Tuesday, February 7, 2012

Adding a skeg

Most dories have skegs to improve directional stability while rowing--probably a good idea given their flat bottoms. I decided to design a simple one made of 1" stock (3/4") a couple feet long and curved so the wear and tear from dragging the boat around wasn't on one point. This would also allow me to add a protective metal half round if I wanted. Many skegs running deeper than the bottom amid ship, but I decided to make it the same depth. From other boats I've rowed there usually enough water flow upwards towards the stern to provide plenty of grid. Also I've seen several boats with longer skegs damaged after some rough treatment being pulled on shore or hitting something underwater while drifting sideways.   Keeping it small would save weight and less vulnerable. If it doesn't work, I can always laminate another strip on the gentle curve.

Just as a started a noticed a problem. I'd designed the transom to a point. My first task was to make it the same width as the skeg. This isn't very hard in Freeship as long as you're careful to preserve the surfaces as you extrude edges, remove or add point and edges. Here are the results:

To add the skeg I selected the three aft bottom center edges and extrude them vertical by about 4 inches. Like this:
I set the vertical height of all the bottom points to zero, adjust the most aft so it slopes in line with the transom and round the two corner points. Next I extrude the whole skeg transverse by 3/8" which is half the final thickness. That completes the skeg (see below). I left the control points in view so you can see how the rounded corners work.



Next time  I'll be designing the seats, and thinking about the framing and bow construction.

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