[Welcome] [Lakes] [Marinas] [Public Ramps] [Marine Supply] [Sailboat Dealers]
[Books] [My Catalina] [Guest Log] [Links] 

[PART 3]
[NOTE:  This electronic manual is a verbatim copy of the printed manual included with Catalina 250 #384]

Tuning The Mast

Your mast is held aloft by the standing rigging (forestay, backstay, upper shrouds and lower shrouds).  The term "tuning" refers to adjustment of the standing rigging so that the mast remains "in column" when under load.  This is accomplished by following the procedure outlined below.

AT THE DOCK: (First part of tuning)

1. Adjust forestay and backstay so that the rake (fore and aft angle of the mast) is approximately four (4) inches.  In order to measure the rake, tie a weight from the main halyard to act as a plumb bob, and measure the horizontal distance between the halyard and the aft face of the mast.
2. Adjust upper shrouds so that the mast is vertical from side to side.  To verify this, using the main halyard, measure the distance from the masthead to the center of the pin at the chainplates; repeat for opposite side and adjust upper shrouds as necessary.

3. Once the mast is straight side to side, increase tension of upper shrouds taking an equal number of turns per side, until the fore and aft prebend induced reaches approximately 1 1/2 inches.
4. The lower shrouds should be adjusted slightly looser than the uppers.  These shrouds will help control the amount of prebend in the rig.

NOTE:  Rigging tensions may be measured with LOOS & Co. Model B tension gauge.

TUNING UNDER LOAD: (Second part of tuning)

The tuning at the dock gives an initial positioning of the mast but it is essential to tune the rig under load in order to compensate for dynamic forces that occur while sailing.

1. While sailing normally to windward, at approximately 15 to 20 degrees of heel, sight up the mast, along the aft face from the deck.  If the middle of the mast (where the spreaders are) sags to leeward in relation with the top of the mast, take up on the weather side lower shrouds until the mast is straight.   If the top of the mast sags to leeward in relation with its center, then take up on the weather side upper shrouds.  Repeat this procedure on both tacks.
2. Observe carefully the behavior of the leeward shrouds.  They should never be loose.

All rigging wire used on yachts has a tendency to stretch, especially on a new yacht, and after you have sailed in heavier wind than you normally experience.  Therefore, you should periodically check the tension of the shrouds and stays, tightening them up if it is required.

Our masts are built to withstand any normal usage, but improper tuning or handling can cause problems.  Rigging as well as tuning becomes all important when setting up the mast.  A knowledgeable person should oversee the rigging and tuning so as to eliminate the possibility of an eccentric load which might occur with an improperly loaded shroud.  Special attention should be given to the initial stretch of the wire over the first few hard outing.

ALWAYS, before leaving the docks, check all your turnbuckles for tightness.  MOST MAST FAILURES HAVE BEEN TRACED TO LOOSE TURNBUCKLES AND IMPROPER TUNING.

IMPORTANT: Final tuning of the mast depends on local conditions and the cut and set of your sails.  Consult your dealer or sailmaker for advice.  More detailed information on this subject can be found in Wallace Ross' "Sail Power", published by Alfred A. Knopf in New York.

Main Sail Reefing

Reefing should always be done before it becomes necessary.  Some sailors use the rule of thumb, if the thought of reefing occurs to you, it is time to reef.  Sailing at extreme angles of heel, 25 degrees or more, is not efficient, fast or comfortable.

Sail Plan

Central Texas Sailor
© 1998 Mark T. Melchior   --   All Rights Reserved

Revised:  20 Dec 2007 16:28:39 -0500

"In a powerboat, you get there in a hurry . . .
in a sailboat, you are already there."