Sunday, May 16, 2010
Check another duanting task off the list.
I was dreading casting the ballast keel. It wasn't that bad. I set up the turkey fryer (we bought it from Northern Tools, or Harbor Freight, I can't remember which) and the stew pot that comes with it. It melted 120 lbs. of lead in about 30 minutes. It was important to me to be able to melt and pour the whole shebang in one shot.
Use the proper filter for your respirator, and wear long pants and boots.
This casting is about the upper limit for what I would pour myself. Anything bigger would have been worth the expense to sub out.
The process was pretty straight-forward: build the form (I allowed a bit of extra height so that I can cut off the "slag" that forms on the top of the pour), gather your safety equipment (including a fire extinguisher) fire up the cooker, and babysit the fire. When the whole deal is melted, scoop out as much of the junk that floats to the surface as you can, and have a buddy help you dump it in the form. I did not cover the plywood sides of the form with anything. They smoldered and got pretty charred, but I didn't think that they would go up. I hung out near the fresh pour until it stopped smoking (just to be sure that the form did not ignite) and that was that.
After about a half hour, the temp had dropped to around 170 degrees (as measured by our IR pyrometer), so I moved the form inside and stripped the sides. I was amazed at how quickly the casting cooled.
The plan is to fit, fair, and bore the casting while the boat is inverted, and attach it when she is righted.
Body work and prep continues on the topsides and bottom.
Next posting will be pretty math-intensive. Be warned.