Hi Bill,

Thanks, but I understood you the first time regarding how shared lift solves the CE migration problem when flying a spi. What I was asking was why an alternative approach wouldn't work just as well if not better. So, without raking the mast, when flying a spi, why not just move the daggerboard forward to a second daggerboard well to match the new CE? And when taking the spi down, why not just move it back to a more aft position? Although it would be an extra step during changing from upwind to downwind, it seems like it would give a balanced helm in all conditions just as well as the shared lift approach. I'm not a boat designer with your years of experience; I'm just trying to understand why this alternative approach is not used.

Jerry

OK Bill,
Explain something to me.
ALL Supercats, SCs and ARCs were and are sold WITHOUT A STANDARD SPINNAKER.
How long has Aquarius even offered the OPTIONAL SPINNAKER?
You told us that to make the ACR 22, you merely added two feet to the bows of the old SC20.
You have continually stated that a spinnaker boat MUST have daggerboards relocated and different rudders in order to handle the change in sail CE.
How is it that your boats are immune to that "Bill's law of physics"?
Is Aquarius selling unbalanced, poorly designed boats which need a spinnaker or unbalanced, poorly designed boats which aren't designed for a spinnaker?
Are your boats designed for spinnakers or not?

P.S. You never have told us the name of the other "boardless 17foot beachcat" that yours is so much better and faster than.

Wait a minute Bill...you moved the board forward to counter lee helm induced by the spinnaker and agree that the rudder loading is increased upwind. To that point you can make the daggerboard smaller but the rudder bigger. Somehow you conclude that the forward daggerboard placement also helps prevent rudder stalling upwind. But you just said the rudder loads are higher upwind now as a result of the daggerboard placement - did I miss something?

Supose we took an I20 and moved the boards forward as you prescribe (this boat runs very little mast rake and it's forward beam is very far forward on the boat). This would only make the windward rudder stalling problem more severe.

Hi Jerry,
Two daggerboard positions would work fine.
Bill

Hi Jake,
With the forward located CB and spin up everything is in balance and no lee helm. Now take the spinnaker down. The CB is still forward. Therefore the CB will be exposed to and carry less of the side load from the sail because the sail CE is now further behind it. What other foil can carry side load? The rudder! Now the rudder will carry its norman side load plus the additional side that the CB is not carrying because of its forward location. The next step is to match the CB and rudder areas to the loads they are carrying. Therefore relative to their base sizes, the CB can be made smaller and the rudder should be made larger. This results in the same effective CLR location as the base boat configuration but with the forward CB location, the CE cannot get in front of it, spin up, to cause lee helm.
Jake, the forward daggerboard placement does not help prevent the rudder from stalling. The increased rudder area helps prevent the rudder from stalling. The trem is called rudder loading and its units are force per unit area or for example pounds per square foot.
Bill

We're looking for solutions of problems that don't exist.

Why does Bill think that leehelm is a "dragon" ? Moreso than weatherhelm ?

Does any of you realize why a boat is setup for weatherhelm upwind ? It appears that the want for weatherhelm has become a dogma that must be satisfied at all costs.

-1- You have weatherhelm on big boats because that is the safety zone for them and because tacking becomes difficult without it.

-2- On smaller boats you have it in order to get some positive return on an item that otherwise only introduces drag.

On downwind the first point is useless; the safety zone here is to lee. How about weatherhelm when singlehanded doucing the spi ? You rather want the boat to track downwind then weathervane up. BLa bla bla Balanced rudders, bla bla bla. IT IS STILL WEATHERHELM ! Put your rudders sligthly of centre and you're gone.

Point 2 is totally mute on downwind legs. Good crews pull up their boards because alot of lateal resistance is really not needed on downwind legs. They leave a smaller area in place to keep some minimal sensitivity to steering. This moves CLR forward as well as on all boats the CLR component of the hull alone is forward of the daggerboard.

I can honestly say that I have never met a leehelm dragon while sailing a cat that was designed to sail with a spinnaker. And to complete it ; I never saw that dragon after adding a spi on other boats except the Dart 18 and a handfull exceptions as well.

I did experience the downsides of shared lift on the 49-er skiff and the downsides of long spi poles.

Excessive mast rake due to spinnaker then ? Nop, haven't seen it or even needed it on my own boats. Mast rake on Hobie 16 or even Taipan 4.9 then ? That is for other reasons and we can't really say that it is holding these boats back CAN WE, Bill ?

Spi pole length at 50 % of hoist height spi to prevent diving ? Great ! F16 runs poles of 3.5/7.5 = 47 %. What a difference those 50%-47% = 3 % makes ! That just doesn't fly with me. So I see really no need to put a longer pole on my F16.

What else was introduced to make the ARC-17 appear superior to all other designs ? Ohh yeah shared lift.

Massive tiller loads when the rudder kick up or when leaving the beach with the rudders trailing (unbalanced rudders !)

In my surf ? No, thank you !

Not using shared lift on other boats makes them slow or slower ? Hum, ARC-17 with spi = rating 70.2 ; Taipan 4.9 WITHOUT spi = 68.1 and to show that there are no ill feelings between us we'll just forget about those 26 % in more (main+jib) sailarea that Bill has put on the ARC-17.

I say that sums it up quite nicely. Thank God Bill uses shared lift on the ARC-17 or else it would be sailing of a rating of 75 and be looking over its shoulder for the fastest Hobie 16's I suspect.

A while back Bill also chastized all other designers for designing overweight boats and you'd expressed F16's were nothing special at 107 kg including all sailing gear !

Well, didn't he prove us all wrong by making the ARC-17 = 126 kg EXCLUDING the weight of the sails (min 8 kg) and spi package (min 5 kg). This puts you on a level with the 1976 Dart 18 design which is of equal length.

To daggerboard wells then : one for upwind sailing and one for downwind sailing ?

I will garantee you that you'll be at the leeward mark behind all boats that use only one daggerboard well.

How much time does it take to move the two boards from one well to another ? 10 seconds ? That is quite fast.

10 seconds that you could already be travelling at full speed under spinnaker = 50 - 100 meters less distance travelled ?

I can assure you that you will never be able to compensate for this loss even if the new position of the boards would make your craft more effecient.

As it is right now in the F18 a 3 second delay in setting the spi at the A-mark is enough to loose you 1 to 5 places in the field.

A lot of crews don't even readjust the jib sheet and outhaul of the main in tight racing as that takes to much time in which they can easily loose a tactical beneficial position. Most of the time they do that later in the leg during a lull or when the skipper has one hand free. Getting the spi up quickly is the most important thing. Repositioning the boards is not what you want to do if that delays the setting of the spi. That is even IF it would be necessary

BECAUSE

The balancing of the rudders that Bills shared lift needs to get rid of the weatherhelm feel on the upwind legs will ALSO remove the feel of the leehelm on downwind legs that other boats MAY have.

So the whole discussion comes down on wether having leehelm on downwind legs (not the feel of it as that can be taken away by balanced rudders) is a SIGNIFICANTLY bad thing performance wise ? If leehelm is assumed to be present, that is.

This does not appear to be the case. And untill a newly designed shared lift ARC F18 starts beating all other F18's on the course I think we'll be at a loss to proof that it does significantly influence performance in a bad manner.

Wouter

Jerry,

I let go of the tiller if I am going forward to adjust downhaul because holding the tiller while moving around on the boat causes me to veer all over the place. Occasionally, I will pull the mainsheet with both hands while on the wire, so I set the tiller down, sheet in, and pick the tiller up. I also put the tiller to rest if adjusting outhaul, mast rotation, or board position. Any one of these is a brief interlude of letting the tiller rest unattended.

Bruce,

I run my boards about 8" up all the time. If I thought I could afford the time, I might pull them another 12" when going downwind but for now, feel that it does not provide enough benefit for my "'round the bouys" racing to take my mind off steering the boat to go play with the boards up and down at A and C marks. I have not seen any difference upwind with my boards up 8" and all the other I-17R's with their boards all the way down.

Hi Wouter,
I saw a T4.9 at the Tradewinds Regatta two weeks ago for the first time. That boat looks like a great design. Did you design that one? It reminds me of Poison Ivy.
Good boat design has weather helm for two reasons: 1) From a boat performance point of view you always want weather helm. The daggerboard is always generating lift to windward. When the rudder is lifting in the same direction, the induced drag from the two foils is a minimun. If the rudder is producing lee helm, opposite the daggerboard, then the daggerboard must generate lift equal and opposite the sail side force plus generate additional side force to windward to overcome the negative side force the rudder is generating, lee helm. This situation, lee helm, makes the daggerboard work harder, generate more lift, which makes more drag. 2)Helm satbility. You want the helm to always to be pulling lightly in the same direction from the skipper for ease of handling. You do not want the helm to reverse between weather and lee helm, especially unexpectedly. This makes the boat difficult to sail well and it is draggy underwater; a slower boat results.
I'm not going to address the rest of your comments because I see an ugly attitude and your goal here is not to help anyone.
So long,
Bill

Hi Sam,
All SCs were sold without spinnakers. That was before 1992, 1978 through 1991. In 1992 the product name was changed to ARC products and spinnakers and self tacking jibs etc became an option or standard on all products, the 22, the 27 and the 30. See the Aquarius-Sail.com web site for this information. These products were/are designed with spinnakers.
>I'm sorry I forgot, the 22 also has the CB trunk located right behind the main beam to prevent lee helm with spinnaker up.
>I am saying that moving the CB forward is a better way to trim a boat out with spinnaker than raking the mast back which leaves the rudder overloaded and the CB underloaded sailing to windward without spinnaker. The boat will sail to windward like this but the induced drag from the CB and rudder is greater than it could be. The boat is out of trim sloop rigged.
>A boat with centrboards moved forward to accomodate the forward migration of sail center of effort due to the spinnaker and downsized boards to match the smaller side load they now are expozed to in this new forward location and upsized rudders to match the new increased side load they are exposed to due to the forward located centerboard HAS THE SAME CENTER OF LATERAL RESISTANCE as the boats original CB/rudder arrangement. The advantages here are: 1) that the centerboard is so far forward that the sail CE with spinnaker up cannot get in front of the centerboard and cause lee helm. 2) With spinnaker down the centerboard and rudder are sized to match the loads they are exposed to and this results in minimum induced drag from the CB and rudder, a faster boat to windward.
> At the recent Tradewinds Regatta I sailed an ARC 17 against several other boats for my first time in 25 years. We sailed poorly, went three times around the long course when I should have sailed two times around the short course, in the first heat. Then on Sunday my crew, who had never sailed on the boat or with a spinaker before, thought we shouldn't try the spinnaker in the 20 knot winds so we didn't. We still won the open class on corrected time and did finish a couple of heats first boat across the finish line. Our assigned PN was 70.2. That number is coming down as a data base is developed for the ARC 17 with spinnaker.
Good Sailing, Sam,
Bill

Mate..
Only 12s are unrestricted these days..
14s have a hoist height of 7626mm with rule 13.e.1 stating "The foremost end of the spinnaker boom, including end fitting(s), shall not extend more than 2743mm beyond the foremost vertical extension or transverse extension of the bow.").
With 16s the rule is 7.12 which states the maximum length of the assymetric spar may not exceed 2700 mm measured from the stem..
There are two 18 foot skiffs these days the "Bethwaite" camp and the "Murray" camp..
The league 18s have rule 11 which states in part "Any pole has a maximum length of 3.8m (12ft 5in) from the stem."

In regard to rigs many 14s do in fact have rigs that are adjustable uphill and down.. Cranking on the stays tightend the uppers and pulls the rig tip back..Some even have an adjustable setup that allows the rig to lay back as required.. Ie adjustable forestay and side stays..
As do many Javelins and Cherubs.. The old 18teens did as well but with Bethwaites strict one design rules these were basically banned.. The 16teens walked the same path as Bethwaites's 18teens..
I dont believe the any 12s have an adjustable rig.. But then I wouldnt like to be trying to adjust much with that much rag up..
But no matter which skiff it is one will find the rig is designed to be far more gust responsive than any cat rig..

Yes skiffs are slower than a cat when one looks at the ratings.. Apart from the 18teens vs a 18 foot cat.. But Im sure a 12 footer crew will also tell you that its far more lively than any cat..
I will stick my neck out here and suggest..
Any of the top 12 footer crews could easily jump on a Tornado/F18/F18HT/F16/M20/F20/F20HT and take her around a course without swimming.. In fact it would be a cake walk.. I would further suggest there isnt one top cat crews who could do the reverse (unless they have a reasonable amount of skiff experience)..

just my thoughts..

I would agree with that assumption...Personally, I don't want anything to do with trying to keep one of those skiffs upright!

With respect to Mr. Robert's implementation of the "shared lift" concept:

1) Would increasing rudder size also increase the apparant "load"(for lack of a better term) on the driver? After about 70 miles, even the "finger touch" tillers tend to cause fatigue. Yanking pizza-pan sized rudders could certainly kill off the weak over 500 or 1000 miles!

2) I can visualize the advantages you describe in windward/leeward sailing (around the cans), but would there be any advantage in a distance format that ends up being primarily close-reaching (no spin)?

Hi!
Are the skiff sailors better SAILORS than the cat sailors? No.

Would the best 12-foot crew have a chance in the Tornado Worlds if you put them on a Tornado? NO. (If they raced the Tornado a couple of years they might be able to give the Austrailian top sailors Forbes/Bundoc a match.)

The differance is that the cat is stable when sailed gently and the skiff isn't. Each boat requires more or less training before you can handle it without swimming. When you stopped swimming and have good speed in most conditions the major thing left is tacktics.


cheers
hakan

Wouter,

Thanks for your comments.

In my limited experience with spi's on a monohull, I have to agree with you that some lee helm downwind isn't a bad thing, although if it's too much I would guess it might set you up for an accidental gybe if you let go of the tiller for too long at the wrong time, especially in waves.

I agree with you that two CB wells would take too much time to manage if you were racing usual courses and if you tried to do it at the time you hit the mark; I acknowledged in my post that it would take more time to change over from upwind to downwind. This is, of course, unless the change was done on the flying hull well in advance of hitting the mark when there's time to do it and at which time it would't have adverse consequences.

Actually, in my original post, I was curious if two wells would work well for cruising, recreational sailing, and long distance racing where it might offer a very light touch both upwind and downwind for long legs avoiding any strain on the skipper, and in the case of long distance racing, might offer a slightly lower drag and more efficiency which could add up to slight performance gains over the times and distances involved.

Jerry

Hi Les,

Thanks for clarifying when you steer "look ma, no hands!".
I've done a lot of tuning on my monohull to be able to do the same thing and I have to admit that it's an awsome feeling when I let go of eveything (albeit briefly in order to attend to something) while the boat remains fully powered up and on it's intended course sailing itself. I guess that is something folks with large keelboats do all the time, but I find the feeling of doing it on a small boat even more fun due to the higher speeds involved.

Jerry

Hi Waterbug,
1)The side load on the rudder is increased with "shared lift". The force to hold the boat straight or turn the boat is not increased. This is acheived by balancing the dynamic forces on the rudder. Most boats already do this today. Note the forward swept leading edge on the rudder.
2) There is no advantage or disadvantage to shared lift while close reaching.
"Shared lift" is a design method to accomodate the large migration in sail center of effort asociated with adding a spinnaker to a high performance beach cat where the spinnaker is sailed primarily on a relative wind reach and the boat is aimed much lower than that relative to the absolute wind direction. The boat sails at roughly twice the speed of the wind tacking downwind.
Bill
Bill

The hull needs to be strong where the centerboard well is located. Two centerboard wells on each hull means more weight. The empty well will create turbulence.

/hakan

Attached is a photo (I don't know the source) of an ARC 21. Check out the placement of the boards as well as the relative size of the boards vs rudders. This shows the unusual balance that Mr. Bill is talking about.

Wow!

Thanks David. That's a big help. Notice the aspect ratio of that unloaded daggerboard. One could not build a board with that aspect ratio with the board in the normal position, shroud chainplate, because carrying very nearly 100% of the sail side force and double trapeze would break the board with that aspect ratio.
Bill