corrosion can affect all forms, especially where the stem meets the
The type of stem which is built from bolted sections is particularly
to fastening corrosion which, can lead to the seams opening.
On older boats iron bolts have been used, these may have worked rather
during their lifetime unfortunately, their life time is fairly
Initially as the joint ‘works’ and increases in size, water
penetrates along the bolts causing them to rust, the rust expands
hole until it widens some more, then more expanding rust refills the
until there isn’t enough sound metal left.
This type of construction can also suffer from opening joints as a
the wood being allowed to shrink too often when it dries out.
One of the major problems I
had to resolve when I
began work on Mignonne
damage to her stem.
The damage had probably been
compounded by the amount of
time she had been out of the water allowing the wood to shrink.
Fresh rainwater had rotted the
top end as well as
accelerating the corrosion of the original iron bolts holding the
The pressure from the
expanding rust on the bolts had
split the dry wood of the knee and had begun to split the ends of the
Before I attempted to do
anything with the stem I had
replaced all the frames which were damaged so the planks would be
I had also raked out what
remained of the old
I could then start to look at
The knee had split along its
length, so it was easy to
finish off the split with a chisel and remove the two halves.
What remained of the exposed
bolts was chopped off and
the ends driven out of the stem with a drift.
The next job was to open the
hood ends (plank ends).
The planks had been fastened
with copper nails, to
release these I carefully drilled off the heads.
Then using wedges and shores I
carefully pried the hood
ends apart in the area of the damage, taking care not to damage the
Fortunately none of the frames
had been boxed in and the
planking held its shape well enough not to need any support.
Before I removed any of the
stem I took a rough pattern
from the original.
The next job was to cut away
the wood close to split so I
could see the extent of damage, then I cut away some more until I
Then, when I discovered that
the splits were not too long
I scarfed the ends. This was rather difficult to do with the saw, due
limited access so, some of it had to be done by chisel.
Having cut out
the damage I now took
another template of the gap and scarfs using stiff card.
Then having planed the replacement
timber to the width of
the original I used the two templates to mark out the new shape.
This I cut out over sized.
Any subsequent adjustments to
size and shape were going
to have to be made to the new piece due to the lack of space between
From there on it was a case of
holding the new piece to
the gap marking trimming and trying again until the scarfs fitted.
Once I was happy with the new
piece I propped it in place
and took a template of the inside surface to cut the replacement knee
The knee was made from the
same width timber as the stem
When I was satisfied with the
fit, both pieces were
propped and wedged in place and the holes for the through bolts
Bolted together with the new
silicon bronze bolts and
having checked and fared all the joints I then released the hood ends
marked the rabbet line, making sure that it coincided with the existing
With the new piece out
again, I fared the line with
a bendy batten.
Then, I chiseled out the
rabbet, constantly checking that
the angles were correct to take the plank ends.
Either end of the rabbet was
left rough for final faring
to the old when bolted in place.
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.