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New Maricats and parts


humungus2

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Hay Mick maybe we can start a dear mick column!!

Here we go! Dear Mick when I sail my old maricat down breeze it is really difficult to sail with both rudders down. There is no helm going to weather and it feels light and easy to steer but down breeze it is a dog with a mind of it's own. CAN YOU HELP ME??

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Sure Scuttlebutt, There are many reasons for this. The first solution would be to kick a rudder up going down wind. Just because there is no helm dosent mean there itsn't a problem. The next is try tilting the mast forward one hole or shift your body weight forward. I find that not hitting other boats or marks on the way round will give you the edge you need. Good luck, I hope this helps.

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Wow Mick Thanks so much you have inspired me yet again to strive for perfection. The whole point is the boat turns very dramatically and then I hit the other boats! I suppose if I was in front it would not be a problem because there would not be any boats around me!! It still has some helm down breeze with only one rubber. is that normal?

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No Mark, this is not normal. In fact this is unheard of. Knowing that your Mast rake is further back than mine, I could only sugest you move it forward one hole and see if that changes things. Your cat must be a very special cat to be so finly ballanced. I may need to try it for myself. Infact I may even do just that. I assume it happens when you have the jib up?

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Dear Scuttlebutt and Humungus,

I had similar problems with my new boat, it had dramatic lee helm so that off the wind it would just head down, which was a bit scary in a breeze.

I too had the problem of running into other boats as I was back in the pack.

I packed out the rudders which kicked them back a bit and this now gives me a bit of weather helm...........but still back in the pack......

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Wow Mick Thanks so much you have inspired me yet again to strive for perfection. The whole point is the boat turns very dramatically and then I hit the other boats! I suppose if I was in front it would not be a problem because there would not be any boats around me!! It still has some helm down breeze with only one rubber. is that normal?

Why would you carry rubbers on your boat Scuttlebut, the proof is in the pudding that you have felt no need for them at other times.

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There would be 4 separate factors at work when helm is generated:

- rudder rake: the amount of rotation as the blade swings down. This mostly affects how much force is required to steer the boat. If the tips come under the boat too far, then the boat will steer itself and tend to pull the rudders into a turn. Not good at all and likely to lead to a blade snapping. With the tips just in front of the steering axis (sight down the rudder pins) the steering should be very light; ideal. With the rudders raked back, the steering will be heavy and hard to keep the boat going in a straight line due to excess force on the tiller extension.

- mast rake: more mast rake = sail further back on the boat, generates weather helm when going to windwards. You need this, as weather helm generates force to windwards, which helps pointing. More rake also helps to stop nosediving off wind, as the sail is generating a small amount of vertical lift, like a windsurfer. Not enough rake puts the sail forwards and can generate lee helm; tendency to bear off all the time.

- body position; where you sit on the boat affects where the boat's centre of hydraulic life is generated. Move back and the centre of effort moves back, so the boat will tend towards lee helm. Move forwards and the centre of effort moves forwards (ahead of the sail centre of effort) and the boat generates weather helm. Always get forwards when going upwind; don't worry, the boat will drive its nose through waves.

- rudder geometry; the amount of bend in each tiller arm, & the length of the cross bar. The bend in each tiller arm creates Ackerman steering geometry, which helps during tacking (the inside blade turns more than the outside one, reducing drag). The length of the cross-bar will affect if the blades are toed-out, parallel, or toed-in. Parallel is usually the go. Lift the back of the boat onto some garbage bins, swing the blades down, and measure between the leading edges and trailing edges. Should be the same measurement. Getting this wrong would make the boat slow, especially in light winds, probably not affect helm that much.

There is another factor is randomly losing control of steering; the rudder blade profile. If the blade is not properly shaped it will stall at speed, so that you lose control. You feel this on the tiller as the steering force suddenly goes away, and you look back and see a trail of bubbly champagne behind the rudder blade. A blade that has a round leading edge, flat sides, and slightly tapered trailing edge will do this. More info at: http://www.stirling.saradioyachting.org.au/Sailing_Hints/rudder.htm

Hope you can sort it out!

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Thanks Tony. will play with the mast and rubber rake first. These foils don't cavitate or generate air bubbles now, ( i reshaped them last year) because of an injury I at times have to let the tiller go to use that arm to adjust main or traveler. as a result I have set the boat up with no helm going to weather. may have to compromise. I willtry not to T bone you at Canberra this year Tony.

regards Mark

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