No. 25 - February 1977


READY ABOUT MORE HELM

Mike Nicoll-Griffith

 

I think I am obliged to reply and add some notes concerning John Charter's article "HELM" in issue number 23: September. Here is a little technology from the rice paddies to help you through the winter.

 

If Sally puts the diagrams on the opposite page, you won't wear out your staple. (The one put in by the Official Class Association Stamp Licker and Envelope Sticker that holds the Newsletter all together.) With luck, you'll get the diagram the right way up, too. (Ed. note: Come on, Mike! We've only been upside down once in 5 years!)

 

a) THE SAILS: In Fig. 1 we are looking down on a heeled T22, close hauled on the starboard tack. (Always do this sort of thing with right of way. Someone may be coming.)

 

The circle in the keel can be considered as a pivot point. The arrow through it represents the total water resistance force which holds the boat back and to weather. Remember we are looking straight down, and we can see the keel because of the angle of heel.

 

The arrow through the X on the port side represents the force from the sails. When the arrows are in line, we have neutral helm. (Check this with a ruler.) If you now imagine what happens to the arrows when the angle of heel is changed, you can understand weather and lee helm.

 

In Fig. 2, the boat is on a close reach under spinnaker. Because the upper areas (the shoulders) of the spinnaker are so broad, the X in this figure is very high above the water level. This means that a smaller angle of heel will cause a larger weather helm.

 

Lee helm is not possible on a close spinnaker reach unless you are heeled to weather.

 

As we approach hull speed on a spinnaker reach, the arrows (the forces) become much bigger and the effect is magnified. A broach occurs when the rudder can no longer cope with this. To flatten the boat; you may be able to release the spinnaker sheet a little and move the X inboard.

 

b) UNDERWATER HULL SHAPE: My experience is that the effect of the sails is about ten times that of the changing hull shape often mentioned.

 

c) THE RUDDER: The position of the rudder area relative to the line of the pintles determines how much of your weather helm you will actually feel. Because the standard rudder rakes aft such a lot with those delicious sweeping curves, you need much more muscle on a T22 than on a Mirage (for example). Have a look at figures 3 "T" and 3 "M". I haven't seen the 1/4 Ton rudder, so can't comment.

 


 

d) SAILING FLAT: Putting my light weight teenager and my 10 year old son on the weather rail never helped me much in a blow. John mentions feathering, briefly, and talks about keeping the boat just on the edge of luffing. This may be a bit misleading, and is probably the Number One Myth of upwind racing in heavy weather.

 

Your best upwind course is a balance between hull speed and direction sailed. In heavy weather, the boat will go close to hull speed whether the jib is luffing or not. My choice is to sail the boat at 15 degrees heel (or at 5-3/4 knots if you have a knot meter), and not look at the jib.

 

 

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