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The finishing of a centre board
The Finishing of a Centreboard
Page 1 of 12
The finishing of a centre board
By: Ton Jaspers (W5011)

Since half the cost of a centre board is in the finishing, it pays to do the finishing yourself. Others may argue the entire
board can be made by a good DIY person. I shall try that next time. This time I started with a professionally glued and
milled board.

This text describes step by step how to finish a centre board. There are many ways of accomplishing this task depending on
sailing needs and size of your wallet. For example my previous board was finished with two component boat paint simply
because I had that available from doing a hull paint job.

This time I wanted to do a job with clear epoxy because it looks much better, especially since I decided on a beautiful
Ibachi / Cedar, planked board. This type of board is much stronger and stiffer than a plywood board because all wood
fibres are in the same direction. The down side is the planks are glued together and the glued area is very small compared
to plywood. This means the planks could break apart more easy than layers of plywood would. I decided, following good
advice from fellow Wayfarers, to add a layer of glass fibre to strengthen the bond between the planks. As a side effect the
board gets stiffer yet.
Requirements
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A planked Ibachi / Cedar centreboard, professionally glued and machine milled to Wayfarer specifications. The board
comes a little smaller (in all directions) than the official drawing to allow addition of glass fibre and epoxy.
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150 grams per square meter, woven glass fibre, which is much stronger than flaked cloth. Woven fibre has fibres
running across the planks to strengthen the bond between the planks and along the planks to give more stiffness.
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Clear Epoxy, The beautiful wood stays in sight and due to its properties (thick like syrup and settles within half an
hour) it is easier to use than polyester, especially by amateur users.
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Since I usually sail in shallow water and running aground is no exception, a protective strip shall be added.

Aqua dynamics dictate a board should not have a razor sharp trailing edge, The trailing edge should be flat, but only a
fraction of a millimetre. This can not be done in wood; the edge would be too fragile. The trailing edge has to be kept
blunt, often up to two or three millimetres. However, glass fibre and epoxy allows us to create a razor sharp trailing edge.
When finished one or two rubs with sand paper will give the minimal flattening required for minimal resistance in the
water. The board manufacturer has accommodated for this and made the trailing edge a couple of millimetres short
compared to the official drawing (measurements are still within class specifications). The wood ends in a flat trailing edge
of about 3 mm thickness. With epoxy and glass fibre we can add an extra few millimetres and create a razor sharp edge
within the limits of the official drawing and class rules.

Tip protection can be made of brass, copper or stainless steel, the latter being the hardest to work with. Since I could lay
my hands on piece of stainless steel 316 easy, I choose to use that material and not continue my search for brass. Stainless
steel can be worked like brass, it only takes more time.
Measurements
Before finishing the board the pivot hole for the centre board bolt needs to be measured and drilled. Also I wanted to add a
stopper block before finishing with epoxy to avoid cutting holes through the protective epoxy layers. A stopper block limits
the maximum centre board angle to 83 degrees as required by the class rules.
Maximum depth
First the pivot hole for the centreboard bolt was measured according to the instructions by Kjell Gjære (W4878)
(see:
http://www.wayfarer.dk/teknik/senkekjol%20-%20placering%20bolt.htm
).
Following his advice ensures the board will be at the maximum allowed depth.
Maximum angle
A little help line drawn with a pencil on the centreboard (later removed) showed the keel line at the maximum allowed
angle of 83 degrees. As soon as the pivot hole was drilled the board was into the boat. With the help line lined up with the
keel I made a stencil on a piece of cardboard that fitted exactly the top of my centreboard case. On this stencil I drew the
contours of the horn of the centreboard. Back home the stencil allowed me to cut away a small part of the centreboard horn
so it follows exactly the contours of the top of the centreboard case. Then I shaped a piece of hardwood to the contours of
the centreboard (see photos). This stopper block was temporary fitted with a screw. After this job I put the centreboard in
the boat again and re-measured all dimensions. The maximum depth and maximum angle allowed were spot on!
The Finishing of a Centreboard
Page 2 of 12
Tip protection
As stated above, I wanted to add stainless steel tip protection. The photos 1 and 3 show the 11 x 5 mm, half round, rod I
used. The shape fitted the existing curvature exactly! The first job was bending it into shape. This can not be done during a
later stage. Once the mounting holes are drilled it will be impossible to bend it evenly. The steel will bend where it is
weakest, over a drill hole.

Photo 1 shows the bending setup I used. Luckily I had a piece of round wood that matched the tip curve on the centreboard
drawing exactly. Others may have to use an iron pipe or some other round material. Important is to use material with a
diameter that results in a curve that matches the official drawing. The photo also shows that the legs are too long. It is
impossible to bend accurately with one of the legs being only 30 mm long. Once the bend fits the drawing / centreboard
exactly, the legs are cut to length and the screw holes are drilled. Finally the drill holes are treated with a 90 degrees drill to
receive the countersunk screws and no screws stick out of the finished centreboard.

Next the cut-out in the centreboard is made. Dont try to fit the steel to an existing cut-out; it is far easier to do it the other
way around, fit the wood cut-out to the bend steel. The cut-out was made with a fine file and a lot of patience. Bear in mind
it is easy to remove material, adding material is much harder. Photos two and three show the finished cut out.
The Finishing of a Centreboard
Page 3 of 12



This photo clearly shows the shape of the SS316 rod I used.
The Finishing of a Centreboard
Page 4 of 12
When a perfect fit was achieved the screw holes were carefully drilled into the wood and the protective tip was temporary
mounted, see photo 4.

Careful filling (try not to touch wood) and lots of sweat are now needed to taper the lower end of the SS tip and perfectly
match it to the official centreboard drawing. (Note the marks where the file touched the wood). After this task the SS tip is
removed to add a protective epoxy layer in between the wood and the SS tip. The epoxy also hardens the inside of the
screw holes so they hold better and in the event water leaks in there is some protection inside the screw holes too.
Sanding
It is needless to say that a good finish requires lots of sanding. It starts with the sanding of the bare wood. The advice given
by the epoxy manufacturer told me to use sandpaper with grain 280. Sanding needs to done careful for we dont want to
remove too much material and alter the shape of the board. On the other hand the board must me smooth and have a silky
touch. It is all a matter of sand paper and lots of feeling, a little sanding and a lot of touching. Once the surface is as smooth
as a babys bottom and all imperfections are gone it is time to start with the epoxy.
The Finishing of a Centreboard
Page 5 of 12
The epoxy system
The system of choice was the epoxy system from de IJssel. The West system is also a good system but much harder to
mix in small quantities. The system from de IJssel has a two to one ratio between resin and hardener. This ratio makes it
easy to mix in small quantities. The downside of this system is that it is available only in tins of 1 kg or more while the
West system is sold in smaller quantities. Photo 5 shows the materials and tools I used:

-
Special Xylene based solvent for degreasing. Never use organic solvent with epoxy! (E.g. toluene based thinner, white
spirit, etc.).
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A special injection resin. It is not required but it penetrates the wood better that the thicker laminating resi