STIRLING MARBLEHEAD YACHT RACING CLUB Inc.

Woorabinda Lake - Stirling South Australia

More Complex Programmable Radio Transmitter for RC Yachting - by Ben Morris

Return to Sailing Hints page to examine other Hints

Time moves on and Spectrum has replaced the DX6i with a more powerful (programmatically) transmitter.  The one thing the DX6i was unable to do was to program a mix with the throttle as the slave.  This has now been fixed so any channel can now be mixed into the throttle channel to alter it's value.  Remember that in Radio Sailing the throttle is used as the main sail servo control.  Mode 2 is the most common arrangement (unless you are left handed?) so I will stick to this arrangement with the throttle (sail winch) on the left stick (up and down) and the steering on the aileron right stick (left and right movement).  Similar steps will apply to any programmable radio where the Throttle can be a slave in a mix.

This now gives us the ability to control the sail winch movement with another channel or switch.

Trimming the Sail servo (Throttle) position with the Rudder action.

What I have done here is to allow fine adjustments to the sail trim by moving the rudder stick left and right.  I use this when beating to windward and wish to trim the sails in (to squeeze up to a mark) or out (when a gust hits).  The throttle stick is completely down (Sails in) and moving the same stick to the left or right  trims the sails in or out just a small amount.

I needed to set up a mix whereby  moving the rudder (master) causes a small adjustment in the throttle (slave).

1. Turn on Radio. Set the Sail winch (Throttle)  to full in.  Trim on Rudder to centre.  DO NOT HAVE THE YACHT ON! Enter the setup area by clicking on the roller
   

2. Scroll down to 'Mixing' and click on roller to select
   

3. You will probably have no mixes set up yet so scroll to Mix 1 or the first unused one.  I am showing this on Mix 2 and click on the rolller
   

4. Select the normal option and click
   

5. The two areas marked as INH (Inhibit) are now changed by scrolling to each in turn clicking on it and using the roller to select Rudder in place of INH on left (Master channel) and Throttle in place of INH on right (Slave Channel)
   

6. Now click on the left most 0% on the rate line and change it to a value like -25%  and the right most one to a value like -40% (You may notice I have switched back to Mix 1 I had already set up).  These values are for a swing rig with gizmo allowing a mucg largere amount to be pulled in.  In a standard rig like a IOM etc the values might be more like -8% and -25%.
   

7. Spectrum has made it easy to see the effect of these mixes here by displaying the positions of a few of the controls including the Throttle *(THR) and Rudder (RUD).   Moving the rudder left and right will show the throttle responding by a small increment
    

8. The amount of movement can be adjusted by altering the % mix values. If your setup places the Throttle display to the left when sails are in then the mix values will need to be made positive rather than negative.  Remember that these mixes will apply at every position of the Throttle stick so it can be easy to over ride the movement you have available in your sail winch set up.

9. Only when you are sure the effect is correct should you turn on your yacht and receiver.  Use the trim action with great care initially to ensure the winch doesn't over wind.  Adjust the %age movements to  suit your system.

The main advantage of this setup is that the minor trim that is applied is temporary as it is on the self centering spring action of the rudder action.  This is MUCH better than using a switch to do this action as I guarantee you will forget that the switch is on and you will be wondering why your speed has dropped off.  It is also much better than reaching for the trims for a short time as then they need to be returned to where they were before (Ah! where were they again??)

It is possible to add these mixes to a switch.  Just select the switch you want to use eg gear or aux and replace the RUD with the switch you want

 

 

 

Do you want more on this? click here to e-mail 'Yes' for more programming examples