Tuesday, March 11, 2014

Plugging Away!

I am plugging away on "TIME MACHINE",,, the keel plug that is. As is the case with many of the parts on this build, and to prevent slowing things down, or just overthinking it, sometimes, you need to just roll up your sleeves and dive right in. We will get started on building an aerodynamic, 165 pound, torpedo shaped chunk of lead, but first we have to make a fake male plug in order to build a concrete female mold, to pour the lead male bulb,,,, I agree,,, a lot of steps.

 I lofted my bulb parts on paper per the plans, I then glued the paper cutouts to 2" building foam, and cut them out on my bandsaw (you could also cut them with a sheetrock hand saw). I had pre-drilled a 1/2" hole, to thread them onto a hardwood dowel, spray adhering each layer together as I went.
 I planed/faired all of this to my control marks, to achieve my final bulb shape. I started my first cote using bondo (an automotive body filler), but decided to change to 20 minute sheetrock mud, as it is easier to apply and sand.
 When I was happy with my fairing job, I painted the bulb with some leftover paint to seal the sheetrock mud. I then coated the plug with wax, and then neatly wrapped the entire plug with (1) layer of saran wrap, waxing the outside of the saran wrap also.
 I mixed and poured the concrete into my pre-built box, then pushed the bulb in place, holding it in position against its buoyancy (about 1/2 its profile) using a couple of wood scraps and screws. I let this dry overnight, leaving the keel bulb in place I added my next box directly over the lower frame. (I had used tongue and groove siding scraps, so it was easy to lock the two frames together).
 I added a couple of plumbing pipes to create pour/vent holes for the lead (pic above).
 The finished mold.
I was pleasantly surprised with a very fair mold. I plan to let this cure for a couple of weeks, before pouring the 165 pounds of lead. I am hoping that by allowing the moisture to evaporate from the concrete, that I will be able to get multiple pours out of the same mold?, although I am not 100% sure if it will, but it would be nice to help out another boat builder, by sharing the mold.

Note: I got all my lead , by going to a few tire shops, when I told the owners what I was trying to do, they were enthusiastic to help out. It is also a great way to recycle those old tire weights.


  1. Hi Mark, I have a couple of questions..
    What mixture did you use for the concrete? Cement + Building sand? Did you add any reinforcement (wire maybe?)
    How do you plan to melt and pour your lead - any furnace plans?

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    1. Hi Will,
      1- I used (3) pre-mixed 60 lb. bags (Quikcrete) of concrete from Home Depot.
      2- I was going to add wire, but don't think it would help with cracking due to heat, or if the metal would cause a problem by convecting heat? (this is going to be a science experiment for sure).3- I am going to melt the lead on my propane powered turkey fryer, using a cast iron pot, and ladle it in continually in one pour.

      PS: I was glad to hear that you, the puppy and boat were in good shape after the mishap.

  3. Haha, Thanks Mark. Puppy won't be in the shed for a while, no longer thinks of the i550 as 'safe' :) Very interested to see how you go as it's not long before I have to pour mine and I'd like to make the mould as re-usable as possible.