No ex­pe­ri­ence fix­ing up a sail­boat? No prob­lem

Popular Mechanics (South Africa) - - Contents - BY IAN MC­NANIE PHO­TO­GRAPHS BY JUSTIN KAN EPS

I’D NEVER SAILED BE­FORE. This wasn’t a prob­lem, how­ever, be­cause we were not sail­ing. We were hob­bling. My new boat, bought for R58 000 from a man who told us only after we’d paid that we had two days to move the boat be­fore he was kicked out of his slip, put­tered out of the Alameda Chan­nel and into San Francisco Bay. A 1974 Tar­tan 34C, No Bub­bles ful­filled the prom­ise of its name. At full throt­tle, the 10,4 kw out­board mo­tor I’d lashed to the tran­som moved us wake­lessly to­ward the Oys­ter Point Ma­rina, 16 km across the bay. It would take six hours to get there.

When I bought No Bub­bles, I knew it needed work. The pre­vi­ous owner had taken the en­gine out to do re­pairs and left it in a dock cart for months, where it rusted into obliv­ion. And that was a prob­lem I could ac­tu­ally see. But I wasn’t de­terred. I work as an in­tern with for­mer Mythbuster Jamie Hyne­man, who of­fered un­lim­ited tools and ad­vice. His shop has ev­ery­thing you need to build any­thing, and he spent years sail­ing a dive boat in the Caribbean. I also work at a ro­bot­ics com­pany. Be­tween the two, I knew I could han­dle the project – es­pe­cially since I’d de­cided to com­pletely re­place the shot mo­tor with an elec­tric one. Here’s how I did it.

Propul­sion At my elec­tron­ics job, we

were work­ing with brush­less 30 kw, scaled-up per­ma­nent mag­net drone mo­tors which are much smaller and more pow­er­ful than sim­i­larly sized in­duc­tion mo­tors. The mo­tors are de­signed for DIY projects like air­planes and cars, and after writ­ing cus­tom firmware for one and trou­bleshoot­ing the pow­er­train, I de­cided to order a 27 kv ver­sion for my sail­boat. “KV” is a con­stant that ap­prox­i­mates the rpm the mo­tor will spin per volt ap­plied to it. If I mul­ti­ply kv (rpm/ V) by my tar­get volt­age (80 V), I can pre­dict that, un­loaded, the mo­tor will spin at about 2 160 r/min. Loaded, this puts it in a sim­i­lar range to the boat’s orig­i­nal Atomic 4 en­gine. To con­trol it, I added a 500 A elec­tronic speed con­troller (ESC) from Alien Power Sys­tem hooked up to an RC trans­mit­ter.

One ben­e­fit pre­sented it­self be­fore I even hit the wa­ter: The Tar­tan was de­signed with the mo­tor right in the mid­dle of the cabin. It takes up a lot of room. To walk through, you have to squeeze around the en­gine cover. But with the new tiny mo­tor, which is only 15 cen­time­tres in di­am­e­ter and eight cen­time­tres thick, I could re­place the en­gine cover with a small step and re­gain all of that floor space.

Prop Shaft Jamie helped me at­tach

the mo­tor to the prop shaft. We fig­ured it would prob­a­bly have enough torque to start mov­ing the prop, so I made it di­rect drive for now, with no gear re­duc­tion. But if the bilge filled up and the bilge pump failed, that would leave the mo­tor sub­merged The salt wa­ter would de­stroy the bear­ings in­stantly To avoid that, I built a small plex­i­glass box around the mo­tor to keep the wa­ter out.

Power The mo­tor runs on six

12 V 66 Ah deep-cy­cle bat­ter­ies in se­ries. On a calm day, it draws about 30 A at about three knots. To make the boat go faster, I’ll even­tu­ally need to change the prop, up the volt­age, and get a new ESC that can han­dle it.

I also found eigh­teen so­lar pan­els on Craigslist for only R2 per watt. Jamie and I welded an alu­minium frame in an arch above the com­pan­ion­way, where we mounted five of the pan­els – power sup­ply and an awe­some rain shield. Dur­ing peak sun, the pan­els can pro­vide 375 watts. That’s fine for charg­ing my house pack, which runs the ba­sic elec­tri­cal com­po­nents of the boat, but the mo­tor bat­ter­ies still need to con­nect to shore power. Even­tu­ally I’ll cover the boat in the re­main­ing pan­els and add a 3 500 W Har­bor Freight inverter gen­er­a­tor. That should pro­vide enough power to run the boat most of the time.

Chain­plate Knees Chain­plates are metal

sup­ports that poke through the deck for the rig­ging wires to clip to. They’re bolted to pieces of wood at­tached to the hull. The com­part­ment sur­round­ing the star­board knee was com­pletely filled with wa­ter. Once I cut out the fiber­glass around it, the ply­wood was so rot­ted I could scoop it out with my hands. I cut a new piece of wood, and Jamie gave me some fiber­glass, epoxy, and filler to seal it back in. My big­gest mis­take was for­get­ting gloves. Get­ting the bits of epoxy out of my arm hair after­ward might have been the hard­est part of get­ting No Bub­bles back on the wa­ter.

A metal ter­mi­nal block con­nects the elec­tronic speed con­troller to the mo­tor phases.

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