Tune In, Jack
Measurements reported in the CR-914 NEWS
The following guidelines are offered to get your boat properly adjusted - and to check during periodic adjustments. You will eventually develop your own ideas for adjustments for optimum performance in different wind conditions.
- 1. Tuning the Standing Rigging
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A. Start by adjusting the jib boom downhaul knot (where the jib boom is tied down to the deck) so it measures approximately 3" inches from the forward end of the jib boom. Do not glue this connection as it should be free to adjust. (Range: 2-3/4" to 3-1/4"). Then adjust the jib boom downhaul line so the boom measures 1-1/4" off the deck surface to the boom's centerline (range: 1" to 1-1/2"). Leave the jib halyard and forestay loose until 1C. below.
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B. Adjust the backstay so it measures 53-3/4" from the edge of the transom to the top of the masthead fitting (on the centerline of mast tube). Be sure to hold the top of the mast forward while adjusting and making this measurement so that the length in set with the backstay taught. (Range: 53-9/16" to 53-15/16").
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C. After B, adjust the forestay and jib halyard so they are equally tensioned and taught. These will later be adjusted based on the wind speed to keep the leading edge of the sail from sagging.
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D. Using a tape measure, adjust lower shrouds until they are equal lengths, thus centering the lower mast section port to starboard. Adjust the lowers so they are taught.
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E. Now adjust the intermediate and upper shrouds to insure the mast is straight when viewed down from the top. These shrouds should be on the loose side.
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F. The jumper stays are usually installed permanently and have no adjustment. However, some sailors use a "slide ring" to tighten these stays. Simply tie a small ring of string around the two upper jumper stays so that it sits naturally about 2" from the top of the mast. If more tension is necessary, simply slide the ring down.
When you have completed this mast tuning, you should have a mast that is properly adjusted in lean forward/aft, called "rake", and standing straight in the boat from side to side. Also, the mast tube itself should be perfectly straight.
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2. Tuning the Running Rigging
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A. With your transmitter and boat batteries ON, move the sail trim lever on the radio to the full trim/in position, and center the fine tune control on your transmitter. The arm on the sail trim servo should be about 11-o'clock relative to the bow. (bow is 12 o'clock)
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B. With the sail trim lever positioned as in 2A, adjust the common sheet (in the cockpit) so the knot connecting it to the split jib/main sheets is just forward of the deck exit/turning block on the aft port deck. The knot should never enter the block.
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C. Adjust the fore and aft piece of the 3-part mainsheet traveler so it measures 7-1/4" aft of the mast (Range: 7" to 7-5/8") Now adjust the port and starboard traveler pieces so the ring is center-lined, and 1-3/4" off the deck (Range 1-3/8" to 2").
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D. With the boat batteries still on and the trim servo in the full IN position, adjust the mainsheet on the boom so the boom is centerlined with no strain on the servo (no hum). When the sail is under load from the wind, it will ease towards the quarter. Make sure your fine tune control on the transmitter is centered.
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E. Now adjust the jib sheet so the centerline of the aft end of the jib boom is 1-3/4" from the centerline of the mast (Range: 1-1/2" to 2"). In this position, the jib boom should be pointing at the shrouds.
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F. Adjust the main and jib outhauls so the draft (curvature) of the sails is about 1-1/2" from the boom (Range: 1-7/8" light air to 15/16" in heavy)
G. Set the boom vang so it is taught.
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3. Adjusting the Rudder Control
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A. With the transmitter and boat batteries ON, the transmitter steering control will self center. However, make sure to center the fine-tune control.
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B. Check the position of the steering servo arm. It should be at 3 o'clock. (Bow is 12 o'clock) If not, remove the screw and adjust it to that position with the radio on.
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C. Looking at the rudder from astern, make sure it is in plane with the keel. If not, carefully disconnect the steering connector rod at the rudder quadrant, and adjust the end piece to bring the rudder to the center position. (Screw end cap clockwise to shorten rod - turns rudder more to starboard) As you tighten, or loosen, the aft end socket on the rod, the rod may also tighten or loosen into the forward piece as well - that's fine. The goal is to have the rudder fine adjustment centered on the transmitter, with the rudder dead centered on the boat
Questions or comments - contact Steve Lang, ModelSailingCenter.com 303-670-4670 or
Steve@ModelSailingCenter.com
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