What has been happening in Andrew’s Warrandyte boatshop recently? You can be sure that the launching of one boat (the Chebacco) also signals the start of another one.
Last year Orlando (my 9 year old yacht designer son) started a detailed design of his interpretation of an American Lake Scow. Assisted by me, he drew plans on a hull design computer package to test his theories on hydrodynamics – or at least to see if it would float.
Computer assisted design takes a lot of the hard work out of the process. Orlando could move the lines around with his mouse till his design was the right size and “looked right”, before pressing the “calculate” button to work out how his hull would work in the water.
We researched American lake scows on the internet to find some design clues and incorporated some theory to help get the underwater shapes right. In particular, Orlando wanted the underwater shape to be a “V” when the boat was heeled 15°. The chines, when viewed from the front or back, are straight lines and the side curvature matches the bottom curvature.
He wrote to friend and noted yacht designer Bob Perry in Seattle for advice and received some pointers.
The sail rig is borrowed from his O’pen Bic skiff, as is the rudder. The centre board is borrowed from a Minnow.
The hull is built from cheap 4mm ply (so called Bracing Ply, at $17 per sheet). The hull construction was completed over his school holidays and it was painted and finished over the next weeks after school.
By last summer he was sailing “Moss Scow” in races on Sugarloaf reservoir and showing that his design not only floated but sailed quite well. Within a few weeks he had won a trophy race on handicap against all of the monohulls at the club – and there were murmurs of how a larrikin with a winged keel had once upset the gentlemen at New York Yacht Club!
The bottom is wide and flat across, but is curved along its length. The bow is very wide above the waterline yet it forms a horizontal knife edge, the other way around to a conventional hull. Scows were developed originally as load carrying barges and were seen on the rivers in Europe, USA, New Zealand and Australia in the 19th and early 20th century. However, in the lakes of the north east of USA they were developed into racing craft, the legendary “American Lakes Scow”. Classes of Lakes Scow continue to be very successful and popular in USA. In Australia the shape was developed into the Moth scow more than 20 years ago.
When a scow hull heels the windward chine quickly emerges from the water and the underwater shape of the scow becomes a long “V” cross-section. This long sleek underwater shape is part of the secret of the fast scow hulls. The design of the chine and the curvature of sides and bottom affect the underwater shape and Orlando spent some time playing with all of the variables to get what he wanted.
So with Moss Scow completed, another boat takes its place in the boatshop – that will be another story.