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Friday, September 2, 2011

Banjo - Night Sailing on Lake Waccamaw NC

Night Sailing on Lake Waccamaw - The Banjo Effect Explained

Map Link to Lake Waccamaw NC

I discovered this, so I get to name it - The Banjo Effect!

I've never shared The Banjo Effect before, always keeping it private for my use!  But I'm going to share that with you now!

Before I get to The Banjo Effect, I want to give a little background.

I spent a lot of time at Lake Waccamaw NC when younger.  We had a cottage directly on the lake, located on the western shore, near Dupree's.

I had been interested in sailing for years, and finally, while in college, had managed to buy an old scrap wooden sailboat (a Windmill - see bottom of this post for more information on Windmills).  I made some repairs to it, and soon was out sailing on the lake, teaching myself how to sail.  It was about 15 feet long, with a mainsail and jib.  The sails that came with the boat included a racing jib (genoea?), which I kept up all the time, as I enjoyed the speed it provided.

For those that aren't familiar with a Windmill, at the time, it was a  wooden boat and very very narrow, so that it was fast enough to plane on the water, and had a center-board (rather than a weighted keel).  However, with it being so narrow and without a weighted keel, it was also very tricky to keep upright in high wind.

I sailed it until a friend of mine ended up taking it out and overturning it, getting the mast imbedded in the bottom, while waves pounded on it; this broke the boat up, and I never got to sail it again.  However, my friend did tell me, if I could get a trailer and would tow it to Boone NC where he was in college, he would help me repair it!  Seeing as Boone was about 6 hours away (and 6 hours back), the boat was wrecked and I didn't have any access to a trailer, and while I thought that was a more-than-generous offer to help me repair the boat he had wrecked,  for some reason, which eludes me now, I didn't take him up on it.

Later, after I was married, I returned to live at Lake Waccamaw for a year after the nuclear industry stopped building plants (I had been a startup engineer for computer controls), while furthering my background in programming in order to make a career change.

While there, I bought a Tanzer, which is a fiberglass boat, centerboard, two sails (jib and mainsail), and slightly longer at 17 feet or so, but a whole lot wider!  It certainly lacked the speed of the Windmill, but it could carry me, my wife, and our two small children, so it was a big improvement.

At some point, I started sailing at night on the lake.  I had sailed back to the house from the front area of the lake, sometimes getting back after dark.  So, I didn't set out to sail at night, it just ended up this way.  An odd thing to note; when I was coming into the land, the wind would always die out, which I realized was probably the trees blocking the wind near shore.

I found that I enjoyed this evening sailing, so I gradually stayed out later and later, until at some point I was going out late, may 9 - 10 PM and coming back at 2 - 3 AM!    I was sailing around the lake, keeping a fairly constant distance from the shore, sailing a great big circle.  For those not familiar with the lake, it's oblong, about 3 x 5 miles.

Sailing at night, I always had really, really good wind!  And this was a puzzle, as I never had this type of wind during the daytime.  I could have good wind sometimes during the daytime, but not always!  At night, it was always good wind!

I began to notice, again, that the wind would die when coming into the shore area, maybe 1/4 mile out from shore.  I would crank my little 1.5 horsepower motor up and putt on into shore.  But it finally began to dawn on me that at night, I had to motor out, and motor back in, but there was always, and I mean always, wind out 1/4 mile or so out, regardless of how still it might be on land.

My sweet wife would always be puzzled, saying how can you be sailing - there's no wind here at the house!  And I would tell her I don't know how or why that is, but there is wind out on the lake, about 1/4 mile out, even if there's no wind here at the house!

Once I realized I had a mystery on my hands, I set out to solve it.  I gradually added another piece to the puzzle:  When I was sailing at night, I never had to adjust the sails!  In sailing counterclockwise around the lake, the wind was always, always, coming from shore, always on my right, even though the sailboat and I were constantly changing the direction we were heading in order to keep a constant distance out from shore!

In the daytime, the wind always had a direction to it; e.g., during the afternoons, it was typically from the South.  At night, when the land was calm, then there was plenty of wind, but it did not have a compass direction to it; it was always from the land, regardless of where I was at on the lake.

So this meant either the wind was changing just right so that it continued to change direction as I sailed, or else it was being pulled into the lake equally from all sides. Well, we all know the wind wasn't keeping track of me and following me around, so indeed it meant the air was being pulled in from all sides.

So, how to test this?  I realized that, if indeed the wind was being pulled into the lake from all sides, then it had to end up in the middle of the lake, but once itwas in the middle, since all of it was coming in and none of it was going out, it wasn't going into the lake, so it had to be going up into the sky!  And, near the shoreline, there was no wind because the tree line was keeping the wind above the trees, where it would slope down to meet the lake about 1/4 mile out - so the trees were creating a dead-zone of wind near the shore.

Well, this was another mystery....what in heck would cause all of this air to be rushing into the middle of the lake, then shooting up into the sky?  Why - if the lake water was warmer than the surrounding air, then it would rise up off of the lake, and go up into the sky.  This would create a low pressure area in the lake, and air would rush in from the cooler-temperature land to fill that void!  And as this air flowed in from the cooler land, it would pass over the warmer lake and be heated, so it was gathering heat as it flowed in to rise up in the middle.  Thus, it would come in from all sides, so that when sailing around in a big counterclockwise circle, it would always be coming in from the right side, it would be constant, and I would never have to adjust anything!  How about that?

Imagine a hot camp fire on a windless night.  The heat from the fire and smoke goes straight up from the hot fire, while air rushes in (wind!) from low on the sides to fill the void.  

I realized that there was one way to test all of this; the air, when it came in from the sides, would have to bend and go up near the middle.  That meant that the wind in the middle would shift from coming from the land, and would now be going straight up.  And that from a sailing perspective, it would be calm and windless in the middle of the lake!  So out I went to test it.....and sure enough; as I approached the middle of the lake, the wind lessened, the closer I got, the less wind there was, until I couldn't sail any more!  And when I moved myself back closer to the shore, the wind gradually got stronger and stronger until I had a constant wind off of the shore!

Bands and Areas
So there's 3 bands, sort of like a bulls eye, which I'll describe starting from the outer edge and moving towards the center:
  1. The first, outer band is the Shore Band - it's next to the shore and has no wind.
  2. The second, inner band is the Wind Band, and like the name says, it has wind.  It's between the Shore Band and the Center Band.  This band, the Wind Band, is subdivided into three areas again moving from the outer towards the inner; the First Area, The Middle Area, and the Last Area.  Each area has it's own wind signature.
  3. The third, Center Band (the bulls eye) is the middle area of the lake, and has no wind.
Wind Bands
Stylized view of Lake Waccamaw
Lake is in the middle (yellow and blue), surrounded by land (brown).

So the 2nd band, the Wind Band, is where the wind is, and to sail, you have to get to it.

This 2nd band, the Wind Band, is broken down into 3 areas in and of itself:
  • The First Area of the Wind Band.  This is the area that ajoins the Shore Band, and it has light wind.  The wind is making the transition from Shore Band has-no-wind to Wind Band has-wind, so the wind is just starting to build here.  So as we move away from the Shore Band has-no-wind, the wind gradually builds until we get to the Middle Area of the Wind Band, where there's the most wind.
  • The Middle Area of the Wind Band has the most wind.  It's midway from the edge of the Shore Band to the edge of the Center Band.  It's between the First Area light-wind and the Last Area light-wind of the Wind Band.
  • The Last Area of the Wind Band, and it has light wind.  The wind is making the transition from Wind Band has-wind to Center Band no-wind, so the wind is starting to decay here and getting light and lighter until you get to the Center Band, where there isn't any wind.
Closeup of Wind areas within the Wind Band
(blue sections)
Dark Blue is strongest wind.

Why, heck - I could sail by being in the Wind Band, then I could decide how much wind and speed I wanted to deal with; if I was in the Middle Area, then by either moving towards the First Area or towards the Last Area I could lesson the wind; if I was in the First Area or Last Area, by moving into the center of the Middle Area, I could increase the wind.  I could fine-tune this however much I wanted.

The only bad news - you couldn't take a short cut home by cutting through the Center Band - you would get slower and slower while running out of wind, and it would take longer and longer to get home. So unless I started up my motor to get through the Center Band, I had to circumnavigate the lake via the Wind Band to get back home.

So there you have it - THE BANJO EFFECT!  If you want great sailing at Lake Waccamaw, then in the summer, when the lake is hotter than the land in the late evenings, then the sailing will be great in the Wind Band, which is between the Shore Band and the Center Band - just like a bulls-eye, half way between the edge and the center.   The wind will always be from the right (when sailing counterclockwise), it will be steady, and you won't have to adjust anything in sailing the whole way around the lake!

It's important to wait for the land to cool down below the temperature of the water.  The cooler the land while the hotter the water, the greater the effect.  Sorta like how a hurricane works.....air rising in the center creating a low pressure point in the middle, with air rushing in from the sides to fill the void.

Some Information about Windmill Sailboats - from the official site (link)

The Windmill is a 15 1/2 foot, 2-person racing dinghy designed by boat-builder Clark Mills in 1953. Having designed the Optimist Pram in 1947, Clark saw a need for a 2-person high performance dingy that can be inexpensively constructed by amateur builders. The class has since evolved with the times to allow fiberglass construction and aluminum spars, yet both wooden and fiberglass Windmills remain equally competitive. The Windmill is a born racer. Its narrow, hard-chined planing hull provides high performance. Being a non-trapeze, non-spinnaker boat makes the Windmill accessible to a wide range of sailing skills.

Contact the class officers for more informaion.
Length Overall 15' 6"
Length Waterline (LWL) 13' 8"
Beam 4' 9"
Sail Area 119 sq. ft.
Draft - Board Down 4' 2" / Board Up 6"
Mast Height 20' 3"
Portsmouth Ratings: 
 89.7     Light air 92.3    Medium 91.4     Heavy 86.4

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