Practical Boat Owner – June 2019

(^19)
Turn the bag the right way out then
feed the drawstring twice around in
the hem so it is doubled. A splicing fid
works well for this, or even a big safety pin.
(^20)
The line I used here was an 8 plait
4mm Marlow braid. Knot the end
and leave a generous loop each side for
carrying or hanging the bag.
(^21)
Job done. It was worth joining two
bits of material because the extra
length in the bag means you can really
draw the top tight.
(^1)
Make sure you
have two
straight edges
which you plan to
join together and
that they are the
same width. Also it’s
not essential but
good to check the
sides are the same
because the finish of
the material front
and back can vary.
(^2)
Put the fabric together so the
insides are facing outwards. Pin the
edges together and then sew them. For
heavy material like canvas I found that
round-headed pins are easiest to push
through the material.
(^3)
Open out the fabric again and with
the sewn seam on the inside pin a
small hem down one edge to create a
round seam where the fabric joins.
(^4)
Sew along this round hem with a
second line of stitching and you
then have a strong seam which will lie
nice and flat.
Whether you want to cut out a base for
a bag or an access hatch, the
formula of Pi works out the
simple maths required to
determine the size of a
circle. Pi is a number
which is usually
rounded down to 3.14.
The formula is the
Circumference = 3.14
(/) x Diameter. Put it
another way the Diameter
= Circumference ÷ 3.14.
Therefore if we have a bag
with a circumference of, say,
74cm for the base, then the diameter will
be 74 ÷ 3.14 = 23.6cm (rounded up.)
The nice thing about making items
like this is that it’s a great way to learn
sewing. Unlike with a sail or cover it’s
not likely to be too closely inspected by
anyone else and if you mess it up or it
looks a bit utilitarian who cares as long
as it does the job. Sewing projects like
this are also an ideal way to use cheap
offcuts – by joining a couple of pieces you
can make a perfectly serviceable length
to use. You can just sew the two edges
together but a round seam as shown here
makes a neater and stronger job.
To get our radius divide this by 2 and
we can then set the compasses
to approximately 11.8cm and
draw our circle. As a quick
check in your head, the
circumference is always
about three times the
diameter. If you have
a hole on board you
want to plug, say for an
old instrument gauge,
a piece of string is an
easy way to measure the
circumference.
A little piece of Pi
How to join lengths of material
MAKE A CANVAS BAG
Smooth runnings
When making any hems double
sided tape saves using pins and
makes the job much quicker. On
heavier fabrics, however, the adhesive
can make the needle sticky and prone
to jam. A quick spray of silicone over
the needle and sewing foot helps
lubricate them to stop this
happening.
TOP TIP
Area = /r^2
Diameter = 2r
Circumference = 2/r
r
Circle and
formulas
Di
am
ete
r (^) (
d)
Radius (r)
Circumference (C)