Building the Rushton Catboat

Drawing the deckbeam crown

The following photos show a mockup of how I drew each deckbeam's crown. The jig is two battens bolted together. It is important that before drawing the crown that the jig be securely fixed so that the jig does not change angle.

Photo showing the jig and the schematic of one of the deckbeams. The two outer points, left and right, represent the width of the hull at the location of a deckbeam. The vertical line at the center is the height of the deck crown at that deckbeam. I derived these heights by running a batten describing the deck on the profile view on my lofting.

I then measured the height of the deck line above the sheer line at each deckbeam.

The jig is set to the angle formed when the two legs are on the sheer points and the apex is on the deck height, or crown.

I hold a marker at the apex of the jig and draw a line while sliding the jig to each side BEING SURE THAT THE JIG ALWAYS RIDES ON THE SHEET POINTS. Here I fixed two sticks to rest the jig against. I actually used a plank of wood to draw my deckbeams for the catboat, driving a nail at each sheer point to provide a rest for my jig.

Quickly and crudely done in this demonstration (sorry) this method makes a fair arc intersecting the sheer points and the deckbeam crown height. Using this jig for each deckbeam results in arcs that will fair with all the other deckbeams. If I were to have bent a batten between these points, each arc would not have faired with one another. In fairness, in a small boat this difference might not have been noticeable.

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