I want to know what this sail is composed of. Looks like a pure film windsurfer sail on a tboat.


When I get my tboat, I'm going to be looking for something like this. I think I'd like being able to see through my sail, it would make starting lines a lot safer imo.

It's probably a lot easier to fall THROUGH it in a capsize too....

Jake,

I'm disappointed, I thought you'd realize by now that rockstars like myself don't capsize.... evar :P

The object for most sailmakers is to come up with the best design, for a given boat, and use materials that will maintain this design over a wide wind range. There are two lifes for a sail,the life of the sail cloth, and the performance life. The performance life, is the length of time that a sail will matain its designed shape. The cloth life, is the time a given materal will last after being subjected to wind loads, flutter, UV exposure, etc.
In most cases, materals that have low stretch,light weight, and good durability are most prefered. There are always comprimises. The materials that best fit this discription, are also the most expensive.Sails made with low stretch materals, can be designed fuller. This gives more power in light winds, and will not stretch and become too full as the wind builds, compared to their more stretchy counterparts.Pentex is a good all around fiber for most beach cat sails. This fiber has twice the modulas as polyester, giving it twice the strength, and about 30% less stretch, as polyester. The price is also good. Using stronger cloth with less stretch, enables the sailmaker to go down in weight, as well. Jibs are often made with a preminum dacron called square dacron. This is a balenced weave and can be used in a triradial cut. This is a fairly low stretch dacron, and will stand up better to the abuse that jibs experance. The mains have many full battens that reduce flutter, they wear much better because of this. Laminates will last much longer in the full batten mains.
Dave

Some times wishes do come true…Thanks Dave for your informed comments. Never saw you post on Cat Sailor before…hope this is the first on many posts…it is so nice to have someone of your expertise take the time to respond.

I use to windsurf on occasionally with Tem Berkstresser, I remember him going incredibly fast on your racing sails, have you kept in contact with him?

Bob

Bob,
Thanks for the mention. It's good to hear from someone that remembers our windsurfer sails. That was a great period for me. Designing, and testing sailboard sails, resulted in some real performance breakthroughs. Alot of this has been applied to multihull sail designs. BTW, Tem Berkstresser just arrived at the loft yesterday. He is picking up a new Vectran screacher, and fullbatten jib for his 60' cat that he designed, and built.(with a little design help from Bill Roberts) It seems that most of the top US windsurfer sailors, and industry people are going to multihulls. Tem's ex partner Pat LeMahaute, is about to finish his 38' Kurt Hughes Tri,and Keith Notery's 60' cat is about done, as well. Many others are racing Corsairs, and beach cats.
Dave

Mr. Calvert,

Is there any information online about said 60' cats?

(pictures would be nice, my cubicle is very boring right now)

I still have one or two of your windsurf sails! I got out of the sport in the late 90's (too much $$ on the arms race) and picked up a beachcat. I guess I'm just one of the crowd! I still keep about 3 boards and a quiver in case I get the urge, though....

I figured my counterparts went to kitesailing with the expectation of bigger air. Being a true sailor at heart, I went "back", but couldn't handle going "slow" again, so beachcats were my only option (until I make gobs more money). Been on the F-boats, but not sure what to think of them yet. Need more crew time, I guess...

Keep up the great work down there, and congrats on your PlayStation accomplishments!

It is great to have you here!

I once bought one of your Hobie 21 square top mainsails (Giles delivered it to me personally) and that sail convinced other guys here to buy from you as well (SC17, SC19, etc.)

Unfortunatelly, so far I received no reply from Arnaldo, but (correct me if I am wrong) what you said is not in direct contradiction with what he said.

I think you said more or less that each sail cloth has its weight, moduli and durability features and the best sail is the one that, using those features, results in the best compromise. Then you gave examples.

Mainly, what Arnaldo said is the following:

a) rigid sails (I think he means those constructed with higher modulus cloth) are more secific to the wind strength they were designed for, then a more flexible sail.

b) Rigid sails (here I think he means 3DL and tape drive) do not keep their shape as long as it would be expected after they leave the mould.

Do you agree with those two statements?

THANKS!
Luiz

If your going square top, I would'nt use 5 oz Dacron, too stretchy. Pentex is the best option cost-wise. You might get a little preformance advantage using Kevlar of Carbon, but that small advantage will be short lived and probably not worth it unless you are buying sails to win the Nationals or something like that. The Pentex sails will be
a little more forgiving trim-wise, and that can be a good thing in chop.


Tell your sailmaker what kind of sailing you do and what
type of conditions you most often sail.

Good luck

I have a Calvert dacron square top for my 5.8. It must be 8 or 10 oz material - weighs a ton. I think the original owner must have asked for a sail that would outlive the boat. It goes like snot in light and medium air , but I have difficulty controling it in heavy air (15 mph +) - that might have more to do with me than the sail design though. In very light air it makes the boat almost unbeatable.

Luiz,
My feelings about "rigid" sails vs. "flexable" sails are this. Sail technolory has come a long way from the cross cut dacron days. The computer generated load maps of sails, has resulted in triradial cuts, 3DL,and tape drive sail constructions. All in an attempt to more acurately oriant the cloth fibers along the lines of stress, or loads on the sails. Materals have also gone from polyesters to Pentex, Kevlar, and more recently Carbon Fiber. All of this technology has resulted from the need to build sails that maintain their designed shape longer.
We build dacron sails only for durability and cost. Most of our customers are racers, and want the best performance for their money. We try to build the lowest stretch, lightest, most durabil sails for their budget. Sails that are "rigid"
and hold their shape over a wide wind range, are, in my mind the objective. We come up with the best design that we can for all conditions,and try to select a material that will maintain that shape. Most beach cats have numerous adjustments to alter the shape for differant winds. If we build sails from stretchy materal, the overall shape will be flatter to begin with, to account for the stretch, resulting from increased wind loads. There is more guess work involved.They tend to be too flat in light winds, or too full for high winds If the proper cloth is selected, the sails should maintain their designed shape for the life of the cloth. I don't know of many top racers, that are buying several sails, to meet the various wind conditions.
In fact most regattas restrict changing sails.
I hope this helps.
Dave

Dave,

Thanks again! I am not sure if I understand it all, but it makes sense to me.

I have excelent news:

The author of the article that started this discussion, Arnaldo Andrade, sailmaker in Cognac/Brasil (and also a physicist), sent me two replies, one of them quoting your words.

He wrote them fast after a day's work and asked me to edit, but I will just correct the typos. Some parts are marked "to be completed" and I will leave them as they are now.

[color:"red"]I will post both replies on his behalf as new replies to the initial post, so please go on with the discussion from there.[/color] I am sure that we will all benefit from the interchange of ideas.

Cheers,

b]The post Arnaldo is replying to:[/b]



Arnaldo's reply



Arnaldo Andrade is a sailmaker in Cognac/Brazil and also a physicist.

I disagree. There is no "best design" for a wide wind range. The more it is "best" the narrower is the wind range. A good example are Zuccoli sails for the Tornado Class, particularly the jibs. They are numbered and cover VERY LIMITED wind ranges. Zuccoly Dacron tri-radial sails still show some desirable geometric changes as the wind increases but their mylar counterparts are really good for their designed wind range, whis is generally a narrow one.

Sails that can be used in a wide wind range are precisely those that do change their shape, though very slightly and "in the right way" (that is, "self-flattening" in the breeze). Aided by important trim changes at the rig level, these sails can perform reasonably well ove a wider wind range.



I agree, the performance life of a Dacron sail, for instance, is usually 1/10 of its "mechanical" life.




The question is "why". It's dangerous to take for granted that only low stretch, light weight materials can make fast sails. In some cases, as for bigger multihulls, other factors become more important. Some self flattening ability, for instance, is highly desirable, since masts on these boats tend to be almost non-flexible.



This may be true for jibs but is not true for many mainsails. The Tornado mainsail, for instance, is cut almost totally flat, whatever the cloth used. It's the mast and the battens that give the sail its final shape. Although enormously successful, the Tornado mainsail is a blatant contradiction to the concept of the "preformed" sail.



This is true, particularly for beach cat mainsails.



Battened jibs (of Tornados' , for instance) can be made of Pentex, too. Other laminates, as the Brazilian Prolam, are made in a different way and resist in a better way the abuses that jibs experience.

Arnaldo Andrade
adrianno@openlink.com.br

Thank you Arnaldo,
Your comments reflect your vast experance with physics, and sailmaking.
I still dont understand why you would disagree on the concept of a "best" all around design, for a given boat.
We have gone thru extensive on the water testing for various class boats. Much like what we would do during our windsurfing sailmaking days.
We would try differant luff curves, twists, draft positions, etc. Than we would switch boats, and sailors, to eliminate variables, and often arrive at a shape that would best perform over a range of conditions. Granted, as wind, and sea conditions change, the shape of the sails should change as well.
But, most of our customers here, don't want to hear that they should be buying not one new main, but two or three to be more competitive in all conditions.
If the sail is very flat, (like the Tornado main that you mentioned)there will be a lack of power, in the light air.
This will result in the boat not being to fly a hull as quick as the competition. This is a disadvantage, like a windsurfer not being able to get on a plane as quick as other competitors. As the wind builds, the mast will bend from the added mainsheet loads alone. This will further flatten the sail, by taking out luff curve. If the mast bends as much, or more than the luff curve in the sail, the sail will distort, the draft will move aft, and performance will suffer.
For these same reasons, a fairly full sail, with stable sail cloth, will automatically self flatten as the mast bends under increased mainsheet loads. The modern downhauls can further flatten the main as needed. In fact we have been suscessful using the downhaul to flatten, and add twist to mainsails in light air, extending their range even further. Jibs, are another story. The jib adjustments are very limited. But again, most racers that we deal with, want one best suted to the local conditions.
You asked, "why" to my statement, "In most cases,materials that have low stretch, light weight, and good durability are most perfered".
Multihull sailors in general, go thru extremes to reduce weight, especally aloft. A light sail, reduces weight, and makes the boat easier to right. Most of the advances in racing sailcloth has been aimed at reducing weight, and stretch. From windsurfers, to America's cup, to the Maxi catamarns, this applies.
My question is, "how"
How can a flexable sail be self flattening on a large multihull, with a non-flexable mast? My experance has showed me that big multihull sails just keep getting fuller, as the wind builds, especally if the material is not stable enough, or the mast doesn't bend.
These are my opinions, based on personal experance with small to maxi multihulls.
Cheers,
Dave

Mr. Calvert,

Can your loft make me a sail like on that tornado that I posted earlier in this thread?

Yes,
We can, and have made cat sails out of monofilm. The Tornado main sail, in the photo, is probally a 6 or 7 mil monofilm.
We made a square top main like this for a Stiletto 23, about 10 years ago. The materal is low stretch in all directions but, not very durabil. I don't recomend it.
Dave

You're probably right. I don't have a very good history involving sail durability

Hi there,

(translated from Portuguese)

Luiz, please check if my answer is worth posting. I'd rather not start too serious a controversy - only healthy discussion. I'd really have no time for it and it is not without a certain sacrifice that I write those texts. Please use a spell checker in my replies because I have none in my computer. My English is rusty because most of the texts I've been writing lately are in French.

If you find anything too strong, please take it out.

Regards,
Arnaldo,

(end of translated text)




Dave Calvert’s paragraphs on the way he arrived to a best all around design are perfect. They help us in understanding that there is no basic contradiction between the quest for an “all around sail” and the creation of a sail with the ability to change its geometry. Such a sail would also be “an all around sail”. The difference is the following: whereas Dave’s way considers the sail geometry as essentially fixed and relies on the rigging for sail shape control; I believe that the sail itself can be part of the solution.

In his description he says:



A sail that could self flatten in the breeze would enlarge its useful range, possibly to a wider extent than could a “fixed geometry” type of sail (since the latter would rely only on rigging changes for shape control).

He then follows the thread by saying:



Whereas PHRF sailors may refrain from buying many different sails, a great number of classes indulge in a frenzy of specific sails. Tornado is one of these classes (especially for jibs), but even old designs as the Snipe do follow this trend - not that I agree with it. I'd rather keep sail inventory to a minimum. What I say is that nowadays many classes admit that a great number of sails may be necessary for a boat to be adequately competitive.

Then the question of the Tornado sail comes back:



First of all, a correction and an apology. I wrote that Zuccoli Tornado sails cover a very limited wind range. I was referring to the jibs. The mainsails do show a wide range of use, for reasons explained below.

In fact, if the Tornado sail I mentioned (99% of the boats use it) WERE flat, I would totally agree with Dave. It happens that a Zuccoli mainsail is NOT flat when set on the mast. It’s just its construction that is flat. The flying shape is not, due to the battens, to the mast and to a small number of almost secret details. The conclusions are far reaching, as they mean that you don’t need to put draft in a sail to see draft when the sail is properly set (*). Zuccoli mainsails are reasonably full in light winds and no one can deny they are a blatant success. But since they are (1) radial and (2) built flat, they respond much better to luff tension, outhaul tension and mast bend than previous sails. It was Dave himself who wrote:



What he is describing is - precisely - a sail that has variable geometry, that is, a self-flattening sail. The only mistake, in my opinion, is his reference to a “stable cloth”. Is is precisely because the sailcloth stretches that the sail geometry changes. The merit of Zuccoli and some other sailmakers, is to have devised a construction of sails in such a way that cloth flexibility is an aid in the control of sail shape, rather than an enemy to fight.



Keeping with the example of Zuccoli sails, it seems that the self-flattening ability of his mainsails could not be emulated on the jibs. The reasons may not fit in the present discussion, but the absence of an efficient way to tension the luff, together with incorrect cloth choice, may account for it. The fact is: one needs to have as much as four different Tornado jibs to work with a single mainsail. For me, this is a clear demonstration that these jibs could profit from a different approach, as construction techniques go. Of course the boats might also have to sport new trimming resources.

The subject than changed to low stretch and low weight:



Dave correctly states that low weight is always better and that is a sought-after characteristic in most sailboat classes. But my question was rather: why BOTH characteristics (lightness and low stretch) at the same time? I still think that a careful choice of sailcloth flexibility, with more stretch on the leach (for instance) may widen the useful range of the sails.

Then comes a new question:



I'd rather refrain from commenting on the exact details, but as you can certainly figure, building features like this into a sail requires a lot of skill and is a labor intensive task. Basically, one has to start by abandoning the pre-conceived idea that cloth flexibility is always bad. Once it is assumed that flexibility can be put to play in your team, instead of against you, the rest will follow - not necessarily in an easy way. But with a researcher’s mind and A LOT of experimentation and hard labor, one can eventually develop a consistent way to create self-flattening sails.

Remark: it may is interesting to note that also on the boats side some improvements are necessary. The powerful purchase on the luff tensioning system of the Tornados is one of these changes.

Cheers

Arnaldo

(*) I said above “you don’t need to put draft in a sail to see draft when the sail is properly set”. This is not new, of course. It has been known for about 3000 years. But the submission of human intelligence to sailmaking softwares is somehow erasing this information from the minds of otherwise well informed sailors.