Otterblog

A record of the renovation of a
Wooden Drascombe Longboat 'Otter'


30th April 2007. Three-dimensional geometry.

The roof of the cabin is a curved surface (radius 1000mm) that slopes towards the front. I chose an angle of 5 degrees. If you look carefully you can see a batten along the centre of the roof.

The sides are curved surfaces following the curve of the gunwale.

I started by drawing a line on the deck parallel to the gunwale. I then clamped on plywood strips to show the position of the sides. I chose an angle of 10 degrees.

When I put a spline along the corner where the roof meets the side I had a strange looking curve. (An intersection of two curved surfaces.) You can also see the batten in the top photo.

I adjusted the plywood strips to get a better line.

I moved the centre one inwards to raise the spline at that point and moved the front one outwards to lower the spline at the front. This produced an acceptable line.

When I was happy with everything I replaced the plywood strips with permanent templates. (Some old melamine-faced chipboard.)

Sounds simple but it took me a day and half of adjusting and re-adjusting until I got it right.

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Unless stated otherwise, Colin Watt 2006, 2007

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Last updated: 1 May, 2007