The F36 plans call for a traditional inboard diesel engine and propeller shaft thru the bottom of the boat. We can’t do a sail drive because we want the boat to be able to sit on its hulls in zero water, as in the extreme tides of Baja or England. So… Here we go “off plan”, switching to an outboard engine on a swing-up mount on the back of the starboard beam. I’ve been thinking up an approach that is both temporary and long term; if we don’t like the outboard the entire mount can be easily removed with only 1lb of hinges left behind and the trampoline put back in the engine’s place. Or when a cost-effective electric pod drive solution becomes available we can switch over. Or if an inboard diesel is really the answer, that can be retrofitted at any future time.
The measurements for a Yamaha 25 long shaft were found online and we made a faux motor of Luan door skins to practice with placement. The net lashings tube almost looks like a motor mount hinge, but it’s not parallel to the waterline and it wasn’t built to the shear forces and weight of the motor. So we need to work around that feature, and not cut it off the boat. The rudder gudgeons seem like a good model for the motor mount hinges and we have some spare G10 tube and a 16″ piece of 1/2″ stainless steel rod that will make a nice hinge pin with the right bushings in place. First up is fabricating the hinges.
The funny shapes of the two pieces are what fit over the net lashing tubes on the beam. The other three will run on the top tab of the motor mount (yellow board is a stand in to see how this is going to work). I’m thinking the motor should be mounted as close to the hull as possible, as the hull shape curves away considerably down by the waterline. The weight should be tucked in close there, and things like the freezer and galley on the port side should counter balance this engine placement.
We’ll pick this project back up next week once the bushings are in hand so we can align all the hinges and permanently affix the two big ones to the beam (instead of that blue tape :)
Thinking we’ll want to wrap them at least 18″ around the beam in both directions with heavy weight uni-directional cloth.
PS – the mounting box will be made to push up against the big diagonal brace under the beam, so the motor forces are spread out on a couple of surfaces, not just the hinge pin.