Question on keel lines

[Noklin]

I am at the point of cutting out the hull panels.

Looking at the plan lines, I can not determine if the stern keel lines are a straight line or a curve. If I am reading this correctly, the plans show an offset of 5/8 inch at the transom, 3/8 inch at the first station going forward,

[Noklin]

I should have indicated that I am building a CS 20.

[Designer]

Yes, the keel centerline is a slight curve which blends into the bow curve.

You should start with a wood batten 3/8" to 1/2" thick and about 1" wide and nail with small nails or brads through or along side the batten into the plywood. After nailing the batten to the marks, you should stand back and sight along the curve to see if it is a nice sweet line and resembles the shape on the plan. If the curve is not fair, go back and check your measurements.

I like to use a batten which is just stiff enough to bend around the curve. This makes it almost self fairing. If the batten is just too thin, you have to fair it between stations and it is therefore harder to get it as fair. Naturally you need a thin batten to go around the bow.

The batten is a very important boatbuilders tool and most boatbuilders have a collection of different lengths and sections. It goes without saying that if you start with an unfair batten it will be hard to get a fair line. I find that trim moulding usually has straight grain and is free of knots.

If you have a nice stiff batten when used flat for the keel line, you can use it on the edge to make it less stiff for the chine line which has more curve.

[Noklin]

I assumed that it was a curve but wanted to make sure before cutting. I was using a piece of trim molding to lay out the lines which worked great for the bow curve, but I found that it was too flexible for other parts. With 42 inches between stations, it would move when I was trying to mark the line. I just picked up a piece of

[Greg Luckett]

If you have some mahogany or sassafras, it can be cut into strip about 1/4 thick then scarfed to make long battens. That works really good.