First, the tuning instructions in the manual are excellent,  but I'm not sure they have ever been updated to include the variance of rigs on the c250.  When first published, the C250 was a water ballast design with shroud chain plates under the shoe box deck joint.  I'm not sure if first wing keel models started with chain plates on the coach roof or if they were moved there after wing production evolved.  Seems like there were a few complaints posted on the board about the necessity to run two sets of jib sheets and Catalina moved the shrouds inboard responding to that (my memory fades a bit).  Now, the deck mold for the wing has been adopted for the center board boat also so the shrouds are inboard on both models.

Early wing owners lamented that they couldn't obtain the mast prebend which is difficult to do on the center board boat.  Even though dynamically the rigging of two boats remain very similar, my comments on this page will refer to the tuning of the centerboard boat with outward shrouds and there may be some variations.

To prepare the way for understanding the tuning of the c250, its necessary to say that sailboat rigs normally enjoy the ability to hardened or softened while on the fly by the use of a backstay tensioner.  A tensioner is used to flatten both the jib and main during a breeze.  In light air, the tensioner is relaxed to pocket (power up) the sails.  The rig on the C250 does not provide for this.  It neither comes with a backstay tensioner or does one fit into the scheme of a rig with radical raked spreaders.  Here's why.

The raked spreaders serve the purpose of the normally used forward lowers, like on a c22 or c25 and hold the center of the mast forward.  With it held forward, the mast truck can be hauled aft by use of a tensioner which tightens the forestay and bends the mast thus flattening both the jib/genoa and mainsail.  But, if the mast truck is hauled aft on a C250 without the foreward lowers, the effect tightens the forestay ok but it slackens the uppers and relieves the forward pressure on the spreaders and allows reverse bend in the mast.  This reverse bend is exactly opposite to the desired effect and will power the main further.

Some of the reasons for not incorporating forward lowers are they make jib handling more difficult, they restrict the jib sheets ability to trim the jib more inboard aiding  pointing, they make setup for a trailerable boat more difficult and they likely reduce the cost of production. 

The result is tit for tat.  No forward lowers = no on the fly tuning.  This all means that a choice has to be made of how we want to tune our boat.  During my Catamaran days, we accessed the wind prior to a race and adjusted the rig accordingly.  In heavy air, we hardened the chain plates by one hole.  In light air we softened by a hole.  The same can be done on a c250 if one wants to go to the bother.  The big problem is, a firm rig is a nuisance on a light air day but a loose rig can be a big struggle in a breeze.  Likely then,  tension will be set fairly firm so that we don't get caught in a blow with a powered up rig.  With these understandings in mind, lets tune the rig.

The instructions in the manual quickly describe centering the mast truck laterally.  To do this, we slacken the lowers and adjust the uppers so that they are firm and then using the jib halyard we measure to each chain plate.  If the port is farther away,  the starboard turnbuckle is slacked a given amount of turns and the port tightened that many turns until the mast truck is centered.   From now on, whatever you do on one upper turnbuckle must be done on the other.  The exception to this is slacking a turnbuckle to facilitate mast raising.  Then, one can be loosened but the turns to do so need to be counted and marked on the barrel with marks-a-lot or masking tape and a pen.  When raising the mast, that turnbuckle then is reset to the proper turns.

Now, level the boat to her water line. This can be done by moving weight if the tuning is done on the water or on the trailer if using a water level or some method to level the boat.  When level, place a weight on the halyard and adjust the mast rake.  Catalina calls for 4 inches of aft rake measuring between the halyard and the mast near the base.  Obviously, this has to be done without wind.  As the c250 is given to increasing weather helm during excess heeling, many owners will reduce the rake to help minimise weather helm*.  Doing so is a trade off to weathering ability (ability to point well on a close hauled course).  Adjust the two uppers and the forestay to obtain the desired rake and upper stay tension.  The uppers should be pretty firm requiring a strong healthy push to deflect an inch. 

I'ts now time to do the lowers which previously were slackened along with the backstay.  Adjust the lowers to about half the tension of the uppers and monitor that the mast is in column (doesn't bow to starboard or port).  The easiest way to check this is to go below and laying on your back, sight the mast thru the foreward windows.  Again, the same rule now applies, whatever is done to the one has to be done to the other.

Now firm up the backstay and then look at the mast again.  What is wanted now is some forward bend to the middle of the mast, its called prebend and Catalina calls for 1.5 inches of it.  Tighten the uppers and then retighten the backstay until it is obtained.  It may be necessary to loosen the lowers if they have been tightened too much.  The lowers if tightened too much will pull the prebend back out. 

Now, as Catalina points out... its time to tune under load.  While sailing to windward under a good load, lay in the V berth again and check the mast for column.  I will vary from Catalina's instructions here because the call for uneven tuning of the turnbuckles.  If the mast sags to leeward, tighten both lowers the same amount until the mast is in column keeping in mind that this may be a trade off as the more they are tightened, the more they will pull the prebend back out.  They should should remain looser than the uppers or reverse bend will result.  If by some chance, the middle mast section is to windward, then loosen both lowers slightly.  The other tack can be checked...but I think keeping the turnbuckles the same turns after the mast is statically in column is a better way to go.  Thats it... the boat should be in tune.

Having said all this,  lets revisit the backstay tensioner.  There are a couple of ways to make use of it.  It could be used on a loose rig where the headsail will be used rather than the main in a breeze.  This would allow firming and depowering the headsail very well in a breeze and having a powered up rig for lighter airs.  This might be a choice for a boat which primarily sails in light air and rarely experiences any heavy stuff. 

The other method is to simulate the foreward lower stays that are part of other rigs that hold the center of the mast forward.  This allows use of a backstay tensioner to depower both the jib and the main.  Needed here is a baby stay.  A stay from the spreaders to the fore deck.  The problem on the c250 is that there is no foredeck area to put one and they are normally used on a boat large enough where their forward presence doesn't interfere too greatly with tacking.  To overcome these two problem, the baby stay has to lead to the the stem and be a retractable.  Leading to the stem is not a problem as a block can be used to turn a line stay back aft to a jib winch.  And, the stay can be made retractable by use of bungee cord.  The problem is the inconvenience and additional step that using it adds to making a tack.  The baby stay has to be uncleated so that it will retract and then reset following the tack.  This is not something that the day sailor or racer would want to add.  However, for the cruiser who often doesn't change a tack the whole day... it provides a good solution to allowing the use of a backstay while serving one other important attribute for the cruiser.  It gives peace of mind that there is a bit of redundancy in case of a forestay failure.  As, on the c250 with a CDI furler with its integral halyard and no forward lowers, the mast is held by the forestay ONLY.  I've written about the baby stay in another of tech tip and wont repeat more on it here.

* Balance of the water line has been an issue on the c250.  Often a heavy extra long shaft motor is used and a loaded boat will set low aft.  Doing so has the effect of raking the mast aft and increasing weather helm.  Many owners add ballast within the V berth locker to aid in putting the boat on her lines.  This can be in the form additional batteries and/or sand bags or other ballast.  Some shimming between the mast and the step can also assist in gaining foreward adjustment to the forestay.  If using the nylon bearing on the cdi furler, it can be counter bored as much as half its height to add turnbuckle range.