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Warren,

Weather helm is a frequent topic on various Catalina message lists, and I expect on other boat brands as well. There is no simple "answer" for your observation, but I will toss out a few thoughts.

The "best" weather helm is considered to be a few degrees of rudder, perhaps 3 to 5 degrees. This would be equivalent to about one spoke of the wheel. What is the "significant amount of weather helm" you see?

The performance you experienced is "typical", but it may or may not be "normal". The first thing to check is the general appearance of the rig. Does it appear that the mast is centered, and does it go straight up without bends to port or starboard? Do the shrouds appear to be about the same tension? I am not talking about a professional re-tune; merely a quick inspection to eliminate any obvious problems.

Weather helm is caused by a number of factors, including environmental, boat design, actual boat construction, rig tuning, sail trim, and steering. One of the most important factors on "fat boats", such as the C42, is the amount of heel. The hull shape is such that a boat heeled 20 to 25 degrees would experience significant weather helm from the water forces alone. Therefore, the first rule of control for weather helm is to drop the traveler. It is not necessary to let the mainsail flog, but in some cases it may be advantageous to trim for an s-shape at the front edge of the sail.

The difference of performance on the two tacks can be caused by asymmetry in the boat or in the rig tuning, but there are other causes as well.

It is common that the wind direction and the wave direction are not exactly parallel. This can cause significant changes in boat speed and therefore overall performance on the two tacks. Any significant current can change the apparent wind speed on the two tacks.

The exact steering of the boat can also affect apparent weather helm. Do you steer to a heading?, to telltails?, to sail shape?, to the wind direction? The telltails on roller furling headsails will often work just a bit differently on the two tacks, because the sun protection strip is only on one side. Wind direction indicators are notoriously difficult to keep aligned.

Some people will discuss the center of effort from the sails, but moving the center of effort by an inch or two is not going to make much difference at 15 knots, and it does not explain the asymmetry.

After you have reefed both sails, and in only 15 knots of wind, you should not see any troublesome weather helm. Something is not quite right, but it will take a bit of investigation and testing to figure out the best solution.

Regards,
Gene Fuller
Yorkshire Rose, C42 #870