Monday, October 12, 2009

Bring on the heavies

So this week and weekend I did some gross tuning on the keel bulb.

I started out by drilling the holes for the cross bolts. I first drilled the recess for the bolt head using a 7/8" standard spade bit. Slow and steady is the name of the game when drilling lead. I know that other builders used loads of cutting oil, but I opted for water as I wanted to avoid extensive cleaning before trying to apply fairing filler. I also set the clutch on the drill to about half to avoid shearing off a drill bit. This worked great. After the countersink was done, I drilled a 7/32" pilot hole through the first bulb half. I then pulled out a 12" long 5/16" diameter brad point bit. With the drill on the low setting, small "bites" into the lead worked awesome. Pulling the bit out to clear it after 50 or so revolutions seemed to be the key. Once I made it through the first half, I laid the bulb over the keel foil to drill that hole, and then laid both on the second bulb half and drilled through. Finally, I drilled the counter sink on the other side.

If I had to do it again, I would have bought a long bit to drill a 1/4" pilot hole all the way through. With a 5/16" hole on the second half, it was difficult to drill the counter sink without the bit wobbling and I had to lug the 80-lb bulb half to my office to use the drill press. Incidentally, I tried a 1" Forstner bit on the second set of countersinks, and when using low RPM, it worked a treat.

OK, so the bolts are drilled and I am good to go, right? But, it turned out that the cast bulb halves contracted quite a bit as they cooled in the mold. This left the a 1/2" - 5/8" gap between the halves when I put then together. A preliminary weighing told me than I was also about 10 lbs below max weight. So I came up with a decent solution to fill the gap and add as much weight as possible. I started by folding a piece of aluminum foil into ~1" strips (probably 8-10 layers thick) and layed the Al strips onto the tacky side of regular old duct tape. I then used my homemade foil tape to create a dam to seal up the gap so that I could do a second lead pour.

My scheme worked great and the duct tape only melted a little. Best of all: no leaks! The second pour probably added about 8 lbs to the bulb weight and I am darn close to max class weight (185lbs for the bulb and keel strut).

I now have a coat of fairing filler on the bulb and fairing continues on the rudder, but it is quite close.

Stay tuned!

Monday, October 5, 2009

Melt With You

This weekend I had a go on the rudder and keel bulb.

On saturday I planed the shape of rudder from the laminated blank I made many moons ago. The keel was good practice. :) An electric planer is great when used with care. As with the keel I traced the profile on the ends of the blank and used the planer to "step" down the blank until I hit the line of the profile. I then planed those steps down until I had the foil nearly smooth. From there, I used the planer to cut a nice channel to recieve the carbon fiber lay up of stiffness. I saturated the carbon, layed it in the channel, and then smeared Microlight filled over the whole foil. Sanding to come...

I also poured the keel bulb yesterday. I have to note that Kevin and his wife gave Traci and I the best (my opinion!) wedding gift: an aluminum pot, an iron skillet, a ladel, and a bottle of champagne---all lovingly lead-tainted (maybe not the champagne). I must say, it was the only wedding gift which required hand-washing after opening.

I used Kevin's excellent blog post as a guide. The unseasonably cool weather this weekend (50-55F) and the wind made the job tough and Traci wanted NO part of the Great Lead Melting. Can’t blame her. :) So I was working solo. I think the temp and the wind made the lead slow to melt, so ultimately I ended up placing Kevin's aluminum pot directly over the turkey fryer burner, rather than on top of the iron skillet as he did. This worked fine, but by the time I was done the bottom of the aluminum pot had deformed slightly to match the grates on the burner. Careful if your pot is thin walled!

The pour on the first half was only OK. I don’t think I had enough lead in the pot when I started pouring, so layers started solidifying before I got the next layer poured. I have a couple of layers of lead that don’t seem well adhered so I think I will wrap the bulb with a layer of glass tape to keep everything together. It will also be bolted crosswise to the strut, so I am not all that concerned about the integrity of the bulb.

The second half went much better. I consistently kept more lead in the pot which meant much less time to melt additional pieces and therefore less time between ladlefuls of molten sweetness.

Interestingly (but not surprisingly) the second half, which I poured in a much shorter period of time, contracted significantly when it cooled. It ended up being a ¼” lower than the top of the mold and 6lbs. lighter than the other half (80 lbs.). I think I will get the halves bolted together and then try to seal the gap with heat-resistant mica tape and fill the gap with a small scale pour. Should get me up to weight, I think.

Thursday, October 1, 2009

One more bit of carbon

Light = fast, right? Definitely my favorite piece of hardware on the boat!

Traci and I had an awesome honeymoon in Barbados following an incredible wedding.

Now it's time to get the Boatworks cranking again!