prospective crew that it was a well-made boat and that I had taken every step to make her safe, but I was also aware that I might not be offering the level of modern conveniences that some people expect on a cruising boat.  My personal taste is to have more of a wilderness-out-in-nature type experience than a pampered one.  I chose and equipped my boat accordingly.  She is a strong sea-going boat, but she is small boat which means that the area where the people live is closer to where the sharks live.  There is no shelter behind which to steer without being exposed to the elements. We do have an autopilot and a new electric refrigerator so we are not living primitively, but I do not have a microwave and I cannot run a hair dryer, much to the surprise of some prospective crew.  I crank my anchor up manually.  I have an electrical navigation system but I really prefer to use the paper charts.

Prior to departure I developed anxiety about losing crew.  Each time someone backed out it was the same.  I don’t hear from them for a couple of weeks, they’re not asking questions about the trip and I end up giving them a call to see what’s up. I became frustrated as I realized that my dependence on crew cut into my coveted independence.  By the time we started I had become excessively accommodating.  I would not speak up when we dropped below my usual standard of neatness on the boat.  I did not enforce equality in cooking or dishes.  I said yes to fishing late in the day just as we were entering the Gulf Stream.  I let people change where things are put away.  I let myself be convinced by crew to leave the dock when we weren’t ready based on an assurance that we could get things done underway.  As we approached Tortola I was going to risk making landfall at night, cutting through some narrow channels, because my crew had been counting the hours until our arrival. I succumbed to pressure in how much we ran the engine.  I took chances with crew like letting one steer with the spinnaker which developed into a situation in which I thought we could lose the mast 400 miles from shore.  Worst of all I deviated from a safe course to one that was much more dangerous when a crew member threatened to leave the boat if I didn't and still was going to keep that crew after he openly questioned my role as captain.

I am not particularly interested in being the authoritarian captain, but I can appreciate how that tradition came to be.  Simple decisions on a boat become complex given the interactions of all the systems and if I have made a decision that I like something done a certain way on my boat then that is the safest way to do it until we have a time to sit down and think of a new way.  Routine is good and with a new crew on board routine has to be enforced.  Also, it takes a considerable amount of confidence to be the captain of a boat.  Threats to my confidence make me less able to see solutions to problems.  I was already uncertain of my own ability.

Interestingly, I think a friend was trying to help me with just these aspects of preparation in the weeks before I left. He recommended some reading and I was surprised that it dealt with how to run sailing campaigns, not about actual sailing. When he talked to me about my preparation he asked me about my watch schedule with a concern for how we would get rest, maintain active roles and facilitate communication.  I thought he still needed to teach me about technical stuff like the wind speeds at which I was going to reduce sail. I had noted the measured intensity with which other captains the year before had approached the days before departure and was aware that my busyness was making it hard to achieve that level. 

First time up the mast

We finished the Caribbean 1500 at the back of the pack which was expected as we were the second to shortest boat in he fleet and the shorter boat’s top speed through the water is always going to be less than that of a longer boat. But I thought my childhood of dinghy sailing and a more recent history of keelboat racing might help me keep up.  I learned that these guys who have done ocean sailing know how to keep their boats moving.  

The boat is now sitting up on land in Tortola, British Virgin Islands. People tend to assume I would feel a sense of accomplishment, but more than anything I am humbled by the experience.  I needed to do all the preparation I did and I needed the pressure of the trip to force that level of preparation.  But I could prepare all I wanted -- I was not going to be prepared for a cognitive and emotional challenge in one of the most remote places on earth until I had done it myself, in my own boat, responsible for all major decisions.  If I had not done the trip, I wouldn't even know what I didn't know.  I could have stayed close to shore or hired a professional captain, but I never would have learned. 

ps: this blog post appeared in Sail magazine

Broken Boom

This is the front of the boom.  It broke approx 75 miles from Tortola. The bar running slightly uphill from left to right was originally attached at the little nub of metal to the right of the wheel. The entire piece was welded to a sleeve that fit inside the boom and secured with rivets. You can see where the weld was on the bottom of the bar. It looks like it peeled away over time. The axle that the wheels turn on was bent. I never heard anything actually break (or maybe I should say that the sounds of things breaking have all been accounted for). We were in calm seas and I just noticed it hanging there. I had been using the preventer on reaches and since it attaches at the aft end of the boom, I wonder if I could have caused some forward pressure on that joint. The axle is secured in the middle but also went into indentations on both sides of the sleeve. It would've bent just as the piece pulled apart.  They re-welded it for me in Nanny Cay and reinforced all the welds.