beams of a wooden boat do more than simply support the
They also have to
stresses and loadings.
The most obvious loadings are the
downward ones, such as
supporting the weight of anyone walking on deck and the weight of
The deck structure will also
be subject to stresses
imposed between the healing motion and the righting motion caused by
It also has to cope with the
stresses imposed by winches,
mooring cleats and any other deck hardware.
Beams need not only to be
strong but built of
rot-resistant wood as they will be difficult to replace when planked
And just as importantly, all
the beams joints need to be
of sufficient strength and integrity to transfer the loadings
or auxiliary beams are those which do not support a hatch
or deck opening.
King, strong or main beams are those which support hatches, cabins
Half beams are those which join hatch or cabin carlines.
Sawn beams must either be cut from timber which has the grain following
curve or lumber sufficiently wide to avoid splitting.
Laminating deck beams is a much more cost effective use of boat
and they can be just as strong.
However, as the curvature of the beams will vary, individual jigs my
have to be
Allowance should be made for the tendency of laminated beams to
slightly when taken off the gluing jig.
Carlines are the
fore and aft beams that support the sides of cabins hatches and
Carlines are supported by main
beams but in their turn
they not only support the hatch or cabin but also the inside ends of
In some cases it is necessary
to reinforce these with tie
Before fitting carlines
consider how the
Trunk is to be
Partners provide a reinforced frame to spread the horizontal loads of a
To spread these loads across
the deck and out to the
hull, the partners should be placed between to two full-length main
It is also advisable to
reinforce these with lodging
knees, although plywood covered decking will help with spreading the
It is not advisable for keel
stepped masts to emerge
through the cabin top as it is unlikely to be able support these
Tie-Rods or through bolts are
needed to prevent the two deck beams from parting and to hold the
Any hardware such as halyard
blocks, pinrails and the
like should be through bolted through the deck and partners.
Partners for un-stayed masts
need to be stronger than
those for gaff rigged which, in turn need to be stronger the those for
Marconi rigged masts.
knees act as
vertical supports for joints while lodging knees are used to join and
strengthen horizontal sections.
Knees can be added to joints
that are highly stressed
such as main deck beam to hull joints and to mast partners.
Hanging knees can also be used
as an alternative to or in
addition to sheer clamps or beam shelf joints.
hanging knee cut with a sweeping ogee curve
has the added advantage of
being a decorative architectural feature.
Sheer Clamp/Beam Shelf.
When is a clamp a shelf and a shelf a
Well it seems it depends on
where you live.
In order to try to avoid
confusion I shall refer to the
beam shelf as being the horizontal piece the deck beam rests on, the
the strake running along the top inside edge of the planking.
The most common method for
connecting deck beams to the
hull is via a combination of sheer clamp and beam shelf.
The advantage of the shelf/clamp
method is that not only is the
beam supported but the loads are evenly spread and the hull sides are
restrained from spreading.
The beam ends must also be
fastened strongly to the frame
heads as well as to the shelf/clamp.
beams carlines and hull sides must be carefully fitted to allow for the
of the deck.
Joints should be notched to
Beam to carline
joints are often notched
with a taper to prevent them from slipping downwards.
Tapered joints also add
strength due the wedging effect
as pressure is applied downwards, however they will also have to be
Half dovetails are used to
help tie carline to beam to
The strength of the joints
will be affected by the type
of covering used on the deck.
Sheet plywood securely
fastened to the deck beams will
help to spread the loads in all horizontal directions, while laid
their own will only spread them in the fore and aft direction.
Very Interesting This was really informative and clarified a number of issues that I have had question about so was a really great read.
Now I come to my point I have …