Both, as use/versatility is a large part of the design criteria. That is what makes the discussion interesting.
Funny that the C-class course originally was designed to test a boat on all headings, and they still tought the wing was the winning solution. But then they have a very limited sailarea compared to todays spi equipped boats.

Hakan,

I have been talking about pure upwind and downwind course as well.

Naturally I also included the more general cases were the crew overstands the mark or a windshift cause them to sail below their highest upwind pointing angle. This latter situation is indeed when the sloop rig is even more favoured. I even included a wide range of sailing craft in my discussion, ranging from slow sailboats to fast landyachts. Basically the comments I made cover the whole spectrum.

Even on a windward-leeward course it is still true that a maxed out sloop rig will be faster then a maxed out uni-rig even on a perfect upwind-downwind course.

Now you are adding a spinnaker to both boats, in addition to a perfect course. Again this reduces the difference between both setups but still the maxed out sloop rig will be faster then the maxed out uni-rig although not by much. Roughly 2 minutes per hour racing windward-leeward. Also, how does adding a spinnaker differ from adding a very large overlapping jib ? Not by very much I say. So basically we all already know how the principles underlaying the sloop rig will make any given boat faster. The ORMA 60 and Ricks Hooter rigs are an intermediate state between this spinnaker and a 25 % jib. The Genua is so too, although more closely related to an actual high aspect jib.

Now Steward goes one step further and introduces the solid wing sails to the mix. Now this the first serious counterargument we had in the whole thread. It is indeed a good suggestion. So how do I disproof it ? Well, as good as all solid wing sails have slots because they found that deviding the total sail area in more narrow slips with slots between them is most efficient in creating drive. The sloop setup of two sails with a slot between them is a rather crude approximation of that, but nevertheless it is. As such the slotted solid wing sails have more in common with sloop rigs then pure uni-rigs (non slotted), it is just that the sloop principles are implemented in a slightly different way.

But there are exceptions. Think of Macquarie Innovation. That craft uses a low aspect solid wing wingsail without any slots; so thatsolid wing may be regarded as a close relative of the pure uni-rig. Does this disproof my comments ? Not really as I had already stated in an earlier posting that very fast moving sail craft like landyachts prevent the effective use of a jib sail because of their speed. For the same reason a slotted solid wing sail will be disadvantaged. I also gave speeds and angle of attacks that would lead to such a situation. Macquarie innovation is doing roughly 50 knots in 30 knots of wind and as such it close to the speed range of landyachts and shares the same angle of attacks. The latter are the real reason that a jib can not be used effectively.

Our soft rig beach catamarans however are nowhere near those speeds and their significantly larger angle of attacts allow the effective use of jibs to increase performance. The same applies to the effective use of spinnakers on our beach cats. On even slower moving sail craft adding a second mast (rig) will improved performance because the angle of attacks are even larger there.

There are also some interesting scientific principles underlaying the sloop rig. For example the jib will produce just as much drive per square meter as the mainsail does but does so at an significantly lower "angle of attack" then it would if it were the only sail fitted. Summerized, it is surprisingly more efficient when it is added to an uni-rig then would be expected. This is because of the interaction between the mainsail and the jib. A compounding effect is that other limits keep the uni-rigs pointing angle rather large and as such it can not make full use of losing the jib. Basically it is the interaction between these two sails (small slot) that makes the whole perform better then what you initially would expect by looking at each sail on its own. If this slot were to be increased to say 2 meters or more then this interation will be lost and with it most of its advantage.

For more info on this read the books by Marchaj and the excellent articles by Arvel Gentry.


The sloop rigs have gotten a bad name over the last decade because of some boat designs and class rules that are made to favour the uni-rig. But this is undeserved. We only need to look at the ORMA 60 tris and 18 foot skiffs to see that a less restrictive sail area limit in the class rules (or none at all) will show the sloop rig to be performing better.

That is basically the whole story.

Wouter

We must also not forget that the course these C-class boats sailed is defined in detail and it contains a disportionally small amount of deep leeward sailing.

From memory it contained a single deep triangle course with a wind-leeward loop at the end. And I think it even had an upwind finish. Basically there is no reaching involved and on the first lap (triangle) you are forced to sail no lower then 120 degrees off the wind to make the B-mark.

Sloop rigs and especially spinnaker rigs will beat downwind between 135 degrees and 150 degrees depending on the wind conditions.

The pure downind leg on the C-class course is negligiable as it is now only 1/6th of the total distance sailed; on our windward-leeward courses this is 1/2 the distance sailed.

Such a course actively prevents any rig that can sail deep and fast from being competitive. Even more so as it makes the pure upwind leg by far the most dominant part of the race. Of the 3 courses sailed : pure upwind, 120 degrees broad reach and pure downwind, the upwind leg is three times as large as the downwind leg and also 1.5 times larger then the 120 degree broad reaching.

Here we see another example of how class rules may well implicetly favour one setup over another. I remember from the miss nylex article that its design team based a good portion of their design choices on the fact that the upwind leg was made so much more dominant by the defined C-class race course. I think they decided against having 2 slots for this reason.

Wouter

Rolf,



May be another interesting question a la Scooby Simon can be formulated here :

Knowing that the M20 has a 20.71 sq. mtr. mainsail and a 25 sq. mtr. spinnaker, we determine its total sail area as just shy off 46 sq. mtr.

What would be the fastest design using the same platform and total sail area but unregulating the rig in any way ?



Many of us (including you) believe that luff length of the spi is much more important in performance then its actual area. May it be beneficial to keep the spi luff length but lower its area a little and use that amount to put a 25 % jib on the boat ?

Afterall a 5 sq. mtr. jib will only reduce the spi area by 20%.

Or better still. Reduce the mainsail area to 20 sq. mtr and give it an aspect ratio of 5 (same mast) and only reduce the spi by 4.3 sq.mtr (17% area reduction).

With the spi luff length unaltered this may only result in a very small performance loss on the downwind leg. Maybe even a negligiable one.

Of course the upwind speed will have been boosted by a larger amount leading to a nett performance gain. If this is the case then the uni-rig vs sloop rig debat for spinnaker boats under the assumption of same overall sail area will be over as well.


Have to go now, time to do some H_infinity controller design.

Wouter

Wouter

For an "under size" sail plan, would you want mainsail only or Main and Jib.

Consider an F16 where you can have (sailing single handed)

Mainsail + mast = 15sqm or mainsail, jib + mast = 15sqm

and both boats carry 17.5 sqm Spi.

What I am trying to find out is

You can ONLY have 15sqm "white" sails (as they are sometimes called), do you want one or 2.

I have already given you my answer in this posting :

http://www.catsailor.com/forums/sho...Number=118065&page=&vc=1


However your questions are becoming increasingly rigged to solicit the answer you want to hear. As such the informative value of both the question and the answer have gone south.

Example :

"Did your wife recover from the last beating you gave her, Simon ?"

Please answer with either "yes" or "No".

Wouter

No. I do not beat my wife, that is a stupid and insulting question.

I do not want to get a pre-defined answer. I am really interested to hear what you think.

If you had the option of sailing a F16 single handed, would you sail as now, or with a smaller mainsail and a Jib ?



Which answer do you think I want you to say?

I thought I had typed up a response answering the original question. Now I see that the thread has nothing to do with the original question.
Guess I shouldn't have bothered.

So, What was the original question?

If a wave crashes in the middle of the ocean and nobody is around to hear it - does it make a "sound"?

To be really honest, I don't know what I will do in your very specifically defined problem.

In http://www.catsailor.com/forums/sho...Number=118065&page=&vc=1 I had given two situations were I would do one or the other, albeit without a spinnaker added. Your problem resides between these two examples and as such the choice will be less clear. Naturally, a crossover point will be found somewhere between these two examples. At at this point it doesn't matter what you choose as both setups will be perfectly matched in performance. It appears to me that your proposed problem is very close to this crossover point. Without exactly knowing where this crossover point is found but still forcing me to be close to it my answer can only be increasingly a guess.

Mostly because I now have to know (estimate) very accurately were this this crossover point lays. I think I have a pretty good idea of where the crossover region lays = set of crossover points (depending on conditions) with a decent margin of uncertainty on either side of it. But when you (needlessly) force me to go into this region then I'm lost for an conclusive answer. In all the other examples, we were sufficiently far away from this region to be certain about what is the favoured setup. Now I'm not.

But this is getting very academic, because the choice on a F16 platform is not confined to having a 15 sq. mtr. uni rig or a 15 sq. mtr. sloop rig. The 3rd option is of course to go with the 18.7 sq. mtr. sloop rig. All of these can be had without changing a single thing on the basic F16 design. So when given the FULL choice of possibilities I would always go for this 3rd option.

I'm really adament that excluding this third option altogether from the choice is one of the tricks used to mislead sailors into believing that the uni-rig design is superior in performance.

Wouter

With 49 posts...... this one did.

Wouter,

Thanks, this is what I was trying to understand.

You feel there is a magic place where for the same all up sail area a mainsail will be the same speed as a 2 sail boat (both with kites). BUT you also believe that both configurations have merits.

This place may move about a little depending on the weather conditions and other parameters like the shape of the race course, but it will always be there when looking at sailboats.




I had already admitted as much when I refered to my landyachts and Macquarie Innovation.

Additionally, merits do not have to be exclusively defined as "being the fastest". Other considerations may well change what is favoured. For example a sloop rig will always be a little bit more expensive.


Wouter

Consider an F16 where you can have (sailing single handed)
Mainsail + mast = 15sqm or mainsail, jib + mast = 15sqm
and both boats carry 17.5 sqm Spi.

Scooby, this question is already answered, the A-class has made the choice and they went for the uni rig solution. After 30 years of development the A-class should know, or could it be that Wouter knows more <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

/hakan

Wouter you keep saying that a fully powered up M20 without jib would be slower than a fully powered up M20 with jib around an upwind/downwind race course, but you have no data to rely on. Finishing times for the M20 on the last two Round Texel doesn't say much when you are looking for these small differances. The only relevant data I could find was the upwind leg on last Texel, and that showed a small advantage for the uni rigged M20.

The only way to prove which version on M20 that is the fastest is an upwind/dowind race.

/hakan

Hakan,

You are not summerizing my comments correctly.

Secondly, there are too few M20's and M20 GTI's about to make any scientifically sound comparison. Additionally these 20 boats are spaced very far apart and almost never meet. They do at Texel but then you throw out those results that don't suit you. Like this we can go around in circles for ever and I'm not going to that. So lets forget about the M20's





But I actually do ! Data gethered from other designs and classes; like the dear old Dart 18 and even the much newer F16's. It is a sign on the wall when adding a jib is enough to make a doublehanded crew just as fast as the singlehanded crew with a uni-rig; IN ALL CONDITIONS. More weight => same performance. I guess that jib must be doing something; like overcoming the hit of carrying 75 additional kg's. Additionally we have all sailed a doublehanded sloop design singlehandedly one time or another. I'm sure you too have sailed your own Hobie 16 sloop as 1-up a few times in the past. Now was that faster then 1-up without the jib or not ?

And if you don't believe me then hook up with an equally skilled friend and do this H16 1-up experiment. Switch boats halveway to make sure that the results are not caused by a difference in sailing skills.

It is sometimes mindblowing how obvious things can be overlooked.

I rest my case.


Wouter

i may be missing this argument ..but it seems like apples and oranges.

For a given stick height.. you can only put so much mainsail on the boat. And it will be more efficient then if you took some of the sail area and put it into a jib. (Hakan's point... I think)

Wouter then comes back and says... Fine... Keep the big main and now add a jib and he argues he will be faster...

Is this correct???

Funny you mention sailing Hobie 16 without jib. We had to do that at the first start in a 35 boat Hobie 16 fleet in Kellenhusen in Germany. Righ after the start the jib fell down a bit so we lost all power from the jib. We stopped a short while and to check what was broken and descided to head for shore to fix the jib. We had to sail upwind to the shore so we continued the upwind leg. We double trapeze sailing only on the main having the jib powerless and my crew was suprised that we wasn't dead last at the upwind mark, we had quite good speed!

Another interesting test would be to add a 5 m2 jib to an already overpowered A-class going upwind....

/hakan

Mark, here's a scenario!
The wind is blowing 15 knots and you are sailing an A-class upwind with full depower on the main (you are trapezing in 6 knots of wind on the A-class). Then add a 5 m2 jib which gives you more stuff (you don't need) to drag around. Will this be faster??

Classes with only sail area limit goes uni rigged. A-class, C-class, F40 (they had to have a very small jib for class reasons). Above the 40 feet limit there might be structural reasons to keep mast height down and add a jib to get more area.

There where some A-class boats in the beginning of the development of the A-class that split the sail area in a jib and main but the uni rigg was faster.

/hakan

Regarding the M20 platform, I'm pretty sure that the jib was added to increase its allround performance (not just upwind).
People who buy an M20 for Texel do this to win line honors and do not like to leave things up to chance (like running the risk of having to beam reach for half the race).