By Paul Butler
illustrations by Marya Butler
Small Boat Journal #53 March 1987
Fabric decks, spray shields, and
cockpit tents are comfortable, space saving, and lightweight.
They can significantly increase your living space, make a rough
passage a bit safer and dryer, or turn sleeping aboard on a cold,
wet night into a pleasant experience.
Fabric structures should be as
low as possible to keep windage to a minimum. Well designed fabric
foredecks and small shelters may sometimes be left in place when
under way. If you want to, you can sew plastic windows, vent flaps,
and mosquito netting into the fabric.
A wide variety of fabric types,
weights, and colors is available. Quality is related to price
— you get what you pay for. Some fabrics stretch, fade, or wear
more than others, and even shock cords may not be able to take
up the slack of cheap fabric or wet, untreated canvas. We’ve found
heavy-weight fabric advantageous in building these structures.
And when in doubt as to the best fabric weight for a specific
application, we call our supplier and ask his opinion.
No matter how it’s designed or
which fabric is used, a structure that flaps, sags, or leaks is
as bad as none at all. A good support system is the key to success.
Every boat offers different options for se- curing and supporting
fabric structures. Battens, ridgepoles, upright poles, and shock
cords can provide tension and support. Fabric also needs slope
to effectively shed moisture. Even a heavy dew will fill pockets
in a flat and loose-fitting piece of fabric. And a bit of flex
is necessary because a stiff and unyielding fabric structure will
strain lines, bend supports, and stretch fabric.
Narrow boats with small spray shields
don’t usually pose difficult design problems, but wide hulls often
require a more complex structure to provide proper support.
Options for framing and support
of a fabric structure are limited only by the imagination. A ridgepole
is the simplest support and does a creditable job (Fig 1). Ridgepoles
usually run fore and aft down the centerline, although they can
also be positioned on one side of a hull for a “lean-to” shelter.
A boom is the classic ridgepole, but we’ve also used a 10-foot
sculling oar supported by a forward tripod and a notch in the
Halyards attached to sewn-in D-rings
provide prime, adjustable overhead support (Fig 2). However, they
offer such strong leverage that you must be careful not to tear
the whole affair off the hull and hoist it to the masthead. When
using halyards, you may have to snub the line to the mast to quiet
flapping in a breeze.
Telescoping supports may also be
situated inside the structure, braced up from thwarts or the sole
(Fig 3). I made three good aluminum supports from an old tripod.
I adjust them by tightening two knurled knobs on each leg. These
sup- ports can be placed in a grommet or rein- forced patch in
Battens & Beams
Support battens may be rigged under
or above the fabric or sewn in between layers (Fig 4). One method
for supporting fabric is an external batten much like a mountain
tent (Fig 5). All you need is a pocket at either end for the batten
and small loops or ties along the rest of the batten length. If
these ties are small diameter shock cord, they can be adjusted
to keep the fabric at exactly the correct tension to shed water
and wind. This structure only requires tie-downs at corners and
along the edges to be self supporting.
You may find fiberglass, plastic,
or aluminum battens that work well and do not require any finishing,
but wood battens are the best looking. They finish nicely and
bend to a uniform curve. Hardwoods like ash or mahogany or straight-grained
softwoods like spruce and fir make fine battens. All wood bat-
tens should be well sealed to keep their strength, since soaked
wood will lose much of its stiffness and may snap in response
to a gust of wind or a sudden load. Three coats of epoxy, followed
by varnish if exposed to sunlight, are best for sealing.
Wood battens made for supporting
a fabric structure usually need to be wider than thick to prevent
twisting and make rigging easier. A successful size for us has
been ¼-inch by 1½-inches, but each application seems to require
some experimentation as to best size and shape. Start big and
keep shaving the batten with a block plane until it bends easily
to the shape you want. Keep in mind that laminated and epoxy-sealed
battens will be stiffer than plain, unfinished battens, but they
will also retain uniform strength under all weather conditions.
You may wish to drill small holes
in the ends of the battens to provide a tie off point. Straight
battens may be slipped out of the batten pockets and rolled in
the fabric, allowing a large assembly to be stored easily in a
small place. In many fabric structures, the battens are different
lengths, and having each batten labeled makes it easier to rig.
If the batten pockets start to wear, consider wrapping the batten
ends in duct tape.
Fabric decks can be supported with
beams that fit into sockets or notches in the gunwale or deck
structure (Fig. 6). Sometimes these beams can be permanent and
the fabric covering removed or left in place according to the
weather. By laminating, you can make the beams to almost any shape
for a small boat.
These beams are best lofted and
laminated right on the lofting board. Make the lofting board of
¾-inch ply and do all the layout right on the board, then screw
down short sections of aluminum angle and use the lofting board
for laminating the beams. We build ours out of 1/8 inch veneer.
The outboard ends of decks, tents,
and spray shields can be held in place with snaps or loops and
hooks (Figs. 8-10). They can be attached to the outwale, under
the outwale, or in the case of hooks even inside the boat if you
drill a small hole under the gunwale to provide access for a small
We favor shock cord loops and hooks
over snaps as a means of attachment. Shock cord stretches in response
to pres- sure on slack and will keep a fabric panel at about the
same tautness whether wet, dry, hot, or cold. Using cords of various
size and length also allows a degree of fine tuning. Be sure to
get the quality cord that comes in rolls in various diameters
a few inches.
If hooks are permanently attached
to the boat, the fabric structure, once adjusted, can be set up
easily, even late at night or in wind or rain. With any fabric
structure, you may need to rig additional lines fore and aft to
provide proper sup- port tension. We always throw a few small
C-clamps in the boat for overnight trips, since you can easily
clamp a structure together in an emergency. Small ply pads protect
the hull from marring.
A couple of words of caution. Anchor
your boat so it can weathercock into the wind. If the wind blows
into the tent from the backside, your ears will pop every time
the thing flaps.
Also, test everything before your
first night aboard. For some reason, nothing ever seems to happen
to fabric decks or tents till late at night or miserable weather,
when you least want to get up and deal with it.