Sail efficiency = speed gained ?

[hprasmus]

Roughly a year ago I asked this forum about the relationship between reduction of skin friction and gained speed. It turned out to be impossible to answer.

This question is in the same ball park:

How much will a 5% increase in net sail efficiency contribute to a sailboats speed (below max. hull speed of course) ?

I have just had results back from CFD-testing that indicates that such performance improvements could be possible by using a different sailbatten configuration than is normally done today.

AND learning from last years experience: NO, I can not display the idea as I am in the process of preparing a patent application.

And YES. the CFD-simulation was conducted by a very well respected professional in US.

For one thing I find it obvious that a 5% efficiency gain would make it possible to reduce the sail area by 5% and thus save on the handicap rating of the boat. Or ?

[Tim B]

Neither question is impossible. It should be obvious that any increase in efficiency (which you need to define... Here I will use in increase in the drive/drag or drive/sideforce ratios) will result in improved boat speed. How much of an increase is dependent on the boat, and how optimised it was in the first place. I think you need to do some basic Naval Architecture before you start filing patents, because for the scope of what you wish to patent, you really should be at least aware of the implications on performance without having to ask questions here.

You should also be aware that increasing the driving/sideforce ratio by 5% won't give you 5% on boat speed. That's pretty simple physics, hull-speed doesn't come into it, but V^2 does.

Do yourself a favour, stop wasting your time and money filing patents for which you don't have the understanding to make a decent case, and do something useful with your life.

Tim B.

[idkfa]

If YOU are going to take this product to market, go ahead develop and patent, if not you will NOT get royalties from an existing manufacturer...

http://www.faqs.org/abstracts/Construction-and-materials-industries/North-Sails-sued-again-by-Sobstad-Judge-awards-54M-to-sailmaker-Sobstad.html

statistically 1:50 patents make money .....Nolo Patent it yourself

[hprasmus]

To Tim B

What an attitude ! It is a simple question, and yes I am not an naval engineer, but if you as an expert, can't answer better than insulting me, I think YOU should search for an other field of occupation ! Thanks

[BATAAN]

I assume by your use of battens you are trying to improve shape and airflow to give more net drive by controlling sail shape. If your computer sim says it helps, that is good, but remember that sails stretch and change shape fairly early in their lives and that is the reason they are replaced often by racers. My point is that the real world is not in a computer and the models used to get results are quite simplified to be usable, and many factors come into play that you may not be aware of.
Build a sail using your ideas and try it alongside an identical boat with same size new sail but the older type. This gives apple/apple comparison and will tell you if you are on the right track.

[hprasmus]

Thanks Bataan !

I have actually already followed your advice, but in a sense in reverse engineering.
Initially I tried the concept (not so much for comparative speed testing as for practical application issues) on Optimist dinghys. It worked quite well and I then moved to model simulation by CFD.

So, now I have the positive results and wish to translate them into actual speed benefits. Obviously to save cost from further outsourced engineering.

Actually a very senior member of this community is involved in this refinement work. At least his company is and I don't think that he knows by now. Just to make you aware that this project is handled very seriously and professionally.

Thanks

[CutOnce]

To Tim B

What an attitude ! It is a simple question, and yes I am not an naval engineer, but if you as an expert, can't answer better than insulting me, I think YOU should search for an other field of occupation ! Thanks

You seem to be interpreting responses you don't like as insulting. It is a common theme here. The other thing I notice is that you are ascribing expert status to someone on the Internet, and that too is a serious potential mistake.

First, publishing very public claims on Internet web sites about pre-patent technology advances is not done. If you were serious and professional about your patent claim, you would remain silent until the letters patent were granted - in multiple jurisdictions covering all countries where the patent would prove profitable. This is an expense in the order of tens to hundreds of thousands of dollars. Previous employers have done this with technologies I have developed, and I have been through the process in the US, UK and Canada. Although assigned to prior employers, I am a patent holder.

Patents cover specific implementations of the technology, not the intangible idea behind the specific technology. You submit plans, drawings and an abstract detailing the specific implementation, along with research and references to prior art, clearly delineating how your concept is different, and then patent agents will consider your concept, search for published prior art that may precede your claim (something they do very poorly) and then grant or deny your patent. I think the previous poster's claim that 2% of patents make money is highly overstated.

Your concept may be valid, and may hold promise - no one here knows enough about the specific implementation to judge. Tim B.'s somewhat direct and uncomfortable opinion is too worth note - he is correct that many factors affect boat speed, ratings and efficiency - and the area your concept claims to address only could apply to one of many factors. There is no one-to-one relationship between sail efficiency and boat speed.

The information you seek regarding sail efficiency and boat speed is different for every boat and every rig - and the only way to determine this is through real-world testing comparing a rig using your specific implementation against a control sample without the technology across a range of conditions and then developing a data set, analysis and conclusions. What you were asking for was a way to predict results on an unknown technology without actual testing. If people could accurately predict the results of your technology without testing, measurement and analysis, then they would be rendering my whole science and engineering education worthless.

Obviously, your excitement for your concept has overwhelmed your acknowledgement of the incomplete state of the research your are doing. You've gone from developing a hypothesis to directly proposing a patentable implementation - skipping the interim steps of building a functional real world implementation, testing in target conditions, collecting enough data, performing analysis, publishing your results and having qualified peer review. Your claimed computational fluid analysis is but one early step in the process.

I'm excited about a possible performance improvement in your implementation - and fully support your ability to protect and gain revenue from it. But your response to an Internet-based comment questioning your assumptions is out of proportion to where you are in the process. Come back when your thesis has been published, showing the credentials of the people doing the peer review, after your patents have been granted and you'll find an attentive, respectful audience here. Until then, you might have to develop a little tougher skin when people (who you don't know and have no idea of their credentials) question your concept.

Best of luck!

--
CutOnce

[hprasmus]

Ho CutOnce and others

I think you and others are quite mistaken about the process of applying for a patent - and getting it. You do NOT need to substantiate a claimed benefit. As an absurd example you could gain a patent for putting wheels on a car. Without specifying how much faster it would move.

Anyway I do have a very pro patent agency supporting me and we have actually already filed for patent. What I am looking for is substantiation of the effect for sales purposes. Quite simply.

Thanks

[CT 249]

As a caution, the fact that your configuration is not common today obviously doesn't mean the patent is valid. I mention this because many people are not aware of what has been tried in the past.

This isn't to anyone's discredit. Very few people have, for example, read about Taffy Bowen's walking stick rigs with split battens and pocket luffs, or the '60s Moths that had a metal projection like a gaff to give a squaretop outline and allow tension on the head to be adjusted, or the canting keel and bow rudder described in the 1800s. About the only way to find out all prior art would be to go through every single sailing magazine and development class newsletter ever published. Who can afford to get a patent attorney to do that?

A classic example is the trapeze. History books almost always say it was developed just before WW2 in International 14s, Kiwis say they did it a couple of years before - but in fact they were described in great detail decades earlier, in the southern hemisphere but well away from NZ, Australia. Another example is the foiler Moth (photographed decades before it was first well known) or the wing-sail Moth (first created about '58).

In battens one can remember writings about steam-pressurised battens to alter shape (Tornado, Canada), inflatable battens, or sailing with battens with a wire running up the leach so that sail depth could be adjusted. That's just off the top of the head, and I've never actually tried to find anything on them in (for example) the bio of Sandy Douglass, or the Moth class newsletters.

The number of inventions that are actually reinventions is pretty large, which would be most dispiriting if one had spent tens of thousands on patents that turned out to be worthless.

[hprasmus]

Dear CT 249

This is my first attempt in getting a patent and I am learning (spending) as I go along.
You are quite right in your stements regarding publication. But then there are many ways to address a specific area of invention. If you do some searched on e.g. espace.net where patents are logged and look for for instance sailboat keels you will find hundreds if not more patents that have have made it. So, it is not only the concept but certainly also the practicalities of the invention that counts.

Even though my patent has been delivered there is no need for me to disclose further details.

All in all this is a theoretical question to professionals: how to translate net sail efficiency intt speed gain ? By net I mean that both drag, side force etc. has been taken out of the equation.

Thanks

[CutOnce]

Ho CutOnce and others

I think you and others are quite mistaken about the process of applying for a patent - and getting it. You do NOT need to substantiate a claimed benefit. As an absurd example you could gain a patent for putting wheels on a car. Without specifying how much faster it would move.

Anyway I do have a very pro patent agency supporting me and we have actually already filed for patent. What I am looking for is substantiation of the effect for sales purposes. Quite simply.

Thanks

You are welcome.

You are absolutely correct in that benefits do not need to be substantiated. Most are not. I have to admit, I was wrong in posting that many patents are not profitable. They are, but only for "pro patent agencies" like you are using. Patent agencies make good money by filing for and obtaining results with patent claims at the expense of the client. My observation about the lack of patent profitability should have been directed specifically to people owning patents. Patent agencies do not survive if they show their clients how many of their clients actually receive value for their services. Much like lotteries or casinos, patents are a fun way to help sustain dreams of getting rich. You never know who will win.

The best real-world example I can think of to help you in your quest to substantiate your dreams of profit from your idea would be the Canting Ballast Twin Foil (CBTF) idea owned and marketed by CBTFco. Easily found by searching the Internet, they have implemented a successful technology in the sailing world that is used to enhance performance of extreme high end keelboats used in racing.

Their concept works, is used in a small proportion of boats and has sold enough to be considered a success. I do not know if they have truly become wealthy from their concept, but they haven't disappeared yet either.

It appears you are looking for SALES substantiation, not design or scientific commentary, therefore you may be asking on the wrong web site. This is a Boat Design website, not a Boat Marketing web site. I'm sure there are web sites out there for helping people generate sales projections.

Best of luck!

--
CutOnce

[yipster]

filing and paying for a patent is not the same thing and alltogeter i'm suprised 1 out of 50 makes money of a patent

i had royalty's once without patent, thats possible too. when those eternal royalty's gave payments euro problems
i told them to gift my royalty's to the blind children at the cote dazur where i too would reside, not very smart

by filing for you have protection for a paralel entree during some months
by paying, about 10K for each country you have a patent for 6 years

at least thats how it works in europe last time i filed a patent
glad i thought the 10K was to much, specially since i wanted a wider patent than just holland
becouse now after a decade "my good idea" still has to become implemented
the filing probably still archived somewhere but the money would have been waisted

"a different sailbatten configuration" i wonder about. Hereshof already used double layer saill and got banned
ruling on full, half, type, etc battens is not light eighther from what i've been reading.
AC cup alinghi expiremented with inflatable battens at the same time i only imagined them few years back

[hprasmus]

Yipster,

Actually, to my surprise, inflateable battens are a fact ! That turned up during the patent agency's screening: http://www.airbattens.com/

My invention is much less sophisticated (potentially less costly) but works along some of the general ideas, but with a different purpose.

I am stilling missing some firm indication of converting net sail efficiency to speed gain ?

Was my assumption that a 5% net efficiency increase could be converted to a reduction of 5 Sqm of a 100 sqm sail incorrect or what ?

[hprasmus]

Uuuuups, if I keep replying to all responses I will probably get the best posts/view ratio on this forum......

Could someone kindly help my negative score on 'reputation' ? I am not a bad boy.....

[CutOnce]

A classic example is the trapeze. History books almost always say it was developed just before WW2 in International 14s, Kiwis say they did it a couple of years before - but in fact they were described in great detail decades earlier, in the southern hemisphere but well away from NZ, Australia.

I had read somewhere that an early (earliest?) trapeze implementation was on Thames A-raters in the UK - long before the Kiwis or Aussies. Huge tall rigs, designed to grab high breeze above the tree on the river banks, light winds. Came about one days after a crew member was hanging off the shrouds with their feet on the rail. I can easily see a bored crew member fooling around and doing this.

Like most things, originality is directly proportional to the obscurity of the source idea. My personal opinion is that more than half of the patents granted should not be due to inadequate research to find prior art. Or as my dad says, "Everything old is new again".

Cheers,

--
CutOnce

[BATAAN]

Yipster,

Actually, to my surprise, inflateable battens are a fact ! That turned up during the patent agency's screening: http://www.airbattens.com/

My invention is much less sophisticated (potentially less costly) but works along some of the general ideas, but with a different purpose.

I am stilling missing some firm indication of converting net sail efficiency to speed gain ?

Was my assumption that a 5% net efficiency increase could be converted to a reduction of 5 Sqm of a 100 sqm sail incorrect or what ?

Sails do different jobs with different relative wind directions. Using a fore-and-aft sail to go to windward relies on aerofoil effects you seem to be enchancing with your ideas of improved efficiency. But crack off onto a broad reach or a run, and total sail area is much more important than perfect foil shape.
On this count, reducing sail area 5% would reduce speed somewhat on any point of sail other than hard on the wind, and only if your idea works as claimed.
Not all sailing is as upwind as possible, though some without sea time would seem to think so.

[Tim B]

I am stilling missing some firm indication of converting net sail efficiency to speed gain ?

Was my assumption that a 5% net efficiency increase could be converted to a reduction of 5 Sqm of a 100 sqm sail incorrect or what ?

You are missing the definition of efficiency. Is this driveforce/sideforce, reduced weight, better sail handling? better sail setting after tacks/gybes? better control through manouvres? Are the improvements upwind, downwind or offwind?

You are also missing the understanding of how the forces balance on a yacht and how drag of the hull and appendages can be calculated based on empirical formulae. Hence if you have improved the D/S ratio, does that mean you get more drive, or less sideforce? This will make a big difference for the change in speed.

Incidentally, I wouldn't describe myself as an expert in any field, but certainly professional in one or two, and educated in the field of Naval Architecture with emphasis on yacht design. So I like to think I know what I'm talking about.

You pose a very hypothetical question which to most of us sounds like you want a one-liner from a Naval Arch. You're unlikely to get one. I think you need to do some basic research into fluid dynamic lift and drag and performance prediction before you proceed, otherwise how will you be able to make sense of your findings?

Tim B.

[idkfa]

hprasmus get yourself some unbiased patent advice, read "Nolo Patent it yourself"

Chances are you can make money from your idea without a patent! That's what you should be thinking of; read boutique co. making product, while the big guys could not be bothered about your few 10,000s in sales. If it does not get banned in racing rules.

NO CO. WILL PAY YOU FOR YOUR IDEA. They will modify or simply ignore your patent and put the onus on you to enforce it.

[idkfa]

Boat speed is not linear. What you can increase is VMG, and there are many factors that go into if you can sail at a higher angle.

[yipster]

Reminds me to exercise some polars
Not so easy to calculate as fe stability or velocityu tho

[hprasmus]

The simulation was conducted in apparent wind angles of 28 to 40 degrees. In that register the performance incresed with the angle of attack. However there should be no loss of efficiency at more off wind courses. The benefits may decrease or be neutral, but no net loss of efficiency should appear.

[Tim B]

Present the data.

Tim B.

[yipster]

Bataan, also remember someone mentionin
as for cars there is no sustitude for cubed inches,
for sailboats thre is no substitude for squared
lots of wisdom, still, engines change and horses for courses and that
than again allyou old salts have that sayimg engraved in your winches


Typed from mobile, srry for my big , was gonna say thu
ps... Sails? Whoooooha0ops

[CT 249]

I had read somewhere that an early (earliest?) trapeze implementation was on Thames A-raters in the UK - long before the Kiwis or Aussies. Huge tall rigs, designed to grab high breeze above the tree on the river banks, light winds. Came about one days after a crew member was hanging off the shrouds with their feet on the rail. I can easily see a bored crew member fooling around and doing this.

Like most things, originality is directly proportional to the obscurity of the source idea. My personal opinion is that more than half of the patents granted should not be due to inadequate research to find prior art. Or as my dad says, "Everything old is new again".

Cheers,

--
CutOnce

The general wisdom is that Beecher Moore fitted "bell ropes" to his Thames A Rater, as you say, and that was developed in International 14s by Charles Currey, Sir Peter Scott and others.

Kiwis say that they were used in an M Class a couple of years earlier (1937 off the top of my head).

However, the use of trapezes, complete with belts, was described by two independent writers decades earlier, with up to eight traps being used in Asian racing canoes. Interestingly, the one academic I could find who was studying craft from that area didn't know about the traps. However, the two articles could hardly be clearer about their design and use and they were definitely traps.

One description is in a 1906 book, another in a US or UK mag about 1920. A patent office search would, as I understand it, pick up neither of these clear examples of prior art. Obviously no one is going to try to patent the trap, but it's a classic example of the difficulty of saying that one was first.

[BATAAN]

The simulation was conducted in apparent wind angles of 28 to 40 degrees. In that register the performance incresed with the angle of attack. However there should be no loss of efficiency at more off wind courses. The benefits may decrease or be neutral, but no net loss of efficiency should appear.

Just the sail is smaller and has less drive on 280 degrees of possible and desirable courses. Less AOA means your performance advantage goes in the bucket after 40 degrees and you just have a smaller sail and less driving force.
Some imagined racing advantage but forget it in the real world.

[BATAAN]

Trapeze probably invented before 1937.

[CT 249]

Great pic, Bataan.

It's certainly not a trapeze, of course. The trapezes that were very well documented in the same geographical region well before 1937 were the same as modern traps, with a line from the mast and a belt around a sailor who stood out horizontally with his feet on the gunwale.

Your pic does seem to indicate that western racers (who seem to have invented the modern rack in the '60s in Moths) were not the first to have that idea, which really underlines how hard it is to find all the prior art relevant to a sailing patent.

[BATAAN]

Modern sailors have had few original ideas.

[daiquiri]

as for cars there is no sustitude for cubed inches,
for sailboats there is no substitude for squared
Actually, it can be demonstrated that squared inches are more important than cubed ones even for cars. :)

[yipster]

sure, but that quote stuck somewhere in memory

[Doug Lord]

Modern sailors have had few original ideas.
----
Really?

[BATAAN]

Actually, it can be demonstrated that squared inches are more important than cubed ones even for cars. :)
I think the referral is to more cubic inches of displacement in a car's engine for performance and more square inches of sail area for a boat. How do they correspond?

[BATAAN]

----
Really?
Modern sailors have had much better boat and sail materials which enable them to push the envelope on stability and strength, but the ideas behind the boats are pretty much the same, just very much more efficient and long lasting now. What's new? Catamarans? Tall light rigs? Hiking arrangements? About the only real modern development that has radically improved performance is the ability to hang ballast very low and cant it to windward when beating. Pretty much everything else is just small linear development of detail and efficiency. Thoughts?

[Doug Lord]

Modern sailors have had few original ideas.


Modern sailors have had much better boat and sail materials which enable them to push the envelope on stability and strength, but the ideas behind the boats are pretty much the same, just very much more efficient and long lasting now. What's new? Catamarans? Tall light rigs? Hiking arrangements? About the only real modern development that has radically improved performance is the ability to hang ballast very low and cant it to windward when beating. Pretty much everything else is just small linear development of detail and efficiency. Thoughts?
====================
I think your original comment was an unfortunate generalization that ignores all kinds of innovation by modern sailboat designers.
Like altitude controlled bi-foiler configurations for monohulls and multihulls. Altitude controlled three foil systems for multihulls. Various altitude control systems for hydrofoils including Dr. Bradfields "wand" and Greg Kettermans solid state "feelers". The John Ilett monohull variation on the Bradfield "wand". Hydroptere with effective retractable surface piercing foils with a wide speed range. Hydroptere.ch with variable geometry hulls that convert to stepped planing hulls when advantageous. Two foil, single strut hydrofoil systems for kites and windsurfers. Self-tending solid wing sails.
Curved lifting foils for multihulls and monohulls. Rudder t-foils for multihulls and monohulls.The Bieker rudder t-foil. Solid, slotted wing sails. Inflatable airfoil kites that float.
CBTF-particularly the facility for collective "steering". Andy Dovalls winged canting keel-eliminates requirement for extra lateral resistance.
Guy Whitehouse/Jo Richards 110 degree canting keel. Ian Oately's 90 degree canting keel system. Hugh Welbourn's DSS(laterally deployable foil).
And more, much more....
Generalizations like this are never true and serve no good purpose, in my opinion. Ignoring recent* innovation in celebration of historical innovation is unfortunate-both should be recognized and celebrated.

*last 40 years or so

[daiquiri]

I think the referral is to more cubic inches of displacement in a car's engine for performance
Yes, that's what I was refering to as well. It can demonstrated that the dimensional factor which mostly influences the engine power output is not the volumic displacement but the total piston area.
So it is actually square inches (or centimeters) for both cars and sailboats. :)
Cheers!

[CutOnce]

Generalizations like that are never true and serve no good purpose, in my opinion. Ignoring recent innovation in celebration of historical innovation is unfortunate-both should be recognized and celebrated.

Generalizations do serve many good purposes. Although they do not technically encompass all possible results, they do allow people to analyze data, develop equations to explain the data, and from those equations enable the ability to predict future results. I'm surprised you are denying this, as you are quite fond of posting predicted performance as solid evidence before actually building and testing something.

Each individual "innovation" has to be measured against historical developments over sufficient time to determine it's place in the pantheon of progress. What seems groundbreaking and innovative today may fade in the passage of time - or may prove to be more important than people today give it credit. I hesitate to label anything as "innovative" or groundbreaking - just as I do not like to dismiss ideas just because they haven't worked yet. Quick to judge is also quick to be wrong.

Generalizations are not popular with the politically correct, with people on opposite sides of issues or people who like to argue for argument's sake. But they are the basis for much science, much development of mathematics to explain results and many things outside technical issues like keeping people safe and secure.

Time is the best jury on innovation, not initial enthusiasm.

--
CutOnce

[hprasmus]

Has everyone given up trying to answering my question ?

How does sail efficiency translate into improved performance ?

[Doug Lord]

Generalizations do serve many good purposes. Although they do not technically encompass all possible results, they do allow people to analyze data, develop equations to explain the data, and from those equations enable the ability to predict future results. I'm surprised you are denying this, as you are quite fond of posting predicted performance as solid evidence before actually building and testing something.

Each individual "innovation" has to be measured against historical developments over sufficient time to determine it's place in the pantheon of progress. What seems groundbreaking and innovative today may fade in the passage of time - or may prove to be more important than people today give it credit. I hesitate to label anything as "innovative" or groundbreaking - just as I do not like to dismiss ideas just because they haven't worked yet. Quick to judge is also quick to be wrong.

Generalizations are not popular with the politically correct, with people on opposite sides of issues or people who like to argue for argument's sake. But they are the basis for much science, much development of mathematics to explain results and many things outside technical issues like keeping people safe and secure.

Time is the best jury on innovation, not initial enthusiasm.

--
CutOnce

=====================
In fact, I wasn't denying anything nor was I referring to the concept of "generalizations", ah...in general. I referred specifically to one generalization that, in my opinion, presents a very incomplete and inaccurate picture of the actual facts.

Modern sailors have had few original ideas.

----


I think your original comment was an unfortunate generalization that ignores all kinds of innovation by modern sailboat designers.

Generalizations like this(referring to the original comment by Bataan) are never true and serve no good purpose, in my opinion. Ignoring recent innovation in celebration of historical innovation is unfortunate-both should be recognized and celebrated.

[hprasmus]

Surely all of those smart guys at North Sails, Quantum etc. have tested and simulated, and know the improvement a 3DL sail has over a conventional sail !

Or maybe they don't - and just ask top dollar for a nice a performance look ????

Someone out there must know......?

[BATAAN]

Yes, that's what I was refering to as well. It can demonstrated that the dimensional factor which mostly influences the engine power output is not the volumic displacement but the total piston area.
So it is actually square inches (or centimeters) for both cars and sailboats. :)
Cheers!

Now I understand, and I guess that modern engines with large bore short stroke high revs do prove your point. Thank you.
The now outdated quote came from Harley Davidson when they were trying to compete with Honda in the late 60s possibly.

[hprasmus]

Just to challenge this forums participants:

If I had been an America's Cup sail developer at say Quantum or North Sails (they do excist you know) and I had asked for this forum's advise on translating a 5% efficiency gain on a main sail and try to turn this into a speed gain, would you have answered as a) arrogant b) not at all or c) helpful but no facts as my question has had the ill faith of being ?

Uuups - now my rating is probably down one more point on reputation. Doesn't really matter when this forum can add no value.

Thanks

[daiquiri]

Hprasmus, you have been given n answer in the posts #16, #17 and #25.
If you expect to see some reassuring numbers, then you'll get old while waiting. That's the essence of the answers you've been given - the advantage cannot be quantified because it will depend on all the rest of the sailboat (which is not made up of just sails). Performance prediction of a sailboat is one of the most challenging fields in CFD, far from being entirely developed and understood. Not even with all the money in the budget of A-Cup teams.
Cheers

[Mikko Brummer]

Can you define efficiency? 5% increase in mainsail L/D ratio, or 5% increase in drive for the same heeling moment, or something else? What kind of boat, what kind of rig? Once all that is known, it's easy to look at a VPP and quantify the gain in knots, if that's ajat you want.

[hprasmus]

Thanks daiquiri,

Your answer suggests that not even the most advanced sailmakers have any idea of the performace gain of their various sails ? Very interesting. So all the hype of sails designed and manufactures to suit cruising, racing and AC are just unsubstatiated marketing gimmicks ?

Is there not a sailmaker out there that could add wisdom to this hypothesis.

Thanks.

[BATAAN]

Has everyone given up trying to answering my question ?

How does sail efficiency translate into improved performance ?

Of course it does, it's basic math, but only if the boat keeps the sail the same size as what is being "improved", not making it smaller, which puts you back where you were in your performance/speed/VMG to windward, but costing more money due to added complexity.
--
Rant alert, click away now.
If we improve something, it's supposed to work better, not just cheat a rule for those who can afford it. But I guess in some eyes, that's improvement.
As with all sailing things that truly fly and compete with each other, BMW Oracle etc and all the techy, foil-ey, wing-ey, solid-foil-sail, always-delicate high speed, usually multi-million dollar interesting boats that are thrilling to watch, but need a support boat with a machinist to keep all in order once a week at least, and has been pointed out above, fads and experiments come and go, and they are just logical steps forward in well-known widely published fluid-flow technologies, like airplanes. The Wright Flyer of 1903 uses the same aero tech the F-35 or SU-27 does.
All are as cutting edge and experimental in pushing the limits as the budget allows in the desire to get to windward first, then get down wind first, and this drive so one can be first and get all the attention is very simian and the usual thing, and once necessary in war (Baltimore Clippers 1812 for example) to impose our viewpoint on others and avoid having theirs imposed on us, but this does not mean these racing gadgets will exist 20 years from now, because they have no economic support other than rich folks experimental toys that are used 8 weeks a year at $100,000 a week to really race, and spend the rest of the time hauled out in Monaco, or break under too-hard use, or inevitably are left behind by the next tiny step in performance efficiency and wind up in a scrap heap like their long line of predecessors. You don't go cruising in one unless you have deep deep pockets and an EPIRB because they break at inconvenient times.
A good new idea is something that lasts.
Earliest cast in stone documentation of spritsail in recognizable modern form on a large trader is on a Roman sarcophagus of the third century AD. This held on in Thames barges making money under sail until the 1960s (documented 1,700 years of continuous, profitable, commercial, not toy use) so was a good new idea and still a great small boat rig.
Since needs these days are no longer carrying manure or bricks, but to experiment in very high efficiency and pushing as hard as possible at the laws of thermodynamics in the quest of pure knowledge and social competition, we see some very cool boats and startling things. But few will be around one thousand seven hundred years from now like the sprit rig probably will in some form, because they do not have a reason to exist other than "gee whiz", and for a lucky few to win money through advertising support as they compete with each other and entertain us on TV, like Gladiators in Rome, only here the stakes are money more than lives.
Announcer: "Well, folks it's pretty gusty today, and they're at the mark and GOOSE is on her foils at 42 knots under the 6 spreader 140 foot tall carbon rig but GANDER is hot behind and extending the controversial inflatable battened headsail, and Wow look at her go! 44, 46 knots but GOOSE is at the mark first and getting her spinnaker ready, and here comes the mark and around they go and GANDER has deflated the battens and unrolled the rest of the sail, and Oh No GOOSE wrapped her spinnaker and she's broaching there she, Oh the rig came down!... Well, there goes 15 million dollars. Ha ha ha, now for our commercial.".
Audience says "What's on Jersey Shore?" as they wonder where their next meal or health insurance payment's coming from.
End rant.

[Mikko Brummer]

Is there not a sailmaker out there that could add wisdom to this hypothesis.

Thanks.

Sure, but first we need to know what you mean the 5% increase...

[daiquiri]

Your answer suggests that not even the most advanced sailmakers have any idea of the performace gain of their various sails ? Very interesting. So all the hype of sails designed and manufactures to suit cruising, racing and AC are just unsubstatiated marketing gimmicks ?

Marketing has it's role, that's sure. Fact is, sailmakers can do their CFD and they can do their wind-tunnel tests, but at the end only the sea will tell the truth. Some "optimum" designs turn out to be the winning ones, and some others turn out to be... not so optimum.

An example: Luna Rossa (Prada Challenge) at Luis Vuitton's cup 2002. A huge amount of money (one of merits of AC event is that it attracts big funds for R&D) have been poured into towing-tank and wind-tunnel testing and optimization of both hull and sails during the design phase. At the end, an "optimum" boat has come out of the yard and was nearly declared by the press and some big names in the sailing world as a future winner of the LVC.
Too bad that during the races it became evident that the boat was not so optimum as it appeared to be on the computer screen. Alinghi has had it done in a different way, and Alinghi has started to win the races. So both hull and sailplan of Luna Rossa have been significantly modified on the go, making the boat somewhat faster and more similar to Alinghi. It didn't help, though - Alinghi eventually won both the LVC and AC.

So be careful when it comes to claims of 5% improvement in anything that concerns boats, if it is backed only by CFD or by theory.

Cheers

[hprasmus]

Even the AC designers have no idea of the performance effect 3DL sails have on their boats ! Only that they are lighter and more stable. So sorry for mocking you folks.

I can't quote my source obviously but it comes from a top AC designer - so all is (NOT) well.....

[hprasmus]

The 5% efficiency gain is based on the simulation across wind angles as the net effect of : side, lift, drag and forward forces

[Richard Woods]

Attached is a photo I took a couple of years ago in the San Blas islands of Panama. I doubt if these fishermen had ever seen an I-14

I agree with Daiquiri. A 5% performance gain is huge.

But to try to help. If your sail generates 5% more drive, then the boat might be 2% faster. Changing from a dacron (ie porous) sail to a laminate sail increases drive by about 5%, which is why no race boat, allowed the choice, has a dacron sail. 2% more speed for no extra effort, just extra money.

Rigs used in the past often had different roles. So the sprit rig was used on Thames barges because it was also used as a derrick in port. It had a boomless rig because many were used to take horse s**t out of London to the farms in Essex. A light high cargo with the sail reefed to clear the top of the pile.

Lug sails were often used by fishermen (eg the Looe Luggers based 10 miles from me). However they used them to sail 10 miles out to the fishing ground on starboard tack in the morning. Then they lowered the sail. Rehoisted it on the other side to sail home on port tack.

A friend rebuilt an original lugger as a live aboard cruising boat. He fitted a lug sail but after the first season replaced it with a gaff rig as he said the lug rig was far too hard a rig for ordinary sailing (and he is big, strong and a very experienced sailor)

Richard Woods of Woods Designs

www.sailingcatamarans.com

[hprasmus]

Thanks Richard Woods,

The most accurate reply I have had so far. And you are right about the complexity as well. My invention i a little bit more cumbersome than changing sailcloth. But nothing compared to changing to e.g. carbon spars. I do believe this idea has a future and I will tell the forum what it is all about when the patent is at safe harbour.

[daiquiri]

Just don't focus on a single aspect of sail operation, like aerodynamic efficiency. Consider things like materials choice, ease of production, cost, ease of handling, seaworthiness, weight and It's distribution (CoG, moment of inertia), and other aspects which will make a difference between success and failure - even more than few knots gained.
Awaiting to see the result.
Cheers!

[Cheesy]

It may have some value, a smaller diameter mast on a sport boat makes a rather large difference in the time it takes to get to the top mark...

[water addict]

hprasmus, I think after 4 pages there is a reason you have not received a definitive answer from some very qualified people on here. Because the query is not strictly answerable given the information. There is no cookbook formula that says for all boats if I have 5% increase in efficiency I get x% increase in speed. The physics is complex, and dependent upon the specifics of the boat.

Also, there are many ways to define efficiency. Do you have the manner in which your 5% number has been calculated? It makes a difference. Also if you get say a 5% better L/D ratio, that does not mean that translates directly to a 5% overall aero efficiency of the whole rig. Ex., you have drag from spreaders, shrouds, the mast that contribute to the total package. Also, you may be increasing weight aloft compared to a typical sail. All of these factors, and others contribute, and an answer cannot be given without knowing all of the required variables. And they will be different for every boat configuration.

I'm not saying you idea may not be a good one, just that there is a lot of input required to answer the question- input which is not readily available.

[tspeer]

...

How much will a 5% increase in net sail efficiency contribute to a sailboats speed (below max. hull speed of course) ?...

I find the term "net sail efficiency" to be ambiguous. I think a better measure is aerodynamic lift/drag ratio, since it includes not only the sails but also the topsides. For example, if you reduce the windage of a boat you will increase the speed without any change in the sail whatsoever. And L/D has a direct connection to sailing performance.

The fundamental sailing performance relationship is

Vb/VT = sin(gamma - beta) / sin(beta)
beta = arctan(drag_aero/lift_aero) + arctan(drag_hydro/lift_hydro)
Vb=boat speed
VT=true wind speed
gamma=point of sail (gamma=0 => head to wind)
beta = apparent wind angle, measured between apparent wind vector and velocity through the water

You can improve the lift/drag ratio by increasing the lift, reducing the drag, or both. Changing the aerodynamics (especially the lift) also has an effect on the hydrodynamic lift and drag. So for the sake of argument, I'll assume you are improving performance by reducing the aerodynamic drag.

If you substitute in the relationship for the apparent wind angle and differentiate with regard to aerodynamic drag (and assume there is no combined effect on the hydrodynamics), you end up with

d(Vb/VT)/dDrag_aero = -sin(gamma)*L_aero*(L_hydro^2+D_hydro^2)/(L_aero*D_hydro+L_hydro*D_aero)^2

You can conclude that:
- an increase in aerodynamic drag hurts performance (minus sign)
- the change in performance depends on the point of sail (gamma), and the biggest change in speed is likely to be near a beam reach
- the change in boat speed is proportional to the true wind speed
- the sensitivity depends on the actual values of both the aerodynamic forces and the hydrodynamic forces, so it's not possible to generalize a specific amount for all boats and situations

If you have a velocity prediction program, you can plug in values for the lift and drag to see what the actual sensitivity is to a change in the aerodynamics.

You should also apply the chain rule, differentiating the performance equation by the hydrodynamic lift and drag and multiplying by the change in hydro force due to the change in aerodynamic force. For example, the hydrodynamic side force must match the aerodynamic load, and there will be a change in the hydrodynamic drag associated with that. So the hydro L/D will change significantly if there is a change in the aerodynamic lift. But you can get these sensitivities from the VPP model as well.