stop water /
Stopwater is much over
looked but vital element in a
All well built traditional wooden boats will have these softwood dowels
across many wood to wood joints, especially those below the
idea is that the softwood will expand if wet, thus filling the hole
tightly, and preventing water from creeping further along the joints by
They should always
be placed across the joints in the stem where they
plank rabbet line.
long scarph joints will often have two stop waters.
They are sometimes omitted by modern builder in the belief that modern
materials, bedding compounds and glues make them redundant.
However, there are areas which
take a lot of abuse where
they are still worth inserting.
Areas such as the
particularly at the
forefoot, keel and the stern structure. stem
Stems are massively built
because they tend to take the
brunt of any groundings collisions as well from the tension exerted by
forestays and bobstays.
These areas as well
as being subject to rot also have to put
up with wetting and drying, shrinking and contracting particularly at
which causes seams and joints to open.
Normally the holes would be drilled and
the bung driven home
This is so the stopwater can
be in the rabbet line,
preventing leaks getting beyond the caulking.
Unfortunately this does mean
that they are almost
impossible to get to once the boat is planked.
They can be reached by
unfastening the plank ends then
opening a seam wide enough, however there is always the danger of
Of course if you are changing
any of the planks it is a
good idea to renew any stop waters which are exposed.
They can however be placed
outside the rabbet line and
But if you do this you must
caulk the joint between the
stop-water and the plank seam.
The dowel or bung needs to be
a softwood which will swell
up to keep the joint tight.
And it should preferably be a
reasonably rot resistant
wood such as cedar.
A wood preservative can be
used to prolong the stop
water's life, particularly as the end grain is exposed.
Using something like creosote
will help lubricate it
while being tapped home.
Whether you cut the dowel to
fit the hole or drill the
hole to fit the dowel, it needs to be as tight a fit as you can make it
allow the dowel to be tapped in without breaking.
The tricky part is drilling a
hole which crosses the
To align the drill bit, so
that it exits precisely on the
joint, it’s a good idea to have an assistant help with the
The person drilling can watch
the horizontal alignment
while the assistant watches the vertical and do use a carpenter’s
I prefer to use a brace and
bit, it may take more effort
than using a power drill but I feel that I have more control over what
Be careful as the bit exits go
slowly so as not to damage
And make sure the bit is not
going to hit any bolts as it
Once the dowel is in cut it
flush and paint.
So whether you are building or
forget those stop-waters.
building methods you are using this simple, old fashioned technique
keep leaks at bay.
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