Sailor Lorenzo Acompañado II has published plans for a 20-foot Paraw. The Paraw is a traditional double outrigger sailing canoe in the Philippines.
Lorenzo has published some information, along with boatbuilding plans for a Paraw, on his website: https://samaloutrigger.wordpress.com/
The following text and pictures and video are shown on his website (and used here with his permission)…
(Click on the images to enlarge them a bit)
by Lorenzo Acompañado II
The aesthetic design varies with island location and cultural influences, but the bottom hull is basically composed of a carved out log. The hull sides can be stitched plank, weaved bamboo, or plywood (20th century). The seams are sealed with tree resin, tar, and lately… epoxy.
The crossbeams are fire-heated bamboo to conform to a desired shape, either in arch or “water spider legs” (elongated letter “M”). The flexibility can be tuned by adding a second beam on top with varied length depending on sea condition and boat loading. This feature can be seen more on sailing outriggers like the Vinta. These working sailboats put a lot of stress to crossbeams and is common to have three beams in such a small boat. On the other hand, the paddled and motorized outriggers have the simplest beam shape.
The bamboo amas are four inches diameter poles. The front end are capped with a wooden plug in a form of a wedge or cone. The lenth of amas are cut at no more than the boat’s length, but no shorter than three quarters of boat length. The exact location of the amas are also tuned. They are lashed a bit more forward for sailboats to avoid digging-in the bow during a run while a bit more aft for motorized bangka to compensate for the weight of motor.
It has no fixed rudder but rather steered by a paddle. With the introduction of small motors after World War II, tiny steel rudders were fitted and controlled by long tiller extension made of bamboo.
Be sure to check out his site, including the Paraw building plans.