Protection for your
worm shoe is a non-structural piece of wood, fixed to the
underside of a wooden boat.
One of the great advantages of a traditionally built wooden boat is
damaged parts can be replaced.
Unfortunately those underwater parts which are most likely to be
damaged by a
grounding are the most difficult to replace, hence the worm-shoe.
why is it called a Worm Shoe?
Of all the words in the
sailor’s lexicon the one which is guaranteed to put the fear of god
the wooden boat owner is ‘Teredo’.
Though the teredo is not a worm
at all but a
mollusc, it is only one of many hungry little vegetarian creatures
nothing better than a good old munch on your boats timbers and not all
live in tropical waters.
It only takes a pinhead sized
hole in your boats
protective paint/anti-fouling for them to get into her timber.
Once in they can munch their
way along the grain until
the wood is as fragile as paper.
The slightest gouge exposing
end grain is akin to opening
a free canteen for borers.
And you don’t need to smash
into coral or rock, the
vast majority of the sea bed is made up of very abrasive stuff.
Even the lightest brush over
sand or shell will rub off
So the point of the
sacrificial shoe is to have an easily
replaceable piece which will take the damage and keep the ‘worms’
occupied and out of the main structural timbers.
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Normally the shoe is
placed under the lowest sections of wood where groundings are most
This is usually the after end
of the keel at the base of
the stern post and under the deadwood.
On a typical keel boat this is
the spot most likely to
hit bottom in shallow water.
However, there is no reason
why the 'shoe' should not
also be added to the front end to protect the stem.
And a sacrificial strip of
wood is perfect for protecting
any vulnerable sheathing like epoxy and fiberglass.
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The 'shoe' does
not have to be of the same wood species as the original keel.
However, it should be
reasonably rot resistant and strong
enough to absorb some of the damage caused by grounding.
As it is a sacrificial piece
it also needs to be
relatively easy to replace, so screw fastenings and definitely no
The screws will need to be
well countersunk to prevent
damage and the heads well protected with bungs or filler so they remain
reasonable condition for when it is time to unscrew them.
Silicon bronze being the
The next important provision
is creating a worm proof
barrier between the worm shoe and the wood it protects.
The last thing you want is for
the worms to progress from
the 'sacrificial shoe starter' to a 'main course of keel'.
A layer of bedding such as
‘Irish felt’ or
tarred roofing felt between the worm shoe and the deadwood should keep
little darlings where they belong, and allow for easy removal when the
Now while we don’t mind if
worms getting into the
shoe it is still better if they can be kept totally at bay.
The sacrificial worm shoe
unlike a sacrificial anode
doesn’t cease to protect if it is painted.
So feel free to give the
'shoe' the same protection as
the rest of the boat, plenty of creosote, paint or anti-fouling.
And don’t forget to check and
if necessary replace
it at haul out time.
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I need to replace the worm shoe on mu cruiser, but what is the purpose of a wormshoe in the first place?
If it is to protect the keel from burrowing …