I drive my kite as Macca described. I pull the sheet tight during the puffs and sheet it out more in the lulls. Of course I've been doublehanding my boat. I found that I got very good speed downhill if not excellent speed. Furthermore I drive deep with the weather hull just skimming the surface when I can and try to stay in this groove by steering and running the main traveller simultaniously. I understand that this can only be done when doublehanded. So together we ride the puffs by sheeting in the spi sheet, sheeting out the maintraveller proportional to the amount of tiller action. The latter is so proportional that I'm even think about hooking my tiller to the travellersheet directly and sail this way singlehanded. That way I can do the same when singlehanded. The Taipan seems to react very well to this traveller/rudder/spi sheet action. You get a push every gust and ride deep till the lulls come and you head up a bit again keeping the boat powered up and waiting for the next time the afterburning fires.

I do share you feeling somewhat with respect to the boat not going proportionally faster with increasing winds. However I find that my boat under spi very quickly reaches high speeds in only little wind. Much more than I ever experiences on a skiff. After this the cat speeds up a little with increasing winds but as it already achieved a large boost at mild winds there isn't much more left. To be really honest I think this to be the better setup. I much rather have 80 % of the speed at force 3 and 100 % at force 5 or 6 than 50 % at force 3 and than double to 100 % at force 6. You got more earlier on a cat and the net result is that you are always faster (way faster) than a skiff in my opinion. In force 3 more so than in force 5 /6. I also found that I can drive my spi in conditions that I can never drive a skiff in. Typically when we have force 5/6 winds than the surface conditions is way beyond a 49-er or other skiff with wings.

I fully agree with how stable and smooth the Taipan F16 feels under a kite. One has to find the right mainsail trim and most rotation (easy to do) but after that she feels like a much larger boat. I really expected it to by much more nervous due to its short hulls but honestly I find it more smooth and relaxed that the I-18 and Tigers I have sailed in the past.

I've been aware of the Cherub calcs for a long time and I think they give the correct reading of the situation. The whole of the boat is lifted slightly while there is more net pressure on the bows. That is exactly supported by the movements of the crew on board. Under spinnaker I'm way back even more than without a spi. Ergo the bows most be loaded up more. And I agree that any angled sail must have a vertical force component = lift. THe thing here is to realize that the first (bow pressure) is the result of a moment (forces time leverages) while the last is the result of a sum of forces). These are two different things AND independent of eachother.

>>( I'm told the 18ht has a planning hull...),

Some guys will tell you anything. There is no planing or even "true wavepiercer" 18HT at this moment. There are just making things up. If anything he jav 18HT is no more than a 90's generation hullshape with a trimmed deck at the bows and sterns. The end result is consistant with this. It behaves like a 90's displacement hull with reduced bouyancy. In most cases this means "Worse".

The only true wave piercer hulls in cat land (and planing is still tentative) are Flyer A-cat, Bim XJ (a carbon copy of the flyer), Capricorn F18, Blade F16 and Blade F18. The Stealth F16 comes closest to planing of all of these. This one is actually far more planing oriented that it is wave piercer oriented. It needs to be realized that planing hulls and wave-piercer hulls are not one and the same. Wave-piercers work for different reasons and the "piercing of waves" doesn't have much to do with that as well. They perform as they do because of a different distribution of bouyancy.

As far as I'm aware the Stealth is not accepting any serious drag hit upwind. At least nothing I've seen indicates that. It actually did rather well on both courses, with its strong point being the downhill that is true. That was against Taipans. I'm not too sure if the Blade rides with it leeward bow out of the water under spinnaker, but then I have only very limited footage of it sailing under spi. I do know that it was designed to sail with it bow just in the water in nearly all conditions. It is not like the Hobie Fox or FX-one.

The solution in my opinion, if you think the bow pressure is limiting the speed, is to look at T-foils rudders first. This seems to be the most simple solution and can be fitted easily enough to any existing boat. Best would probably be to be able to actively engage the T-foils on the downwind legs. I heared somebody say that the T-foils may not be very effective upwind. And I figured that to make full use of them you need to angle them downward to provide downforce at normal hull attitude (keep wetted surface low) So my immediate thought was to have the T-foils rotate freely upwind. weathervane themselfs and to lock them into a downward angle downhill with a flick lever system. On the other hand I though that by driving deeper I can make more ground in a race and keep the boat fully under control at speed. Personally I feel no need to fiddle here.

Wouter