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FAQ - Servo 

What are the Rules regarding the Servo

    Here are some answers to some of the frequently asked questions. Click on the link to view the area of interest.

3.0 Displacement and Ballast

The minimum ready-to-sail weight shall be 4.5 pounds. The ready-to-sail weight includes radio receiver, batteries, steering servo, sail control unit, sails and rigging.

5.5 Alternate Sail Controls

The manner in which the main and jib sheet are controlled is left to the skipper's discretion.

7.0 Radio (2001)

A maximum of two channels shall be allowed. One channel shall be used for sail control, the other for the rudder. Standing rigging shall be adjusted only by manual means. The arrangement of radio equipment and the method of fixing radio equipment to the hull is not controlled.


Do I have to use the wood in the kit to mount the servos?...............NO

Here is an alternative rudder and sail servo mounting by Brian Roberts

This is drawing gives a general cutaway view of how the rudder servo is mounted.






From a side view the critical item is the spacer.  The spacer thickness is chosen so that the rudder push rod will exit the hole in the cockpit wall as per the plan and not require any bending.

 The distance of the servo from the wall is enough for a full rudder servo movement  without the servo arm touching the cockpit wall. 



Looking from above shows the positioning and the size of the "servo tray". The tray size is not critical, width is wider than the servo and length is long enough to fit and be secured under the cockpit sole.

Standard rudder (S3003) can be used, or for weight management a micro servo (S3001) will work and has enough torque to operate the rudder, if the boat has been tuned for minimal weather/lea helm.

  Two screws through the cockpit sole is all that is needed to secure the tray to the hull.

For the Sails servo this view will give you the overall idea. Using this method single or double purchase of either or both sail sheets can be achieved.  

Shown is the single purchase rigging on both main and jib. 

The copper wire is attached to the end of the sheets and passes through push rod connectors.  Once the sails are on the boat and the radio system is set for close haul, the copper wire can be slid in the connectors to adjust each sail position.  Once the adjustments are complete a small piece of modeling clay with keep the water out.

Now a few detail on the sail servo box.  The end pieces are about 1/4 thick with a groove down the middle to allow the servo cord to fit.  The sides can be very thin (1/16).  Wrap the servo in plastic (plastic is used to prevent servo being glued to wood and hull)  fit the wood together, glue the wood with epoxy and use rubber bands to hold it all in place.  Sand/saw the excess from the bottom of the box after the glue is dry.  Score the hull well where the servo will sit.  Mix more epoxy, and add  micro balloon filler, then spread it on the bottom edge of the box.  Place the box in the hull in its final position.  Remove the servo from the box, throw away the safety plastic, use screws to hold  the servo in place.

 (For my latest boat, I created the sides of the sail servo box from the plastic removed when cutting out the hatch cover.  Using the kit plastic glue as an alternate for the micro balloons/epoxy, it makes a much stronger bond).

The Sail servo arm is fabricated from ally, with just holes in the end for single purchase, or small pulleys on the end if you intend to rig for double purchase. This length will fit in the hull without touching the walls.  Shown is an equal length double ended servo arm, you could affix the servo disc off center, but you will also need to mount your servo box off center in the boat.

These last two views give you ways of  how to rig the boat, the first is for single purchase.



This last shot shows double purchase rigging.

 I use Velcro on the battery pack, and the receiver.  I have put the other side of the self stick Velcro in the hull to hold the Rx and battery pack in place. 

If you have questions contact me by e-mail. 

 Brian Roberts

What Servo is Recommended for the sail winch?  

The S3003 known as a standard servo is considered to week in strong winds, it is only 44oz/in torque it is recommended to use a servo of at least 100 oz/in torque.

There are many possibilities and many are listed here. 

Manufacturer Number Size Weight oz. Torque oz/in Transit time Comments
Futaba    S125    1.79x0.91x1.66  2.3 129.2 0.62 sec/60o  Arm (Discont'd)
S3003 1.59x0.78x1.42 1.3  44.4 0.22 sec/60o Standard Servo
S3302 2.33x1.13x1.96 3.6 111 0.19 sec/60o Arm
S3801 2.33x1.13x1.96 3.8 194 0.26 sec/60o Overkill
S3802 1.8x0.9x1.7 2.6 122 0.50 sec/60o About Right
S5801 1.82x0.98x1.73 2.9 109 0.6 sec per rev Drum
Hi Tec HS725BB 2.30x1.10x2.00 3.8 193 1.3 sec per rev 3.5 Revolutions
HS715BB 2.30x1.10x2.00 4 193 0.21 sec/60o
Airtronics 94581 3.65x1.58x1.78 4.9 170 5.00 sec/170c  
94158 1.54x0.79x1.48 2.1 130  0.09 sec/60c  
94161 1.54x0.79x1.65 2.5 135  0.25 sec/60c  
Hobbico CS-80 2.59x1.18x1.26 5.4 275 0.19 sec/60c  
Hobby People CS-80MG 1.60x1.49x0.79 2.1 129.8 0.25 sec/60c Arm
Tower TS-71 1.60x0.80x1.50 2.1 110 0.23 sec/60c  
RMG SW-380 3.10x2.10x2.00 5.1 294 Drum Variable.  


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