Bulb cast

With some equipment kindly donated by Scott Murphy we were able to cast our lead keel bulb yesterday afternoon.

The lead was purchased from a scrap metal supplier at $2/kg which is the cheapest we've ever come across, it was cheaper than the $3/kg we paid four years ago while building Shazza.
The bulb mould was made out of mortar cement, same as I've done for my previous two keel bulb pours.

Lead flashing used in housing gutters

 

Scotty lent us three gas burners and a metal box with an outlet at the bottom. This box has been used to make a 600kg bulb so I was never going to have any problems of not being able to do our pour in one hit. Scotty also supplied us with the 44 gallon "heat cover" drum. All in all it was a very effective system and took around 45min to melt all 100 odd kg of lead we put in the box.

 The 'box' with the lead being heated is nicely trapped under the drum which is there to help keep the heat in, there is a 'viewing lid' at the top of the drum to check on the melting progress in the box underneath. The pouring "tap" can be seen over the mould, point the tube down and out she comes once the tube is heated at about the corner.

The good, the bad, and the ugly.

The good thing is we got the bulb poured in one piece in one go.

The bad part was the mortar mould was still too 'green' and started steaming at about half pour. At this point the two mould halves separated and lead started escaping out the sides. Once the pour was started there was no stopping it safely so I had to just stand and watch. Then when the pour was just about done the steam build up caused a "Mt Vesuvius" kind of situation with the lead bubbling and spitting out of the top of the mould--very dangerous and thankfully I was standing back.  This left a lot of hollows at the top of the bulb and the top of the bulb was quite 'pitted'. There was also a lot of excess material around the edges where the mould had come apart and at the top where the volcano impression was happening.

The ugly bulb is happily in one big ugly lump that is easily fixed with a hand planer, a bit more of a lead pour to fix up the big holes in the top (did that today, it took about 10mins of heat to a kitchen pot and about 4kg of lead, the equivalent of about 1/2 or 3/4 litre of water).
I slapped on some epoxy bog today to start the fairing process which wont take that long or be very hard, it's still basically the right shape.

The bulb after its hand planer clean up and the top hollows filled with a second pour of lead.

 

 

I discovered when I poured my last bulb that any daggy bits of lead you want to get rid of is easiest and tidiest done with a good old hand planer, it doesn't create heat and make a mess like power tools can.

Slap on a pile of epoxy to fill the pitting and into my 'bake booth' for a quick epoxy cure of three to four hours rather than twenty four hours on the cooler days.

 

 

So all in all I'm pretty happy, the bulb is cast, it's one solid piece, and it's lighter than I was expecting to produce and that's ok too because I was probably going over-kill with the weight anyway.
I was planning on producing a 100kg bulb. We volume weighted the bulb plug twice to make sure it was the right size.
Well it came out at 87kg, I don't understand how but I will happily take it. The keel blade itself is 13kg so I will still have a total of 99kg under the hull which is just fine with me.

The heater for the 'bake booth' is just a household little heater. I get the temp up to a nice hot day (35deg C maybe by closing the area totally with the sheet) and leave it going for two to three hours then turn it off and leave it alone for another few hours or till the next day if I don't feel like playing anymore like today.

 

Next job will be to put keel and bulb together in position in the boat. I am not looking forward to that as I will have to figure out how to get the sucker under the boat without breaking my back. Then we get sails and rope and we're sailing but not racing as yet until we can afford an engine and all the safety equipment required by the rules and common sense.