Tuning Guide

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MARICAT 4.3 CAT RIG HOW TO

Borrowed and modified from the Maricat Association NSW by Richard Eveleigh

SET UP Platform

Should be rigid with the tendency to twist minimised. 3 things ensure this:

Beams have a tight mating fit to the hulls. Rebog with polyester resin and micro balloon filler if necessary. Ensure bolts are tight (but don’t overdo otherwise you will strip the threaded aluminium blocks embedded in the hull). The dolphin striker should be set at a tension that the main beam has a bend 5 to 8mm higher at the mast step than it would otherwise have with no dolphin striker tension. When normal rig loads are applied when sailing (main sheet hard on) the beam will then come to its correct level. (Ensure you check the dolphin striker rod or wire, nuts and associated fittings each season end. It is the most important structural item on the boat and small attention here can save a lot of expense if it breaks at sea) Trampoline – tight is right. It should be as tight as a drum. This contributes enormously to the rigidity of the platform. Leak proof the hulls – vacuum cleaner on blow shoved up to the drain hole, and soapy water

Rudder Alignment

The following article is by Don Grant ACT Maricat REP ex Association President, PH: (02) 6231 0365. There are many theories floating around on how to make these boats go faster, so here are a few of mine. The idea of the exercise is to achieve an effortless, responsive, fast boat to sail.

Rudder Alignment

Toe in With the boat on the trailer and the rudders locked down hard in the rudder boxes, line one rudder up with the for stay saddle on the bow. Standing back and sighting it is the most successful way of pointing the rudder in the right direction and hold in that position. Sight the other rudder through to the other bow to check for 25mm of TOE IN measured at the bow. To adjust the rudders either shorten the rudder bar or drill out the rivets in the rudder box and twist the tiller arms until the rudders are aligned with the required TOE IN Re rivet the tiller arms after drilling new holes through the rudder box casting and tiller arm. The rudders work better if they are working slightly against each other.

Weather helm

Can be decreased by raking the rudders forward under the boat - just how far is a bit of trial and error. To start with, have both rudders locked down tight and sight across the two to see if they have the same rake to begin with. If one rudder is trailing slightly, release the down lock and bump the rudder forward into the rudder box so that it leaves a dark mark from the aluminium casting on the rudder. With a course file or rasp, file off the dark marks and repeat this procedure as long as necessary while locking the rudder down occasionally to compare the rake with the other rudder. When the rudder is adjusted sufficiently forward, lock it down and do the same to the other rudder until it comes forward to line up with the first rudder. I suggest a maximum of 10 mm adjustment at any one time (measured at the leading edge of the bottom of the rudder) then test the boat on the water. The other way is to pack out the top rudder mounting on each stern of the boat but remember that there is a s/s bolt into an aluminium casting and very few of these like to be removed. My (Richard Eveleigh) preference for this rather than filing away at the rudder blade, which can weaken it in a high stress positions, is to relocate the pivot point of the blade and is as follows:Remove rudders from castings and bog up pivot pin hole with Polyester resin and chop strand mat. Fair off flat. Place rudder blades back into castings and G-clamp castings tohold blade in correct position and to stop blades falling outs. With leading edge hard against the casting rotate the blades so that the tip of the leading edge of the blade is about 50mm in front of the line of the pivot pin when sighting down it. Redrill the pivot pin hole. Repeat procedure with other blade ensuring that it is perfectly parallel along the leading edge with the first blade. Get rid of any slop in the rudder system\r\nGet rid of any scratches and dings on rudder blades that can cause cavitation or humming. Alternatives to the rubber knuckle steering system The rubber knuckles which allow the rudder bars to hinge are not only hard to obtain but expensive (around $ 25 each) and seem to only last 1 or 2 seasons. Many sailors use improvised steering systems. Rubber hose works well with a large diameter piece over the rudder bars. Other ideas are reproducing the knuckles with rubber hose the same diameter filled with a rope and putty for strength and rigidity. Metal hinge systems can also be used but make sure that it is adjustable so that the rudders can be set to the right angle (slight toe in).

Mast, Rake and Rotation

Matching mast to sail Main sails vary in many different ways so what rig configuration works well on one boat is not necessarily suitable for another. They can vary with the quality of the cloth, slight differences in the way they are cut and sewn together, the sailing conditions that they have been through, storage with battens left in tight (bad habit. Always release battens before storing a sail and roll sail to keep battens straight not twisted), bolt rope shrinkage or distortion from general use. To check sail and mast compatibility with the boat rigged and the battens tensioned as you do normally, centre the traveller, pull on your down haul and outhaul as hard as you can. Then tension your main sheet to about the pressure required in 15 knots of breeze. Under this strain the mast should bend to the luff curve of the sail leaving the sail dead flat. If the sail is still full try stiffer battens, extend the bolt rope or more mast rotation allowing the mast to bend sooner to take up the luff curve. If the sail flattens with say a 12 knot effort the mast could be over rotated, or too soft, the battens far too tight. I have destroyed many good battens over the years tapering and softening but now realise the shape is in the sail and the battens should be firm enough to support that shape. The only value in over-rotating a mast is to allow it to bend easier while the effect of the angle into the apparent wind is negligible. Tapered or untapered battens Tapered battens are generally faster but give a narrower groove which – unless you are a very sensitive person – is easy to drop out of. Untapered battens are more forgiving ie easier to keep in the groove but are marginally slower. I was never a sensitive person and found that the untapered battens gave me the tolerance needed to stay ahead of the pack.

Mast Rake

Mast rake allows you to carry more power higher up the sail and get more stability up wind. While tacking is slightly more difficult, too much mast rake will make it impossible. My mast rake for cat rig is with the tip of the mast 200mm in front of the back beam. Hounds position The hounds position ex factory is good for the average skipper at say around 80kgs’ for lightweight skippers of around 65kgs lower by 100mm (promotes early mast bend). For heavy buggers of around 100kg raise by 100mm

Rotation

Standard rotation is suited for most, however if you’re a light bugger more rotation can be created by filing back the rotation stops promoting more mast bend.

Boom block hanger

The factory position is ok but I believe the Maricat responds to mast bend in heavy breezes through flattening the sail through mast bend. This is promoted by generating thrust from the boom through moving the block hanger back on the boom 100mm.\nThis also allows the mast rotation to be locked in when sheeted on hard. A desireable attribute particularly for sloops to counter the derotation forces of the jib.

Controls

Make it easy and responsive and keep the control lines as short as possible, readily accessible to hand.

Down haul should be no less than 6:1 and best finishing to swivel cleats each side of the mast looping round the sidestays and ends tied together. 4 to 5mm soft outer rope.

Vang powerful as the rules allow. I used to have a 32:1 lever vang till the rules banned them. Wire and 4 to 5mm soft outer rope 2 part system. Mainsheet 5:1 or 6:1 low profile with enough mainsheet + traveller sheet to allow for heavy weather down wind sailing and absolutely no more. 8mm to 10mm. Heavier mainsheet will reduce the ability to run freely.

Rudder pull downs Standard system is ok but the Nacra pulley system to the deck is far superior and allows you to get out through surf breaks.

Traveller sheet should be as thin as you can comfortably handle ie 5 to 8mm max.

Rigging Cat rig

Leave the boat flat on both hulls facing into wind. Lay the mast between the hulls so that about 2 or 3 ft of the mast (at the step end) is beneath the trampoline. Attach the stays to the mast hound and lay the stays out toward the chainplates. Attach the 2 forestays to the respective bow rings. The tensionsing cord should be extended some 200mm+ from the normal sailing position. Attach the 2 sidestays. At this stage, you are ready to lift the mast and step it. But before you do, have a good look at the apparent mess you have before you. The mast and stays are all connected but laying on the ground they can seem pretty messy. Visualise what it will look like in the vertical. Make sure that the stays are not twisted or caught anywhere etc. You really want to avoid anything that forces you to lay the mast down again, or worse, lose control of it. OK, now that everything looks as though it will be in the right place, you are ready to proceed. It is best to have two people in the process. Firstly, you lift the mast to the vertical on the ground, then you lift it from the ground onto the mast step. Here is how you do it. Lift the mast from a point just below the hound. Check again that everything is rigged in the right sense. You lift the mast to the vertical by ''walking'' your way down the mast and at the same time bringing the base out from under the trampoline so that once vertical the mast will be resting on the ground in the centre of the boat and abutting the mast step. Wedging the mast against the dolphin striker provides added leverage that assists the lift. Keeping hold of the mast, stand on the trampoline (beware wet feet or slippery footwear etc) and once again make sure that everything is rigged in the right sense. Hold the mast about 3 - 5 ft from the base and lift it into the mast step. This operation is manageable by one person but until you get some practice, definitely have the second person stand in front of the mast step and assist with the lift. You are now ready to hoist the mainsail, attach the boom and mainsheet blocks and tension the rig.

Rig tension

Tension the forestays cords to give the desired rig tension which is just off sloppy for moderate hiking conditions. Firm for light conditions where some slop is evident. If the breeze is heavy then tension up the sidestays to give a firm rig tension. De-rigging is the reverse. De-tension the rig, remove the mainsheet blocks, boom and mainsail. Stand on the trampoline and steady the mast while the other person releases one of the side stays (the downhill stay on sloping ground). Lift the mast from the step and place the base on the ground in front of the front beam. Keeping hold of the mast, get down off the boat and move to the front of the mast. Then lower the mast by ''walking '' out toward the hound, again using the dolphin striker to help control the base of the mast. As you lower the mast to the horizontal slide it part way under the trampoline to slacken the sidestays. Check all shackles are tight and circlips and pins secure. Tape up all the critical ones particularly before a championship series.

BASICS – on the water

How do I right the boat if it goes upside down (turtled)?

Get your weight as far aft as possible standing with your foot against the rudder and leaning back and out. The boat will swing around to a sideways position from which you can right it in the normal way. If your mast fills with water the boat will be nearly impossible to right so make sure it is watertight. You could try attaching a float to the top of the mast while you are learning to help prevent your boat inverting once capsized. Good practice is pressure test the mast and replace/ seal all leaking rivets and fittings.

How do I tack a cat rigged boat?

Ideal roll tack

Get lots of speed, flying a hull Look for flat water spot ahead or 2nd choice is tack going up a wave as the bows break through the top. Move smoothly back to the rear beam as you commence and progress the tack. Move the rudder smoothly to 45o Hiking as the windward hull comes down to the water keep on the this hull till the bows have passed through the eye of the wind letting off about a metre of mainsheet as you start to cross. If your responses are good allow the other hull to just lift before crossing. As you come across and change hands with the tiller ensure that the tiller remains at 45o Bear off as you get in position to get boat speed and sheet on coming back onto course. With practice this can be done almost as fast as a dinghy. It is always harder to get a cat rigged boat through a tack so here are some general hints. Get lots of boat speed before attempting the tack. Uncleat the sheet before moving the rudder. Move the rudder to 45o as this should be the optimal steering angle. As you start to turn let out about 300 to 600mm of sheet. At the slightest hint of stalling (ie your roll tack is not working), as soon as the boat loses forward motion reverse the rudders and let out another 600mm of sheet. If you are severely stalled, reverse the boat onto the other tack by reversing the rudder and push the boom out full out. Only pull on the sheet once you are completely on the new tack. Jibing in big breezes If the windward rudder is up – put it down Check sheets and traveller rope for tangles and potential to wrap around things (feet, neck etc). Look for a flat stretch of water ahead or aim to bear off down a wave. Mainsheet should be cleated. Get maximum speed up and smoothly turn into the jibe grabbing the mainsheet and passing it across at the same time swapping hands on the tiller. Do not allow boat to round up – certain recipe for a nosedive. Keep your weight as far back as possible during the manoeuvre. Settle down, clear up the sheets, resume course, flip up windward rudder.

Sail settings –

cat rig Upwind Light breeze

Downhaul just sufficient to take wrinkles out of sail

Outhaul 50 to 100mm depth measured at centre of boom Vang – light tension only

Mainsheet light tension. In light breezes the wind speed at the top of the mast is significantly higher than at the boom thus your apparent wind at deck level may be 40o but at masthead it is 50o therefore pay close attention to the tell tales on your sail. It is very easy to oversheet and stall the leeward telltales on the upper sail. Make sure you have just enough twist. If I feel I am not moving well I generally ease sheet and gradually sheet back on.

Traveller – down about 50mm

Position yourself well forward to keep the transoms out of the water but still keep the bows out from burying.

Medium breeze

Hiking strongly but not overpowered. You will be between the sidestay and rear beam.P

Pull on downhaul sufficiently till boat is sailing with the windward hull just above and occasionally kissing the water. For upwind trim, keep the boat as flat as possible, with the windward hull only just in the air. A lot of people in all forms of catamaran sail with their windward hull too far out of the water

Outhaul no more than 50mm

Vang – Tight

Mainsheet hard

Traveller down 100 to 200mm. Your traveller is your key power control. The boat becomes a lot freer as you drop traveller and does not kick up and down in the gusts but accelerates. However dropping traveller looses in pointing so experiment and play it in the gusts.

Point only when necessary, footing off for speed frequently looses little in height but gets you there fast – and that is the objective.

Heavy breeze you are overpowered

Hiking from a position getting close to the rear beam to keep the bows from burying,

Pull on downhaul till you feel your fingers about to break and give it another 50mm

Outhaul hard on

Vang – Tight

Mainsheet hard on – very – note that when you release the mainsheet in a gust it allows the mast to straighten and therefore the sail gets fuller and gives you more power just when you don’t want it. So use the traveller in gusts and the mainsheet as a last resort.

Traveller down to foot strap maybe even more if it is really strong. Depends on your weight and wind strength. You let it out to a point where you are hiking hard, going fast and not flicking up and down and being blown sideways.

Rotation. When it is really honking allowing the mast to derotate causes the whole top of the sail to fall away and depower the rig big time. Looks horrible but mast have rarely broken. If you do this bring the traveller back to about 100mm or you will lose too much height.

[humungus2]

Well done Rod,

Lots of work has gone into that. I just hope somone reads it so I can have a bit of compertition.

By the way. I was pushing the new boat so hard the other day in a big wind that I had to get over the back beam on a reach. Yes! I nearly did a nose dive which I thought just could not have happend. With Peter on my tail I am certainly keeping my skills up.

[Pointed Reply]

This basic tuning guide has been around for a while but most bits are still pretty right. There is also information on the Maricat web site. Most of the Tanilba guys have ground out their mast steps so the mast can rotate to 90 degrees but others don't. In the end it usually comes down to the guy or gal hanging onto the tiller.

[Pointed Reply]

Bump

[windrider]

Looking for a diagram of rigging for 4.3- Windrider

conv_161.pdf

[NixonJr]

Hey Rod,

I have stuck this so its on the top now

Thanks for your contribution to the forums,

Rob.

[Dr Peter]

What a really useful post. I'd already sorted my rudders and that helped. The big take home I got was the vang tension and the double block on the traveller. Mine was set up with a straight pull and had no finesse at all. It made a huge difference. Two weeks ago I was dicing with a 29er in a club race; usually, those guys are just gone! For last weeks race, a real drifter, I stuck a couple of long d shackles on my front stays and i was pointing as well as a Laser and making progress.

A great post. Thank you. It helped my sailing.

Peter

[Scotti]

Excellent information.

Thanks heaps

Scotti

[Idle]

I have attempted to put some formatting back in to make this information a little easier for me to read (got lost in change of web servers?) and have attached it in case anyone else finds it useful.

Maricat.rtf