How to Make a Sail for an Aluminum Boat

Determine the gravitational center of the boat hull by hanging the hull from a single point where it remains in balance. If your boat is small and light enough, tip it on its side and lift it with both hands placed together on the hull edge. Shuffle your hands down until the boat hangs evenly balanced on either side in your hands. That is your gravitational center.

Build a base for your mast on the gravitational center of your boat on the floorboard. You can use a wood base, glued down onto the floorboard. Add a lock and pin arrangement for attaching the mast to the wood base so the mast does not move and can't be pulled out. Add ironwork, such as cleats and snap-close hooks, onto the hull to anchor your stays and cables -- used to keep the mast upright. You can drill these into the edge of the hull above the water line, and use bolts and screws to keep the hardware on tight.

Measure the length of the boat to get the right height for your mast. The measure of the mast should be a 1-1 ratio with the length of the boat. Place the mast in place and run four stays from the top of the mast, one forward, one aft or back, one on either side, and tighten down. Add ballast below the mast base to the gravitational center for more weight. Add the boom to the mast with a closed hook-and-eye system to allow for free movement back and forth with the wind changes. Measure the rigging dimensions to determine the size of the sail.

Lay out your fabric in a right triangle design with the long side going up the mast and the right angle down where the boom meets the mast. Cut the fabric and add a double edge to all sides of the triangle to keep the sail from ripping. Cut holes in the edges and reinforce with grommets so the holes won't rip out. Add closed-latch hooks to each hole.

Lay the sail on the boom and attach the hooks to the boom. Slide it over to where the boom meets the mast. Hook the top of the sail to the top mast attachment and begin hauling the sail up, attaching each sail hook to the next mast hookup. Once the sail has reached the top, tie off the rope securely to the cleat at the bottom of the mast. Slide the sail hookups out so the sail is now fully extended. Hang on to this rope, as you will control the boom and your sailing direction by the wind with this rope. Consider adding a small removable rudder on the back to help with steering the boat where you want to go.