ASTRA will depart from Puerto Calero, Lanzarote, The Canary Islands on the 1st December 2021 to complete a World First:
’Round the world circumnavigation (Via the Capes) on an owner/skippered full displacement motor boat of less than 24 metres’.
The circumnavigation will start at Lanzarote and involve crossing the equator twice and travelling through 360 degrees of longitude at a minimum distance of 26,600 nautical miles. The route will take the vessel around all of the Capes in the Southern Ocean.
This involves passing south of:
Cape of Good Hope, South Africa
Cape Leeuwin, Western Australia
South East Cape, Tasmania
South Cape, New Zealand
Cape Horn, Chile.
What Defines a Circumnavigation:
A circumnavigation by sea requires the crossing of all lines of longitude, plus the equator at least twice, with a minimum distance covered of 21,600 nautical miles.
The minimum distance of 21,600 nautical miles is based on the length of the earth around the equator, ie 360 degrees of longitude at a distance of 60 nautical miles in each degree (360 x 60 = 21,600 NM).
Challenge of this Circumnavigation Route
The circumnavigation route normally undertaken by power driven motor vessels is via the comparatively benign waters of the Panama and Suez Canals. However, the route that ASTRA will take is the more challenging one of the southern oceans around the southern Capes of Africa, Australia and South America. Crossing the equator twice allows ASTRA’s route to be classed as a ‘circumnavigation’.
The route will be approx. 26,600 miles and is a ‘big seas’ route that is generally only taken by merchant shipping or expeditions heading to the southern continent of Antarctica.
Vessel and Crew Selection Process
The vessel ‘ASTRA’ was selected for this attempt because of its full displacement characteristics and its safety characteristics. It is a historic ice classed vessel that served with Swedish Sea Rescue Service between the years 1995 and 2016 and is credited with saving many lives and keeping the northern ice waters environmentally sound.
Iain Macneil, an ex Merchant Navy seafarer is captain of Astra, and all of the crew are experienced hands who have previously sailed with him. The voyage will be completed without sponsorship and is being completed for the challenge it represents and not for charitable fundraising.
Technical Bit – Displacement and vessel type/Hull Form
The defining characteristic of a motor boat is its hull form, which determines the way it travels through the water.
ASTRA is a full displacement motor boat. This means that the shape of the bottom of its hull generates no significant lift out of the water and it moves through the water rather than on top of it.
(This is in contrast to a ‘planing’ boat such as a power boat, which floats on top of the water at a speed largely determined by the size of its engine).
The maximum speeds for a full displacement hull are determined not by engine size, but by the following formula:
The maximum speed is, therefore, based on the square root of the boat’s waterline length multiplied by 1.34. This is the fastest speed in knots that a full displacement hull can physically achieve (regardless of the amount of engine power applied to it).
For Astra, with a waterline length of 21.21 metres = 69.5 feet, the maximum speed of the hull is 11.18 knots