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Thread: Inflatable sail anyone?

  1. #1
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    Default Inflatable sail anyone?

    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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    Default Re: Inflatable sail anyone?

    Not really impressed. Their vids of the inflatable sail on a Laser sailing against a stock Laser aren't convincing, because the stock Laser is poorly trimmed and sailed and still no slower despite being put in bad wind at times. The idea that you can gybe a sail around the front is something that any Laser sailor can prove to be an invitation to an instant capsize in a breeze, and it would be just as bad in a keelboat.


    There's been a complete rash of thick wingsails over the last decade. The America's Cup aerodynamics designers have stated quite clearly that the thick wings are NOT more efficient, per se, than a conventional thin sail. The earlier cruising wingsail developments have promised the world and delivered nothing so far.

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    Default Re: Inflatable sail anyone?

    It could have some advantages on a small open boat, you certainly aren't going to turtle. As for sail shape, it's early days, theoretically it should be better than a normal sail?
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    Default Re: Inflatable sail anyone?

    Wonder if a catamaran would be self-righting.

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    Default

    The sail uses fans to at the front of the luff to inflate it so it would need a capsize valve to stop water filling the sail. The mast could easily be made to cant to aid righting as per G32 (look at 6.20) https://youtu.be/OIsbtjvseZs

    Re fans, wonder what they do about rain and spray getting in because that would be a massive issue




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    Default Re: Inflatable sail anyone?

    Weird, Strange, Exotic! Might be better in shape as is a junk sail. The multiple sheets, on a junk, can control the twist for optimum wind angle. It could also bifurcate down wind like the old twin wings boats were set up. Always fun to experiment. Leave it to the Swiss to come up with a new one when you think all has been done.
    Jay

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    Default Re: Inflatable sail anyone?

    Quote Originally Posted by PeterSibley View Post
    It could have some advantages on a small open boat, you certainly aren't going to turtle. As for sail shape, it's early days, theoretically it should be better than a normal sail?
    As Tom Speer (Boeing wing designer and America's Cup wing designer for Oracle) and Mark Drela (MIT aerodynamics professor, designer of world champion wings and foils and Oracle wing designer) both say over on Boat Design Forum, a thick wing has no theoretical advantage over a normal sail. A thin foil actually provides better lift/drag characteristics although they are over a narrower range of angle of attack. A wingmast can be more forgiving and it has great structural advantages for the AC boats, but it comes with its own set of issues. As Tom says, the reason aircraft wings are thick is NOT because thick is better, but for structural and other reasons.

    Similarly, modern CFD is confirming what eons of practise has shown, which is that a good mast doesn't destroy the flow over a mainsail as old theories and bad tests showed. Marchaj's tests, for example, used grossly over-sized round masts which were totally unrealistic. CFD actually shows that the mast provides lift.

    This stuff provides the answer to the reason why decades of experimentation with things that "clean up" the leading edge and with wingsails have almost always failed to provide the theoretical advantages that were claimed for them. I've got four wingmasts and a dozen or more sails with big pocket luffs, rotating battens etc, and the advantage they give is not consistent and pretty small at best.

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    Default Re: Inflatable sail anyone?

    But flotation in a small boat ?
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    Default Re: Inflatable sail anyone?

    Not inflatable but David Tyler sailed around most of the planet with this rig.
    8496E079-D000-4CBC-AC70-472372BBDF4D.jpeg
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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    Default Re: Inflatable sail anyone?

    As far as I can calculate it (and I may well be wrong) the sail's pressure is so low that it would collapse instantly under the pressure of even 1m of water.

    I think Mark Drela also pointed out the issue with the multi-section telescopic mast. You normally need overlap between each section even when fully erected; I think it's about four times the chord? That means that essentially you've got double the thickness and double the weight for most of the spar.

    The really odd thing about all the soft wingsails and double surface masts that are being promoted these days is that everyone has the time and effort to put up a website, but apparently something is stopping them from actually getting out on a racecourse and lining up against other boats to show the claimed speed improvements. The Omer soft wingsail's creator promised boat-on-boat trials in around 2005, if I recall correctly. They've put out press releases and test rigs since then but apparently something is stopping them from actually giving hard evidence of their claims by doing something as easy as entering a race. One manufacturer (Seascape) tried an Omer soft wingsail. The video looked interesting but the company reports that the actual performance was not up to scratch when they did boat-on-boat trials.

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    Default Re: Inflatable sail anyone?

    I put up the OP not because I like the idea but because it is an unusual approach to sail design, in my opinion anyway.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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    Default Re: Inflatable sail anyone?

    Quote Originally Posted by WX View Post
    Not inflatable but David Tyler sailed around most of the planet with this rig.
    8496E079-D000-4CBC-AC70-472372BBDF4D.jpeg
    Yes, but did he put it up against an identical (or similar) hull in an objective test and prove that it was faster and/or more easily handled?

    I'm NOT saying that speed is all, but the sailors who sail 18 Foot Skiffs, 12 Foot Skiffs, R Class, Moths, Formula 16 cats, A Class cats, Raceboard windsurfers, NS14s, Merlin Rockets, Suicides slalom windsurfers, Bembridge Redwings, Stars, 18 Squares, International Canoes, speed windsurfers and offshore multis have been trying double surface sails and similar devices for about a century. The people involved have included leading physicists, naval architects, sailmakers and Olympic gold medallists. During those hundreds or thousands of hours of effort, such devices have proved marginally faster in about three specific fields. Otherwise they are slower.

    In a fraction of that time the same bunch of people have basically created the modern foiler, the modern skiff types, the windsurfer etc, so they are far from unsuccessful in terms of developing new ideas and technology. So the general lack of success of wingsails and similar devices almost certainly isn't down to incompetence or lack of effort.

    The thing seems to be simply that as world-class aerodynamics experts like Mark Drela (designer of the foils used in the world human powered flight record and the water speed record) say, there is no inherent advantage in wingsails.

    That's not to say it's not interesting to watch the development - it's just putting up a view on the topic. Personally, I find the psychology behind the development and the reception of these things really interesting. The way the sailing media reports on soft wingsails etc is really interesting - they seem to suspend their critical faculties entirely.

  13. #13
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    Default Re: Inflatable sail anyone?

    Quote Originally Posted by Chris249 View Post
    Yes, but did he put it up against an identical (or similar) hull in an objective test and prove that it was faster and/or more easily handled?

    I'm NOT saying that speed is all, but the sailors who sail 18 Foot Skiffs, 12 Foot Skiffs, R Class, Moths, Formula 16 cats, A Class cats, Raceboard windsurfers, NS14s, Merlin Rockets, Suicides slalom windsurfers, Bembridge Redwings, Stars, 18 Squares, International Canoes, speed windsurfers and offshore multis have been trying double surface sails and similar devices for about a century. The people involved have included leading physicists, naval architects, sailmakers and Olympic gold medallists. During those hundreds or thousands of hours of effort, such devices have proved marginally faster in about three specific fields. Otherwise they are slower.

    In a fraction of that time the same bunch of people have basically created the modern foiler, the modern skiff types, the windsurfer etc, so they are far from unsuccessful in terms of developing new ideas and technology. So the general lack of success of wingsails and similar devices almost certainly isn't down to incompetence or lack of effort.

    The thing seems to be simply that as world-class aerodynamics experts like Mark Drela (designer of the foils used in the world human powered flight record and the water speed record) say, there is no inherent advantage in wingsails.

    That's not to say it's not interesting to watch the development - it's just putting up a view on the topic. Personally, I find the psychology behind the development and the reception of these things really interesting. The way the sailing media reports on soft wingsails etc is really interesting - they seem to suspend their critical faculties entirely.
    He single handed around the world and he was over 60 when it did it. It may not be a racer but as a cruiser it more than served the purpose. Bit complex for me though, I like my low tech JR.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

  14. #14
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    Default Re: Inflatable sail anyone?

    Quote Originally Posted by Chris249 View Post
    Yes, but did he put it up against an identical (or similar) hull in an objective test and prove that it was faster and/or more easily handled?

    I'm NOT saying that speed is all, but the sailors who sail 18 Foot Skiffs, 12 Foot Skiffs, R Class, Moths, Formula 16 cats, A Class cats, Raceboard windsurfers, NS14s, Merlin Rockets, Suicides slalom windsurfers, Bembridge Redwings, Stars, 18 Squares, International Canoes, speed windsurfers and offshore multis have been trying double surface sails and similar devices for about a century. The people involved have included leading physicists, naval architects, sailmakers and Olympic gold medallists. During those hundreds or thousands of hours of effort, such devices have proved marginally faster in about three specific fields. Otherwise they are slower.

    In a fraction of that time the same bunch of people have basically created the modern foiler, the modern skiff types, the windsurfer etc, so they are far from unsuccessful in terms of developing new ideas and technology. So the general lack of success of wingsails and similar devices almost certainly isn't down to incompetence or lack of effort.

    The thing seems to be simply that as world-class aerodynamics experts like Mark Drela (designer of the foils used in the world human powered flight record and the water speed record) say, there is no inherent advantage in wingsails.

    That's not to say it's not interesting to watch the development - it's just putting up a view on the topic. Personally, I find the psychology behind the development and the reception of these things really interesting. The way the sailing media reports on soft wingsails etc is really interesting - they seem to suspend their critical faculties entirely.
    Interesting, the design of the ‘modern’ foiler has been around for nearly 70 years but it wasn’t until the advent of accessible high strength to weight materials that it became truly practical.

    The advantage of the junk rig is that it is very easy and quick to solo adjust sail area and have optimum drive as the weather changes. Though the inflatable wing sail may not stack up against a full race Bermudan rig it must have an advantage over the Junk. If the soft wing sail can work without the extra sheets perhaps in the cruising world it is worth developing.

    The complexity of luff fans and telescopic mast would put most cruisers off this particular concept.

    But back to my opening point, is there a new material that could be developed to make these type of sails practical?

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    Default Re: Inflatable sail anyone?

    Quote Originally Posted by tink View Post
    Interesting, the design of the ‘modern’ foiler has been around for nearly 70 years but it wasn’t until the advent of accessible high strength to weight materials that it became truly practical.

    The advantage of the junk rig is that it is very easy and quick to solo adjust sail area and have optimum drive as the weather changes. Though the inflatable wing sail may not stack up against a full race Bermudan rig it must have an advantage over the Junk. If the soft wing sail can work without the extra sheets perhaps in the cruising world it is worth developing.

    The complexity of luff fans and telescopic mast would put most cruisers off this particular concept.

    But back to my opening point, is there a new material that could be developed to make these type of sails practical?
    I don't know about that. The modern cambered panel sail and the even newer split rig are pretty good rigs. The windward performance, the ease of handling and the low tech are very big pluses.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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    Default Re: Inflatable sail anyone?

    With respect, WX, it depends on what you're looking at in terms of windward performance. The boat the Junk Rig Association points to as an example of a "high speed" junk rig is an X-99 fitted with a very expensive carbon fibre mast and cambered panels. It's rated by the owner as being 9-10% slower than a standard example of the class, which is an enormous amount from some angles - it's about the the same as the speed difference between the 33ft X-99 and its smaller and older sister, the 26ft X-79. So putting on a carbon mast and cambered junk sail cuts your speed down the same as if you had a similar boat 7 ft shorter.

    None of this means that the JR is inferior or should not be used; it's just that by some standards the windward performance is not very good.

  17. #17
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    Default Re: Inflatable sail anyone?

    I've noted I can't match speed to windward but for coastal cruising I wouldn't bother. I would wait for a more favourable wind. How high would you expect the average cruising yacht to point?
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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    Default Re: Inflatable sail anyone?

    I don't know - I've never checked. Nor, unfortunately, do I get to wait for favourable winds or like motoring, so I often go upwind and often enjoy it, especially for shorter sails or during longer (600 mile +) passages. I know one sailor who doesn't like extensive windward legs; he's the one who spent about two months sitting in a port he was bored of, waiting for the trades to stop blowing.

    Even around my local waters there's extensive beating involved. Perhaps because our harbours tend to be sheltered from the south and the summer winds are NE, we often seem to be beating to favoured anchorages.

    Obviously rig choice is very personal and the result of individual weighting of all the various factors; I'm just interested in looking at valid comparisons and quantitative data about the different aspects.

  19. #19
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    Default Re: Inflatable sail anyone?

    The only wind I wouldn’t sail north in from Tweed is a north easterly. A mate of mine in a 40ft BM rigged yacht did 40 nm just to go 15. I gave up after 5 and went back home.
    The figure I hear quoted for reasonable windward ability is around 45 degrees, that’s true wind not apparent wind angle.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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    Default Re: Inflatable sail anyone?

    45 is pretty common, but of course it's all relative to speed and going slow but high isn't efficient. Many craft will sail much higher, but only by losing speed.

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    Default Re: Inflatable sail anyone?

    I was able to get about 45 degrees in my folkboat, but that was in good sailing conditions... go to typical cruising conditions and that windward ability is not nearly so good. That very tall mast is more useless than tits on a bull in strong winds when only a fraction of the main can be raised.

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    Default Re: Inflatable sail anyone?

    Quote Originally Posted by Chris249 View Post
    45 is pretty common, but of course it's all relative to speed and going slow but high isn't efficient. Many craft will sail much higher, but only by losing speed.
    Give me a rolling swell and fine, give me choppy head seas plus headwind and I might as well go home. Coming back from Southport in SW at around 5 knots and I was averaging 2.5 knts on a course of 155 degrees M. By no stretch of the imagination do I consider myself a cruising sailor and 5 years on I am still learning how to handle my rig and boat efficiently.
    The definition of stupid has got to be the belief that more guns will negate the bloodshed done with guns.

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