WEIGHT ANALYSIS - DISPLACEMENT (V1.1 [2021])

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DESIGN WEIGHT - It's very different working in paper and cardboard, compared to marine alloys. We should also consider that our model tests will mostly be conducted in fresh water which is 1 kg/liter as opposed to 1.025 kg/liter for seawater - meaning that the full size vessel will have that advantage also, unless that is the operators intend navigating mainly in rivers.

One of the most important considerations during the design stage is the mass of the hull, hence the displacement in water. The weight of the hull dictates the power required to drive a ship from one destination to another. That, and the design of the hull. Which includes the design of the superstructure, hence air and water drag. The air drag element often being overlooked. Especially in sailing boats, where the air drag, or sails, is used to drive the vessel.

Since this page was posted in 2021, the vessel has grown. See 2023 V2 weight analysis.

As you can see from the estimations below, the bulk of the vessel is the aluminium used to fabricate the hull and the energy storage batteries. Of these two items, we can alter the mass of the batteries significantly, once we know the safe operating parameters from trials in the Atlantic. Defining a formula for solar and wind powered ships is one of the main objectives.

People often ask for the formula before the experiments have been undertaken to furnish such rules. That is putting the cart before the horse, but then we have to start somewhere. For the sake of safety, we have allowed a 3 day reserve at a reasonable operating speed. If we already knew what to specify, we'd not need to build the Swann. To quote Albert Einstein, a person who was frequently asked if he knew what he was doing: "If we knew what we were doing it would not be called research."

With this project we have 3 stages of development, all interactive with the other:

1. We have first to design a ship in principle.

2. Test the hull configuration in small scale tests in a towing or other tank, called a water basin.

3. Only then might we proceed to building the full size yacht.

1:20 MODEL SHIP TARGET WEIGHTS (tank tests)

 ITEM KILOGRAMS DESCRIPTION Hull spaceframe 1.30 Aluminium Hull active arms x 2 .80 Alloy Hull main hull 1.96 Aluminium Hull cones x 6 1.00 Composite Hull outriggers x 2 .88 Alloy Hull helm developments x 2 2.00 Aluminium Hull foils x 4 1.00 Aluminium Wings honeycomb .55 Composite Wings frames .50 Alloy HULL subtotal 9.99 PV CELLS .34 Polycrystalline BATTERIES  (radio control & navigation) 0.25 Lithium BATTERIES (storage) 0.00 (12.75% = 2.178 kg ballast add) E MOTORS including transmission 1.00 WIND GENS including boom 1.25 NAVIGATION instruments .50 AUTONOMOUS sensors 1.50 COMPUTERS 0.50 ACTUATORS 0.50 PAINTS 0.25 2 pack _____ TOTAL (35.44 lbs)    16.08 (17.26 kg ballasted - 38.04lbs)

Weight estimates for the model are not so critical, but when it comes to cutting metal full size, mistakes can be costly. Hence, working in scale for all design conceptualizing. The value in constructing a small scale model is not limited to just tank testing. Potential design issues are frequently encountered, giving the project managers useful advance information of obstacles to be overcome.

FULL SIZE SHIP TARGET WEIGHTS

 ITEM KILOGRAMS DESCRIPTION HULL 12,000 5083 Aluminum WINGS 3,000 ACTIVE ARMS 3,500 5083 Aluminum PV CELLS 3,000 BATTERIES 7,000 Lithium E MOTORS incl transmission 500 WIND GENS incl boom 2,000 NAVIGATION instruments 400 SENSORS & computers 500 SCREENS 200 HYDRAULICS 1,500 LIFE SUPPORT 1,800 CREW of 6 900 _________ TOTAL 36,300 kg

HULL DRAG - The weight of the hull determines our hull drag - dependent on many variables, such as conversion efficiency. You can see from energy estimates graph, that to reach our 10 knot goal, we need around 27kW of continuous energy across the Atlantic, for which we'd need ideal conditions. A more easily achieved target would be 7.5 knots, requiring 14.5kW continuous. While the present record of 5.3 knots, held by PlanetSolar, could be equaled with just 7.5kW of energy from the sun, if our mass is 36,300kg, for our wave piercing trimaran design.

2. A single central wave piercing hull stabilized by outriggers as a trimaran including:

a) Ultra light superstructure purposed designed to harvest energy from nature via b) and c) below,

b) Solar wings that track the sun and fold for storms, in concert with

c) A turbine generator on a mast that tracks wind conditions and furls for storms.

- Hull drag estimates

- Interior design

- Propulsion

- Weight analysis

The theoretical displacement we are working towards is: 30,000 - 45,000 kilograms (target) in 5083 marine grade alloy.

SHIP BUILDING MATERIALS

Steel

Steel is one of the most popular materials used for working boats and has consistently been the material of choice for the past century. Its high strength, durability, resistance to abrasion, and relatively low cost are some of the main reasons why steel is widely used in the industry. The drawbacks are weight and corrosion, but as yet these impediments have not slowed its use for larger ships on economic grounds.

In sustainability terms, steel has an airtight production process that produces minimal constructional waste. It is 100% recyclable at the end of its life cycle and hence is a sustainable material for boats.

Aluminium

Aluminium is preferred by a lot of boat manufacturers on account of its being lightweight, especially when compared to steel. Aluminium boats are more stable and seaworthy and can travel faster due to reduced weight. This means that you get better mileage for the same quantity of fuel from an aluminium boat. Easy workability and properties like chemical and corrosion resistance, imperviousness to magnetism, and tendency for plastic deformation make aluminium a good option for boat building.

On the downside, aluminium is expensive. Also, aluminium is a soft metal and hence more susceptible to abrasion. Aluminium is 100% recyclable and marine grades do not need painting, save for abrasion resistance and anti-fouling.

Fibre-reinforced plastic (FRP)

Fibre-Reinforced Plastic has come to heavily dominate the smaller boat material sector over the past few decades. A single structure that is light, speedy, strong, watertight, durable, and corrosion-free makes for a great solution. FRP has permeated all the levels of maritime applications and is increasingly used as a substitute for wood and steel today.

Economical viability is not one of FRP boats strengths, because though the material required for manufacturing these boats is moderately cheap, the process itself requires skilled labour and a knowledge of boat making principles. However, when you consider the return on investment, FRP boats have a much better ROI on account of their longer life and are hence by far the most popular building material for boats. Being a thermo setting plastic, FRP boats are not recyclable. According to the Boat Digest, 95% of 7 million pleasure boats were built from fibre-reinforced plastic.

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HULL WEIGHT ANALYSIS DISPLACEMENT PERFORMANCE CALCULATIONS FOR THE ELIZABETH SWANN