Contenu
Most PVC pipe catamaran builders use large diameter 10- and 12-inch pipes for their custom craft. While larger diameter tubes are prohibitively costly for many hobbyists, smaller diameter thin-gauge drainpipes in geometric bundles can provide enough flotation and strength to enable the construction of large watercraft. Their symmetry and uniqueness alone attract a lot of attention on the water and off, which, besides the sport, is sufficient reason for the true innovator to give it a try.
Design Strategy
The major advantage of many smaller pipes is that in the event of rupture or breakage of one sealed pipe, the remainder retain their integrity. Four-inch PVC drainpipe has an inner diameter of 4 inches. These can be joined using 3-1/2-inch diameter Schedule 40 pipe as interior couplings and almost any length catamaran pontoon can be constructed. A 15-foot section would have a submerged flotation of 75 pounds. If half-submerged, each 15-foot section would bear a useful payload of about 38 pounds. In groups of nine tubes on each side, the overall useful net flotation would be more than 600 lbs., enough for the entire construction and two adventurers. Total flotation is over 1,200 lbs. The pontoons are 15-feet long. They are smoothly bent at the 13-foot point, which provides a graceful bow curve and a smooth entry of the pontoon to oncoming water. The 4-foot by 8-foot deck is constructed of ½-inch thick pressure-treated plywood in a slotted 2-inch-by-4-inch pressure-treated wood stud frame.
Materials
You will need 27 4-inch diameter PVC 10-foot long drainpipe sections, 18 end caps, one 10-foot length of Schedule 40 4-inch diameter pipe, and 18 3-1/2-inch diameter Schedule 40 end caps to seal the rear openings. Three 8-foot 2-inch-by-6-inch pressure-treated wood studs and a 4-foot-by-8-foot sheet of pressure-treated plywood comprise the lumber. Use nylon strapping in four spots to hold each pontoon together as well as to the deck assembly.
Fabrication
Cut eight tubes into 5-foot long sections. Bend the 10-foot sections at the front by slightly heating with a heat gun over about 1 foot and bending the short ends up at about a 20-degree angle. Cement the 6-inch sections at the 3-inch point into the long ends of the bent tubes. Then cement the straight 5-foot sections onto the 3-inch stubs. Keep the joints straight to set. Cement the 4-inch caps on the front and the 3-1/2 inch caps inside the rear of the tubes. Bundle the nine tubes with straps on each side in rows as follows, from the top: one, two, three, two, and one that totals nine tubes each side. The top tubes will be further back. Assemble the top wood deck frame and cut two sets of rounds on the lower 3 inches of the 2-by-6 studs to retain the floats. Affix the floats to the deck with straps and adjust their positions carefully.
Variations
Try a larger deck, or turn the deck in either direction to change the catamaran’s shape. Power can be sail or small outboard.
