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Connor.kainalu

Legal "Wingmast" for I/14

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I'm getting into the I14 class and have read the rules expressly prohibiting "rotating masts".  In his wonderful book High Performance Sailing, Frank Bethwaite devotes a chapter to the development and efficiency of the wingmast. His data shows a 5-10% increase in rig efficiency. As a designer, I think that I've found a way to get that efficiency from a non-rotating mast. FB mentions that they tried having elongated socks on the sails , but the leading edge was too blunt to stop the air currents from separating. What we were thinking is that we could stop the leading edge from being blunt (and therefore stop or delay the separation altogether) by putting a flexible insert (kind of like the fairing on the front of the mast when he talks about rig flexion) inside the sock, in front of the mast. 

     The idea works great until you add a jib, stays and a spinnaker. How would the fairing rotate? How would you hoist the sail?

here are some sketches that portray the idea

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Before you start posting about this sort of thing, you should try reading the class rules. I would draw your attention to the following.

12.d All sails shall be capable of being fully lowered while afloat, without detaching the forestay or requiring that the boat be capsized.

Tell us how you intend to get around that rule, because that is the whole ball game. The other problem is making a sail like that work on a non rotating mast. When you have everything tensioned properly, it won't rotate around the mast.

Trying to find a way around this on the I14's (and other classes) is nothing new but nobody has found a way around it yet. Once you find a way to make it work, we can discuss refining the set up but until then, it seems pointless. As an aside, look at the Moth rig to see why the round section mast problem is a bit of a red herring and why it is the least of your challenges.

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Start with the class rules, as GBR said, and this thread. If you can find content on the 7 skiff that'll be very interesting but it all seems to be gone. A quick google didn't bring anything up for me.

Much of this idea is hashed out and what you're talking about with the mast fairing isn't really feasible. The closest solution is a wing mast like you see on an MG/NS14 or two handed cat like a Nacra or Tornado.

Wing masts aren't popular on skiffs but they do have their advantages. Like all things, it's a balance of performance, ease of use, cost, etc.

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The trouble with wing masts is that they have never really lived up to the benefits that theories would suggest. FB wrote that book a long time ago now - essentially that section is about development he did in the early 1970s. 

The rotating fairing on a pole mast is not a new idea, I know Julian B has speculated that it might be worth exploring. There are going to be much easier classes to explore the idea on then the I14 though. Its probably as well to do this sort of thing on classes where you aren't liable to get into rule trouble - and the I14s have a long history of banning new ideas...

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For any mechanically rotating fairing, you'll need a pretty straight mast, and even the new stiff single-spreader rigs bend a bunch (and are falling back out of favour it seems).

I gather what you're trying to do is reduce the separation bubble (particularly to leeward) caused by the sailtrack on the mast being upwind of the leeward stagnation point (talking inviscid flow now).  So a forward fairing isn't going to be a huge help.  And from the looks of your first sketch you might run nto the prohibition on "double-luffed sails".

I think the more important question is, what boat are you sailing, where, and how much of it do you plan to do!?!?  It'd be great to see some more East Coast 14ing!!!

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I don't have a boat, and unfortunately I'm moving to San Diego. One of the ideas we had was to stuff a pool noodle that had been sanded to shape up the front of the sock, and if it didn't twist, we might be able to get a slightly more efficient shape 

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Also, this is just a bit of a crazy idea for experimentations sake, most likely it wouldn't be used in competitive racing 

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I've thought about small boat testing, but the gains in efficiency would be so small that I couldn't measure them 

 

by small, I mean remote controlled 

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What is banning you from using a non rotating wing mast section? I suspect nothing but cost. The efficiency gains may not be there.

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1 minute ago, samc99us said:

What is banning you from using a non rotating wing mast section? I suspect nothing but cost. The efficiency gains may not be there.

It would be both flexible and stiff in both the wrong directions, to say nothing of aerodynamics.

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I'm not sure how the I14 rigs work. I can say that the carbon wing mast can be tuned to be stiff in whatever direction you want, though its shape inherently leads it to be stiff fore and aft and less so side to side. However the latest aluminum and carbon rotating beach cat wing masts are very stiff side to side which lets them flex fore and aft more.

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Yep think you aren't allowed a rotating mast in the rules.

General good sense indicates that if you do anything that compromises bend and sail shape then its a waste of time, and if you did run a rotating mast (outside class) then you have different bends at different rotations. I guess cats manage it. Plus in 14s if you know a good sailmaker they can cut something appropriately, but it'll probs take a few goes.

I14s need to run high rig tensions too as the shroud base is narrow compared to a cat and a fairly big jib to keep a straight luff on. That would not make rotation any easier. Then you are running something like 400kg of vang upwind which would make rotating the mast through tacks a right laugh, so you may have to go to a cat style mainsheet on traveller arrangement, somehow.

You can get an awful lot of boat cheap with an older i14 But I would urge caution - to do anything like this properly will take ages and cost loads, which is OK if you prefer getting dirty and burning cash more than sailing!

I faired in the track on my S3 selden on my i14, and have aero shaped spreader so it looks a bit more wingy, reckon that added ~ 300g and took maybe 10h in total. Possibly an incremental aero gain which is more than wiped out by the myriad shortcomings in my sailing abilities.

Dan

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Getting some great responses here for some very intelligent 14/skiff sailors.  Great that you are thinking outside the box.  But, don't think you are the first one to make efforts this way.  There is a reason the 14 class is the oldest internationally recognized dinghy class in the world.  My first thought on your drawings was the double luff rule (thus the reason we don't have gnavs like a 49er).  Everytime you think of something new, there is a price to pay for it.  There are much smarter people than I who have worked on these problems much longer than myself.  Thing is, you have to get out and sail the boats first.  Will take lots of time just to get off the dock and keep the boat upright.  Might be best to buy an older boat and just get going when you get here to SD.  A few available locally, or others along the west coast.  Several very well thought out and very competitive boats.  But nothing wrong with getting a less expensive boat and trying your theories.  Just don't get lost the the tweaking and not learn to sail the boat.  Look forward to meeting you when you get here.

 

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37 minutes ago, BWR said:

Getting some great responses here for some very intelligent 14/skiff sailors.  Great that you are thinking outside the box.  But, don't think you are the first one to make efforts this way.  There is a reason the 14 class is the oldest internationally recognized dinghy class in the world.  My first thought on your drawings was the double luff rule (thus the reason we don't have gnavs like a 49er).  Everytime you think of something new, there is a price to pay for it.  There are much smarter people than I who have worked on these problems much longer than myself.  Thing is, you have to get out and sail the boats first.  Will take lots of time just to get off the dock and keep the boat upright.  Might be best to buy an older boat and just get going when you get here to SD.  A few available locally, or others along the west coast.  Several very well thought out and very competitive boats.  But nothing wrong with getting a less expensive boat and trying your theories.  Just don't get lost the the tweaking and not learn to sail the boat.  Look forward to meeting you when you get here.

 

Having sailed i14s for many years a big +1for this one.

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I sail a 12' skiff and built a pocket luff #2 main for it (about the same as an i14 main, but slightly less powered up).

Long story short - solved the problem, and it worked pretty well.  Made my own cams, had cool spreaders to deal with the pocket, re-luffed the sail to suit etc.

Wasn't any faster, couldn't tell the difference.

There may have been a slight advantage if you're overcooked and trying to pinch upwind.  I think for moths it can generate more camber, ie more lift offwind, but we have spinnakers so it doesn't matter.  

I have reverted to a normal sail in a track and focussed on rig dynamics, twist, perfecting leech tension etc.

I spoke to Alex Vallings about his same effort on the 18' and his conclusions were uncannily similiar.  'no difference, just a pain in the ass'.  Some benefit if you want to 'zip in' a different luff round if your number of sails are limited (do i14's let you change luffs on the main?)

Fill with water when you capsize, heavier sail, harder to tune, more sailmaking to get right, slower to rig.  Leeward separation bubble can go suck itself!

Some babble on it here: http://z10.invisionfree.com/12ft_skiffs/index.php?showtopic=551

Some pics here (my photobucket account seems to have choked):  http://s981.photobucket.com/user/BG_172/library/Tank Girl rigs

http://s981.photobucket.com/user/BG_172/library/Tank Girl rigs?sort=3&page=1

 

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I don't want to offend people, but probably will do anyway, so apologies in advance. I really do commend people in development classes that try new things.

But........

I cannot understand the thinking behind the few people who try pocket luffs with camber inducers and then dismiss them like they do. When developing a new regular sail shape, it is common for it to take a number of iterations to get it right. When developing a whole new rig concept, it takes many goes at it. To date, I have yet to see a pocket luff rig on a skiff that looks as if they got it right first time. I am not saying I could - actually, I am saying the opposite that nobody could get it right first time. I look at the pictures of both the 12 and the 18 and always think of what the next iteration should look like. The thing that always strikes me is that they look like conventional sails with pockets and camber inducers added.

In considering moving to the A Class, I made some enquiries about rig development. A friend who sails them and who used to sail Moths had spoken to Amac (Mach 2 and Ka sails) about a Moth style rig for the A. His view was that it could be done but it would be an expensive exercise because he anticipated it would take at least 6 iterations of both mast and sail to get right. If one of the leading proponents of pocket luff sails says it takes that long to get right, it highlights the challenges faced by others and why results are likely to be inconclusive initially.

I would give a slightly different assessment of pocket luffs for skiffs. If the attempts we have seen show no disadvantage when they are so unrefined, then it suggests there is a lot of potential if somebody has the time and money to develop it properly.

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11 hours ago, Team_GBR said:

I cannot understand the thinking behind the few people who try pocket luffs with camber inducers and then dismiss them like they do. When developing a new regular sail shape, it is common for it to take a number of iterations to get it right.

I had pretty much the same discussion fifteen years or more ago with Alex Vallings of C-tech, who's one of the people who has tried and abandoned radical rigs on Skiffs. As I recall what he said was something on the lines of  - if current solution is at 95% of potential, and new concept is at 70% of potential, which would be pretty good for a first pass, how big an advance does new concept have to be to look fast?

I can't speak for AV or the others, haven't talked to anyone about what they abandoned radical rigs, but my thinking has been something like this. I first had a wing mast on a dinghy of mine back in the 70s, and I've played with them intermittently since then: indeed there's been a Bethwaite wing mast in my garage for the last umpteen years. However its one thing to give a concept a good go and see how you get on, and quite another to do a real development process if you are just a self funded amateur - or even owner of a small business where you have to fund it yourself in your own time.

My feeling is that if you're developing stuff on your own, whether as amateur or self funded professional, then a serious development process *guaranteed* to deliver whatever the potential is in an idea is going to eat up probably half a dozen masts, twice that number of sails and goodness knows how many recuts. And even more to the point, if the only real comparison you have is class events, its going to eat up three or four sailing seasons in which you are going to be uncompetitive and inconsistent. That's really quite a chunk out of your sailing life and your wallet. And if it turns out the potential was never there...

True, a professional sponsored sailing team with two boat tuning, full time sailors  and ample budget can compress all that into months or less. And even a handful of committed amateurs, if they are local to each other, can get results quickly and within a reasonable budget - 6 masts and 12 sails between 3 people with two boat tuning exercises or just weekly racing is a lot more practical. But if you haven't got that... I've three times considered radical rig projects on top of new boats, but every time I've reluctantly decided that actually I want to play it a little bit safer and actually go racing, not just be testing within a racing fleet. So to my mind that's the reason why the things get dismissed. Its one thing to build a rig and give it a good go mate, but if your good go comes up disappointing, well its quite another to put in a sustained development process.

But going back to the OP, to my mind the 14 is the wrong platform for radical rig development. They have both a lot of restrictive rules (although nothing like as bad as they used to be) and a long history of banning radical developments if they show potential. There are other boats that would be a better choice.

 

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Rotating masts have also been tried in Merlin Rockets, but the avenue of development was abandoned.

Really the only classes that have successfully adopted are multihull classes, the Tasar and NS14 ... I guess that the issue, as previously noted, is that the gain is apparant wind sailing downwind, so an assymetric kite negates the potential gains.

There are functional issues relating to the halyard sheave for the kite, though I guess that these could be overcome with inginuity, though I cannot readily see how a sheave that is twisted to windward, and a halyard that has to pass through the mainsail luff sleeve would have good aero.

Also, northern hemisphere rigs have been developed to perform across the wind range by using mast bent to flatten and depower the mainsail, I am not sure that this is a benerfit of rotating rigs, but again there may be a solution that development can throw up.

Having overcome all of the above, you then need to consider the potential gain on the diminishing return curve.

Having said all of that, the joy of a class like the I14 is to do this sort of thing ... however in my time in the class I learnt pretty quickly to watch what the developers were doing and buy in when they had resolved the issues, usually a couple of months before a big event.

 

 

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22 hours ago, Ben G said:

I sail a 12' skiff and built a pocket luff #2 main for it (about the same as an i14 main, but slightly less powered up).

Long story short - solved the problem, and it worked pretty well.  Made my own cams, had cool spreaders to deal with the pocket, re-luffed the sail to suit etc.

Wasn't any faster, couldn't tell the difference.

There may have been a slight advantage if you're overcooked and trying to pinch upwind.  I think for moths it can generate more camber, ie more lift offwind, but we have spinnakers so it doesn't matter.  

I have reverted to a normal sail in a track and focussed on rig dynamics, twist, perfecting leech tension etc.

I spoke to Alex Vallings about his same effort on the 18' and his conclusions were uncannily similiar.  'no difference, just a pain in the ass'.  Some benefit if you want to 'zip in' a different luff round if your number of sails are limited (do i14's let you change luffs on the main?)

Fill with water when you capsize, heavier sail, harder to tune, more sailmaking to get right, slower to rig.  Leeward separation bubble can go suck itself!

Some babble on it here: http://z10.invisionfree.com/12ft_skiffs/index.php?showtopic=551

Some pics here (my photobucket account seems to have choked):  http://s981.photobucket.com/user/BG_172/library/Tank Girl rigs

http://s981.photobucket.com/user/BG_172/library/Tank Girl rigs?sort=3&page=1

 

Could you rehost your photos on imgur or google photos or something? Photobucket is shit.

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Ben Gs effort is really first class I chanced upon his blog a while ago. 

Well considered design really nicely done execution - I hope he is getting lots of fun from her. 

 

Its bloody interesting this whole subject, and something I have dabbled in a bit with varied results. I think that the 6 masts 6 sails thing is a decent if conservative basis if you are going for an entirely new rig concept.

You get to a paretos law situation ie the first 80% of results come from the first 20% of effort, The last 20, or realistically 10% towards perfection, whatever that is is the hard bit. Obv if you are just having a go at a sail only that is a different story. 

A good product for smod use will require a lot less finessing than getting last 1% performance in a  development class. The effort for smod is in designing enough cost out whilst keeping sufficient capability. 

I think that if the sailor or owner of the process is either a sailmaker or engineer, the process can happen a fair bit quicker. Similarly if the sailor or sailors have a really keen engaged sailmaker/ spar maker on board (often but by no means always a function of potential earnings ) then that can significantly expedite things. 

if it's just a sailor or sailors pushing shit up hills with an Unengaged sailmaker/ spar maker then it's a bit of a case of how many monkeys with typewriters are needed to write the collected works of Shakespeare. 

These days some bigger lofts and spar makers have sophisticated software that can do coupled aero and structural calcs that can significantly fast track these sort of wholesale rather than incremental developments. In big boats they make a lot of use of that, but as you get smaller the cost of making prototypes becomes competitive. Of course as with all software, rubbish in rubbish out so somebody has to know what they are doing and what they are aiming for. 

Absolutely agree that if results on water are your primary concern leave all this shit well alone and cherry pick what someone else has done once it's mature and demonstrably better than what went before. 

 

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1 hour ago, DavidG said:

Rotating masts have also been tried in Merlin Rockets,

But only in very poor implementations using the wrong sorts of section if you give Bethwaite's research any sort of credibility. 

Nicky Bethwaite won a Cherub worlds with an over-rotating rig, so its not altogether true that only single sail classes have adopted them successfully. Incidentally at the time they were credited with exceptional upwind speed. They weren't really seen in the class after the Bethwaites moved on, but a lot of that was that it is extremely hard to do a decent Bethwaite style mast in aluminium (the Tasar mast is rather compromised). Carbon and other fibres open up all sorts of possibilities that are to my mind yet to be explored.

What has happened though, since Bethwaite's research, is that pole masts have developed dynamically way beyond anyone's expectations, and we have learned that the dynamic response of rigs brings enormous benefits in boat speed and handling. Bringing those benefits to a rotating rig that supports a spinnaker seems to be very challenging. We've also leaned that a lot of the old thinking about mast drag and section shapes was hugely overstated, and a simple pole mast isn't nearly as problematic aerodynamically as we always thought. In particular the old thinking about advantages of a smooth leeside flow seems to have been fundamentally flawed.

I've never had the slightest concern with kite halyards, and in these days of masthead kites any problem is minimal. Similarly there are all sorts of options with mast bend. But getting it all together is a big challenge, there's no doubt, which is why I haven't tried recently!

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On ‎2‎/‎08‎/‎2017 at 0:54 AM, JimC said:

What has happened though, since Bethwaite's research, is that pole masts have developed dynamically way beyond anyone's expectations, and we have learned that the dynamic response of rigs brings enormous benefits in boat speed and handling. Bringing those benefits to a rotating rig that supports a spinnaker seems to be very challenging. We've also leaned that a lot of the old thinking about mast drag and section shapes was hugely overstated, and a simple pole mast isn't nearly as problematic aerodynamically as we always thought. In particular the old thinking about advantages of a smooth leeside flow seems to have been fundamentally flawed.

 

Good observations here.

Also with HM Carbon, the mast diameters to achieve the same stiffness have reduced by 15-20% over alloy and there is typically less weight and bulkiness of standing rigging. This has to close the gap significantly on any theoretical benefits of wing sections.

 

 

 

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On 8/1/2017 at 6:13 PM, JimC said:

I had pretty much the same discussion fifteen years or more ago with Alex Vallings of C-tech, who's one of the people who has tried and abandoned radical rigs on Skiffs. As I recall what he said was something on the lines of  - if current solution is at 95% of potential, and new concept is at 70% of potential, which would be pretty good for a first pass, how big an advance does new concept have to be to look fast?

I can't speak for AV or the others, haven't talked to anyone about what they abandoned radical rigs, but my thinking has been something like this. I first had a wing mast on a dinghy of mine back in the 70s, and I've played with them intermittently since then: indeed there's been a Bethwaite wing mast in my garage for the last umpteen years. However its one thing to give a concept a good go and see how you get on, and quite another to do a real development process if you are just a self funded amateur - or even owner of a small business where you have to fund it yourself in your own time.

My feeling is that if you're developing stuff on your own, whether as amateur or self funded professional, then a serious development process *guaranteed* to deliver whatever the potential is in an idea is going to eat up probably half a dozen masts, twice that number of sails and goodness knows how many recuts. And even more to the point, if the only real comparison you have is class events, its going to eat up three or four sailing seasons in which you are going to be uncompetitive and inconsistent. That's really quite a chunk out of your sailing life and your wallet. And if it turns out the potential was never there...

True, a professional sponsored sailing team with two boat tuning, full time sailors  and ample budget can compress all that into months or less. And even a handful of committed amateurs, if they are local to each other, can get results quickly and within a reasonable budget - 6 masts and 12 sails between 3 people with two boat tuning exercises or just weekly racing is a lot more practical. But if you haven't got that... I've three times considered radical rig projects on top of new boats, but every time I've reluctantly decided that actually I want to play it a little bit safer and actually go racing, not just be testing within a racing fleet. So to my mind that's the reason why the things get dismissed. Its one thing to build a rig and give it a good go mate, but if your good go comes up disappointing, well its quite another to put in a sustained development process.

But going back to the OP, to my mind the 14 is the wrong platform for radical rig development. They have both a lot of restrictive rules (although nothing like as bad as they used to be) and a long history of banning radical developments if they show potential. There are other boats that would be a better choice.

 

IMO, AV has got it wrong and this is common in rig development. In almost every development program I have been involved with, you end up taking backward steps before you move forward. The first iteration is likely to be way off, even if it looks half decent like the 12 rig. There seem to me to be little point in starting down such a route if you aren't prepared for the inevitable development cycle. The reasons you go for a new development rig don't go away after the first try.

As Jim points out, for most, the costs are simply too high. Look at the I14. I agree with Jim is probably a tough class to do this particular development for a number of reasons, not least because the boats are so hard to sail that it is hard to know if the gains or problems are down to the development or the sailors. If you have the time, money and the right team, you can make big gains, as we saw some years ago when a small group in the USA, funded by the Kahn family, developed a new rig/boat. They were top sailors (Shark, Trevor Baylis, Euan McNicol, Howie Hamlin) and they worked with a good sailmaker over an extended period. There were crazy stories about how much the campaign cost ($50-60k per boat) but the end result was, as a team, they dominated the world championships (1,2 4 IIRC).

This sort of rig development is rarely attractive for a sailmaker. Development classes in general don't sell enough sails to warrant the investment. Development costs can be recovered by selling on development sails cheaply to people lower down the fleet who will see an improvement compared with their old, tired sails, but that only applies if the development sails aren't too radical. Sailors are also a problem, because they do it to get results which means they are more likely to revert back to something proven than stick the course. Think about it as a sailor. Any development you are involved in only gives you an advantage for one championship because then the sailmaker needs to sell to everybody else to make his money ad others can copy. How many average results would you give up to gain an advantage for 1 championship? Even then,and particularly in the UK, it is really hard to keep developments secret, so sometimes getting that 1 championship benefit can be difficult. 

Regrettably, this means that development tends to be evolutionary rather than revolutionary.

 

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To say nothing how crappy the Aero of a curved plate is, even with a shaped leading edge (although that can help, esp re an una rig).  As soon as a jib/assym is added, everything changes.

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I remember Russell Bowles (a Kiwi), having a pocket luff main on his 12 foot skiff at the 1969 Inter Dominion in Sydney, and he won every race bar one.

The MG14 a spinnaker and trap' version of the NS14 sails with a rotating mast, so it can be done.

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2 hours ago, Rainbow Spirit said:

I remember Russell Bowles (a Kiwi),

Russ Bowler - later half of Farr Yacht Design. That boat was so full of new ideas and techniques that later became widespread its hard to pick on the sail...

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Hi, in deference to Dad, the major reason why wing mast are not "cost effective" and by cost here I mean performance, is that the skiff carries a quite low lbs/ft² or kgs/m² compare to say an NS14 or a Tasar or most multihulls, so the advantage gained by increasing the pressure differential, by using a rotating mast or a cuff luff is grossly outweighed by the complexity.     I assure you we tried it, particularly the cuff-luff with the LE fairing, we hot wired EPS foam.   Bora did it not so long ago on his Moth, we did it 20+ years ago.

But complexity outweighed benefit and it was discarded, pretty quickly.

DW as soon as you pop a spinnaker, then any argument to increase CoL goes out the window!

Not saying it won't work, but more so because of the drag reduction coming from the smaller LE radius.    Total drag from a mainsail set behind a round mast, like a 49er is only 15.4%, and the jib alone is 12.3%  (of the total drag pool) so the drag of the mast itself, is going to be 2-4%.    To put that in perspective, if the 2 crew trapeze at different heights, you will generate more drag than the entire mast.     There are better, more efficient places to reduce drag. 

With the advent of foiling and the dramatic reduction in Hull (hydro) drag, then the whole game changes.  mostly the significant "over canvassing" that has been a part of skiffs for literally hundreds of years, will become more modest, and we will see another Russel Bowles, or a Terry McDell or dare I say Bethwaite minimalisation drive and the sail area will become less and then you will see increase in things like cuff luffs with LE fairings.

But with 230+ ft² of UW area on a I14 (or similar on the 49er) the gains are just not there.

Think about the clothes you wear and lock in, trapezing UW, and the gains will be greater.

Things like rope trap wires are very light, but they are also very draggy, much more draggy than similar strength 1:7 wire.

For the extra 50gms in weight, the wire ain't all that bad.\

              Jb

 

 

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7 hours ago, JulianB said:

But complexity outweighed benefit and it was discarded, pretty quickly.

And one should never forget the human factors... I'm completely convinced by the case you and your father put for the 49er et al mainsail cuff. It seems to me it just has to be a good thing even if it counts as measured sail area. So when I got a new main for my IC I sized it so there was the area available for a cuff, and I had one made. It lasted about three races. The reason is that I don't use a self tacking jib, and being unable to sight the position of the jib clew and ensure my sheeting was *exactly* right psyched me out completely. I spent the upwind legs worrying about the sheet position instead of watching the wind... 

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On 1 August 2017 at 9:43 PM, BR3232 said:

Could you rehost your photos on imgur or google photos or something? Photobucket is shit.

Yeah - It was fine last time I looked at it but agree now its shit! will add re-hosting to the list ;) 

I think there's a lot of points well made in this thread... and thanks for the compliment Daniel!  Definitely getting plenty of fun out of her.  Now have two toddlers so development has somewhat slowed these days.

To Team GBR - while I agree there was more to get out of the (pocket) rig, the question was what could be improved on the rig to make it faster?  It essentially worked as intended, the mechanics were fine and the sail set reasonably well, (and after a couple of seasons perfecting details) only the aero (&elasticity) would be improved.  

On 1 August 2017 at 7:17 AM, Team_GBR said:

The thing that always strikes me is that they look like conventional sails with pockets and camber inducers added.

 Why would a pocket luff sail look different to a conventional sail with a pocket on it?

The solution (a conventional  sail in a track) was a much lighter, flatter sail on a stiffer mast with more area in the square top head.  It's pretty fast now although the luff round still needs a half inch +- here and there. 

With no initial performance difference with a pocket, developing the pocket further seemed only a slower more expensive route to achieving the same % improvement.

 

If anyone is interested, I have 4 carbon cams to suit a ~55mm Mast, and matched NC machined alloy moulds to suit both a 55 and 65mm masts, iirc.  

Their section shape was roughly based on what Tom Speer published on wing mast shapes, 10-ish % chord ie ~2-2.5m chord sail.

PS.. for an i14 wouldn't you optimise three different rigs for light, medium, heavy wind depending on whether the worlds were in UK, Perth, or SanFran?

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Think that you get a really big range of conditions in the U.K, plus there has never been that much culture in 14 of developing condition specific kit, possibly as a result of the expense, people choosing more to try and get the best through the range out of their rigs. You can get 4 seasons in one day here as well.

some people run 2 jibs as allowed by rules but it only really opens you up to psyche out when you have to chose one. 

Seems on the whole that the U.K. Teams are superior internationally over the full range of conditions, with some Aus teams being very good in the breeze, some of the other international teams being strong in the light. Whether that is down to weight or condition specific setup or just skill/style it's hard to tell. 

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On 8/5/2017 at 2:09 PM, Ben G said:

 

I think there's a lot of points well made in this thread... and thanks for the compliment Daniel!  Definitely getting plenty of fun out of her.  Now have two toddlers so development has somewhat slowed these days.

To Team GB

No sweat - always helps with the motivation / progressIMG_0264.JPG.df2d8ce3859d3fb7382a7e35386aa8b7.JPG when trying to execute one's own silly design and build programs in the midst of a young family!

DSC_0324.JPG

IMG_1354.JPG

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On 05/08/2017 at 11:09 PM, Ben G said:

 

 Why would a pocket luff sail look different to a conventional sail with a pocket on it?

I am probably the wrong person to ask but the way I understand it, the entry looks different because you aren't battling to re-attach flow. The position of maximum draft changes (moves forward?)  and the amount of camber is less. I cannot remember any more, but i do remember Amac of Moth fame saying you couldn't simply take a a conventional sail shape and change it by adding a pocket. 

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19 hours ago, Daniel Holman said:

No sweat - always helps with the motivation / progressIMG_0264.JPG.df2d8ce3859d3fb7382a7e35386aa8b7.JPG when trying to execute one's own silly design and build programs in the midst of a young family!

DSC_0324.JPG

IMG_1354.JPG

IMG_0032.JPG

IMG_0130.JPG

Is this the latest Cuckoo? Good Looking boat. That waterline beam looks mighty narrow... how is she going in the results this season?

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2 hours ago, Irrational 14 said:

Is this the latest Cuckoo? Good Looking boat. That waterline beam looks mighty narrow... how is she going in the results this season?

Yep that is cuckoo #3. I think a number 4 is imminent.

My intent was certainly to get a narrow waterline, but it still measures in as per r.o.f by a mm or two so that part of the intent was met.

I think Archie in #2 has been having some race wins and great flashes in all conditions mixed with a load of teething issues. My season has been heavily interrupted by arrival of a second child. I only lined up properly last weekend vs other 14s and again had good spells but was rusty as hell, some rigging errors etc, some changes needed on rig.

POW is in a few weeks so hopefully we can be all sorted and get a better idea on performance.

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Good stuff. Totally understand how life gets in the way sometimes... Good luck w/the Cuckoo and hope to see you at the Worlds next Summer in SF.

Paul

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On ‎8‎/‎08‎/‎2017 at 11:25 AM, Team_GBR said:

I am probably the wrong person to ask but the way I understand it, the entry looks different because you aren't battling to re-attach flow. The position of maximum draft changes (moves forward?)  and the amount of camber is less. I cannot remember any more, but i do remember Amac of Moth fame saying you couldn't simply take a a conventional sail shape and change it by adding a pocket. 

That sounds about right..  The sail that wasn't bad but I reckon it could have done with less seam shape and the draft forward.  Change the setup to run with more Cunningham on in general (so you're never in the position where you're sailing with a loose Cunningham).  Had a battle with batten stiffness for a while to get the cams to rotate evenly, and the right amount.  Also adjust batten stiffness so the leech was twisting / opening correctly through it's range.  I'd stiffened the mast once by vac bagging IM uni's along it but it needed more stiffness, it was hard to get the setup going well with a bendy mast.  Adding a Carbon track later helped things along immensely!

i14 masts probably a good candidate as they're already very stiff, although not sure whether the high hound position would work.  A stiff mast with an even bend profile probably better than the flexy tip bend profile (think latest moths are going this way coincidentally). 

The straw that broke the camels back was a nationals race a couple of seasons back - a Gusty front came through changing from 5-10knots building to 15-20knots offshore just after launch time.  Everyone had their big rigs loaded, then did a last minute change to second rig as the change became apparent.  We need about 5 minutes more rigging time than other setups so couldn't risk missing the start.  A quirk of the rigging sequence meant the kite needed to be rigged after the mainsail (halyard had to come through the pocket), making the rigging sequence more sequential, so more difficult for two people to rig the boat independently.  again, this won't be a problem on an i14!

 

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