Floorboards are an ideal addition to an aluminum boat. They will provide a buffer from the pumping action of the boat's bottom against the water for your feet and gear. The false bottom will also allow water to drain into the channels in the true bottom and run aft to the drain, thereby keeping your feet and gear drier. It can also keep your feet warmer when boating in cold water by keeping your feet separated from the cold metal of the hull. With woodworking skills, you can make sturdy floors that are custom fit to your boat and your needs.
Measure the length of each compartment to be lined along the fore-aft axis. Measure on the forward compartment from the front of the bench seat to the point where the bottom begins its rise to the bow. Cut the boards for the front section to the length you actually measured. The boards for the compartments that are captive between the bench seats must be cut down 1 inch to allow for easy installation and removal. Lay out your cuts to minimize waste and cut all the floorboards for each compartment's set.
Place the loose floorboards into their respective positions on top of the aluminum ribs running across the bottom. Center the boards between the boat sides. Lay the outermost boards down on top of and parallel to the others and scribe them to fit any curvature there may be in the boats sides. Cut these lines with a Skilsaw (or jigsaw) to create your custom-fit edges to your floorboard sections. Lay out and dry-fit all the pieces to ensure you like the fit. Hold a 1/4-inch space between each plank to allow water to drain through and not collect on the floorboards. Lay your boards out "pretty side" up.
Mark each board with a matchmark in pencil so you can reproduce your arrangement. Mark the locations of the athwart ship ribs where they cross the floorboards. Avoid the rib intersections when placing your lateral supports. Cut at least three lateral support pieces for each section reaching to each outboard edge of the longitudinal boards. Place one ahead of the front rib, one in the middle and one aft of the after rib in each section. Sections with more than three ribs will require one between each rib.
Glue the lateral boards and lay them down on a flat work surface. Place the longitudinals on top and make sure they are square and not racked. Once everything is positioned, screw through each floorboard into the lateral support below. Allow the screws to pull into the surface a bit and countersink themselves to eliminate a snag or tripping point. Allow 24 hours for the glue to dry before using or stressing the floorboard sections.
Dry the sections well in the sun or in a climate-controlled compartment. Once fairly dry, you can prime with a stain-killing primer. Killz works well for this. Paint the whole section including bottom sides and between the floorboards. Snip a small corner off on each section as a finger hole to help with removal and paint that raw edge as well. The last coat may be "sanded," which means you lay down a heavy coat of paint and dust it with sand while it is still wet. This will provide good traction in wet conditions.
- Pick a board length that will make multiple cuts with as little waste as possible. Each plank in the bottom must be a solid, uninterrupted board with no joints in order for it to have any strength. Strategic layout of your cuts can reduce the 30 percent waste factor, but it is a good rule of thumb so you don't run short on material.