Wednesday, August 10, 2011

Wednesday, August 10



This was a challenging day.   The keelson was beveled, the floor boards were mounted, a pattern  was made for the garboards (the first strake or fore and aft board next to the keel), transferred to 3/8” plywood the the strakes shaped.

A bit more detail. At the point the keelson crosses each mold, a saw kerf was cut running from the centerline parallel to the adjoining part of each mold. This provided a guide for the subsequent planing; the angle changes as you move along the keelson. The rolling bevel is a common structural challenge in boat building. The bevel was cut initially using a hand power plane followed by hand plans. Frequent inspections were needed to insure that the bevel angles were correct along the keelson, and that, as always, the lines remained fair. The centerline on the keelson is sacrosanct; the bevel cannot erase it.  For photos of this, click here.

The floor timbers were fastened to the molds on the “downhill” side of each mold, i. e., on the bow side toward the bow and on the aft side toward the stern. The molds were appropriately marked, moved things along. The floor timbers were examined for fit. They were removed and some work was done with a Nicholson #50 rasp. Filing or rasping, one of our philosophical conundrums for today.

Once the fit as acceptable, they were screwed back to the molds, countersunk holes drilled through the keelson into the timbers and screws partially driven in. The keelson was then pulled away, thickened epoxy smeared between the floor timbers and the keelson, and the (1 1/2” #10 bronze)) screws driven the rest of the way.  This sequence can be seen by clicking on floor timbers.

Geoff then gave a talk about screws, pilot holes, and countersinks and introduced us to the Jamestown Distributors catalog.  Go to Jamestown Link

Next we needed to fabricate the garboard planks. To do this we constructed a pattern from ¼ “ luan (cheap) plywood. Distances were marked from the keelson centerline and the first inflection on the mold using a compass. The pattern was then placed on more ¼ inch luan which was hot gued together to provide sufficient length. The garboard was then transferred to the long luan blank and the blank cut out.   It was then fitted to the molds and corrections noted (e.g., +1/4 inch or -1/8 inch) at specific points. Once a satisfactory fit was achieved, the blank was placed on top of a  $75 4x8 piece of 3/8” meranti plywood. The long blank had to be traced in separate sections onto the plywood in such a way to make efficient use of the plywood.   A 3” scarfing pattern was made (just a 3” wide piece of luan). The parts 3 parts of the blank will have to be joined using a wedge shaped (side view) cut on adjoining pieces. The slope of this cut is 8:1, so for 3/8 inch plywood, the angled cut starts 3 inches from the edge.  The spiling and plank forming photos begin here.


End of the Day Progress Photo


All photos of the Ness Yawl 2011 class may be viewed at: http://www.flickr.com/photos/21597525@N00/collections/72157627358772597/ 

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