I recently heard from a very experienced cat sailor/racer that it was his experience that flying a spi in 15 kts singlehandedly on a cat with "planing" wave piercing hulls caused the bows to bury and made the cat difficult to control even though the boat's handling characteristics in all other conditions was great. In contrast, he said that flying a spi in similar winds singlehandedly on a different cat with "plowing" wave piercing hulls the bows didn't bury as much. He summarized his comment by saying something like "spi + planing wave piercing hulls don't mix!". Clearly this is one experienced guy who likes to push the limits, but it would be nice to know that if the wind builds that you could still control your cat while flying a chute. This was the first time I had heard this issue raised in this way and stated so clearly.

My questions are:
1) Has anyone else seen this? Cat and windspeed?
2) Has anyone seen this on cats with "plowing" hulls? Cat and windspeed?
3) Why does this happen to "planing" and not to "plowing" hulls?
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)?
5) In picking a new boat, how important is this issue?

Jerry

It'd be interesting to see a planing cat despite the fact that its a displacement boat.

Just exactly what is a planing wave piercing cat?
Can you tell us the boat models that were discussed???

Hi MauganH17,

Just to clarify, by "planing" hull I was referring to cats with flat bottom hulls like the Flyer A-cat which tend to jump over waves (also called "slappers" by some) vs "plowing" hulls which tend to more smoothly cut through the waves with rounder or v-shaped bottoms. I think everyone agrees all cats are primarily displacement boats with brief periods of planing caused by dynamic lift. I didn't mean that flat bottomed hull designs truely plane and that others don't and are displacement only. See discussion in prior posts under "Singlehanded Cat Sailing"...

Jerry

We realy should be starting to descriminate between different types of wave piercers (I dislike that description as well by the way.) We have several shapes right now after the Flyer introduced the concept. And the Flyer hull is different from teh FX-one which is different from the Bimare shapes which in turn can not be compared to that of the Blade. Some designers try to design "wave piercer hulls" by reducing bouyance fore and aft in the hull. Others by moveing this bouyancy away from the extremeties towards the centre under the main beam. And another implements this by only redistributing the bouyancy in the vertical direction while keeping the destribution in the horizontal sense unchanged. The different paths lead to the boats behaving differently under certain conditions. There is even a difference between the Hobie Fox and the Hobie FX-one in my personal experience. Therefor I don't think it can be stated that :"spi + planing wave piercing hulls don't mix!". It dependent on the design path followed.

The same must be set about displacement boats however. An Inter-18 is different from a Nacra F18 in this respect as well despite the fact that neither are regarded as "Wave piercers".

My questions are:

1) Has anyone else seen this? Cat and windspeed?
2) Has anyone seen this on cats with "plowing" hulls? Cat and windspeed?

No further comment on these points, I'm too involved.

3) Why does this happen to "planing" and not to "plowing" hulls?

It can to happen to both depending on the individual design of the boat.

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)?

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


Wouter

Wouter,

Thanks for your input. A few clarifications:

Can we agree on terms?
1)plower = cutter and planer = hopper
2)we don't mean plane as true planing or plow as displacement only
3)most cats share both of these characteristic depending on many factors including sailor weight position but some cats due to hull design show one of these characteristics to a greater degree much of the time

I had said:
"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?

But in an earlier post "Single Handed Cat Sailing" you had said:
"The cutters more smooth and silent. The Taipan is a cutter and I believe the I-17 is so as well. The FX-one, Stealth F16 and Blade F16 are more of a hopper ... With respect to F16's ; Taipan 4.9/F16 is definately a cutter, Blade F16 and Stealth F16 are planers."

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

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

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)?

Thanks for the great input,

Jerry

Mast rake can have a large effect on stuffing. For hull shape, boats with more bouyancy forward are generally harder to stuff.

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

Wouter,

As usual, thanks for an extraordinary and very clear reply. I've read your comments previously that all wave piercing hulls are not created equal, but didn't make the connection to this specific behavior under spi.

What has become abundantly clear after getting great input from you and others is that to properly evaluate a cat it is really necessary to understand it's sailing characteristics (either in person or via experiences from others who you trust) for each possible mode (ie, cat rigged, sloop, spi, and sloop/spi), with each mode sailed under a very wide range of wind and wave conditions. So in this regard, even the usual good advice often given of "sail each cat once before you buy a new one" should be taken with a grain of salt since you might get a very incomplete understanding from a limited test sail under only one sail plan in non-stress test conditions. I don't like to be surprised!

I am so impressed with the quality of contributors to this forum and the enthusiasm with which everyone shares their experiences, expertise, and ideas. Only in this kind of forum would it have been possible to hear from one experienced sailor "this is what I observed" and get an insightful analysis from another "this is why he may have observed that".

Guys, what can I say but thank-you!

Jerry

Going back to the original question.

My first thought would be that the spin pole is too short on the boat that is burying.

Next I would look at mast rake (WAG 0 to 1 ft aft) and the look for water in the hulls.

Finally I would try to take both boats side by side and if one was still burying, I would swap spins to see if that was it.

The torque from the spin in winds over 10 knots is pretty big in comparison to the torque from the bouyancy at the bows for boat under ~20 ft. So, in general the spin is set to lift the bows. The longer the spin pole, the qreater the lever arm to torque the bows up and the greater the percentage of the force of the spin force that goes into lift.

This even works on boat that have no bows like Waves.

My $0.02's