Here in the San Francisco Bay Area the A class cat (potato chip) fleet is exploding in popularity. The Santa Cruz Yacht Club has no fewer than eleven A's (five more than last year), and Cali. wide, the fleet has drawn the current I14 World Champ,and runner's up as well as a gaggle of essentially professional and world class skiff sailors...
To be honest, if I weren't buying a Moth, i'd be calling Matt at V marine to get one of them Italian potato chips to put atop my F16 on the trailer... Additionally,the fleet has a powerful cross gender appeal as two of the top three Acat sailors in Cali. are woman (who wants to bet $10 bucks a lady makes the podium at the Worlds in '07?).Since Doc was (priorities?), often off, restoring site to the blind this season I alone was left to halt the Alien invasion and to ponder why sailors pick the Acat over the clearly superior F16...My point? As a fleet the F16 has some great stuff going for it and I respect the contributions of you talented zealots who've created something out of nothing with the international F16 fleet!But, if I were granted four wishes for the F16 and on behalf of the greater good of the class i'd :

1. eliminate the tip weight (sea worthiness - Que!?) rule for the mast. Reducing weight aloft (maybe as much as 30%),would be an important performance and marketing advancement for the class.
2. Reduce the minimum all up weight by a proportion equal to the weight savings conveyed by carbon beams and kite pole.
3. Lifting foils and unlimited rudder gudgeon extension aftward.
4. Let us stiffen the platform by eliminating restrictions on the tramp.

Yes, i'm aware of the oft expressed notions of keeping costs down; avoiding making the class a $'s battle and the questionable performance benefits for the extra $'s...It is though healthy to occasional raise the issues for consideration...

Thoughts ?

PKilkenny

We are building both A-cats and F16, and get quite a few calls from people questioning which of the 2 they should look at getting into.

Both are excellent platforms, light responsive, fast and very fun to sail but the choice of which one is for you depends on what you want your sailing experience to be.

The A is essentially a 1-up racing machine. It is the epitomy of simple for a set up standpoint with only 1 sail and being so easily moved around. They are sensitive beyond sensitive as far as tuning adjustments and very technical from a driving stand point to make them go fast. It is a finesse ride. There is a good class although only in certain regional pockets. It is rare one will venture out in a blow, but for the loner finess racer it is a good fit.

The F16 gets down there in the wieght catagory, making it also a very fast and sensitive platform. The selling features are the versatility. If you do not allways race solo you have the option. The addition of a spin provides not just performance but a real adrenaline rush. Relatively light air days are now fun, and the boat can handle quite a blow, and being you can take 2 out you feel safer venturing from shore when it is up. The sensitivity is still there for learning fine sail control, and for those want to continually improve their skills there is a pretty big curve in learing to run an asym spin well off the wind. The racing class is our biggest weak point in getting more involvement as it is so new. The people involved though are doing a supurb job of getting it going from out of nowhere.

As a class are we going to get more people involved by making boats more than they are now. The Blades we are making now are 110kg. If I added carbon beams and mast we would be quite a bit under min weight but at a considerable increase in cost. A couple of people may want to buck up for that but I do not see that as something that is going to provide a class growth. We could remove the tip weight, but look at the guys who have been racing A's for any length of time, they all have been through a few masts. A little bit of weight for a little bit more strenght is not always a bad thing.

The banana foils on the C class have proven to be very difficult to control and places some limits on the conditions the boat can sail in. Another cost feature for limited benefit. The A class is now fighting this for no other eson than to try and protect the growth of the class. They increase the cost of the boat with questionable results and present an impression that non-banana foils are obsolete, lowering the resale of exisiting boats and limiting those who would want to come into the class new.

We as a class had better look closely at what we are doing to try and grow this. What are we selling, if it is unlimited development, are we moving in the dirrection of the C-class as there are only a handfull of them and less than that that are cometitive. If it is good cometitve formula racing with the ability to set up to your own preference then lets promote that.

Matt

Well said!

Very!

For me: (1) and (4) are potentially interesting. (2) sounds like a bad idea, and (3) I'm unsure on.

But what are you actually trying to achieve? Are you trying to make the boats quicker so that they're more of a match for the As on the water? Or faster so that they're quicker than the As? Or allow might high-tech stuff so that they appeal more to gadget freaks?

On SCHRS, the F16 is already on an equal footing with the As and I believe that that is correct. We've had a few events in the UK that have shown this, most recently Grafham: when I managed to keep the boat up the right way, and there was a reasonable wind I managed a couple of 4ths in a decent fleet of As. I have no doubts that the people beating me were better sailors.

I believe that the reason that people choose As over F16s is partly because there are more of them around and their Nationals/Worlds attract some big names making them more attractive as a racing class, but mostly it's because they've got no friends and so have no need for a boat that can be sailed 2-up <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Paul

What limitations de we have on our tramps though? Are you referring to this rule?
1.2.4 The hulls, beams and trampoline shall not be permanently fixed to one-another. the Formula 16 Class authority may demand that these items be disassembled, but only at a time when doing so does not directly affect the fairness of racing.

How can a fixed tramp help? What is a fixed tramp though? A solid platform?

From a personal point of view I wouldn't want the true benefits of the F16 class (light weight, versatility of crewing, freedom of equipment choice and layout, freedom of platform) to get lost for the sake of a few marginal and spurious 'improvements'.

Personally, I believe that a foiling F16 would be a VERY BAD THING in terms of the future direction of the class. It has the potential to make F16 esoteric and niche sailing. Where the future of the class surely lies is in growth of numbers of boats sailing - through a technical but fun-to-sail platform that provides for range of budgets and abilities.

If we start messing with tip weights we marginalise strength, if we optimise foils for a particular condition we risk compromising the design in other conditions. It's the same for hull design, beam scantlings, rudder design and position etc.

F16 will grow bigger and stronger if it is not too radical or too exotic. We must play to our strengths, our core values, and not compromise those in search of some perceived but unproven gains. With respect, I don't think there's anyone out there currently sailing F16 who doesn't believe that there's more to be had from their boat just by sailing it better! <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

I make the following comments as a private F16 sailor only, Be free to completely disagree with me and even say so out loud. I'll welcome that even.

Still, I do have some info and experiences left over from my past involvements that are pretty significant.

First Pauls points :



Choosing the tipweight last time was a careful balancing act. I won't go into detail now but I can assure everybody here that nothing like 30 % weight can be saved on the mast. Currently the tipweight rule allows carbon masts that weight as little as 13 kg overall. For our designs this is very effective. It allows the boat to be right singlehandedly by very light skippers in all conditions and isn't pushing the limits of engineering too much. Reducing the weight of the mast by another 2 or 3 kg is not going to make a significant difference in the performance of the boat. Additionally the current tipweight rule keeps alu mast competative.

Also we must not forget that several builders are really NOT looking forward to the "go carbon" rat race and these builder know what they are talking about as they have plenty of experience in usign carbon in cats. So to keep everybody on board we designed the tip weight rule such that it balanced all demands a level acceptable to all parties involved. My strong advice in to not open up this rule. The immediate effect now would be to hold class growth, mostly because carbon is still in short world supply at this time, making it artificially expensive.

As a designer I'm not really interested in lighter carbon masts; the ones currently allowed should be able to get by far most of the benefits out of the design which a lighter mast won't significantly improve upon.

It is also my opinion that it will be bad marketing for the class. We shouldn't try to become A-cats unless we can really beat them at their own game. Going halveway is not going to help one bit. If a buyer finds extreme lightweight mast convincing then he will in the end always decide to go for the real thing, A-cat, and not for a poor imitation. It is my experience that it is far better to totally go you own way in this situations. Even as far as to stay with aluminium and still beat them because that really freaks them out ! It will also make the buyer reconsider. "3000 bucks cheaper and still beat them ?" It is hard to go against this by saying: "But we are 5 kg lighter !"






Estimated weight saving are about 5 kg in total here, not more. Apart from the costs it will also be foolish. Currently we are able to achieve platform stiffness with aluminium that even carbon beams would claim as a great achievement.

Additionally we don't need the weight savings for performance at this time, currently we already shame all carbon boats on the water. Think M20 and A-cats. For all their money investments and carbon usage they can't sail away in significant measure.

Do we want to make F16's faster ? Then we should fully focus on rig optimation.

Overall weight, mast tip weight, platform stiffness and even daggerboards have no all been adressed (although not everything has been implemented yet). NONE of these are limiting the F16 performance in a significant way. We would be foolish to spend much money on pretty meager improvements if any.


3. Lifting foils and unlimited rudder gudgeon extension aftward.


Not needed as this time and to much of a "single-gear-race-car", bad for races over the full windspectrum and very bad for our greatest selling point = "capable racers, that are relatively simple to learn to sail, with great versatility, for attractive price".

Gudgeon extension aftwards are a skiff thing because they try to do nearly impossible things within their boxrules. Honestly which designer would choose 12 ft length for his racer ? However, because historical circumstance 12 foot was permanently fixed and now they try their best to break out of that mould.





Absolutely not needed anymore. I can't go into details but believe me that in the relatively nearby future we are going to see F16 platforms with alu beams that will have no significant flexing anymore. I'll be surprised if any A-cat would better that. Why waste carbon-money for a thing that can be achieved for as little as 200 bucks.





It is definately healthy and yes I appreciate somebody bring the topic back up again.

Sadly I'm bound by some confidentiality clauses. But I can tell you that I've seen test data that I simply would not believe the first time I heard of them. I will explain in more abstract details.

I thoroughly dislike the "carbon !" mentality, I think that in many cases it is an excuse to disquise poor engineering. And I find it often to be an easy way out for many designers who don't want to spend time redesigning parts to better specs using more easily available materials.

For me the F16 project has always for a part been a project to show what can be done by skilled engineering using basic materials. This also kept costs really down. I'm a bit of a performance to cost ratio junky.

I now believe that this is now our biggest selling point after the versatility of the boat. It is even becoming our unique signature. Our permanent underdog charm. "Bring the best that you got and we on our 13.000/glass/alu stuff will give you a haircut".

I find that this really freaks out our competition. And believe me even a nice number of A-cat sailors are freaked out by it.

So instead of trying look more like the other but never quite complete the metamorphoses I propose to totally go the other way. Lets not become anything like another class, lets stick to our guns and principles and design the best catamaran possible using plain materials and then have decent crews shame the "buy-a-win" crowd. Because nothing hurts as bad as sailing an 60.000 M20 or 23.000 nacra A2 and having to engage a 13.500 F16 in a tacking duel on every single upwind leg. And it'll be the most fun you'll ever have on a F16.

And the new design (test)data I've seen makes this a very real possibility. We only need to get really down on the rig now to complete the picture, first steps are being taken. But then, believe me, those carbon boats will be cursing the day the F16 class was formed. Because what Matt and Gina just did will become a recurring sight.

And of course the other classes can't copy us in this approach which will make us relatively unique, a thing that always works with customers as they all want something special. This must be our policy and the proposed changes are not in-line with that.


I also predict a serious hit in the "all carbon and over specilized" design sector. You may quote me on that in 5 years time. More then a few sources have expressed that there simply is not enough profit in that area. And the new developments in formula boat classes have pretty much overtaken the "overspecialized" designs by simple modifications. The M20 design is dead, guys, the only nation to ever saw more the 3 in a single event (The Netherlands) has turned its back on its major design concept. As good as all M20's in NL are fitting jibs to their boats, the lightweight carbon masted uni-rigs with spi have proven that they simply can not compete well with the alu/glass/sloops. Apparently the jib does provide a significant amount of drive, a thing that has been known for over 100's of years.

A 800 buck jib setup setup beating 10.000 bucks of carbon fetishm ! Now that hurt and that impression is going to last.

A uni-rig without a spi ? Forget about that one too guys, it is not going to be a succes anymore. And no amount of additional carbon or weight reduction will ever correct this. It worked when their main competition were mediocre strickt one-design classes. Now that the formula classes have show how it needs to be done the challenge to light uni-rigs without a spi is significant. With their unattractive profit margin more and more builders are falling away. I predict a serious issue to arise over the next 5 years. Especially with Matt quoting the plain Blade F16's at 110 kg ready-to-race and fully fitted and a low price to match this fabulous picture. AHPC is going to join this group with a new design shortly. All the more reason for us to NOT go the route of the overspecilized carbon boats and join them in such troublesome times.

What we have done so far has proven to be exactly the right path. We should continue on that path.

Wouter

P.S.

I'm all for relatively simple boats that fit like a glove and are fast because of excellent control and well mannered behaviour. No secret wapons, just good designing with what you got to work with.

Wouter

Hi wouter

to the theame, sloops verus cat riggs.
It has to be said, that for a given sail aerea, in the lower windspectrum ~ from 1 to 3 Bft ~ the cat rigg is faster on a windward/leeward course. You didn't say that in this year two Catrigged M20 had line honours on the round Texel race. They didn't win after corrected time, which actually only a matter how the ratingsystem weights the different riggs.

I also like the simplicty of our uni rigged boats.

Hello Andi,

Allow me to reply to your post in an argumentive way, this is however not at all linked to your person. I just happen to strongly disagree with the counter example you provided.




Neither did you say that after 4 hours and 11 minutes and 49 seconds the first sloop boat finished, only 75 seconds behind the first M20 and 61 seconds behind the second M20. The first Tornado finished 4 min and 18 second behind the first M20 and the first F18 did so only 5 min 56 seconds.

The Tornado was definately sailed by a capable crew but not a crew of the likes Bundock, Booth, Hagara, or Figuroa. The F18's did see their usual go fast crews, although Booth was on a Fox.


I dare claim that the shy 6 minutes the F18 lost over 4 hours of sailing can be totally attributed to them being a good 50 kg's heavier and the M20 having a 20 % larger spi, NOT because they sacrifized some mainsail area into a jib. Also note that the F18's and M20's are sharing as good as the same upwind sailarea. The M20 spi is however 20% larger as said earlier.

It stands to reason to claim that an F18 at 53 less kg weight can be expected to have closed the gap of 6 minutes over 4 hours sailing. The Texel rating difference in this suggests about 10 minutes to be gained that way.

Lets face; this was about as perfect Round of Texel for the M20's as it ever was going to get.

Winds around mixed single and double trapped (10 knots) with the two long legs being downwind and upwind and 8 M20's were entered. If the M20's couldn't dominate now then they never will.

It certain lead to their best result ever. After a shy 7 years of trying.

If anything it is clear that the uni-rig concept has failed to proof significant superiority over a broad range of racing conditions. Yes, in whisper winds it is very fast in anything other is it is only a more efficient hole to sink your money into. The A-cats are proving this now as well.

We are not even basing this discussion on handicaps, if we would then the picture will be more depressing.

We must not forget the M20 being a 32.000 a Euro boat ex shipping. That is a whole lot of money to gain a 6/(4*60+10) = 6/250 = 2.4 % speed advantage over a 18.000 F18 and a 14.000 F16. A thing a M20 at the Alter Cup qualifer found as well. Carla Schiefer raced a M20 in the 2006 Texel race as well and came 21th on elapsed time, behind 7 F18's. Through this connection the comparison between M20's and the Blade F16 is now founded.


Yes, you are right, these uni-rig can't make their handicaps as these are easily rated 5 to 9 % faster then the F18, mostly becuase these uni-rig weight so little as well. And that is exactly my point. Make a F18 at 130 kg and watch the uni-rig eat humble pie. 50 kg is alot of weight and it certainly seem to make a whole lot more difference to performance then putting all the sail area in the mainsail.

We must of course also not forget that the M20, F18ht and A-cats have carbon mast while their main competition is still sailing with alu. Another difference that if it means anything favours the uni-rigs in this comparison.


This is actually a perfect case of how little expensive stuff improves performance and how much skilled engineering does.


Now I fully respect the M20 and F18ht and A-cats and their owners. Love to have them on the water and fully respect them as classes. My points are not that there is anything wrong with them. My points are that the uni-rig revolution is over by vrtue of not showing sufficient gains, if any. And in some cases we can also put the "all-carbon" revolution to bed. None of such boats (CFR 20, M20, M18, Eagle 20's, F18HT, Fox special project, etc) made an significant impact with the possible exception of the A-cats.

Designs based on much more modest but agressively developped materials and concepts were extremely succesful at keeping the difference negligiably small. I mean if a All carbon hobie Fox special project boat with Booth/Dercksen on it can only stay 38 secons ahead of a Capricorn F18 sailed by Kenbeek/Brouwer after 4 hours then the carbon boat has a REALLY serious problem.


Also note how the M20 is now almost exactly the same as the F18HT's. In the past the M20's used to be both lighter and carry more sailarea.

F18HT
130 kg
20 sq. mtr. mainsail
10.30 mtr. luff length

M20
127 kg (first versio : 108 kg)
20.71 sq. mtr. mainsail (first version about 23 sq.mtr. if I remember correctly)
10.25 mtr. luff Length

I gether they found the need to depower the boat (M20).


Wouter

Hi Andi,

Will be fun next year.

I should manage a couple of races against you on my stealth.

Bye

Just a small comment on the M20/Texel debate. Wasn't there a period with (almost) no wind for the leaders this year? If so, it would give the slower boats a good opportunity to catch up with the leaders.

Uni rig faster upwind/downwind than a sloop.. I think this leads us back to a discussion on ratios and conditions. The uni rig is more efficient (higher aspect ratio, less sailarea down low where the wind is "dirty" etc.) But even in theory it is not faster in all conditions. In real life, classes with limited sailarea like the A and C class have evolved into uni-rigs, so there is a strong argument that uni-rigs probably are faster on a windward/leeward course (C-class had their own courses earlier, with lots of reaches and strange courses sailed to really test the designs on all points. Wings are very competitive on reaches). One of the really good arguments for uni-rigs are the lower structural loads on the platform, so they can be buildt lighter. With the minimum weight we have in the F-16 class, there is no need to optimize for a uni-rig.

Only when we do handicap calculations or are looking at crews spaced significantly apart. However, I based my entire post solely on ELAPSED time results and Remco Kenbeek was one of the leaders during the whole race.

A F18 that is only minutes behind a M20 is not helped in any way (on elapsed time) if the wind dies somewhere halveway on the course. Both will float at the same speed. However, from the video's it doesn't appear that the wind died completely. I guess it lightented up significantly, but if anything that favours the M20 again.





Most of the Dutch M20's seem to have converted to a sloop rig now. They add a bridle foil and everthing is dandy. Also how much additional glass do you need in each hull to withstand the bridle loads ? The vertical loads on the hulls are much the same, only the sideways ones increase. 5 kg per hull at max ? 10 kg in total ? A jib sized at 25 % of the mainsail will add about 5 to 8 times as much performance to the boat then reducing the weight by 10 kg. So if you had to decide as an engineer you would choose the jib.

Wouter

I dont know the details around this years Texel race, I just watched the video coverage posted on the internet. However if there are two different windsystems, getting into the right system is vital. If I remember correctly there was a convergence zone this year where you had to choose to go close to land or further out. Mitch Booth on his carbon-fantastic-Hobie-Fox choose the wrong side (went out from the shore) and lost the M-20s there. Both leading M-20s went towards the shore and got the best conditions. Coming from behind and being able to see what is happening in front is a massive advantage, enabling you to position yourself so you can avoid the largest "vacuum" spots.
Agree that in low wind conditions the M20 should be favoured with it's taller rig and light weight.




Why are the M20s converting to sloop setups? Breakage or more versability in distance racing?

If sailarea is unlimited, it's a no-brainer. With limited sailarea it's a bit more unlcear. The C-class dont have a minimuim weight, so they are crazy about weight. The A-class used to have 90kgs (?) min weight, but went down to 75kgs later on. Less weight on the boat (and crew) is generally faster. In addition a taller rig with higher aspect ratio is more efficient use of the available sailarea. But it boils down to one of your favourite adagios "it's all about ratios"..

You are 100 % correct here.

But for some reason most people forget about one of the most important ratio's of all.


! Sailarea per boat !


No uni-rig can effectively canvas as much area as a sloop rig on a, apart from this, identical boat.

So yes if class rules limit the total sail area to an amount that can reasonably be put in a uni-rig then such a setup CAN have advantages. However if class rules allow much more sailarea then can be controlled in a single mainsail then adding a jib becomes very attractive. Classes, like the 18 foot skiffs, that have no limit on overall sail area all have jibs and having one here is an absolute must.

Some sailors and designers are focussed too much on the specific circumstances of their own classes and assume that every design is restricted to some rather low limit in overall sailarea (as their designs are) and then claim that it is always better to put it all in the mainsail. This maybe true in their own class but it is simply not the whole picture.

You can't just remove the Tornado jib and add its whole area to the mainsail; even if you did that and increased the mast significantly then it would still end up being a really bad overall boat. So you have to take away some area from the new mainsail and hope that the improvements in pointing angle are enough to compensate back for losing overall sailarea. In most cases it won't.

A-class, for historic reasons, started with a limit on overall sailarea that actually is significantly lower then a sloop rigged singlehander can realistically carry efficiently. If say they had chosen earlier on to limit area to 18 sq.mtr. then they would al be sailing with selftacking jibs now because of their limit on platform widtht (contrary to 18 squares). Actually this is one example of how the A-cats have their own set of ratio's, unlike those of other designs, that makes their designs as special case. This as an illustration of my often used statement that A-cats are often so much different in their set of balances that things that work there, may easily not work on other platforms.


When we set up the F16 class rules we quickly learned that no more then 16 sq. mtr. could ever be put effectively in a F16 mainsail. We could however put as much as 4 sq. mtr. in a jib if we reduced the mainsail by 1 to 1.5 sq. mtr. Now mainsail area may be more efficient in an absolute sense but it was never going to be 3 to 4 times more efficient. And there were other arguments against not having jibs either, like versatility between 1-up and 2-up.


The M20's can simply carry alot more sailarea with a jib fitted then when just fitted with a mainsail. The crews are now fully going for line-honours and totally forget about handicaps. Actually a M20 with a jib was leading a good portion of the Texel 2006 race ahead of the standard M20's. So even Goran could have chosen to go for the shore because the boats ahead showed him that that was the way to go. The M20's didn't lead the whole Texel 2006 race.

Additionally the time between the standard M20's and the first F18 was the same at 3 hours in the race (oudeschild) as at the end. So in the following 70 minutes the gap remained the same, meaning both boats matched eachother speed for over more then a hour (all the way to the finish). So who is not to say that Gorans lucky break came in the shape of a dying wind halveway through the race.


Wouter

Sure, it goes both ways. Good post!
Fun to hear that the M-20 owners are modifying their boats to be "line honor" hunters while the weight increases. I have a dream/vision/goal about participating in the Texel race with a plywood 20 footer based on a Tornado rig and wings (on the hulls that is). It will not happen this year, too busy wit the Blade and other things at home, but.. Those M-20s and carbon wonders present a very interesting challenge.

Regarding my "wish list" for rules mods to the F16 - rebuttal points well taken (particularly this notion of practice as a means to improve speed !).

I expect the F16 solo sailors will soon be deriving benefit from the experimentation being done by the SCYC Acats.Rumor has it the rig/ sails will soon see pretty radical changes (?).Example: my Glaser sail is pretty nearly the same as an Acat main in terms of draft and is really fast from about 6kts. of wind and greater.The sail seems to suffers a bit in really light air. I noticed this design(attached),allows for more power in the equally flat Acat when wind velocities drop off (just let off diamond tension). I also really like the rotator bar being closer to the tramp as its hard to reproduce rotation settings with a bar just below the boom.

Paul

Paul,

I have found exactly the same thing as you: once the wind drops to really light, the As definitely have an edge. I'm not sure how much difference on-the-water diamond adjustment makes to this particular aspect, but I do know that there's already at least one F16 in Europe sporting this system.

Paul

Paul and Paul,


Funny enough I'm actually working on this aspect right now. But I'm trying to go for the most simple solution. I think such a thing is possible as we F16's really don't need to adjust our mainsail settings much for the downwind legs. Certainly not to the extend the A's have to do this. I think we F16 sailors can get away with optimizing our settings for upwind and just use what we got with under spi. Any prebend fine-tuning here is not going to make much difference at all.

However I need more time to develop the model and test it against real life measurements.

But I think I can give you guys a quick fix for in the mean time.

Assuming your sails behave almost the same as the A-cat sails, then I believe that the A-cat sail tops stay more flat when they derotate their mast in very light winds. Our masts have more difference in stiffness between fore-aft and side-to-side then the carbon A-cat masts. This means that when we derotate our masts our tops fill up, meaning the draft increases considerably and our leech stands up. Both these things are bad in very light winds. Here you want to have a rather shallow draft over you sail with a significant amount of twist (open leech).

In order to correct this we alu F16 mast sailors need to pull on heaps of downhaul to bend the top in its stiffer plane. The bend flattens our sails and also opens up our leech. However, if you are still sailing with the prebend settings for more mast rotation and stronger winds then the middle section of your mast will now bend away to far or too little. I haven't determined which one it is. However it is pretty certain that the prebend is not where it must be for the right draft in the middle of the sail. It is here either too deep or too shallow. My guess is that it is too deep. At least that is what I experience on my own boat in very light winds and I have to sheet out more to correct somewhat for this. Drawback is that my top leech opens up too much as a result, the top section of my sail is now generating less drive then it is able to. This works relatively well on the water, especially when suddenly the wind drops away and you have to do something with the controls that you've got, but still there is something to be gained here. As said earlier your rig may just a well have too little draft. So check for yourself which it is in your case.

The only quick solution for me is to INCREASE pre-bend before I go out in light winds. A more engineered solution would be to stabilize the bottom section of my mast more by changing the spreader setup but that is too much work for this time. So I just turn-up my diamond wire turnbuckles (just as landenberger wrote in his tuning guide). I still haven't done this often enough to give you guys a good estimate on how much is needed.

By increasing prebend when expecting to sail in lights winds the draft in the middle section is reduced. Additionally there can be a sufficiently large added flexing of the mast top to open up the leech even more without affecting the draft there. But this latter reaction is still being researched, it can't quantize it yet.

Anyway, the combined effect is that you can reduce mast rotation a little to reduce profile and then apply downhaul so to reduce draft in the top and open up the leech, both of which were negatively impacted by the derotation. The negative effects on the middle section are then corrected by proportional adjustment of the mast prebend you made on the beach.

You should now have a pretty small profile combined with a shallow draft and the leech has significant twist to compensate for windshear ; this is fast in really light winds . NOTE : we are talking about really light winds here, not just simple light winds. Think 0-5 knots.

Of course the mainsheet is sheeted on very lightly.

After the light winds have passed you just release some diamond wire tension (the amount you added) and you have regained your medium and heavy settings again. Simply counting the numbers of nutt or turnbuckle rotations will be sufficient.

Of course it can be that your sails are to shallow in light winds and then you guys must do the opposite of what I described here, you'll be reducing diamond wire tension for light winds then.


Some A-cat sailors are doing these adjustments while sailing (most when turning to sail another course) using the system shown in the picture. I suspect most of this setting is tuned when going from upwind to downwind, because here their sheet tension changes alot. From on hard to rather loose.



Personally I think we F16 sailors can mostly do this tuning on the beach and then forget about it for the rest of the day. This because we only need to adjust this setting for the winds and not when switching from upwind to downwind, we have the spi there remember ? That thing takes care of everything we may lack in mainsail trim on downwind legs !

That spinnaker has now become an integral part of the F16 designs. It allows us to cut corners (complex tuning systems) and thus produce cheaper and simpler boats without sacrifizing performance. The extra sail area we got up there will limit the hit we get when we decide to sail without the spi, but that only goes so far. In the really light stuff sail area is not that important, proper sail trim is, hence the experience that we can't really stay with the A's there. Of course the fact that the spi won't fill in these conditions is contributing strongly to this as well, we just lost 5% performance there. But by fiddling a little with your mast settings you should be able to win some back.


Good luck,

Wouter