02 shaping the hull

March 21, 2021

Add masking tape along the center line of the board (can be along the middle of the centerline so very middle is flat).
Add masking tape along the edge of the board to use as a guide to create the depth of the V. The tail of my board had a very shallow V, increasing to only about 5mm of V at 1meter from the back of the board.
Sand the board with a long sanding board to make the V using the tape on the board edge as a guide.
Repeat on the other side to complete the V in the hull.

I only wanted small concaves in the front half of the board. (See the main picture above). I masked off a section on the sides toward the front of the board that I wanted to leave flat - did not want the concaves to be too large.
Draw perpendicular lines 10cm apart in the area that you want the concaves. These are very useful as depth guides, and a visual way to see how much concave you have created and the shape of the concave.
Sand the concaves using a curved sanding board. My concaves were very subtle - approximately 5mm at the deepest part.

To add the V, the sanding board should be long enough to go from the widest edge of the board to the center line with a few extra inches at either end. I used a 4" x 1/2" x 18" board. Use contact cement to glue 60 grit sandpaper to the board.
To use the sanding board, I found it best to hold an end of the sanding board in each hand, and tilt the edge of the sanding board near me up slightly, so that only the far edge of the sanding board was touching the EPS. I then pulled the sanding board toward me in long strokes until the desired V was created. If laying the sanding board flat on the EPS and trying to go back and forth with the board, it would "catch" on the EPS, and risk creating a dent.