Adventures in the Shipyard 2010 – New Stern Bearing
Our month in the shipyard is finally over and we are back at our slip with the David B looking beautiful. Over the month of February we got a lot accomplished. I spent most of the month working on sanding, filling, painting and oiling. We had amazing weather for painting and I took advantage of every rain-free pacific northwest day. While I was busy running the sander, Jeffrey had a full to-do list. His first project was to send out the propeller to have it re-shaped. It’s always been too big for the boat and Jeffrey has been worried that the propeller bogs down the engine too much, so off it went to the Prop Shop in Seattle.
After the propeller was removed, Jeffrey began inspecting the new high-tech stern bearing we had replaced two years ago. He noticed that it had moved in the housing and we then proceeded to remove the bearing to see what was going on. It had been chewed up a lot and after discussion with the shipyard, who had installed the bearing we decided that we would go back the old style of a Babbitt bearing that had worked for the previous 78-years. Since it turned out that machine shop which made the new bearing had gone out of business three weeks before we hauled the boat out, we poured our own new Babbitt bearing and then took it to a machine shop for finishing.
The picture above is the set-up we used for pouring Babbitt into the housing for the stern bearing. Once the metal was melted Jeffrey poured in the molten Babbitt in between the bronze housing and the pipe sticking out of the housing.
Below is a picture of Jeffrey holding some material called bear s#!t. This stuff was packed around the places where the molten Babbitt might leak out.
Here’s some real bear poo to compare.
Once the metal had melted it was time to pour. Watch the video below to see Jeffrey pour hot molten Babbitt into the stern bearing housing.
Once we finished the pour Jeffrey removed the mandrel and we then took the bearing to a Grant’s machine shop in Seattle to finish up the inside of the bearing.
We arrived at Grant’s shop at 4:00 in the afternoon to set up the lathe to machine the bearing to the right size. It was a long evening of taking measurements and making jigs. Grant needed to first make the bearing housing concentric, then he was going to need to make the cutter bar which would be attached to his lathe. The bar with the cutter ran through the inside of the housing and it spun rapidly as it was attached to the lathe. The housing itself would be secured to car that slowly moved back and forth while spinning cutter trimmed thousandths of an inch of metal off the inside bearing per pass. After each pass Jeffrey and Grant would measure exactly how much metal was removed.
In the photo above you can see the cuter Grant set up to trim the outside of the bearing housing to make it concentric.
Above shows the housing once it had been centered.
The bearing housing was placed and secured on the lathe.
Here’s a picture of the cutter that was used for removing excess Babbitt from the stern bearing. Between passes Jeffrey and Grant measured how much material was being taken off. They continued to make passes until the inside of the bearing reached the right size.
In the video above you watch the cutter making a pass through the inside of the housing. It was an amazing process to watch. We worked on the bearing until 2:00 am. At midnight I took a nap so that I could drive a tired Jeffrey and our new bearing back to Bellingham. We got home at 4:00am and the next day we took the bearing down to the boat to be fit. Not only did it look great, but it went back on to the boat just right.
This was only one of the projects we did this year in the shipyard. Besides the bearing project, Jeffrey also worked on the rudder post by pouring a modern-day tallow in to the rudder post box and he installed a new oil filtration system in the bilge. Now that the boat’s back in the water we are schedule for an engine alignment and valve cleaning, along with more painting and more varnishing.
For more pictures of pouring the Babbitt bearing and other work we did on the David B this year in the shipyard, visit us on Facebook and become a Fan of the David B.