Lead Ballast Fairing

Anyone have any tips/ tricks or manuals on how to fair down this lead ballast?


  1. Freeze it.

  2. Sharpen a small wood plan using the “scary sharp” method (google will find it).

  3. Dip in mineral oil, plane with very light cuts. Keep it wet with oil as you proceed.

  4. Clean up thoroughly before eating or drinking.



Somehow, I inherited a “Lead Body File” from a brother-in-law who used to do automotive bodywork. The file, with very coarse diagonal teeth 7 per inch on one side and 9 per inch on the other, was used to rough-plane leaded bodywork where body panels would meet. (In the days before fiberglass, polyester resin, etc. all dents were filled with lead and then smoothed down prior to prime and paint). Thus the nickname … “Lead-Sleds” for the customized 1950 hotrods and custom cars.

I heard these files still are available from auto parts stores - the good ones, not the chain stores that only sell part. You might have to do a search of local bodyshops to see if any still use them. Most have moved away from lead and gone to glass and “Bondo”.

Once shaped to desired smoothness (remember, as you plane or file, the bulb gets lighter), -or - you can mix up some epoxy, thicken it with microballoons or microspheres, or even “baby talc” to thicken up the epoxy and apply to the lead. After cure, using coarse, then finer grades of sandpaper, sand it back to where all hollows are filled. You could also use “Bondo” paste, but be sure ti coat - the stuff does draw in moisture. Once sanded smooth, prime and paint.

For the sake of ecology - if you are concerned, I prefer to encapsulate the lead bulb in epoxy. As Earl notes, be sure to wash hands and wear a respirator when sanding.

Just another way to accomplish the same goal.

Breakwater, that’s a pretty nice looking lead bulb you have. Did you make it or was it a purchase? Nice blog layout too.


The file that Dick mentioned is called a 'Vixen" by virtue of one of the old time brand names.

Another method, if you have a drill press as follows; The bulb has some pins in the ends. Drill a hole in a wood block the same size as the pins, arrange the wood block such that the hole lies directly below the center line of the chuck. Chuck one end and lower the bulb so that the pin in the other end enters the wood block hole. Run the drill press VERY slowly. Use number 60 or 80 sandpaper to smooth the surface, change to 180 paper…Do wear a dust mask and clean up carefully after this procedure. You can get a near perfect casting with this method.
I expect that you could do this routine with a cordless drill and wood block. Run the drill slowly and carefully.

Thanks for the help/support everyone…

I ordered the ballast from Bantock. the lead is the one thing I can’t home-build (at least yet), and I didn’t mind paying for something of good quality.

They gave me two screws with a circular shaped nut on the end. What do you suppose those are for? I assume bolting an unbolting the ballast, but when I look at it now it seems like trying to put a square peg in a round hole. :zbeer:

You might be right that the screws could be used to attach the bulb to the fin. I remember reading something about a special screw in Bantock’s Bulb instructions. http://www.sailsetc.com/downloads/2006/TI_23_ballasts.pdf

Also Lester Gilbert talked somewhere on his great site about adjustable cant ballast. Might these screws be part of that? http://www.onemetre.net/Design/Bulbcant/BulbCant.htm

I might be totally wrong though…!! :slight_smile:

Well, Here’s the screws that I’m referring to:

Haven’t found a solution yet.
A canting bulb or a removable bulb would be awesome, particularly since the boat is a new-build, and I really can’t tell how it’s going to float until, it floats!

I have used the following method for a general estimate of location:

After you build, but before you cut your keel slot - float the boat in pond (or bathtub) and place keel inside boat lying flat against bottom. Place your lead bulb inside and on top of the keel and move it forward or aft, side-to-side until the hull sits on or close to it’s designed waterlines. This will pretty much give you a hint where it will be located. Depending on class and displacement, allow from 3/16 to 5/16 more depth after adding radio gear and deck/rig/sails.

These dimensions are rule of thumb and all depend on what you add to the hull that increases it’s weight. Keep weight toward the rear, because you have to remember that when sailing to windward and a gust hits, the bow will be depressed deeper into the water. I prefer a slight bow up with knuckle of bow just clearing the water when static and not sailing. Once the boat starts to move, the bow gets pressed down progressively deeper as wind increases. If you start out with the bow down, you just become a submarine that much faster. It gets you into the ballpark with out committing to a fixed keel location until you are sure.

Hi. Top bolt and ‘round nut’ from your picture is used to attach the fin to the hull (fin box). Drill a hole matching the ‘nut’ diameter through the fin near the top. Drill a second hole from the top of fin into the fin matching the bolt diameter. Insert the ‘round nut’ and check the bolt reaches it. Bottom stud, long hex nut, and ‘round nut’ from your picture is used to attach the bulb to the fin. Mount the ‘round nut’ in the bottom part of the fin as before. Drill the passage through the bulb and bottom of fin to take the stud. Mount stud into fin. Countersink the hole in the bottom of the bulb, and use the long hex nut to attach the bulb onto the stud protruding from the bottom of the fin… Good luck!

Thanks Lester

That’s Exactly it!
I asked Lorna Bantock in an email what they were, and Got a similar response.
Here’s here response verbatim to corroborate your story!

People who are familiar with our boats will know how those parts are used so we have no drawings as such. I’ll try to describe it. A hole is made across the fin 25 mm from the upper end to take the threaded round part of the INS-040 (larger). Drill down from the top of the fin to meet that hole with a drill large enough to allow the M4 bolt to slide through. Bond the threaded round part into the hole with epoxy resin so that the bolt can engage properly with the thread. This can then be used to attach the fin to the boat. For the other one - hole is made across the fin 25 mm from the lower end to take the threaded round part of the INS-030 (smaller). Drill up from the bottom of the fin to meet that hole with a drill large enough to allow the M3 studding to slide through. Bond the threaded round part into the hole with epoxy resin with the studding engaged properly with the thread. The length of studding that emerges from the bottom of the fin can then be used to attach the ballast to the boat.

The nice thing (well one of them) about the Bantock bulbs is that the brass rod lets you chuck the bulb in a drill or lathe and turn it while filing and sanding, keeping the bulb profile consistent.

With two people, I have turned one with a cordless drill on one end and the other end on a makeshift V block with one person running all that while the other used files and strips of emery cloth to smooth out most of it.

I also chucked one up in my small lathe, with a support block on the other end and performed that same smoothing process single handed.

Once you have it mostly smoothed you can trim the brass rod and hand file it to the pointed shape you like.


That is a great idea!

Barry, You win the fairing contest. Thats exactly what I’ll do. It seems like for consistency and simplicity’s sake that method will definetly give the best results for a nice-smooth ballast.


I did my bulb last year, and ended up with a good result. I put a sanding disk on my electric drill. Then I clamped the drill in my vice. Then turned on the dill and constantly rotated the lead against the sandpaper. I started with 60 grit and ended up with 220.

I weighed the fin and subtracted that from the max allowed. Then I worked the lead down to weight. I then took off another 30 grams to allow for coating the lead in epoxy and paint.

When I was reducing the lead, I took more off the top, near the slot than evenly all around. That made me feel that I was getting a lower CG.:slight_smile:

Worked well. Cost very little. (I don’t have a lathe). Wear a breathing mask, and sweep/vacuum up all the lead shavings.

Good luck