I'm calm, I just "speak" (type) whats on my mind. I like Mary's analogy though, made me chuckle.

Perhaps Maugan was a bit strong...but the manufacturer and designer bashing is wearing on me too. If everybody else is so bad why do they sell so many boats? Bill, I don't think anyone doubts that you have designed some great boats but there are a lot of boats out there designed by other smart people too.

>>The instrumentation that I use for testing is made up of a compass and speedometer and slip angle measurement. I also carry a windspeed instrument.


And I thought your were talking about gyroscopes, GPS units and stress sensors. Everybody carries a compass on board and speedometers are outdated. Just use a GPS unit with tracking ability and make sure there is no current on the body of water you're sailing on. Having a reference boat around with reference crew helps a lot as well.

Talking about GPS tracking here is one from my personal archive. Note how the top speed (30 km/u=16 knots) of the sloop rigged craft is reached on ALL courses !

But then again I'm not a real designer.

Wouter

Hi Chris,
Slip angle is the angle between the boat centerline and the path of the boat through the water. It is simply a weather vane that runs in the water and the base is clamped to the boat. The vane is connected to a pointer just above the clamp/bracket that indicates the direction of the vane in the water as the boat sails. The difference in the vane indicated direction and boat centerline is the slip angle.
I have done alot of sailing with instruments on my boats because I don't have another boat to sail against so I sail against the instruments. This has helped me develope boats that are the fastest US Sailing has on record and cost 1/15th as much as a Formula 40 boat for example.
Bill

Hi Magee,
I'm only stating facts,not rhetoric. If you don't like them, I'm sorry. I wrote the comments that you don't like in the style I did for emphasis. I think boat safety is NUMBER 1 in order of importance. That is why the SC/ARC boats are the shape they are, elliptical hull cross section shape. That is why all SC/ARC boats come with a righting system from the factory. As soon as you leave the shore on a beach cat and the water is over your head, you are "at risk" and your beach cat put you there. Your beach cat better be able to take you out of an "at risk" situation, like a turn over.
SAFETY, SAFETY, SAFETY is NUMBER 1 in order of importance in any boat design.
And by the way, Magee, some day all beach cats with spinnakers will have the daggerboards close behind the main beam or maybe just in front of the main beam. It is just going to take a while for them to get there.
Some day all beach cats will have self tacking jibs. It is just going to take a while for them to get there.
Some day all beach cats will come from the factory with righting systems. It is just going to take a while for them to get there.
Good Sailing,
Bill

You are right, Wouter, you are not a real designer. You are a buyer and a user and a talk abouter. Back in the 1970s and early 1980s when I was doing my basic beach cat design/study work, there were no GPSs. What would you suggest I do; wait until the 1990s to gain understanding about the design and performance of beach cats using a GPS? The last clean sheet design I did on a beach cat was 1979, the RC27, winner of the Bol De Or race in 1989.
Dream on, Wouter.
Bill

Bill,

What have I done to deserve :"Wouter, you are not a real designer. You are a buyer and a user and a talk abouter" ?

Apparently I'm also a GPS user taking measurements upon which to base sound conclusions IN 2003 !

Not 1978.

And who exactly were you refering to in :

"... who speak loudly and don't know what they are talking about. They have never built a boat and never done scientific studies. Never put instruments on a beach cat and taken measurements upon which to base sound conclusions ..."

I get the funny feeling that that "who" is somebody I know personally.

Wouter

Hello to EVERYONE,

...just so you know,..I learn from ALL OF YOU!

...just so you know,.. diversity and different points of view is what drives innovation

..you all are just great,.....except for one ting, mon

...you should be packing up your boats to come sail down here....Rolex in St. Thomas is last week in March, 5 days later is BVI Regatta

...we can sail all day......

regards,
Bruce
St. Croix

ps; my next boat is a ARC 27,...I need something a little bigger down here

Man oh man. I love the islands. If I don't get a job with the FAA, My Wife and I are just going to sell everything and move there. I'll figure out where to work once I get there.

Hi Bill,

What you (and others) said about lee helm under spi (without CLR correction) sounds both obvious and right and is concordant with many peoples experience; however, I still wonder if it's as simple as you say because today when I discussed this very issue with an experienced I20 racer he SWORE to me that he has a nearly neutral helm under spi (as well as upwind as a sloop).

Why?

Could it be that when one raises their boards off the wind and significantly reduces the magnitude of their CLR the migration of the CE becomes a non-issue (ie, they are not seeing lee helm because they are side-slipping downwind on their broad reach)? This effect might be pronounced on cats with flat bottomed (semi planing) hulls and not observed on cats with deeper hulls - hence different sailors observe different amounts of lee helm. Also, at speed, couldn't the rudder/aft hull be generating sufficient lift to compensate for some forward sail CE migration (when their boards are raised)? Finally, wouldn't the very presence of a spi augment the mainsail's lift (ie, slot effect) effectively moving the aggregate CE back somewhat? (I hope my inexperience and/or naivete isn't showing too badly...).

Who else out there has spi experience on an I20: do you see lee or neutral helm? Anyone else out there on any other (non ARC/SC) spi cats ever see neutral helm?

Jerry

Jerry

I have followed this discussion with interest since I am the designer/builder of the Stealth F16, one of the boats mentioned.

Most of the posters are right, and are actually agreeing with each other, but unfortunately the argument has become a personal one and the answers to your questions are a bit lost in the mud that's flying around.

Your question about whether spinnakers produce dificulties in certain types of boats.

Well I think that it is too simplistic to put cats into these two camps of Hoppers and ploughers, my experience is that all the cats around today are pretty easy to sail with spinnakers. Some respond better than others but I suggest that the main difference is in the developement that has gone into the boat in the first place so that it is more a question of refinement rather than, the effect that the hull shape has.

next on the point of weather helm or lee helm

It is a simple fact of life that if you stick up a spinnaker you move the centre of effort forwards, now if you have a balanced boat to begin with you will end up with lee helm, if the boat is balanced with the kite up, there must have been weather helm before you put it up. You cannot have a balanced boat both ways unless you mave the daggerboards forward when you put the kite up.

Some boats, the I20 is one, have very balanced rudders, so that you cannot tell if there is weather or lee helm, but it is still there.

Bill is right in that his design will make a more neutral helm when the kite is up, but he failed to mention that his design must have more weather helm when the kite is down, its just that he has balanced rudders so you can't feel it.

The real question is whether or not any of this is a problem, and the answer is that it is not, just select a boat that has been designed by a good company, and develeloped with the spinnaker on it and you will have no problems with any of this.

Any of the boats you are looking at will do in this case

Bill,

I have some questions on slip angles going to WINDWARD, and ballpark numbers are good enough, for as they say 'government work'. What kind of relative numerical difference between board vs boardless?


For say SC20 catamaran (which I have had the pleasure to sail on):


Is slip angle more practical as a design tool, than for practicing by yourself to improve VMG?

The slower you go the higher the slip angle, and the converse, the faster you go the slip angle approaches zero to the same true wind angle?

Going to windward, what angle to the true wind will the slip angle begin to zero out?
(mathematically never, but for practical use go to windward)

Is there a boat speed at which point the slip angle almost zero's out?

Did anything supprise you, while you were doing your research on SA?
ie. the rate of change of slip angle from 1kn to 10kn.

Using a slip angle you can determine the optimum amount of board to use for a given wind speed? and if so, any comments?

The higher a cat points into the wind the higher the SA? For practicing to improve VMG would you sail lower angles to the true wind until SA plateau's out? If so when does it plateau out?

Bill, should I buy North's SA meter-z1, or Elvstrom's SA A04-meter? (LOL)
Thanks again,
Chris

Thanks for making the answer so clear, John, as with all your advice. A while back I asked how to get rid of lee-helm, the answer came from John : Rake the mast back until the lee-helm is neutral, or at least not too unmanageable. Then rake rudders forward so that the weatherhelm upwind from increased mast rake is not a problem. It`s still there, it still loads up the rudders, but it isn`t transferred to the tiller, so you get to keep your shoulder joint in one piece. Apparently some weatherhelm helps the boat track upwind as the loaded up rudders create lift. (If I`m mis-informed here please don`t kill me, I spend my time designing buildings, not boats, and very seldom consider the hydrodynamic properties of concrete, although I imagine they`re not worth discussing. No, this is not an invitation to ressurect the thread about concrete canoes ).
Although my boat was designed without a spinnaker in mind, I`ve found that this advice has helped tame the rudders.

Cheers
Steve

“Perhaps Maugan was a bit strong...but the manufacturer and designer bashing is wearing on me too. If everybody else is so bad why do they sell so many boats?”

Come on Jake…you already know the answer to that one…LOL…MARKETING!!!! More than quality of design... More than quality materials... More than after the sale support...it’s all about MARKETING! If you can get a person emotionally involved with a product, logic goes out the window.

What do you think was the cause of Hobie selling so many H16? A stellar beach cat design? Or the most brilliant advertising campaign in catamaran history selling the “Hobie way of life”?

How can you get mad at Bill for stating known facts about the H 16?? How can we move toward better catamaran designs if everyone pretends “it doesn’t get any better than this”, and ignores the glaring short comings of past designs? They call that denial…LOL

What I see in this thread is, logic clashing with emotional brand loyalty.

Bob

FYI:

I'm far from brand loyal to hobie. In fact, I'm still quite bitter about quite a few things about my boat, and feel that hobie should have given me a more straight forward answer about it.

Which is why my next boat is non-hobie. Its actually manufacturer-free, which I love.

Hi Jerry,
In answer to your first question: A balanced rudder, a rudder swept forward until 20% of the rudder area is in front of a line through the pintle axis, will feel neutral, light touch, no matter what the side load on the rudder.
Further discussion:
How did we get where we are? Why are CB trunks on beach cats located at or very close to the shroud chainplates? Answer: Because that is where the CB trunk should be located relative to the CE for the SLOOP rigged sail plan. Now add the spinnaker. Does anything change relative to the CE and CLR locations? I think so and the proof of it being so is that so many boats have lee helm with spinnakers up. What can be done about this? Lean the mast back which moves the spinnaker aft. This moves the whole sail plan CE aft and brings the CE and CLR into better alignment with spinnaker up and may be sufficient to get close to a neutral helm for most spinaker sailing situations. Now, how does this leave the CE/CLR situation without spinnaker or sloop rigged? We have moved the CE well aft from the normal position with the large amount of mast rake. We have unloaded the daggerboard and loaded up the rudder. (Remember the N6.0s, Worrell boats, with spinnakers; the masts were raked way way back. This was the correct trim because they were going to sail all day with spinnakers up.) This will make the rudder prone to stall sailing to windward but once you know it is touchy, you can live with it. A larger rudder would be an improvement in this trim/balance situation because the rudder is carrying a larger side force than it was originally designed for.
This situation of trying control the CE migration due to adding the spinnaker to the sloop rig led me to the CLR design scheme that I call "shared lift". The increased sharing of sail generated side force is being sharred between the centerboard and an oversize rudder. Instead of running a large amount of mast rake to move the CE aft, I have chosen to move the CB trunk forward and run a more normal amount of mast rake. The rudder side load increases with more mast rake or moving the CB trunk forward so the rudder is upsized in both cases. The CB side load has been reduced; it can be downsized. Sizing the centerboard and rudder to match the loads they carry will reduce the drag they generate due to making lift.
Good Sailing,
Bill

Hi Bill,
I have often wondered why there are not good slip (call them leeway) indicators on the market. They give information that is not unavailable from a GPS and a compass in practice. An inexpensive flux gate compass might be within 2 or 3 degrees - just no good at all for measuring leeway.

One tough part is keeping the vane perpendicular to the water. A pendulum seems like a good way, but then you have to damp the swing somehow (maybe use an Airpot?) AYRS once had plans for a leeway indicator but it mounted to the bottom of the hull, and did not remain vertical. Maybe there is an updated version. Now, if you could indicate apparent wind direction on the same display...

I really appreciate the technical portions of your posts.
Thanks for taking the time.

Talk to you later
-colin

Bill,
What I understand from your post is that putting a larger rudder set on the boat will have the same effect of "load sharing" whether you move the CB forward, or rake the mast back ?
If you upsize the rudders, is it necessary to make the CB`s smaller in area ?
Obviously can`t move my cb cases forward, so I`ll go with the "more rake" option.

Steve

I think you guys are making this way more complicated than it needs to be.

All older designs that add a chute end up with lee helm because there COE was not designed to work with a chute. Some people try to correct for this some by raking the mast waaayyyy back but it can't correct for all of the lee helm.

New boats like the I20 have Neutral helm upwind and downwind because they were designed to balance the helm. They moved the front crossbar forward to balance the boat. The I18 is also designed like this.

However the Hobie Tiger still seems to suffer from lee helm issues. However that lee helm doesn't seem to slow the Tiger down any as it is competitive with any F18.

I just heard this past Sunday that Performance Catamarans has a larger rudder now available for the I17R. It is not class legal yet but is available.

As it is now, I can only rack back so far until I get some rudder stalling problems going to windward.

Tom Turlington

I17R #124