The Luomas built dozens of these between the 1920’s and 1940’s. At one time they were everywhere around Nanaimo. There were certainly other builders but the Luomas were well regarded and considered the finest rowboats by fishermen. This particular boat was found on Protection Island many years ago and saved by Steve and Graham Ellis. It was used by Wayne Gorrie to build his mold for fiberglass versions produced in the 1980’s.

]]>Of course I realize the problems are not anything close to simple, and the only real cure is to eliminate the need of people fleeing their homelands in search of physical safety or economic betterment. Can this be done? Of course, but it will take real effort over a long term. Meanwhile there’s a stability problem to address.

People are drowning because these boats are overloaded. Overloading does a couple of things, one is the boat sinks lower in the water, reducing freeboard which means the boat downfloods at a lower heel angle. It also immerses topside seams (for wooden boats) that are less watertight than bottom seams, so leaking increases and the risk of free surface (unconstrained water inside the hull) pulling the boat over increases. The other factor in overloading is the huge number of people on deck raise the center of gravity, again reducing reserve stability.

Capsize of Refugee Boats in the Mediterranean

Controlling the passenger load is the only way to reduce these capsizing incidents. Probably the only way to control loading is education of the passengers, which is why I’m posting this.

So how many passengers would be an acceptable number? Naval Architect Stephen Ditmore has done some work on this question, and based on earlier work by NA Cyrus Hamlin, has come up with a very simple loading rule.

Number of pass = L x B^2 / 6

L is length of the vessel, B is beam, both in meters. So if the boat is 15m long and 5m wide, you have 15 x 25 divided by 6, which equals 62 people. Small children can be taken as half a person.

]]>I was appalled to see the two lead investigators for the Transportation Safety Board could not, during their press conference, answer a simple question on Leviathan II’s hullform. Someone asked, “Is the boat a planing or full displacement hull?”. The investigators claimed “we haven’t looked at that.” My god, millions of people have seen the seen the pictures, the boat’s service speed is 20 knots, surface drives, 1000 Hp installed…..of course it’s a planing hull.

]]>Hydrostatic Nomenclature

B or CB – Center of Buoyancy, the center through which the buoyant force acts. The CB moves as the underwater shape changes as the hull moves up and down (or rolls sideways) in the water. If the hull is floating free to trim or roll, the CB will always be directly under the center of gravity. During launching this doesn’t happen because the hull is “aground” forward.

M – Metacenter, the theoretical point around which the boat rolls or trims. There are separate transverse and longitudinal M’s.

K – Keel or baseline, the fixed line from which all vertical measurements are taken.

G – Center of Gravity of the vessel. The center of all the various weights that make up the boat. Addressed separately as VCG (Vertical Center of Gravity), LCG (Longitudinal Center of Gravity), and TCG (Transverse Center of Gravity). In computerese X is longitudinal, Y is athwartships, and Z is vertical.

GM – Distance from G to M in ft. or metres. Considered a general indication of a given vessel’s stability. To be stable G must be below M. A larger GM means the ship is stiff, a small GM (say less than one ft) is a tender vessel, a negative GM indicates an unstable ship.

GZ – Righting Arm in feet or metres. A horizontal distance between the CG acting downward and the CB acting upward.

V – Volume of the hull (underwater portion) in cubic feet or metres. The displaced volume (underwater) will be equal to the total weight of the vessel divided by the weight of the water she’s floating in. So if your boat weighs 5000 pounds(2273Kg) on the trailer, afloat she will displace 5000 pounds(2273Kg). Seawater weighs approximately 64 pounds(29Kg) per cubic foot so underwater volume (V) is 5000/64 = 78.1 cubic feet, or 2273/1000 = 2.27 cubic metres.

I – Inertia of Waterplane. The waterplane is a cut through the hull at the waterline. The distribution of this area affects stability. A barge and a needleboat could have the same waterplane area, but very different stability.

BM = I/V – Key stability equation. Inertia of the waterplane (I), divided by the displacement (V), is equal the distance from (B) the center of buoyancy, to (M) the meta center.

Ultimate Stability Angle- Called the angle of vanishing stability, this is the heel angle where righting force is zero.

Downflooding Angle- The heel angle where water starts coming through some hull opening (doors, windows, ports, hatches) and degrades stability of the vessel.

Free Surface- When the contents of a tank (fuel, fresh water, wet fish) slosh to one side it sets up a heeling force, which can degrade stability.

Here’s a picture of Leviathan II’s sistership, Miss Interfor, from the back cover of March 1998 Westcoast Mariner Magazine. This was on the occasion of the re-powering of Miss Interfor.

So this is what Leviathan II looked like originally, fast and light with lots of freeboard and the passenger cabin set low in the hull. Stability of this boat would not be an issue.

What’s known about the accident is this Transportation Safety Board Prelim. Report

My understanding is that the vessel was certified for 46 passengers. At the time of the accident there were 24 aboard, along with 3 crew. Stability is assessed in various load cases and the ship must meet requirements in all cases. Usually there is a “worst case”, and often (almost always) it’s the Arrival Condition. This is on return to port with mostly empty tanks but still full passenger load. The assessing NA will distribute passengers over the three (in the Leviathan case) decks until the boat meets requirements. Then the owner will post a sign stating maximum passengers on the upper deck. It’s up to the crew to enforce this. But there is no requirement(that I’m aware of) to assess stability with various partial passenger loads. This is something I’ve long been worried about but I just dealt with it by severely limiting the number of passengers allowed on the upper deck.

Under Canadian regulations stability must also meet minimum requirements after a “passenger heeling load” has been overlaid on the righting arm curve. The passenger heeling load is established by pressing all passengers against one rail and looking at the resultant heel angle. This is deducted from the available righting force and what remains again must meet minimum requirements. But, if there are only half the passengers aboard, and all are on the upper deck, stability is different than what was assessed.

]]>Why oh why can we not have heavy displacement cruisers that look like boats? The two boats shown here have almost the same accommodation, despite my sketch (above) being only 44′ x 14′ compared to the Nordhavn (below), at 55′ x 18′. Both have a separate pilothouse with seating and a bunk, both have a big galley and saloon, both have a day head, and both have two full width staterooms with en-suite heads. And both have restricted headroom enginerooms…….No flying bridge, bilge utility room, or aft cockpit in my sketch vessel. My boat has half the HP (165 vs 325) and two-thirds the displacement of the Nordhavn. I believe my boat could be built (bent-frame carvel planked) new today for about the asking price of a used N55 (approx. $1.3m usd).

From any viewpoint forward of the beam, the Nordhavn looks freakishly tall. The windage is alarming, it’s no wonder these boats are equipped with bow and stern thrusters. The motion on the flying bridge in a seaway would be very quick and uncomfortable. In a sea I want to be down low, close to water level where motion is least. How do you put out a bowline when you’re 10′ in the air? The only place to get off this boat is at the stern, which is strange. I can’t help but think these boats are marketed to people afraid of the water, and they want to be as far from the wet as possible…….

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