A Bulkhead in
a wooden boat does more than simply divide up the interior space.
They play an important role in load spreading
They reinforce those beam, carline and
They tie deck beam and frames together.
They are instrumental in holding the hull shape.
They reinforce area of high stress such as near chain
keel and mast step.
They help support carlines.
"Sailors, with their
built in sense of order, service and discipline, should really be
running the world."
There are two basic types, structural and non-structural
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The 'structural' are those which are specifically
support high load areas of hull and deck.
However these will often double up as space dividers.
Then there are the 'non-structural' designed simply as dividers
areas or to support furniture.
Yet these too, if designed well will help with structural strength.
Watertight/collision bulkheads, because they are full width tend to be
very strong and structural.
These, because they are caulked and have no limber holes should have
It is possible to use permanent structural bulkheads in place of frames
but they will need to be of similar thickness.
On Mignonne the original structural bulkheads are 2inch 50mm thick
The Tick or Joggle
I was fortunate that Mignonne's
structural bulkheads did not need replacing, just refastening.
However I did have to build
all the 'non structural ones.
At first I curt cardboard
templates but these left me with a lot of trial and error fitting,
scribing, shaving, re fitting, scribing again, shaving a bit more and
wasted not only time but timber.
I then tried making up
template from scraps of light timber glued together in situ with the
hot glue gun. This worked reasonably well but I quickly ran out of
Then someone introduced me to the 'Tick /
This is without doubt the most
accurate and practical method for making any odd shaped pattern.
The 'stick' can be any
scrap timber preferably a stiff piece the length will depend on the
shape you want to trace, for a bulkhead perhaps about a third of the
beam of the boat.
Cut a point at one end and a
couple of notches along the length, these are to make it easy to
relocate the concise position of the stick later.
Next you need a scrap piece of
reasonably stiff plywood.
This needs to be large enough
to be tacked or clamped firmly, vertically along side the proposed
position of the new bulkhead, this will be you 'pattern board'.
The board also needs to have a
clean surface so you can draw on it with a pencil, a coat of white
undercoat will give a perfect surface.
Now that you have that set up, with
the stick flat on the 'pattern board' place its point at a position
the hull that you want to record and then trace the outline of the
stick onto the 'pattern board' with your pencil.
You will need to be able to
put your stick on to the trace in exactly the same position and same
later, this is where the notches come it as reference points.
Repeat this for as many points
as will be needed to create a complete profile of the hull shape
including frames chain-plates etc.
Now take the 'pattern board'
out and lay it on the panel that you wish to cut out.
Clamp it firmly to the
Now take the same tick/joggle
stick and place it onto those penciled outlines on the pattern, then
mark the position of the point onto the panel.
Do the same for all the
positions you have marked then join the points up with a spieling baton
and straight edge.
Cut it out and hope it fits
but don't expect the other side of the hull to be a mirror image.
Better to slap some more white
undercoat on your pattern and do another trace for the other side.
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The most obvious material for many is
sheet plywood because of its high strength to weight ratio.
While plywood panels are an
excellent choice, they can be difficult to fit in one piece once the
deck is in place.
This can be over some by
laminating two or more layers in situ, the sheets can be arranged to
overlap to create the joints however, clamping the sheets, in situ
while gluing will be a problem.
In my opinion, any one
building or renovation a solid timber boat should paint any plywood
that is visible.
Plywood, no matter what the
just doesn't have the same look or feel as solid timber.
Unfortunately, even if you are
going to paint the panel you will have to pay for a hard wood veneer as
it is difficult to get a good finish on a softwood one.
The panel edges will need to
be capped and the wood completely sealed with paint or varnish before
And if you do use plywood it
is a false economy not to use marine quality because of the danger of
delamination and movement due to moisture ingress.
An alternative is to build it
up from tongue and groove planks this will result in a fine looking
panel which can be painted of left natural.
However it will require a
tremendous number of fastenings.
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To get the full benefit of any bulkhead
it should be firmly fastened, preferably through bolted to the deck
beams carlines and frames.
Fastening to steam bent frames
will be a problem as they are rarely straight or entirely vertical.
Boats which have been framed
with steam bent frames usually attach the bulkheads on to specially
sawn futtocks, either set between the frames or in place of a frame,
these should be fastened through the planking as would a regular frame.
Fastening a part bulkhead to
the deck beam and joining it to its opposite number with a beam at the
bottom will in effect create a strong ring frame.
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