Version 2 7 1 July 2021
easing both booms well beyond their normal settings or haul them in. This can be done by
manual winch control or using Sw A to invoke Sports mode. See later explanation.
Rudder Mid-Point Trim and Weather Helm
It is ideal for the DFs to sail to windward perfectly balanced (i.e. no rudder adjustment necessary).
If one tack has a marked tendency to round-up on the other tack, it may be due to asymmetrical
sheet settings and this should be checked, particularly the position of main sheet bridle on both
tacks. It may also be due to the rudder being slightly off centre.
This mid-point can be reset during racing by the rudder trim tab below the stick. When used, the
audible tone indicates the direction of movement and the mid position. Alternatively, when not
racing the rudder mid-point can be set using Functions setup/Subtrim/Ch 1 and the UP/DOWN
buttons.
Rudder Movement - Rate
This can be useful when running downwind in strong winds, when even very slight rudder
movements can have a dramatic effect on direction. In its factory setting, rudder movements are
proportional or linear. A 50% movement of the stick to the right will result in a 50% movement of
the rudder to the right, within the pre-set range.
There are two ways of controlling the relationship between stick movement and rudder movement.
The first is Rate, the other is Expo. They can be used alone or together. The impact of the setting
is shown graphically in the LCD display.
When Rate is used, a default setting of 100 will result in a full rudder throw. If the End point has
been set at 35 deg. a full stick movement will result in a rudder movement of 35 deg. If a rate of 50
is used the rudder will move half the distance or 17.5 deg. A rate of 50 and a 50% stick movement
will result in a rudder movement of around 9 deg. In effect, use Rate to de-sensitise stick
movement in a linear way over the entire stick range.
Rudder Movement - Expo (exponential)
Expo is the other way of controlling the relationship between stick and rudder. Rate and Expo can
both be used to control rudder movement, either singularly or combined. A second set of
Rate/Expo settings can be use using Switch A (SWA) to invoke the Sports mode. More later.
With the use of Expo, the stick/rudder relationship changes from linear to one of a theoretically
infinite number of exponential curves. For example, with Expo, a 50% stick movement to the right
(or left) might result in only a 30% rudder movement – depends on the Expo setting. More rudder
movement leads to proportionally higher response.
The extent of Expo applied is a matter of personal preference.
So, both Rate and Expo alter the default linear curve to one that either is less sensitive (positive
expo) or, more likely, more sensitive (negative expo) around the middle range. When using Expo, a
typical starting point might be 30%. - depends on whether Rate is also used.
Rudder Movement Using Sport mode
Use Switch A (SWA) to invoke the Sports mode to provide a second Rate/Expo setting. Only one
set of End points can be used.
How to Set Dual rate/Exp. For Alternative Rudder Control
- Power-up Tx/Rx
- Select model number as described above.
- Using the Function setup menu, and short OK, index through to Dual rate/expo. Select
with OK.
- Short OK and if necessary, index to Ch1 (Rudder is selected)
- Throw Switch A (down) and Sport will be displayed.
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