Plywoods

I’m building a planing boat by bolting two surboards onto the underside of a piece of marine plywood so that they form a catamaran.
The whole thing will be powered by an outboard motor of 5HP.
Will this start sliding slideways and doing uncontrollable stuff on me if I make turns at speed, or will I be fine?
What do you reckon I need to do to make this handle safely?

Keel would defeat the shallow thinking. No, you want a mid-
length dagger board you can pull up or have hinged so the
vessel can skim over shoals. Even a lee-board to one side
fixed to swing backwards; say, fixed to a spar laid side to side, and fixed by "U" bolts? Either way requires elimination
of the aft surfboard fins because they add drag. Better look
at raising your platform higher (Writer whould junk plywood
for all-bamboo grid), experiment with adhesives in extension footing before bolting, and keep a kayak paddle handy.

3 Responses

1. Matt M Says:
   February 23rd, 2010 at 10:32 pm

   I have a 19 foot catamaran outboard fitted with a 90 hp Yamaha. While it’s much larger in scale, I think your contraption should be OK if you think about these things.

   I have noticed that these power cats don’t allow their outboards to pivot to the side as much as monohulls. The Yamaha is only rigged to turn about 20 degrees in either direction. I assume that is because if you could whip it around to a 60 or 70 degree angle, it might power the opposite pontoon down into the water too much.

   I assume you are going to mount the motor in the center? I would hope so, otherwise you are going to go in circles. I also assume you are going to mount the gas engine in front, so you are not stern heavy. You may also have to think about where you are sitting.

   Good luck.
   References :

2. kavekarst Says:
   February 23rd, 2010 at 11:09 pm

   Keel would defeat the shallow thinking. No, you want a mid-
   length dagger board you can pull up or have hinged so the
   vessel can skim over shoals. Even a lee-board to one side
   fixed to swing backwards; say, fixed to a spar laid side to side, and fixed by "U" bolts? Either way requires elimination
   of the aft surfboard fins because they add drag. Better look
   at raising your platform higher (Writer whould junk plywood
   for all-bamboo grid), experiment with adhesives in extension footing before bolting, and keep a kayak paddle handy.
   References :

3. Franky Says:
   February 23rd, 2010 at 11:59 pm

   Klar solltest du eine Möglichkeit mit einbauen das Ding auch zu lenken. Wie sieht das denn sonst aus, ein im Kreis fahrender Doppelsurfboard-Katamaran.

   Gruß
   Franky
   References :

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