Making Spline Weights
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By Steven David Roberts - Marshfield, Massachusetts - USA

One of a Yacht Designers most prized tools is his Spline Weights (also known as "Ducks" or "Whales"). These are used to hold the drafting spline in place as it forms one of the many curves necessary to draw the lines of a shapely boat. Spline Weights can also be used when lofting the plans full-sized onto the floor of your shop. The cost of a Spline Weight is in the vicinity of $30. This may not seem to outrageous until one considers that you will typically need between 15 and 20 Spline Weights to design a boat by hand. This brings the cost to as much as $600. The steps that follow describe a cost-effective method for making your own Spline Weights. If scrap lead can be found, the cost can be as little as a couple of dollars per weight. While these are not fancy, they get the job done as well any other Spline Weight.

The steps that follow describe a cost-effective method for making your own Spline Weights.

(click images to enlarge)

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Before getting started, it is extremely important to understand the risks of heating lead. Here are a couple of things to know, but further education is strongly recommended before considering this method:

  • 1) Lead vapors are extremely toxic and should never be inhaled under any circumstances. Take the necessary precautions.
  • 2) Liquefied lead and moisture of any kind do not mix (even the slightest bit of water) and will "erupt" and splatter everywhere. Be sure that your molds are free of any moisture.

MAKE A TEMPLATE

The pattern for this method is based on the measurements taken from an article in the July/August 1994 issue of WoodenBoat Magazine. From the pattern measurements make a template out of paper or Mylar.

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Make a template out of paper or Mylar.

MAKE A MOLD

The mold is made out of a 2x4 and two 1x4's, all about 3 feet in length. This is sufficient for making 4 weights at a time (a good sized batch for the amateur). The pattern is cut into the 2x4 by tracing the template (4 times) along one side of the 2x4, so that the open edge of the template falls along what will be the top edge of the 2x4 mold. These are then cut out.

The mold is made out of a 2x4 and two 1x4's, all about 3 feet in length.

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The 1x4's are then secured on both sides of the 2x4 with wood screws to complete the mold. These will need to be as tight to the 2x4 as possible to eliminate any gaps.

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I didn't have 3' long sections of 1x4 so had to improvise, but the result is the same.

SETTING UP

Because of the serious dangers associated with working with lead, it is recommended to work outside. The mold must be secure from movement. A WorkMate workbench works well. Melting the lead in a large can over a camp stove is a sufficient method. Work gloves, pants, long-sleeved shirt, safety goggles and a properly rated gas mask are a must. A long pair of grilling tongs works well for handling the can of melted lead.

Melting the lead in a large can over a camp stove is a sufficient method.

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MELTING/POURING LEAD

Only melt enough lead for one Spline Weight at a time. The weights will be about 5 lbs a piece. Since you'll always get residual lead sticking to the inside of the can, melt about 6 lbs at a time to be sure that you have enough. It takes a bit for the lead to start to melt, but once it does the rest will melt quickly.

As previously mentioned, be sure that the molds are free of moisture before pouring the lead. Also, be sure that everything is ready to go before taking the lead off of the stove. The pouring process needs to happen quickly since the lead hardens rapidly. Pour the lead into one of the molds as quickly as possible without splashing. Since the lead will shrink a little, pour as much lead as possible into the mold. If anything, pour it slightly above the top of the mold... the lead will actually be higher in the middle than it is along the edges (this will need to be filed down, later). Continue this process until all four molds have been filled.

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As previously mentioned, be sure that the molds are free of moisture before pouring the lead.

After the lead in the mold has cooled, take the mold apart by removing the 1x4's. Turn the mold upside-down and strike the bottom with a rubber mallet to free the weights. You'll notice that the inner portions of the molds are burnt... this is normal but I wouldn’t recommend using a given mold more than 4 times. Put the mold back together and start the process, again.

You'll notice that the inner portions of the molds are burnt... this is normal but I wouldn’t recommend using a given mold more than 4 times.

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Repeat until you have the number of weights you require.

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Repeat until you have the number of weights you require.

FINISHING

When all the weights have been molded, they need to be smoothed down with a file or rasp. Even out the bottoms and round over the edges. You can spend a lot of time smoothing down the weights, but it won’t make them any more effective. In fact, a rougher surface is easier to handle when drawing.

You can spend a lot of time smoothing down the weights, but it won’t make them any more effective. In fact, a rougher surface is easier to handle when drawing.

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The next step is to paint them. This is necessary to prevent getting lead on your drawings. You can get as creative as you want, but 3 coats of black Rustoleum spray paint is a safe choice.

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The next step is to paint them. This is necessary to prevent getting lead on your drawings.

To protect your drawings, cut and stick felt material to the bottom of each weight (you can purchase sheets of black felt with an adhesive side, that work well).

ADDING THE HOOK

Finally, the hook must be added. I made mine from 1/16" thick copper rod I found at craft store. However, after using mine for a couple of years, I might consider trying 1/8”. The length of these will depend on your need and how deep of a hole you drill to set them in. NOTE: Lead is a pain in the neck to drill. Have a few bits available to get the job done. Drill one hole in each weight centered horizontally at its fatter end and about an inch high. Set the rods in the holes with glue or epoxy. After the glue has dried bend the rods to shape and cut to the appropriate size

NOTE: Lead is a pain in the neck to drill. Have a few bits available to get the job done. Drill one hole in each weight centered horizontally at its fatter end and about an inch high.

 
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Finally, the hook must be added. I made mine from 1/16" thick copper rod I found at craft store. However, after using mine for a couple of years, I might consider trying 1/8”.

Steven David Roberts
http://www.get-outside.com/

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