28 http://www.yachtingmonthly.com MARCH 2016ANY QUESTIONS
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ANY QUESTIONS
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QUESTION OF THE MONTH
Q
In your used boat test of the Van
de Stadt Legend 34 (December
2015 issue), Duncan Kent said
the genoa needed reefi ng fi rst when the
wind got up over 20 knots, which, he said,
‘balanced her out and took some of the
weather helm away.’
Surely this is the wrong way round, and
reefi ng the mainsail fi rst would reduce the
weather helm more effectively?
Frank CoghillA
Duncan Kent replies:Tradition
does indeed have it that you need
to reduce the mainsail to alleviate
weather helm and this is because thegreatest area of the mainsail
is behind the lateral pivot
point of the boat (yawing),
so the wind effort pushes the
stern of the boat to leeward
and the bows upwind.
If you have a large,
overlapping genoa, however,
it may be sheeted well aft
of the lateral pivot point. A good deal of the
pressure on the genoa is pulling at the genoa
car, well aft of the mast, having the same
effect as the mainsail. If you’ve any doubt
about this, try sailing to windward in a strong
blow with full, overlapping genoa only. If you
roll away ten per cent of the genoa and movethe genoa car forward, it noticeably reduces
the boat’s inclination to head up.
Furthermore, reducing any sail keeps
the boat more upright so that more rudder
area is under the water, as well as being at
a more effective angle. The boat becomes
easier to steer and lighter on the helm.PHOTO: COLIN WORKCan I reduce weather
helm with the genoa?
With a large genoa, a couple of rolls can reduce weatherhelmA
Lance Godefroy, general manager at
Navionics UK replies: The errors
were not attributable to Community
Edits (originally called UGC). It is very easy
to spot Community Edits, which all have a
coloured ‘+’ icon and are only visible if the user
has enabled the Community Layer on their
mobile phone or plotter.
The errors were simply that – errors as occur
on any chart. Once we were made aware of
the issue we investigated and corrected them.
This update was published and made
available to download very quickly.
Users may report errors in a number of
ways: through the ‘Help’ section of our
website or via the ‘submit feedback’
option in the app.
In addition to Community Edits, we
also have SonarChart. This crowd-
sourced data uses the power of the
boating community to improve depth
information for everyone. SonarChart
and SonarChart Live are user-selectable
and are totally separate from our
nautical charts and are not used in the
creation of our nautical charts.
There are videos on our website to
help with many of the functions of the
Navionics app.Where do electronic chart errors come from?
The sonar layer can sometimes vary from the standard chart. The errors on the standard chart that Tony
spotted appeared to resemble the sonar layer. When he reported the error it was quickly correectedPHOTOS: NAVIONICS
Q
While sailing up the Medway in the
dark recently, my crew was piloting
with the Navionics iPad app.
Suddenly he warned that we were about to
hit a buoy, then go aground on drying patch,
both of which I knew did not exist. When
I reported these errors, Navionics quickly
corrected them.Other chart publishers only use offi cial
data from agencies such as UKHO. Navionics
also collects data from echosounders on its
users’ boats. Could these mistakes be caused
by ‘user-generated content’ (UGC) and how
closely is this data scrutinised? How should
we report errors we fi nd?
Tony Lavelle