Wednesday, April 13, 2011

Day 2 of the Haulout

The hardstand electrical supply jury-rig

The battle with the cutlass bearing and improvised tools...

An old zinc plate
Marquesa in her new home

Well, Dave hopes to get done in a couple weeks. We shall see...
Today I learned a bit about drive train components. The cutlass bearing is the bearing that holds the shaft after it exits the hull. It's a bronze tube with a very hard carbon/rubber-type interior that contacts the shaft. It is pressed into a bronze housing that bolts to the hull. Slots in the housing let seawater in to keep things cool. Everything is pretty big and strong and redundant. The 'bronze' is silicon bronze, which is made of copper and tin, plus 1-3% silicon and 1 % either iron, nickel, or manganese. You wouldn't think something made of copper and tin would be a lot stronger than stainless steel, but it is. Most fittings on boats are made of it. Even the rigging up top that looks like stainless is usually silicon bronze with a shiny chrome coating. Dave actually missed getting all his original stainless steel rigging hardware replaced by superior silicon bronze for free when Taenna did a recall (he heard about it 2 months after it ended). Another benefit of silicon bronze is that it's a natural dielectric - electric flow called electrolysis has a potential to eat up metals on boats if they are placed next to a dissimilar metal - a dielectric metal doesn't provide a pathway for this electrical flow. More on electrolysis later when I understand it better. It's a phenomenon that constantly comes up in conversations at the boatyard. I notice with interest that everything in the cutlass bearing housing is bronze except for the studs which hold it on. They are stainless steel because they screw in to a stainless steel plate inside the boat (cheaper than bronze for the manufacturer) and, more importantly, because stainless is more corrosion resistant than bronze. The housing is held on redundantly by double nuts - the outer nuts have holes drilled through them for cotter pins. The bearing is pressed into the housing and also held in place by set screws.
Dave normally replaces his cutlass bearing whenever he has the drive train apart - every few years. It gets a lot of wear, and isn't too expensive, so it just makes sense. At home, he has a press to take out the bearing. Here in Whangarei, we end up heating the housing with some MAPP gas, and alternate hacking at the bearing's plastic and sticking a socket into the housing and banging on it violently. In typical beginner's fashion am starting to have visions of an elaborate pressing contraption involving an overhanging concrete wall, some boards, and a bottle jack, when finally what's left of the thing reluctantly slides out. Improvisation is fun.
I wet sanded the cuprous-oxide antifouling paint with 60 grit and stressed out about whether I was actually removing the green algae layer or just making it disappear behind a thin layer of liquified red paint. I'd be very anal if this was my boat, so I really try to be up to what I take to be Dave's standards. Though the hull looked clean from a distance, there was a lot of algal growth and embedded little shells to be removed, especially at the waterline, the bottom 2', and the rudder.
I finished sanding the hull while Dave did a blur of other things, including weirdly jury-rigging one of the batteries to power the boat (which had to be removed to take apart the propeller shaft) using a cable and a couple sets of locking pliers. I try to stay away from that general area now. He also cleaned all the drive components, took the prop to be polished and balanced, took the cutlass bearing housing over to be sandblasted, took the propeller shaft to multiple shops to be inspected as it had some major wear, ordered a damper...

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