Ahh Bill,

Not much has changed. I'm really not hung up on the ARC-17. I expect it to be a great boat and would love to see more of them on the water. I'm still comfortable with you as well; next time I see any of the SC in NL again I will again take their picture and send it to you (like I did a Texel) and convey the regards of their crews.

The thing that got me going was the "story" around the ARC-17 design and its quite implied dissing of several other designers and related designs.

Really you are not the only designer who has experimented on cats or taken measurements. Nor are you the only one confronted with the issues around a spinnaker. You solved it in your way the others in their way. The real life results are different from what was stated as undeniable truth. Therefor the theoretical model you used was not describing the reality accurately. It is by all means a "feels right" model but inaccurate none the less.

Without hard proof the views expressed become dogmatic. Hence the gauntlet thing.

Now on my my part I haven't quite worked out why it behaves differently but that is mostly because of lack of effort. When something is not a problem than I'm less willing to explain why it is not a problem. I tend to accept it and move on.

Factors that may result in the different behaviour :

-1- Spi is fitted asymmetrically to the boat. The normal rig pushed the boat along almost along the centreline. The Spinaker is to the lee of this and thus its lift factor will induce a weatherhelm effect as well.

-2- The conponent of the total lift force that lies along the centreline may be several times greater than the component perpendicular to the centreline. It may be that

Leehelm component - weather helm component = lever 1 * force perpendicular to centreline - lever 2 * force along centreline = close to 0 or very small.

To give another example. Yachts without a spi have greater weatherhelm on deep downwind sailing legs than on upwind legs. With spinnaker they balance out again. A different setup I agree but it shows that there is more to the system than the simplied model that was used in this thread.

This is my last post in this thread.

Now, indeed Fair winds to you and I'm looking forward to more race results. If anything it helps to improve on the understanding we both have on the subject.

Wouter