How to draw those complicated curved lines that are the poetry at the heart of wooden boats.
Spilings; In carpentry
and shipbuilding, the dimension taken from a straight line, a moulds
edge or rule staff, to any given side or curve of a plank’s edge. (Smyth, A. W. (2005). The
Sailor's Lexicon (Rev. ed. of Sailor's word-book, 1996 ed.). New York:
Hearst Books, p, 643)
One of the problems associated with restoring or building
a boat is that almost all components have complicated curved shapes.
But it is those curved shapes and lines that make a boat such a thing
A spiling batten traditionally is used to record
the shape of the
bottom edge of each new plank at the moulds.
The batten is then used to transfer this shape to the planking stock.
When it comes to replacing an old plank or panel the most obvious way
is to copy it by simply tracing around the old one.
However, getting an old plank out without it breaking or distorting is
much easier said than done.
Many boat builders and restorers have a favourite way for tracing out
the shape of a plank or bulkhead.
The most common rely on using an intermediate, partial ‘pattern board’
or ‘spiling batten’ on which the distances to salient points on the
object to be copied are marked in such a way that they can later be
transferred to either a full sized pattern or the planking stock.
These points can then be joined by a continuous line using a fairing
Other methods include tracing and building a skeleton mock-up.
This is probably the simplest and most accurate method for copying an
oddly shaped plank or panel.
The ‘stick’ can be any old scrap of stiff timber cut to a suitable
length, pointed at one end and notched asymmetrically.
You will also need a ‘spiling batten’, this can be a scrap piece of
For copying the shape of a plank the ‘spiling batten’ wants to be the
full length (several pieces can be butt jointed with glue or staples)
but narrower than the original plank.
The ‘spiling batten’ needs to be tacked or
clamped to the ribs in the
gap left when the old plank has been removed.
There should be sufficient clearance to ensure that the batten is not
distorted by pressing against the planks above and below.
Giving the board a coat of white undercoat will make it easier to see
all position marks.
Before starting to use the tick stick it is worthwhile marking the
positions of all relevant underlying structures such as ribs, fastening
Now you have that set up place the ‘stick’ flat on the ‘spiling
batten’, place its point at a position on the hull/plank that
you want to record and then trace the outline of the stick onto the
‘pattern board’ with your pencil.
Repeat this for as many points as will be needed to recreate a complete
profile of the plank shape.
When you feel that you have sufficient data on the batten take it down
and lay it and clamp it firmly to the new planking stock or panel.
Now place the tick/joggle stick carefully within those pencilled
outlines on the batten and then mark the position of the point onto the
Because of the asymmetrical notches on the stick it will only fit
within the pencilled outline the same way up as it was when the outline
Then all the position points can be joined up using a faring batten and
or straight edge.
The faring batten is just a long thin strip with straight edges that
will bend evenly, straight grained wood is ideal for this.
If you also transfer all the positions of ribs etc these will help when
it comes to drilling for fasteners and as datum marks for positioning
It is almost inevitable that the plank will need some trimming, it is
imperative that these datum marks are used to offer up the plank in
exactly the same position each time.
Some builders/restorers use a similar technique but instead of that
notched stick they will use a pair of dividers or compasses or even a
small block to mark the positions.
Certainly these methods will work but extra care must be taken to
ensure that the distance between the divider points remains the same
for every mark and the angle at which it is held must also be the same.
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Another way to spile is to make a truss
This can be done for almost any shape.
The template is made up using scraps of light timber or plywood glued
together in situ with the hot glue gun or stapled.
For a plank, using long flexible battens for the upper and lower edges
will provide an almost perfect pattern.
Do remember to mark all reference positions such as ribs etc.
A hot glue gun is convenient way to make ‘trusses’ because the glue
sets quickly and is easily controlled. #
I am perfectly aware that the majority of
Wooden Boat aficionados are sensible folk.
However, I need to point out that I am an amateur wooden
boat enthusiast simply writing in order to try to help other amateur
wooden boat enthusiasts and while I take every care to ensure that the
information in DIY Wood Boat.com is correct, anyone acting on the
information on this website does so at their own risk.