Draft – MV Simple Life

We had a quiet night on anchor in the Alligator River. Our anchor spot was just off the ICW and was an “easy in” and “easy out” in the morning. Note: some anchoring spots can have shallow or tricky entrances.

The sunrise was amazing.

Alligator River Sunrise

Sunrise over Alligator River

We had no sooner got through the Alligator River Swing Bridge and we hailed the large cruise ship, Independence, coming up on our stern. The captain was very friendly and thanked us for giving him exclusive use of the narrow channel.

MV Independence uses AIS just like us so it was easy to acertain their ship’s name and hail them directly. I simply let the captain know that I saw they were going to overtake us and stated we would manuver to starboard and allow them exclusive use of the entire channel for a “2 whistle pass”.

Cruise Ship 1 — American Cruise Lines, MV Independence

As the channel got narrow we had to get in line behind this sailboat who did not seem to have their VHF radio on. (repeated hails from us and the Alligator River Swing Bridge with no response). On the ICW you must monitor channel #16 (the international hailing channel).

Note: the ITU (International Telecommunications Union) designates 3 channels internationally as “Safety Channels”.

Channel 16 (156.800 MHz) – Distress, safety and calling

Channel 13 (156.650 MHz) – Intership navigation (bridge-to-bridge)

Channel 70 (156.525 MHz) – Digital Selective Calling

DSC Discussion (skip this technical section if you like)

CH 70 or DSC or Digital Selective Calling is a new technology that uses EM wave pulses on channel 70 to send digital (1s and 0s encoded in electromagnetic pulses over a radio wave transmitted on channel #70’s designated frequency)

This channel is not for human voice transmission but for ships continually broadcasting their current position and heading. The data is received by your VHF antenna and processed by your AIS transceiver before finally being plotting on your chartplotter. Instead of just a radar blip on my chartplotter, I see a triangular icon representing the ship and if I click on it I get all sorts of info like:

Ship Name: So I can hail them by name instead of “Motor vessel off my port bow”
Heading
Speed
Ship length
MMSI #
Sail or powerboat
CPA (Closest point of approach or how close will they come to our boat if nothing changes)
CTA (at what time will they be the closest to us).

DSC also has a well hidden secret function where you can use a ship’s MMSI # (like a personal phone number) to call them directly. By this I mean you don’t hail them by name (ie. “ship name, ship name, this is motor vessel Simple Life on channel 16”. Instead you type in their MMSI number and a channel that you want their VHF radio to automatically tune to. Hit the PTT (Push To Talk) button and a loud tone plays over their VHF radio and their radio automatically jumps to the channel you wanted to communicate with them on. It’s a great feature but I must say I have not used it, nor have many other boaters. Maybe it will just take some time till the early adopters start teaching other boaters how to use it?

As we approached Coinjock, NC, there were large plumes of smoke coming from shore. I saw that the smoke which had started as grey/black was now white indicating that it was burning itself out (Where are my firefighter friends here, keep me honest). Maybe it was a controlled burn of the low lands?

Close Up

Far Away

Getting Closer

As we were pulling into Coinjock Marina, named for the NC town of the same name, we were aware that our port fuel tank was running on fumes. NOTE: we had some reserve fuel in the starboard diesel tank.

We had made two long runs up the coast and at almost 9 kts and burned lots of fuel. Coinjock about 20 cents more per gallon of diesel than the marina we were heading to next. While not the cheapest place to take on over 300 gallons of diesel it was convenient. I mentioned to the dockhand that the next marina North was 20 cents cheaper a gallon and he responded, “Oh, our costs are higher because we sell more fuel than them”. I just smiled and thought, I’m pretty sure this friendly dockhand skipped school that day in business class 😉

When choosing a location for diesel be sure to chose a location that sells a lot of diesel. Common wisdom says: the more they sell, the less time the deisel sits in storage tanks acculmulating condensation water or other contaminations. If you have ever had your engine die offshore due to bad fuel you’ll agree that it’s better to spend a bit more for the likelihood of clean fuel.

The cruise ship which had passed us on the ICW was now docked in Coinjock to take on 5000 gallons of diesel.

Cruise Ship Coinjock — MV Independence Docked in Coinjock NC

I believe in large ship terminology, the captain and crew talk about the amount of diesel they have in terms of weight rather than gallons. Diesel is about 7 lbs / gallon while gasoline is about 6 lbs / gallon. When you take on 5000 gallons of diesel you need to be thinking about how much that excess fuel weighs and what it does to your ship’s draft. Draft = how deep your boat sinks into the water. Air draft = how tall is your boat is above the water for fitting under low bridges.

MV Simple Life took on about 311 gallons or 2,177 lbs of diesel while we were there. We also filled our water tanks (8.3 lbs / gallon) so that adds another 3,700 lbs to our boat. If you ever read the specs for a boat it will list it’s dry weight as well as it’s water draft. Always remember that when you load your boat up with your possessions, passengers, dogs, food, fuel, water, etc that it will sink your draft a few more inches into the water. When a boat is designed they guesstimate the weight & displacement of the boat from summing up the weight of every item in the CAD drawing. This we know thanks to the ancient Greek scholar Archimedes and his “Eureka” moment when he figured out that a body (boat) displaces it’s exact weight in water.

An engineer friend of mine who also loves physics, Andy, once asked me this fun question about a man in a canoe in a pool who drops a stone into the water and asks how high will the water rise?

Boats with sharp narrow hulls must sink lower in the water to float while boxy square hulls like that of a barge need only sink a small amount to displace their weight in water. The boxy square shape to the cruise ship allowed it to have ashallower draft than MV Simple life. So don’t follow the cruise ship up the ICW thinking… ”if there is enough water in the channel for them, we can easily follow them”.

We are leaving St. James Plantation Marina in Southport, NC this morning but made a promise to come back and spend more time with our friends Jim & Wende. They were very gracious hosts while we were here and we got to share in the experience of being in a “private town”. So very interesting though I must say Kelly & I will have to investigate exactly what that means?

Thanks Jim & Wende, you showed us a great night off the boat and we promise to come back and spend more time.

The night before we had anchored in Sloop Point, NC and the trip down to Southport was an interesting one. We saw heavy equipment dredging around what looked like a new pier going in. I know what salt water does to steel and I still shudder at the thought of dipping an excavator’s arm into salty water. I’m sure the water in the ICW is brackish but still.

I was checking my ICW bridge list and realized that I would not make the Figure Eight Swing Bridge in time for their restricted opening time. This meant that I would be waiting for the next opening. However the bridge tender who I had hailed on the VHF asked me about my air-draft. Your “draft” is your vessels depth in the water and your “air-draft” is your vessel’s height above the water. I replied that I believed it was somewhere between 21-22 feet. The bridge tender remarked that he currently had 22′ of clearance. Every bridge along the ICW has a “height board” that is partially submerged under the water with height markers at the waterline. While all bridges on your nautical charts will list their height at an average high tide, the actual vertical clearance varies with the height of the water. The bridge tender offered to come out of his office and stand under the bridge to check my clearance if I wished to approach the bridge slowly. This can be a tricky maneuver as there was a current pushing Simple Life toward the bridge. I slowly edged the boat idling in reverse to the bridge and bridge tender assured me that I had a good 6″ of gap between the top of our boat and the bottom of the bridge. MV Simple Life’s air-draft is 21′ 6″.

Below is a stock photo of the Figure Eight Swing Bridge as I was too busy at the helm to snap pictures. You can see I circled the “height board” and at the time this picture was taken there was slightly less water under the bridge giving even more clearance than the 22′ we had the other day.

Just a few more miles down the ICW and we had to pass through the Wrightsville Beach Bascule Bridge located at statute mile 278 along the ICW. This is a restricted bridge that only opens on the top of the hour.

As we continued on to Cape Fear (Southport, NC) we were delighted at the scenery.

We passed many Atlantic Ocean inlets that had high sandy bluffs and marshy islands dotting the entrances. You could see and hear the surf breaking in the shallow inlets and it makes for nice scenery. The last of those 4 photos is one of a fixed dock that just barely exceeds the height of the water level. Interesting choice of fixed dock heights as this surely must be slightly submerged at times? Slightly submerged docks must be fun to walk along but just like submerged rock jetties that often protect many of the ports we enter they can be dangerous if boats come into contact with them.

As we got the point where the ICW connects with the Cape Fear River via “Snow’s Cut” we were passed by a US Army Corp of Engineers survey boat. These folks use sophisticated sonar to accurately probe the depths of these constantly changing waterways. He kindly slowed down as he passed and got back on plane once he was in front of us. However, just then the VHF crackled on channel 16, “Trawler in Snow’s Cut, are you OK?”. I quickly answered the hail with “comeback to the trawler in Snow’s Cut”. It was a boat in a marina that was hailing us stating that they “saw what had happened”. I replied, “If you are referring to the ACE boat that passed us, yes we are OK”. I found this communication amusing and I can only guess that the survey boat had passed the marina giving a large wake and making the marina boat unhappy and maybe this was her way of shaming the ACE boat publicly on the VHF?

It would seem the kids in Snow’s Cut like to party at this old bridge abutment. “Party on” Capt B.

Once in the Cape Fear River it became quickly apparent from the size of the docks that extend out into the river that this river is used by large ships. Passing these behemoths must be done at a distance.

A quick turn back onto the ICW, by a dilapidated building and we arrived at St. James Marina.

Time to push on to Georgetown, SC where we’ll update with a new post of what we saw along the way.

Tag: Draft

Coinjock Marina Going North

St. James Plantation with Friends