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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  
SlackWater_SF

F-18 Main Decksweep

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So the complete package for this is the new main design w/decksweep foot, and half wishbone curved boom? That's it? Would like to see if they changed the rotator location and downhaul.

Also curious as to how they manage heavy air jibes for the crew. Is he still going in front of the mast?

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The rotator is on the mast base, possibly angled down(?horizontal?), somewhat hidden behind the jib track support, looking at the finish line picture by the RIB.  Click the pic for a larger jpg, download 4530x2548
 
 
 
 
Other:
34572867033_088095f432_z.jpgIMG_4175_DxO
 
 

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6 hours ago, Irrational 14 said:

 

Also curious as to how they manage heavy air jibes for the crew. Is he still going in front of the mast?

Crew goes behind sail 1st then helm

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Umm I know we are fascinated by deck sweepers but for them to work as an end plate effect, they have to be totally sealed as in no air can leak from one side to the other in the join between tramp and sail. Now that patently is never going to happen. Now couple that with the jib is some 0.5m above the deck sweep part so no jib effect can be gained on the lower part of the sail. The loss of CoE height means you can't fly a hull as early as if the sail area was higher, in light air you are in a disadvantage. The F18 is never going to be fast enough, unlike the foilers, often enough to gain any benefit from the sealed tramp which is integral to any chance of end plate effect. 

Am I missing something here or is this just a bunch of sail makers going "Xmas is on its way early this year ".

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1 hour ago, Waynemarlow said:

Umm I know we are fascinated by deck sweepers but for them to work as an end plate effect, they have to be totally sealed as in no air can leak from one side to the other in the join between tramp and sail. Now that patently is never going to happen. Now couple that with the jib is some 0.5m above the deck sweep part so no jib effect can be gained on the lower part of the sail. The loss of CoE height means you can't fly a hull as early as if the sail area was higher, in light air you are in a disadvantage. The F18 is never going to be fast enough, unlike the foilers, often enough to gain any benefit from the sealed tramp which is integral to any chance of end plate effect. 

Am I missing something here or is this just a bunch of sail makers going "Xmas is on its way early this year ".

You may be right Wayne. Looks like they found a loophole in the tight development rules in F18. Next thing you know they'll discover carbon!!!!

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As soon as the gap below the foot sail is smaller than 3% to 4% of mast lenght, viscosity help to improve the Oswald ratio.

So even if there is a tiny space below the deck-sweeping sail and the trampoline, it will always be better than a classic sail.

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6 hours ago, Waynemarlow said:

Umm I know we are fascinated by deck sweepers but for them to work as an end plate effect, they have to be totally sealed as in no air can leak from one side to the other in the join between tramp and sail. Now that patently is never going to happen. Now couple that with the jib is some 0.5m above the deck sweep part so no jib effect can be gained on the lower part of the sail. The loss of CoE height means you can't fly a hull as early as if the sail area was higher, in light air you are in a disadvantage. The F18 is never going to be fast enough, unlike the foilers, often enough to gain any benefit from the sealed tramp which is integral to any chance of end plate effect. 

Am I missing something here or is this just a bunch of sail makers going "Xmas is on its way early this year ".

For a-cat the difference is notable. I have an old trampoline, but I'm faster (I think) and the boat is way easier to sail. 

Part of it is the lower coe, some vortex, but also the smaller head makes the sail more efficient, because the lower part of the sail can be trimmed better, and I'm not that dependent on the big head automatically trimming the sail in lulls and gusts (I think).

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3 hours ago, lars75k said:

For a-cat the difference is notable. I have an old trampoline, but I'm faster (I think) and the boat is way easier to sail. 

Part of it is the lower coe, some vortex, but also the smaller head makes the sail more efficient, because the lower part of the sail can be trimmed better, and I'm not that dependent on the big head automatically trimming the sail in lulls and gusts (I think).

I used a decksweeper on a floater for a while. It was faster upwind in any breeze and downwind over 12 knots. Under that downwind it was death! I figured that would be the case based on why we developed the big head sails. The same sail on my foiler was great. More than enough power downwind. 

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10 hours ago, Waynemarlow said:

Umm I know we are fascinated by deck sweepers but for them to work as an end plate effect, they have to be totally sealed as in no air can leak from one side to the other in the join between tramp and sail. Now that patently is never going to happen. Now couple that with the jib is some 0.5m above the deck sweep part so no jib effect can be gained on the lower part of the sail. The loss of CoE height means you can't fly a hull as early as if the sail area was higher, in light air you are in a disadvantage. The F18 is never going to be fast enough, unlike the foilers, often enough to gain any benefit from the sealed tramp which is integral to any chance of end plate effect. 

Am I missing something here or is this just a bunch of sail makers going "Xmas is on its way early this year ".

 

8 hours ago, Bench Warmer said:

As soon as the gap below the foot sail is smaller than 3% to 4% of mast lenght, viscosity help to improve the Oswald ratio.

So even if there is a tiny space below the deck-sweeping sail and the trampoline, it will always be better than a classic sail.

I need yo take issue with Wayne, yet again. This time he is both wrong and rude.

Besides the technically wrong comment about needing a total seal, his comment about sailmakers doing it just to sell sails is offensive. The first sailmaker to put a decksweeper on an f18 was Steve Brewin. He only makes a very few F18 sails, mainly for himself, and doesn't have the time or interest in trying to sell F18 sails because he struggles to keep up with demand for his A Class sails. I believe he only used the decksweeper in competition when he damaged his regular sail. Mischa has been trying to win the F18's for the best part of 20 years and the idea that he would use gear that wasn't as quick as standard is crazy. If it was one of the big, mainline F18 sailmakers doing it, the accusation might have substance, but seeing it has been 2 top A class sailors who have had significant success with decksweepers, it is hardly surprising they tried it.

I think Wayne owes Stevie and Mischa an apology but I guess this is anarchy so you can say what you want and you just carry on.

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Gosh A Class Sailor you don't half get your titties in a tangle, man you don't half dramatise everything to such an extent that at times I half to worry whether this forum is really for you. You need to chill out and not read into things that the writer didn't actually mean nor write.

Ah where did I implicitly say that Steve Brewin or Mischa were specifically doing this to sell their own sails. What I was saying in a more general way was that due to the herd mentality of many of the owners of F18's, if it won at the worlds, I gotta have one. Now each owner will have his or her own sail maker and my betting is no sail maker is going to say, mmmm not sure you really are going to improve and win the Nationals if you don't have a deck sweeper, more like, mmmm we would like to develop one for ourselves and would gladly make one for you. That's how they pay there bills, making sails.

As to end plate effect. I'm way out of date here but when we were messing with adding winglets ( sort of end plate effect ) to gliders back in the 90's, we did quite a bit of study and used the most up to date information from the Akerflieg universities who had done a lot of research on this. If you had a fully sealed wing to winglet and got maximum gain, predicted best gain was about 2 - 3% gain but that was that at about 70 - 100 knots air speed where there is a smidgeon of viscosity to the air mass and with an incredibly efficient wing section with almost ideal air mass around it.

Now at 10 knots air has pretty much negliable viscosity compared to water and I reckon a good fart would have more. If you think that a 3% gain can be made from a totally unsealed sail / trampoline combo, of about 1m in length, that has a trampoline material below it that is not exactly in perfect alignment, with totally disturbed air flows from all the rigging and masts, then by all means direct me to the report from the studies that have proved it. I'm open to be convinced but at this stage, my betting is on a lot of other things that are giving the probable gains.

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Part of the gain will actually be in the lift distribution from removing area at the top. A tapered wing planform is better than a rectangular one. And then even a partially sealed root will help the overall efficiency of the wing. However, the positive effects vanish quickly with small imperfections in the seal.

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7 hours ago, Waynemarlow said:

Gosh A Class Sailor you don't half get your titties in a tangle, man you don't half dramatise everything to such an extent that at times I half to worry whether this forum is really for you. You need to chill out and not read into things that the writer didn't actually mean nor write.Ah where did I implicitly say that Steve Brewin or Mischa were specifically doing this to sell their own sails. What I was saying in a more general way was that due to the herd mentality of many of the owners of F18's, if it won at the worlds, I gotta have one. Now each owner will have his or her own sail maker and my betting is no sail maker is going to say, mmmm not sure you really are going to improve and win the Nationals if you don't have a deck sweeper, more like, mmmm we would like to develop one for ourselves and would gladly make one for you. That's how they pay there bills, making sails.

When you wrote the following, it looked like a direct dig at the 2 sailmakers who had first used decksweepers. 

21 hours ago, Waynemarlow said:

Am I missing something here or is this just a bunch of sail makers going "Xmas is on its way early this year ".

Even now, reading it in light of your comments, it still looks like you were having a dig, because i read that as "just a bunch of sailmakers trying to sell sails", but that is the problem with the internet. It's easy to say something that others misconstrued.

Quote

 

As to end plate effect. I'm way out of date here but when we were messing with adding winglets ( sort of end plate effect ) to gliders back in the 90's, we did quite a bit of study and used the most up to date information from the Akerflieg universities who had done a lot of research on this. If you had a fully sealed wing to winglet and got maximum gain, predicted best gain was about 2 - 3% gain but that was that at about 70 - 100 knots air speed where there is a smidgeon of viscosity to the air mass and with an incredibly efficient wing section with almost ideal air mass around it.

Now at 10 knots air has pretty much negliable viscosity compared to water and I reckon a good fart would have more. If you think that a 3% gain can be made from a totally unsealed sail / trampoline combo, of about 1m in length, that has a trampoline material below it that is not exactly in perfect alignment, with totally disturbed air flows from all the rigging and masts, then by all means direct me to the report from the studies that have proved it. I'm open to be convinced but at this stage, my betting is on a lot of other things that are giving the probable gains.

 

I am not going to get all technical, because I can't but I believe that what you were looking at and what we have with a decksweeper have significant differences. The aspect ratio is rather different. then, we are talking about the widest part of the wing and in aviation terms, the root end of the wing where it attaches the the fuselage. I disagree that the rigging gets into the equation at all and a lot has been done to tidy up the flow over the main beam and across the tramp.

The biggest reason i am confident that gives a significant gain is that the first person who did it on an A was a designer from ETNZ and he was pretty open about the gains being "very significant".  He was effectively ignored until Mischa went C Class sailing and went up against Groupama who started without an insert at the bottom of the wing and then fitted one. the performance improvements were very noticeable. I believe they then did some analysis (his boat had a net tramp) and saw the gains which led him to make the A Class decksweeper.

The 2 variables that i can see is the sealed double sided tramp and the tidy layout and the decksweeper itself. I know of people who have fitted the new tramps with the old rig and seen no gain. I believe that on its own it must be better, but it is hard to measure based on real performance. I also know people who have fitted a decksweeper to old style tramps which are air porous, and they do not go as well as those with a non porous tramp. It's most noticeable upwind and this has been validated when people have then fitted the new style tramps. Without knowing any of the technical stuff, a process of elimination suggests that the decksweeper is doing some good. 

There was some CFD studies doing the rounds a couple of years ago when they first came out showing the difference between a conventional sail and a decksweeper. Again, you could see a huge difference in the airflow at the bottom of the sail and across the tramp. Without knowing numbers, it was hard to believe that there wasn't something significant going on. I will see if I can dig out the pictures.

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If I remember that CFD study was done with out any influences of the main hulls obscuring the air flows, as in just a tramp and sail setup. I think there was some discussion about this being relatively " theoretical" and didn't really prove anything in either directions.

Having just been following a news program on some study by a known doom monger, of how mortality age is flattening out in the UK after continuing rises over the last decade, it was interesting how the media all took their take on it. The BBC in true " Luvvie " fashion decried it was hideous and totally down to austerity and yet the age was actually still increasing, just not at the same rate as previously when some of the modern drugs and living habits that had actually been driving the rises, were in their best prime. The Daily Mail on the other side seemed a bit more relaxed and deemed that although it was slowing down, it was all good and that austerity was sharpening up every ones wasteful tendencies of drinking too much alcohol and sugar intakes, as we longer can afford such luxuries.

What I'm trying to say is that there are typically a hole load of parameters and identifying one by chance that seems to bring benefit and then do a study on that one parameter without taking into account all the other changes influencing that one parameter, is almost meaningless. And yet almost certainly we will have acolytes of that one change saying its the next big totally game changer.

A Class Sailor I would put you in the "Acolyte" category. You are totally addicted and have worked yourself up into such a lather into believing that the A Class is the best of everything sailing. Anything marginal in gain is the next greatest thing, but only if an A Class sailor was to first use it. You dissect every little statement that mentions the A Class  and then profound upon it as either a personal attack on the A Class or as only the A Class could have come up with it first.

Sorry to disillusion you, but everything we see today in sailing is not new nor game changers, everything is just a refinement of what people have been and done before.

     

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Wayne, you are right about a workpaper trying to modelize the flow around the foot sail of a C-Cat.

It was a Canadian study, but I don't remember if it was for a floating C-Cat or a foiling C-Cat.

Whatever, it is not very risky to say that the best benchmark regarding wingsweeping trampoline is without any contest Groupama C.

If you compute the wind gradient of apparent wind for any foiling cat you will see where the wind is  actually coming from?

And at the trampoline level it is coming from the front, very front (ie: 17° windward and 19° downwind for an  foiling A-Cat  sailing  @ 19nds windward and @ 26 knts downwind )

For a C-Cat just consider higher velocities and narrower angles and you will be in the ballpark.

So even if this study has some merits, I believe it has missed the essential.

Below the tramp, with the funneling* effect of the 2 hulls, this apparent wind is almost @ 0° that is why the "Aero keel" pionnered by OTUSA 17, has been generalized for the following cup in a one desgn draft, it is just another mean to increase the effective aspect ratio, especially if area for end plate effect is limited by the rule box. 

*(not sure it is the correct word, but it is Sunday and I am lazy and I am sure you get it).

But you must know that all the information necessary to make your own judgment independantly from any self claimed cat gurus exists.:

And this info is available on the Tom Speer website.

If you search on Google using a few appropriate keywords you will fish in T Speer workpapers, you will be able to make your own self education in Fluid Dynamics very easily.

Deck sweeping sail or wing have several merits for an A-Cat

It cuts the induced drag by 40% 

It increase the effective lift coefficient by a bit more than 10%

It lowered the sail CoE to 42% of the height ( Assumed an Elliptic load distribution along the span at max righting moment).

As soon as you are overpowered, the load distribution can become triangular by adding twist in the top and the CoE can be reasonnably assumed to migrate toward 33%.

That is why the Elliptic sail plan we can observe since we have decksweeping sail on A-Cat is not a consequence of removing area from the top to put at the bottom, but it is an optimization of induced drag, consistent with the deck sweeping concept.

If you agree with the above statement, you should agree with the following one:

Any foiling boat which has not a deck sweeping rig, just testifies its architect understands poorly what he is doing. 

Have a good week-end.

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Ah you are right in regards to a foiling AClass, here we are discussing an F18 deck sweeper mounted on a180 kg tank that busts its way around the course in a somewhat well refined manner. Different boats, different strokes

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For sure the heel angle of an F18 does not help the deck sweeping sail, but the jib windward and kite downwind has a positive effect on the flow around the main, and I believe deck sweeping sail are still an advantage for these boat too.

Another reason is these heavy beasts need power 

power = high lift coefficient

Induced drag= f (lift coef ^2)

So an F18 or F16 rig, works probably at much higher lift coef than A-Cat or C-Cat.

For both these boats, sooner or later I feel confident we will see triangular "Kite container"  settled between the front bean and the forestay attachement.

It will add the end plate effect to the jib while storing the kite at the same time.

I bet a pint of Guiness on that point.

Cheers

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The Hurricane 5.9 I have, has this already, not sure that the aerodynamic drag of all that stuff sticking up into every point of wind is ever gained by the end plate factor on the jib. I have had a F18 snuffer set up on mine all last year as I had just converted an older boat over to the SX setup, this year I have the full Monty. It's really noticeable up front and in low wind speeds it's a real pain when coming into the beach. Without any sort of testing I couldn't meaningfully compare.

if you want to go putting bets on, at some future stage you are going to see a full central beam which mounts everything from the front forestay back to the mast and then splits to form a Y, within which conceals the spiny. There's no real rear beam to speak of, simple light weight front beams mounted more forward than normal and very lightweight hulls. 

Will it ever be produced en mass, nah it would cost to much.

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14 hours ago, Waynemarlow said:

A Class Sailor I would put you in the "Acolyte" category. You are totally addicted and have worked yourself up into such a lather into believing that the A Class is the best of everything sailing. Anything marginal in gain is the next greatest thing, but only if an A Class sailor was to first use it. You dissect every little statement that mentions the A Class  and then profound upon it as either a personal attack on the A Class or as only the A Class could have come up with it first.

You really can be a nasty bit of work who consistently posts incorrect crap on this forum and then tries to wriggle out of it. We see that again with the rubbish you have spouted on this thread where you go on about your glider stuff and then, when shown you are wrong, try to make out that you were only referring to the F18. I go with Bench warmer and call you out on this as well. There is a positive effect even on slower boats like the F18. It might not be as big as on a foiling A or C Class, but it is there. On the A's, it is a lot more than the amount you tried to suggest.

FWIW, I know that there has been little we have seen on the A's that is new but what you don't seem to understand is that the A's are the only place outside of the AC at the moment where there is anything going on to test and refine these ideas for cats.  Almost everything else is about the development of one designs, where the incremental gains aren't worth chasing and where the priority is about meeting the needs of the target market. Even the Moths are taking some of the ideas.

Decksweepers are nothing new on cats but it seems that people either ignored or forgot about the advantages, maybe because it was first seen on a one design so there was nothing to compare it with. They first appeared on fairly slow cats and it has been interesting discovering the early rational which turned out to be exactly the same as we have today - it tidies up the airflow off the bottom of the sail and makes the bottom 25% work more efficiently.

What is currently going on with the A's is one of those "moments in time" things that don't come along very often. You have 2 key components.You have many of the top designers turning their attention to making the A's faster. Almost all the guys designing for the A's are or were AC designers and it is the chosen class for the AC tec types. The other factor is the sailors doing the testing with some of the very best cat sailors making it their focus. What it means is that there really is proper validation of ideas through on the water testing. 

You say I dissect every little statement that mentions A's. That might be true, but before I can do that, somebody has to mention the A's and if, like you seem to, the comment is incorrect, I will post. It's pretty straight forward. Stop writing incorrect stuff and I will have little to comment on :P

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A Class sailor once again you have totally screwed any meaningful conversation on this F18 based discussion, by your total and absolute almost Zealot like insistence that everything is A Class based. Non foiling F18's and A Class's are two quite different animals having quite different sail design requirements.

Can I ask you to substantiate that a small tiny less than 1m long section of a sail area made of clear mylar ( that when you look at the photos has little or no wing shape to it from about where the normal cut  of the sail would be ) gives a " 25% more efficient bottom of the sail " on an F18, by listing the computer studies and where those studies have been documented in real life testing of an F18 platform with directly measured speeds using an identical platform ( and no winning races does not constitute this ) . All the readers and owners of F18's here are pretty interested in finding this information, as it is quite a statement to make and if that is the case, then we will all adopt it pretty quickly. I for one would be like to educated and thus wouldn't be able to pass on crap information in the future.

Is it 25% of say the bottom 50mm of sail and confined to only about the 1m long sail section along the tramp area. Does it make the whole sail say, 2% more efficient. Appease me by doing a quick calc and publishing it so those more knowledgeable can pass scrutiny over it.  Please though make your claims based on the average speeds of the F18 and also put into the parameters that a greater percentage of time the front beam, is not level, nor offering any sort of ground effect or wind alignment once a hull as been lifted clear of the water. Also put into the equation that the snuffer and associated wires and sundries are effecting the wind flow around that front beam level. Anybody out there, can you think of other parameters we should include ?

But I'm open to learning and always have an open mind about things. If you are correct that there are some quite large gains to be made, then I would be the first to put my hand up and say that you have expanded our knowledge base and well done, after all that is what these forum discussions should be, a way to expand the knowledge base of many quickly, by bringing a much larger knowledge base together.

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Wayne, 

Thank you for your PM, so I have a clear picture of your SX package.

As you know the kite snuffer goes beyound the frontstay attachement,

It seems to have a nice flattish section in order to minimize windage, but it is smaller near the front beam than beyond the jib, and it is above the deck level, so it can feel the apparent wind.

Windward its aero drag is likely to create a moment which will push the bows downwind.

My bet or "suggestion" is to have a snuffer, which is very flat, has a triangular area between the frontstay and the circular jib track on the main cross beam, and which meets the jib foot in any situation: windward & downwind.

Of course the circulation of the kite inside this triangular snuffer must be tested a little bit.

 

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Wayne

I live in a very practical world. I don't care much for papers and studies, even less for CFD which I can do myself but too often it fits into what i was recently told really stands for "Colours for Directors", or in other words, a pretty picture to impress decision makers. All too often what is predicted in theory isn't seen in practice.

What i know is this. On the A, it has been found by direct testing that there is a speed increase that  can only be attributed to decksweeper. With the F18, there hasn't been the same in depth testing but there does seem to be a consistent picture about the impact of a decksweeper, both observed by the users and by those they have raced against. It appears there is no benefit in light winds but as soon as the breeze is up above, say, 8 knots, there seems to be an upwind advantage. The story seems consistent both here in Australia and in Europe. An added complication seems to be that in every case, the rig has been tried on the Scorpion, a design that is hard to sail fast in light winds. I therefore believe that we don't yet know enough about the performance of the decksweeper on an F18 in lighter winds.

I have to reject the comments about it not working n the F18 because of angle of heel and the boat being slower. It has a proven on the A upwind in non foiling mode (and therefore with the boat healed) at speeds close enough to what an F18 achieves. I can understand that the benefit won't be as much as you get at higher speeds when foiling and upright, but there seems to be plenty of evidence that it is still there. 

There could be a placebo effect on the F18's, but I don't think so. I base this solely on instinct. I am pretty confident that Mischa would not have used it if he didn't think there was an advantage. He has been so desperate to win the F18's and had time to test it both in races and in training it seems highly unlikely that he would use it if there wasn't a proven benefit. He is too smart a sailor to be sucked in by a placebo. Also read the comments from "Tony-F18" on the other thread.

Adding it all together, I see on the water evidence plus there seems to be some theoretical evidence as well, that a decksweeper would be a benefit on the F18's through enough of the wind range to make it worthwhile.

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If someone presented a sailor with a way to have a significantly longer luff length with no taller mast, wouldn't he most likely want it?  If someone could do some deck sealing of any kind, would he want to try it?  Jibs on monohulls that lean over have emphasized decksweeping for decades.  Do we see 505s setting jibs with their class limited area up high and letting the wind blow through the deck?  

As A Class and others have noted that are specifically relevant for the F18:

1) it was proven very fast upwind by Pete Melvin in 2014 on a C board boat in the A-class with his work with Jay Glaser.  He is on video / write up, I don't recall which, saying how much of a difference it made on power and speed upwind.  I believe he noted the vortices off the bottom of a typical sail limit the advantage of easing outhaul and powering up the bottom of the sail.  Makes sense to me.  The deck sweeper can allow more curvature down low without so much drag.

2) it has proven to win here in the USA on C board A-cats, primarily due to upwind speed, even in light air.  We see many top C board boats now winning with deck sweepers.  They are superior upwind to the older sails.  Jay Glaser here is building deck sweepers different to the AUS approach with a bigger head and more power up top.  In fact, the winner of a very light wind winter series in the A-Class here won with C Boards and a big headed decksweeper.  That deck sweeper was rejected for foiling as it has too much power up top, but it's good for flying a hull downwind or going deep and mild.  

3) Mischa just won the worlds with it and the video I saw was stunning on his upwind speed.

Every boat is different, but if I had an F18 or F16, I would be working in that direction.  Probably not a foiling sail plan with very small head, but the concept is right.  I bet Jay has a good idea as an F18 sailor on how to do it and of course, getting a set up from Mischa would be ideal.  

Benchy raises some good questions on all the rigging and mess up front on the F18 or any spinnaker / jib boat.  Would be very cool to see a way to clean that up and make it be an advantage.  

I'm surprised no on here is taking about the panel layout that Mischa chose.  I haven't seen something like that in the past and it has almost a checkerboard look with pentex broad seaming rather than a tri-radial.  Thoughts?  Anyone seen a layout like that before?   

 

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Has anyone done any work on cleaning up the snuffer drag. I know when I used to put the kite on my old Taipan the extra drag was like a handbrake uphill. Maybe the next area for improvement? Glad I have a wildcat and don't have to go out and buy a new sail(s) as yet.

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1 hour ago, Rawhide said:

Has anyone done any work on cleaning up the snuffer drag. I know when I used to put the kite on my old Taipan the extra drag was like a handbrake uphill. Maybe the next area for improvement? Glad I have a wildcat and don't have to go out and buy a new sail(s) as yet.

Not sure I understand. It's an F18. Or do you want to keep sailing against the other Wildcat in AUS:)

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When kites were first put on cats and had tramp bags and not snuffers, the dutch came up with a figure of 5% penalty sailing upwind with just the bare spin pole and halyard.  I was very reluctant to add a snuffer later on - especially the early ones that were like a forward-facing funnel!     A guy called Arie vd Plas jnr made flat entry snuffers himself - i got one of those as the best option

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4 hours ago, Lost in Translation said:

If someone presented a sailor with a way to have a significantly longer luff length with no taller mast, wouldn't he most likely want it?  If someone could do some deck sealing of any kind, would he want to try it?  Jibs on monohulls that lean over have emphasized decksweeping for decades.  Do we see 505s setting jibs with their class limited area up high and letting the wind blow through the deck?  

As A Class and others have noted that are specifically relevant for the F18:

1) it was proven very fast upwind by Pete Melvin in 2014 on a C board boat in the A-class with his work with Jay Glaser.  He is on video / write up, I don't recall which, saying how much of a difference it made on power and speed upwind.  I believe he noted the vortices off the bottom of a typical sail limit the advantage of easing outhaul and powering up the bottom of the sail.  Makes sense to me.  The deck sweeper can allow more curvature down low without so much drag.

2) it has proven to win here in the USA on C board A-cats, primarily due to upwind speed, even in light air.  We see many top C board boats now winning with deck sweepers.  They are superior upwind to the older sails.  Jay Glaser here is building deck sweepers different to the AUS approach with a bigger head and more power up top.  In fact, the winner of a very light wind winter series in the A-Class here won with C Boards and a big headed decksweeper.  That deck sweeper was rejected for foiling as it has too much power up top, but it's good for flying a hull downwind or going deep and mild.  

3) Mischa just won the worlds with it and the video I saw was stunning on his upwind speed.

Every boat is different, but if I had an F18 or F16, I would be working in that direction.  Probably not a foiling sail plan with very small head, but the concept is right.  I bet Jay has a good idea as an F18 sailor on how to do it and of course, getting a set up from Mischa would be ideal.  

Benchy raises some good questions on all the rigging and mess up front on the F18 or any spinnaker / jib boat.  Would be very cool to see a way to clean that up and make it be an advantage.  

I'm surprised no on here is taking about the panel layout that Mischa chose.  I haven't seen something like that in the past and it has almost a checkerboard look with pentex broad seaming rather than a tri-radial.  Thoughts?  Anyone seen a layout like that before?   

 

Good news LiT on the more powerful head decksweeper. As not elsewhere I've found the normal decksweeper excellent on a floater except in under 10-12 downwind. 

With the upcoming vote on the floater division for A Cat events around the world it will be an incentive for more sailmakers to focus some development on decksweepers for floaters. I believe they can be advantageous. 

Sorry for the red herring. 

Now back to F18 discussion:)

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Guys you are forgetting the one thing that makes an F18 fast, that of getting one hull out of the water. If you can't do that then you are are at the back of the fleet in a flash. Now we all seem to be getting the message that under 10 -12 knots of wind speed that the deck sweeper is not as good ( I would bet 60 -70 % of time I sail in those conditions ) and if we acknowledge that the COE is lower than a normal sail, isn't that telling us that we are going to be slower to get the windward hull out of the water. That in my case probably means for all the gains in stronger winds ( where you can de-power if you want ), there's an even bigger penalty in the lighter winds ( you can't add power ) probably up to that 10 - 12 knots. Does anybody know what sort of wind speed the worlds were held in ?

Looks like we are going to have to have two setups at any competition as one is quite unique to stronger conditions. Now that is going to really screw with the moral compass of the F18's aims, how long before deck sweepers are banned ? In my case where I sail in mainly gentlish conditions you would have to opt for the standard rig, it would be a handicap to then enter a comp with regular good sea breezes where others have a deck sweeper set up for these stronger conditions ? Equally enter a comp with light winds forecast and out of the bag would come all the standard sails. Mind you most at the top end would have a quiver of sails for various conditions anyway.

Interesting ?

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22 minutes ago, Waynemarlow said:

Guys you are forgetting the one thing that makes an F18 fast, that of getting one hull out of the water. If you can't do that then you are are at the back of the fleet in a flash. Now we all seem to be getting the message that under 10 -12 knots of wind speed that the deck sweeper is not as good ( I would bet 60 -70 % of time I sail in those conditions ) and if we acknowledge that the COE is lower than a normal sail, isn't that telling us that we are going to be slower to get the windward hull out of the water. That in my case probably means for all the gains in stronger winds ( where you can de-power if you want ), there's an even bigger penalty in the lighter winds ( you can't add power ) probably up to that 10 - 12 knots. Does anybody know what sort of wind speed the worlds were held in ?

Looks like we are going to have to have two setups at any competition as one is quite unique to stronger conditions. Now that is going to really screw with the moral compass of the F18's aims, how long before deck sweepers are banned ? In my case where I sail in mainly gentlish conditions you would have to opt for the standard rig, it would be a handicap to then enter a comp with regular good sea breezes where others have a deck sweeper set up for these stronger conditions ? Equally enter a comp with light winds forecast and out of the bag would come all the standard sails. Mind you most at the top end would have a quiver of sails for various conditions anyway.

Interesting ?

Tried putting the crew on the leeward hull and skipper well inboard? Should be popping windward hull in most breeze that way. If it doesn't work that way it's too light and you are best staying in the bar. 

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3 hours ago, teamvmg said:

When kites were first put on cats and had tramp bags and not snuffers, the dutch came up with a figure of 5% penalty sailing upwind with just the bare spin pole and halyard.  I was very reluctant to add a snuffer later on - especially the early ones that were like a forward-facing funnel!     A guy called Arie vd Plas jnr made flat entry snuffers himself - i got one of those as the best option

Early on, we ran a snuffer that ran diagnal under the tramp and came out of a ring in the tramp.  It was a LOT less windage upwind however to set and drop, you had to soak deeper than those with pole mounted snuffers.  The tack also had to travel out 4 meters to the end of the pole compared to around 1.6mtrs for the pole mounted snuffer.  We later changed to the pole mounted snuffer as whilst there were advantages upwind, it was more than offset by the disadvantages on the sets and drops.

Cock of the Bay #1.jpg

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+1 TA, that was my thought on any change to the snuffer.

+2 Lost, I agree with everything you say. Mischa can have your decksweeper ready in 2 weeks.

Wayne, I hear you entirely and I am aware of the risks. They are worthwhile. I say this because Mischa finished 3rd at a Worlds race in 5kts of breeze with his completely unrefined and untested decksweeper! I say this as it is also possible to build a sail exactly as Lost describes, where you still have a big head and most of the decksweeping area ends up coming out of area low on the sail. This is where the F18 is headed and it makes complete sense based on a lot of information posted here about total rig efficiency.

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Thanks, guys and good advice WetnWild. 

Other catamarans need to fly a hull too so that argument seems limited in its use against the configuration.

I have seen boats in light air win races with a deck sweeper.  Classic and foiling.  Have done the same myself.  Not sure what else to say on that particular topic.  

Traditional rigs are not bad and can win in the very light, especially if a lot of chop, but deck sweepers are better overall.

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7 hours ago, WetnWild said:

Tried putting the crew on the leeward hull and skipper well inboard? Should be popping windward hull in most breeze that way. If it doesn't work that way it's too light and you are best staying in the bar. 

And yet those light air conditions are what we too often still decide to go racing in....fortunately they had free beer waiting back at shore and it was available not only after racing but before....

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10 hours ago, Waynemarlow said:

Guys you are forgetting the one thing that makes an F18 fast, that of getting one hull out of the water. If you can't do that then you are are at the back of the fleet in a flash. Now we all seem to be getting the message that under 10 -12 knots of wind speed that the deck sweeper is not as good ( I would bet 60 -70 % of time I sail in those conditions ) and if we acknowledge that the COE is lower than a normal sail, isn't that telling us that we are going to be slower to get the windward hull out of the water. That in my case probably means for all the gains in stronger winds ( where you can de-power if you want ), there's an even bigger penalty in the lighter winds ( you can't add power ) probably up to that 10 - 12 knots. Does anybody know what sort of wind speed the worlds were held in ?

Wayne

I believe that you are missing some important differences between various decksweepers which make you 10-12 knot assumption incorrect. The F18 worlds had light wind races on the last day and in what Cat Sailing News reports as being 6-8 knots, Mischa got 2 firsts and a second. I am also pleased to hear from LiT that in the US, they have decksweepers that work well on non foiling A's in light winds. While I don't doubt that WnW found that the decksweeper he tried had issues below 10-12 knots, others have reported different results, so using a single example so definitively seems unwise.

The key differences between decksweepers is the size of the head. For the foiling A's, the aim is to lower the CoE and the head size has been reduced significantly. On the F18's, the head size does not seem to have been reduced, at least on Mischa's rig. He seems to have played with the distribution of area by taking it out of the leach lower down. I suspect that the CoE of his rig is far less of a drop than on an A. I believe that this approach allows for more adjustment of the CoE through downhaul and blading out the top of the sail. The question then becomes that because the bottom of the sail works more efficiently and there is less drag low down, plus I believe the aspect ratio is better, does that overcome the slightly reduced CoE? Considering that Mischa isn't exactly one of the small guys and he got great results in light winds which have always been his weakness, there is little evidence from the F18 results that a decksweeper hurts in light winds.

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20 hours ago, WetnWild said:

Not sure I understand. It's an F18. Or do you want to keep sailing against the other Wildcat in AUS:)

7 Wildcats at a recent winter regatta W&W, biggest fleet if IRC and not an A Class in sight, maybe all scared of a little weed (sea weed that is)?

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1 hour ago, Rawhide said:

7 Wildcats at a recent winter regatta W&W, biggest fleet if IRC and not an A Class in sight, maybe all scared of a little weed (sea weed that is)?

Excellent. I've only ever seen your boat and the one Mal had recently. We have only one F18 sailing regularly locally. Goodall boat I think. Weed is a pain on most boats I guess. Isn't it on the WC?

We get 20+ A's at our local events. 

See you at Vincentia in Oct for a beer. 

Resumption of normal F18 chatter. 

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Wayne, 

Sorry, I cannot see your link, I am not yet on Catsailors forum, I will suscribe asap, but I am a bit overbusy at the moment.

 

Sam,

I cannot find the Canadian workpaper I mentionned, I probably deleted it as it was not very important for me.

I searched on Google but cannot find it again, but here is the guys who are likely to provide you with it:

http://etsclassc-rafale.ca/en/home.html

Nice discussion where every body, brings his ideas, suggestions & true life experience, and so far no troll pollution....It deserves celebration!!!

 Let's have a pint of Guinness ....Never mind if it is only 10 a.m here. 

Cheers

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