Sheeting System Shock Elastic Diagram

Under the rules you are allowed to fit a piece of shock cord elastic in the the line running from the winch up to the point where the main sheet attaches to this line. Fitting this will reduce the load on the winch bearings and extend battery life. Be careful to fit the elastic in the starboard side line aft of the attachment point (see diagram below). After fitting the shock elastic you will readily see the length of the elastic changing as the winch turns. This clearly demonstrates the great job the shock elastic is doing. The change in length is due to the sheet running up on itself within the winch drum thereby changing the effective diameter on which the sheet is feeding – just like when you wind your garden hose onto its wheel.



Shock Elastic Diagram

The above procedure for adding a shock elastic is best carried out (but not essential) if accompanied by a change from the monofilament sheeting line supplied with the boat to a Dacron or Dyneema sheeting system. The Association is now able to offer a ‘conversion kit’ to make the task much easier. However, we do urge to read the caveat below before proceeding.

NOTE : Radio Control Sailing Australia sell a dyneema sheeting kit that incorporates shock-elastic

If you wish to do-it-yourself then Dacron or Dyneema (50 kg breaking strain) can be obtained from most fishing tackle shops.

WARNING: This is not a task for the fainthearted and is not essential. You should obtain many, many hours sailing from the sheeting system supplied with the boat. We cannot guarantee this method is foolproof but we hope it will at least give you an idea of what is involved and how to approach the task in principle. And remember this procedure is only recommended if you wish to obtain longer life from your batteries.

During the description of this procedure we may refer to:

The Sheeting Control Stick – this refers to the left hand of the two transmitter sticks when the aerial is pointing away from you.
The Sheeting System Trim Tab – this refers to the small ‘slider’ positioned just to the right of the Sheeting Control Stick.
Pulling the Sheeting ‘IN’ – this means moving the Sheeting System Control Stick towards you (or down) and recalls the action of ‘pulling in the mainsheet’ on a sailing dinghy.
Letting the Sheeting ‘OUT’ – is merely the reverse of the above.
Now for the procedure.

1. Place your hull on the table after laying down an old towel to stop the hull sliding around during the procedure. Add batteries to the radio gear and switch on the transmitter then the boat.

2. Move the left hand transmitter stick and the trim tab, just to the right of the stick, to the fully ‘IN’ position, i.e. move both towards you as you hold the transmitter in the normal ‘sailing position’ (aerial pointing away).

3. The mainsheet connection point to the sheeting system should now be up close to the bow pulley.

4. Make a note, or better still a sketch, of how the line leaves the drum i.e. on the lower section of the drum the line leaves on the port side and vice versa. Note that the winch makes four complete turns from the mainsheet fully ‘in’ to mainsheet fully ‘out’ position if you push the stick away from you and back again.

5. Now, undo the screw fixing the winch drum to the winch servo (small cross head screw in centre of drum).

6. This is now the point of no return .
Place you thumb and index finger on the drum either side of the drum ‘bridge’ and gently pull away the drum from the winch servo spigot. As you do so the tension in the monofilament line may cause the drum to fly away if you are not careful.

7. Remove the monofilament line from the drum noting, for future reference, how it is attached (i.e. passed through the holes in the drum towards the centre and knotted. You will not, however, knot your new line when you change over – you will use beads to stop the line running through the hole).

8. Now take a long length (more than twice the hull length) of Dacron or Dyneema line and attach one end to the lower section of the drum in the same way the monofilament line was attached. However, we recommend tying a small bead to the end of the line to prevent it slipping through the hole in the drum. Wind the line five turns clockwise around the drum (when looking down on the boat). This will form the port side part of sheeting system.

9. Run the line through the bow pulley entering on the port side and leaving on the starboard side.

Holding the drum roughly over the position it will eventually go back to pass the free end through the hole on the lower section of the drum and pull it through, leaving some slack in the the line running back to the pulley. Now give that line five anticlockwise turns (this will either take up the slack or there is not enough surplus you will have to pull through some of the surplus at free pu;;ing it through the hole in the drum). Leave the end free at the moment – do not attempt to tie on a bead at this moment.

10. Replace the drum onto the servo spigot and replace and tighten the screw (a spot of Vaseline or Blue Tack on the end of the screwdriver will assist in locating the screw).
You should now have a line running from the port side of the drum up through the bow pulley and back to the starboard side of the drum passing through the hole in the drum. The line maybe quite slack at this point and will still not be tied at the starboard side of the drum. This untied end gives freedom to adjust the amount of line in the sheeting system whilst you make the elastic ‘shocker’.

11. Before going any further you must now check the sheeting system position. Pull the stick towards you – the ‘sheet in’ position.

12. When the winch stops rotating tie the first loop (about 10 mm in diameter) for the shock elastic in the sheeting line about 3 cm from the bow pulley (see diagram below) . Then tie the second loop (same size) about 5 cm sternwards from the first.


13. Take your short length of elastic (or a cut rubber band) and tie a loop of elastic between the two sheeting system loops (see sketch) such that the length of sheeting line between the line loops goes quite slack.

14. Return to the free drum end of the line and tug the free end so the line slips round the drum until the elastic shocker starts to stretch a little. Now pass another bead over the end of the line and tie it in place yet. This is tricky as the drum is now back on the spigot – you’ll find a way.

15. Take a look at your work and make sure you are happy with everything. The elastic shocker should be stretching and shrinking as the winch turns. Go to the fully in and fully out positions a couple of times to make sure everything is operating satisfactorily. You may now remove any surplus Dacron/Dyneema or, you may wish to carry out the following checks first.

16. One more check is recommended and that is to put the trim tab fully forward and run the sheeting system in and out again carefully. If all is OK the shocker will not get caught in the bow pulley or winch drum at the extremities of travel. If it does, some adjustments to your work may be required. This adjustment can be made by undoing the drum securing screw and lifting the drum off the servo spigot as before and rotating a notch or two before returning it to the spigot and replacing the screw. The sheeting system should never get caught in the bow pulley. If any ‘overrun’ is to occur it is better that this take the form of overrun onto the winch drum. Ideally, in the ‘sheet fully out’ position the point of attachment of the mainsheet leading to the boom should be in the area of the mainsheet eye on the deck.

17. The final step, yes it really is the last, is to retie the mainsheet to the sheeting system AT FORWARD LOOP OF THE SHOCKER.

And there you have it! Job well done.

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