RBJ wrote

"4) If others have observed this, how is it influenced by boat weight and hull length (and why) - ie, would the same phenomenon be seen on A-cats, FXOne, and planing F16's such as Stealth/Blade (but not seen on I17 and T4.9)?"

And you replied:
"In your list of examples you have actually listed boats under "don't" that do and visa versa"

I'm assuming you're referring to which boats are plowers/cutter vs planers/hoppers?


No I'm not. I'm refering to diving under spi or remaining relatively stabil. Thus answering the original point of your post.

I all dependent on the hulls and also tuning setup. But I know hullshapes that most of the sailors call wave piercing that confirm the comment that you heard from an experienced racer and I also know a wave piercer hull that doesn't. Therefor the link between wavepiercer lable and diving under spi is not a good one.

This is mostly the result of an explosions of flyer copies which are all called wavepiercers but may be very different in behaviour just the same.

>>I had thought I was classifying the boats as you did; did I misunderstand you?

I was comment on the wavepiercer and spi don't mix; I wasn't at all refering to planing or plowing (or which other synonimes are used for this)


>>>One of the reasons I raised the original question of spi + planing hull is related to another comment you made during the same post:

"With regard to the term planing. No cat planes fully and probably never will. It is indeed more like "having a (small) portion of its weight carried by dynamic forces created on the hull. I personally believe that such surfaces allow you to drive the boat harder without picthpoling and that explains more of the (possible) speed increases than the actual "plaining"."

So I had thought that a cat with planing hulls would be more resistant to pitchpoling and not less so while flying a spi and driving it hard. Yet the experience of one cat sailor goes against this.


I think I have an idea on which boat the sailor making the comment has sailed but I can not comment on specific boat types in this manner in public.

I'll repeat what I stated earlier I know of "wavepiercers' doing well under spi and of wavepiercer not doing well. Visa Versa for "plowers" and spi. Therefor I think the comment made by the sailor is type specific and not "wave piercer" specific.

Of course I still think wave piercer is by now a useless term. It has been highjacket by several producers who make cosmetic changes to their boat to make it look like one but in all honesty don't understand what is really going on with the orginal wavepiercers. Others however do know and here the boats are better behaved.


>>Which brings up a related question: how much of the pitchpoling characteristic of any hull design is due to boat setup/tuning?

Mast rake can be important in the ease in which you initiate a dive, however hull shape determines whether this ends in a pitchpole or not. Therefor I would answer your question with tuning is not very important in pitchpoling and you can't trim it out of the boats without trimming away power or efficiency.

Fast and efficient boats are the ones that allow a boat to recover fully and with ease when it finds itself in a dive. The better the recovery the more powered up a boat can be trimmed and more to the edge you can sail it. Having said this I also know of a boat that can be sailed right up to its edge under full power without much diving or even bow down attitude BUT that will disappear from under you when you step over the edge. It is superior to others all the way up to the edge but you pay for it by having to learn the exact location of its limit.

This may not be the answers you are looking but this setup is a multivariable equation and simple rule often don't do it justice.


>>You and others have showed previously how changing the tuning of a boat can dramatically change sailing characteristics (ie, in reference to BroBru's I17). How much of this one cat sailor's experience might have been due to the boat he was sailing not being tuned well for the challenging conditions - and if so, what can one change on a cat to allow it to be driven hard off the wind cat rigged or spi that would help it avoid pitchpoling?


In general flying a spi on a catamaran will make it less dive sensitive. Quite a number of crews overhere pull spis in big wind not because of performance but because they feel they have a better controlled boat with it. I share this experience. It is weird to see a boat being actually worse off. I know the Dart 18 didn't take well to the spi. The only reason I can think of that would cause a cat to dislike a spi is that a hull doesn't have sufficient bouyancy in the bow and/or stern in relation to the leverage of the rig. I know some builders tried to imitate the wavepiercer concept by remove bouyancy at both ends without changing much else in the hull shape. I would look at these designs first if I had to name designs that could suffers under spi.


>>>Speaking of tuning, one unrealted question: when you sail a cat such as a T4.9 or I17 cat rigged vs sloop vs spi, is it generally necessary to adjust standing rigging (ie, mast rake) or otherwise retune the boat for each configuration in order to allow it to sail properly (ie, balanced helm, pitchpole resistance)?

I personally just trimmed the boat to an good average between modes and leave it like that. However, this does mean you can get some extra out of the rig by retrimming it when you are sure in which your are going to sail. I didn't really experience much problem with helm or pitchpole resistance. You know which boats I sailed and none appeared to be very sensitive to changes in setup. All cats with spi have leehelm, however I don't think this is a bad thing. After all the safety zone for sailing under spinnaker is to your lee and not to your luff as is the case when going upwind. It may not be excessive but that is logical.


Thanks for the great input,

Jerry