The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

208 First Production Steps
Section A
(through stem)
Stem – thin
laminations of
mahogany
Cap – thin laminations
that can be bent
around stem profile
easily
Planking
Figure 19-1 Three section views through the stem and keel of the 60' (18m) trimaran Rogue Wave. Note the plywood laminated
into the main keel. <strong>The</strong> cross-grain in this lamination counteracts the splitting forces of the keel or centerboard.
gain more bonding area, we have eliminated it. Instead
of rabbeting, we laminate the keel and stem and then
shape them to accept the planking, which generally
covers the entire keel and most of the stem. <strong>The</strong>
planking is eventually covered with a laminated
hardwood cap, illustrated in Figure 19-1. <strong>The</strong> cap
becomes an extension of the keel and performs the
functions of a rabbeted keel. Our technique is fast,
accurate, and potentially less wasteful of materials, and
it produces a joint which is structurally superior to a
rabbeted joint.
Planning the Keel/Stem Lay-Up
A good deal of thought must go into planning the
keel/stem complex. Determine the finished size of the
lamination so that you can laminate together enough
stock to form a blank from which to cut, shape, and
A
Planking
Plywood
B
Plywood gusset
Section B
(through forefoot at scarf)
Mahogany keel
Frames
Cap
Plywood frame
Plywood
Mahogany cap –
covers end grain Mahogany keel
Thin laminations
of stem
keel
Section C
fair the final piece. Keel laminations can become
complex because they may have different widths and
thicknesses along their lengths, depending on the hull
shape and the requirements for bonding surface area.
Some keels will be very simple, and their entire length
can be made out of one size of stock. Other keels may
be considerably wider in the middle than they are at
the ends, or much thicker at some points than others.
Stems also may be much wider at the deck intersection
than they are at the waterline.
To develop all of these dimensions, you need to go to
the lofting board and develop the keel shape at each
station. If the designer does not specify an exact keel
size, begin by drawing the section view of the keel into
several stations on the body plan. <strong>The</strong> basis on which
we develop keel shape and/or size is surface bonding
area. Wider keels develop more bonding surface and
C