Cross Sections – Reference Lines

The Sea Ranger’s (black) reference lines are drawn on the HDPE to center the drilled “snap-on” holes in the Shallow “V” at the offset locations. As such, the Sea Ranger’s reference points may vary from those of other designs in the same way that Section 1 and 8 of the Sea Ranger differ from Sections 2 through 7. You will need to determine what “looks” best for a particular design.


Draw Reference Lines (Sections 2 – 7)

Use a ruler and permanent marker to draw lines from the gunwales to the keel. Next draw lines from the chines to the deckridge. These lines will be used to establish the position of the stringer holes.

Draw Reference Lines (Sections 1)


Due to the cross section shape of section 1, the reference lines are drawn from the gunwales to the chines.

Draw Reference Lines (Sections 8)


Due to the shape of cross section 8, the reference lines are drawn from the gunwales to the chines and the chines to the deckridge.

Stringer hole centers


Place a mark 3/8″ inside of the offset points. This mark is on the line just drawn. This represents the center of the 3/4″ stringer hole.

Stringer Hole cutoff

Draw a diagonal line 1/4″ inside of the offset points. After drilling the stringer hole, cut the HDPE along the line. This cutoff is 1/8″ past the centerline of the hole and allows the tubing to “snap” onto the cross section.

Stringer hole centers


Use a hammer and nail to mark the 3/4″ stringer hole center. This mark will make it easier to locate the hole center while drilling

The cutoff line needs to extend past the 3/4″ hole so that it’s position will be established. If not drawn now, it will be more difficult to establish it’s location after the hole is drilled.

Drilling HDPE

hdpe-cross-sections-11A 3/4″ Forstner bit is used to drill the stringer cutouts in the 1/2″ HDPE Cross Sections. HDPE is very easy to drill, and the bit will last through many boat building projects. Clamps may be used to secure the HDPE in place for drilling, though the material can be held in place by hand. The small nail indentation at the hole center insures that the drill bit will be easily aligned.


After drilling, the cutoff line is visible. This line is 1/8″ from the hole center. When cut off, this allows the aluminum stringer to “snap” onto the cross section. This simple process eliminates the need for the mechanical connectors normally found in folding kayaks.