Steve,

Sloop rigged Taipan and Mosquitos are definitely faster then cat rig Mosquito in wind over 20 knots. While I may have beaten sloops in those conditions I certainly don't think its the norm.
Cat rig Taipan versus Cat rig Mosquito in wind over 20knots, I would expect to race with Taipan cat rig backmarkers and beat the first Taipan on handicap if VYC yardsticks are used.
As for the standard of the sailors I race against, they are club sailors like myself.

No more from me on this thread,
Darryn

Yeah, the cat rigged taipan back-markers are my benchmark atm without kite. If I can keep with them then I'll be happy.

The taipan sailors at the club have also said a mozzie will perform very well in a breeze. Now I've got to stop breaking the thing in a breeze!

I will post photos as soon as the mast is sorted.

Nick.

Hi Nick

Keep posting the information on your mainsail. This is definitely the right place for it. It's great to have someone making the effort to try out an idea like this. There's no other way to find out if it will work.

The Taipan is wider as well as having the taller & bigger rig. You are right that in most other respects it's like a Mosquito.

Mosquitos are competitive in a drifter, but as the wind increases bigger cats get on trap earlier and leave the Mosquitos behind. Once the Mozzies get on trap they are back in the race.

As far as performance goes, what we see at regattas in Victoria is:

• Cat rigged Taipans are definitely slower than sloop rigged Taipans once everyone is trapezing.
• Cat rigged Mosquitos are slightly slower than sloop rigged Mosquitos above 15 knots and in waves.
• Cat rigged Mosquito is faster than sloop in 10 knots or less.
• Well sailed Taipans are a lot faster than well sailed Mosquitos (note: despite the rumours even a Mosquito with a spinnaker can still be beaten on handicap by a good Taipan - see last year's
  Wildcat results).
• However,a Taipan that is not sailed well performs well below it's handicap and can be beaten around the course by a well sailed Mosquito.
• A Mosquito with a spinnaker is fun to sail in everything up to 20 knots (maybe more) whereas the Taipans do not want to use spinnakers in 20 knots (what's the point when you are already at terminal velocity ).

Thanks, Tim & Darryn for clearing up my misconception. We (the RSA Mozzies) had believed that your uni fleet would be faster around a course than your sloop guys, even if it was windy. We must have got that info from someone / somewhere, but these last two posts clears things up a bit.
Having said that, when our National champ sails uni in up to 14knots he is still damn hard to beat if I`m sloop, over 14knots it only gets a little bit easier to stay with him, and that includes us both on spi. downwind. But in over 20knots sloop is just so much faster.
Skill level still plays a huge role, as you said Tim, well sailed Moz can beat an average Taipan sailor, I have had Hobie Tigers behind me but then I know there is a difference in skill levels, it proves nothing about the boat`s potential.
Darryn, I was not questioning your integrity about finishing ahead of Taipan sloops in 20knots, just letting Wouter know that from what I`ve heard you are no slouch against the Taipans in these conditions.

Steve

Going back to the subject of sail twist with the fat top sail, I just found this recent photo of Gary on Altered.

What does everyone think? Right or wrong? Could he make this leech stand up? Would it be possible to over sheet it? Gary should be able to tell us from the mainsheet blocks, whether he has it sheeted in or not here.

Hard to tell without seeing telltales. I reckon it's under-sheeted, but I'm a n00b to cat sailing...

Nick.

Hi Tim,
As usual, a great photo of Gary styling on an awesome boat.
I think that he looks pretty much sheeted in max there, looking at the blocks. Most cat mainsails are designed with a certain amount of twist built into them, so if your leech stands up all the way to the top, you are in effect oversheeting the bottom 2/3 of the sail. I`m certainly no expert here, but from what I understand, twist is good, not only to depower the sail, but aerodynamically as well. Something about the wind higher up flowing faster than lower down, or at a different direction, whatever. Maybe the aeronautical engineer`s who visit these forums can explain it.
Looking at modern windsurfer rigs, the sail is designed to have quite a lot of twist, so much so that when you look at the sail on the beach, the leech is floppy, this depowers the rig before you have even sheeted in, but also has the effect of creating a large amount of twist. Now why would they do that if they could rather rig a smaller sail and have the leech stand up straight, it would still depower in the gusts due to the flexible mast. The answer must be that a large sail with a twisted off head is faster than a smaller sail with a straight leech. Perhaps in cat-sailing this is all different, maybe too much twist will hurt your pointing ability, but if your speed is much better you might still be first to the weather mark.
Just my opinion, so all those who have a degree in aircraft or sail design, feel free to straighten me out.

Mmmm, very interesting. The theory I have running around in my mind right now is that as the boat pitches and accelerates/decellerates over/through waves causing the sail to move back and forth through the wind, the apparent wind moves forward and aft very quickly, say through 10-20 degrees for every wave that is encountered.

So you need to be able to change the sheeting angle of your sail to obtain the maximum thrust from this ocsillating apparent wind. As the boat pitches backwards the apparent wind shifts aft a bit and as the boat pitches forward the apparent wind shifts forward a bit.

Changing the sheeting angle is very difficult, or impossible, to do fast enough on many boats. So another technique needs to be developed to allow the sail to operate efficiently at all these different angles of attack very quickly. Dinghies do it by pumping and "bouncing" the crews body weight through waves, although it is illegal, as this moves the rig towards the wind and counteracts the apparent wind moving aft as the boat/sail is pitching aft.

Cats don't tend to operate the main much upwind so a different technique has evolved, big head mainsails with the right amount of twist, not too much, not too little. With the right amount of twist, the sail will "on average" operate more efficiently as different sections of sail at different heights change between being highly efficient and then inefficient. So while one section at the top may be operating poorly, a section at the bottom may be operating highly efficiently. Then when the boat pitches the other way the top will start operating highly efficiently while the bottom operate poorly. But on average, a correctly twisted sail will operate better than an over-twisted or under-twisted sail. This all depends on the conditions ofcourse, if there are no waves, more of the sail can be in the best position more of the time.

The first principle to get straight is that the apparent wind oscillates/rotates across the sail as the boat moves through waves. A cross section of a sail works best (produces best thrust) at one angle of attack. Twisted sails have many angles of attack to what is referred to as the steady wind direction. All of these sections up and down the sail at sometime during the oscillation of the apparent wind, due to pitching, will be at their most efficient angle of attack to produce thrust. This means that the centre of thrust is actually moving up and down the sail with each pitch. Over time, this thrust will add up to be more than is produced buy a sail that is setup with too much or too little twist since both these scenarios have a section of sail that will rarely operate at its most efficient angle of attack.

This might explain why it is a common indication of a correctly twisted main that the top leech telltale should be flowing about 50% of the time. The top section of sail is only operating at its best angle of attack to produce thrust about <50% of the time (telltales will stream slightly either side of best angle of attack though). While the top section is operating poorly, the other sections of sail are operating efficiently. Imagine the apparent wind angle as it moves up and down your sail. It will tend to slowly move forward as you go down the sail and will tend to move aft as you go up the sail.

I might be a nerd and crunch some numbers later to see how much the apparent wind will rotate at the head of a pitching sail. That will give an indication of whether or not my theory is correct.

How this relates to square head mains may be that the sail area is distributed more evenly up and down the sail so the instantaneous thrust is pretty much the same during the tiny oscillations.

Be careful with my terminology, I have used rotate, move and oscillate interchangeably with reference to the apparent wind angle throughout the post depending on the scenario I'm trying to explain.

Excuse my long sentences, I wanted to get it out quickly before I forgot it.

Nick.

Can you actually get a degree in sail design? I know it's a craft where you can be an apprentice and do a masters test when done as apprentice. But can you go on and do a degree on saildesign?

As for wind shear, it depends on what kind of wind you have, stable or unstable. My literature suggest it can be quite pronounced (25deg) even in the height-range of catamaran masts (I have never experienced it so pronounced). It can also be as small as 2degrees at your masttop. (Ref: David Houghton and Frank Bethewaite). What you are thinking about is probably how friction between wind and earts surface, and earths rotation (coreolis effect) wil influence the wind. Short version is that becouse of friction between the wind and the surface, and becouse the earth rotate wind further up will have a different direction than closer to the surface. As earth rotates in the same direction all the time, you will need less twist to compensate on one tack than the other.
My experience is that twist is beneficial in some conditions, but should be avoided in others. When overpowered (as Gary looks to be in the picture), twist is good to shed power and eliminate form drag. Twist is also beneficial when powering trough waves or accelerating. In flat water, looking for power, I feel faster with less twist. This will increase power (again, depending on wind shear), but also increase form drag from the sail.
Sloop rigs need to twist their mainsail to compensate for the jibs influence on the wind. On our Tornado main we have used 8 degrees of twist, and I think it's a bit too much (might be a problem with cloth stretch and luff curve). I have also heard that 11degrees of twist are designed into Tornado mains. For a uni rig, I would expect less twist designed into the sail. But how it's trimmed on the water is what decides how fast it is (unless it is out of the ballpark).

When trimming windsurfer sails, it's critical in my experience to have the correct mast for the sail. I trim downhaul until the leech just goes slack when looking for power with it. In stronger winds, I put on more downhaul to keep the sail manageable. With the wrong mast, your leech will go slack to early, or overpower you completely
The main 'brakes' you can put on when sailing cats are form drag from the sails. If you go out in 0-1m/s winds, wind shear will probably be pronounced , so you need twist to power up the top and keep the telltales flying. You have probably also heard that in weak winds you need deep sails to make the boat go. So, how do you induce twist while keeping the sails full? You let out on the mainsheet. That way you will have a full sail and decent twist. If you have tried this, you know that you will not go well to windward and be slow. If you crank on the downhaul and sheet in (still fly the leech telltales 50% of the time) to flatten the main, top will twist off while the lower part of the leech still stands. What you really have done, is remove a large part of your sails form drag as the wind dont have to move over that deep curvature (and probably detach from the surface underways) but instead follow the much more efficient shallow curvature. If the wind increases, you can trim your sail deeper with less twist as the increased power generated by the sail is larger then the added form drag.





Sorry for the rambling.. I just find this stuff very interesting.

Just better clear something up about wind angles. The true wind is not changing direction significantly the higher you get up your mast. The true wind speed is however changing significantly, as you said, because of wind shear/the boundary layer. In other words the wind closer to the water surface is affected by friction and slowed down compared with the wind up higher.

Since a boat always moves at an angle to the true wind an apparent wind is created. Apparent wind is what you feel across your face while sailing. The apparent wind angle changes significantly as you move higher because the wind speed higher is faster. A thing called vector addition lets you calculate the apparent wind speed and direction very simply as indicated here:

Apparent Wind Calculator and Diagrams

The guys at the twisted flow wind tunnel are the gurus when it comes to apparent wind and required twist. There is a diagram that perfectly shows what is happening to the apparent wind at this link:
Twisted Flow Wind Tunnel - Auckland

Anyway, enough from me.

Nick.

Hi all,

have been flat out with sailing and working away alot. Interesting to catch up with the posts. So many things to comment on.

Firstly Altered picture, I was sheeted hard at the time, basicaly as much as I can pull on with 6 to 1 from trapeze. Twist is all from downhaul or cunningham, Glenn advised me I was not using enough, so I upped to 12 to 1 and can now give it heaps. Basicaly I sheet in hard then adjust downhaul so that I am pointing at the hieght I want and travelling at the speed I want. The twist in this photo gives better VMG than when I was sailing with less twist causing me to point higher. When I got this sail I underestimated how much and how early I needed to start downhauling. I am now back to being happy with my upwind speed in stronger breezes, although I do still need to check it against some faster cats.

I am not sure about this idea that Fat head sails are easier to sail with in strong winds. I have heard this ever since I started sailing cats but from my experiences on large Multis and Altered, Fatheads give you a higher centre of effort making them power up earlier, but not easier to sail. You have to be more careful with leech tension off the wind as the head will drive the bows under if oversheeted, also overpowering earlier just makes it harder work. From my experience there is nothing easier to handle than a standard Mossie sail in high winds, it twists and depowers readily and it's low centre of effort takes more wind to over power.
Don't get me wrong I love my big fat head (easy boys) I wouldn't consider sailing with anything else, as it gives me speed in 5-10 kts. that is not possible with a pinhead. But it and others I have used are harder to handle when it is windy.

As for speed of respective cats, I now recite to myself as I get chased by those Mossies, IT'S EASY TO SAIL A FAST BOAT SLOW. From what I have seen around regattas the faster it is, the easier to sail slow as evidenced by Tornado's being beaten by Mossies. I used to think that Taipans especialy cat rigged where not much faster than Mossies having beaten fleets of up to 13 to windward marks many times on my Mossie. But recently I have come up against the Aust cat rig Taipan champs on Altered and I can tell you in 20 kts. they are very fast beating most of the A class fleet. Sounds familiar doesn't it.

Now for Mossie cat rig versus sloop rig. Being one of those guy's that delight in cross referencing useless info. I looked at times from recent Mossie titles at Loch Sport comparing front of cat rig fleet with sloop rig times, as expected the cat rigs where faster in the light winds but to my surprise they where also faster in the strongest winds gusting 25kts., in fact there was only one race at the Nats that sloops beat cats. In one race in about 15 kts. the first 5 cats beat the first sloop. Before anybody goes making to big an assumption, I think it should be said that the flat water and gusty winds helped the cats here as it was hardly the conditions to get a sloop in the groove upwind something I know they like to do from experience.

Regards Gary.

Sorry fellow Mozzie people but I'm a bit confused.
Why do all the skippers who own mozzies and are discussing all the modifications to a very well designed cat want to try to change it ? This happened about 15 years ago and the class numbers dwindled into the doldrums. (when the Tiapan was born)It is now showing a big resurgance again because in my opinion the mozzie (a tried and tested to be a excellent allrounder at a respectable price) it's strict one design. If you wish to sail in something more powerfull, exotic, faster or whatever why not buy a cat that is already designed to what you want. More than likely most of the skippers in the mozzie class enjoy the cat for what it is because of it's affordability and performance. Most can't afford all the changes you guys would like to implement.(fathead mains, spinnackers, long masts etc.) Perhaps you should all join an unrestricted class see if you can keep up with finances then.
Please don't get me wrong, I'm not against development of the sport of sailing but there are classes where this can happen at your wish. Please leave the Mozzie alone in it's strict one design because that is why the class is as strong today as it was 30 years ago.
Everyone on a well prepared boat has got a chance of a win, not necesarilly the skipper with the most resources to cover his inability to sail fast with the same equipment as everyone else.
Regards,
Switch[color:"red"] [/color]

Hi Switch

You seem to have picked up on the tail end of discussions and activity that have been going on for many years.

The old "15 years ago the class changed the rules and the numbers crashed" line has been regularly wheeled out, mostly by people not involved in the class. This is just one of those rumours that if you say it often enough people start to believe it must be true. The facts are that the Mosquito rules were never changed 15 years ago. There was a lot of talk at the time and people threatened to leave the class if the rules were changed.

Well the rules weren't changed and they left the class anyway, many to sail Taipans - which were after all designed by Mozzie sailors to replace the Mozzie.

Mosquitos now are the same as they were in 1967 except that, like all one-designs, the boat has been refined within the tolerances to get the best performance. They still look the same but the subtle hull shape differences and the way the modern boats are rigged makes them a much more efficient boat.

Currently there are NO proposals around to change the class.

Back in 2000 some work was begun to try out a taller square-top rig. This looked nice but the cons outweighed the pros and most people in the class lost interest.

The spinnaker has been in use since 2002. We don't have to talk about adding a spinnaker because it has already been done, without any need to change the basic Mosquito class. About half the active Mosquitos in VIC use spinnakers outside of titles - and with good reason - the performance is awesome.

This thread is now only about a boat in Queensland that is trying out a fat-head mainsail. That's just Nick's experiment, not the class changing it's rules. It's good that people try these things out though.

As far as I'm concerned the Mosquito fills a niche in the range of off-the-beach cats that are available, because it manages to combine a very refined, lightweight hull design with a low-aspect (these days) rig that is easy to handle but still very efficient, and all for a low price. In addition to this I like racing Mozzies because we seem to have the best social group of any class I see at open events and the competition on the course is fierce (one bad tack is enough to cost you a race).

The Mosquito has a lot going for it right now. Bad luck for those that don't sail one


Old:


New:

Aye Tim.
As I indicated in the previous mail I am not adverse to the development of sailing experiments in a unrestricted class but again the rumours of class regulation changes (even if it only be experimental and viewed in discussion group forums )_is detrimental to prospective members to one design craft. I didn't join the discussion to create an unrest in the forum group but just to voice my opinion. Now all that is said My background is from mono hull dinghies, sharpie and most recently Fireball. The Sharpie fleet all started experimenting with bigger kites and rigs and eventually the regulations changed and the class is now falling into minimal numbers with only the guys with all the ready resources ($$$$) being able to afford a very rolls royce type dinghy. (your everyday racer cannot afford it anymore). The Fireball is very strict in the regulations as well but experiments and regulation changes to allow a larger spinnacker along with the PRO choice of Olympic or Trapizoidal courses has now made it that you must have both kites in your gear selection.(another $1,000 bit of gear you must have to be competive). I have now rejoined the ranks of mozzies after leaving them back in 1992. My club has now gone to Mozzies in considerable numbers,(arguably the biggest fleet in Sth. Aust.) The attraction of Strict one design and fleet numbers being the draw card. This is why I have rejoined the class and maybe a better explanation for my concerns about experimental performance enhancers because in my experience over my last couple of classes and years things tend to happen without many people knowing. Please don,t allow a very fine piece of sporting design fall to the grips of the haves.
Regards,
Switch.

Hi Switch

We could start a new thread on the decline in sailing numbers generally. That is a whole huge topic in itself and everyone has opinions on what happened, who to blame and what to do about it. That would be a good one.

We are fortunate at the moment that Mosquitos are one of the few classes which are growing rather than shrinking, and I agree that there's no need to be proposing big changes to the Mosquito right now. It's a great boat at a great price and we're all having a great time racing them (especially those of us with spinnakers!).

I don't think we need to discourage the discussions that go on on these forums though. Before we had the forum experiments went ahead all over the place and no-one heard about them except usually by rumour. On the forum here we can talk ideas over and sometimes they won't get past that stage, and sometimes the idea may sound so foolproof and wonderful that someone will try it. And then usually we get to hear the results. Not all ideas involve changing the class - we can do a lot within our rules. I think this is all healthy and it's a good thing to have an active, thinking membership.

Just don't mention "15 years ago the rules changed ...etc". It's like a red rag to a bull!

Tim,

Well done. Your 2 recent responses hit the nail on the head.

The popularity of the Mozzie comes down to the cost of purchase and the one design philosophy given that there are a set of tolerance bands that are used. The class rules also allow some freedom for playing with rudder and centreboard designs and boom size. Even old Mozzies can still be competitive with a few minor modifications to deck layout, a new sail and some tuning of foils!

The number of rig options also has provided the class with considerable growth and has made other cat owners look at the Mozzie with some envy; having a Mozzie with spinnaker keeping pace with a F18 must turn heads. <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

Regards,

Peter

Aye Tim and Peter.
The red rag to a bull statement seems to have the hand brake on. Perhaps seeing as the last couple of posts on the subject of fat head sails and spinnackers on a fine piece of cat design has touched more than a few people with guilt who think the same as I.(no response for about a fortnight) Restricted classes have their place in the world and unrestricted classes have their place as well. It's a shame when some individuals in the world seem to try and influence others by constant badgering until they achieve what they set out for. Regardless of the cost to others and their thoughts. I'm sorry the world is not full of sheep and (if it is) this can only be detrimental to the success of something that is a success already. As only a newcomer to the class again after exiting it 15 years ago the talk of all the great ideas will only shut the door to many potential competitors again. I don't think I would be alone in this thought. I would have hoped that a few more people would have joined the forum discussion, but maybe I am wrong in my point of veiw??
Please don't take this response as aggressive but topical and wonder if anyone else out there cares to respond in favour of my opinion?
Regards,
Switch.

Agree entirely with switches comments, particularly regarding the constant badgering, endlessly repeating the same argument with out addressing legitmate responses.
After breaking several past Mosquitos and recently cracking several front beams while sailing Mk1 I have doubts about doubling the downwind sail area when the structure appears to be marginal already for the particular area I sail in.
I'm not the only one who cracks beams locally, you would be surprised by the number of Mosquitos out there with cracked beams.
Darryn
1704

Ok I'll put my 2 cents in.

The question to be asked is why do we always need to change something that is going ok ?. Do you always have to keep up with the Jones's ?.

As an example look at the Moth class. In the 70's to 80's they were everywhere and they were producing champions galore, in a good class which allowed a fair amount of design variation. The designers went crazy with pencil thin skiffs, the scows became obsolete, the skiffs were harder to sail, numbers plumeted. Innovation or progress as some call it has seen a class be almost destroyed.

I can see the reason behind the MK 1 Mossies to add a spinnaker, but talk it through with everyone to get a good cross section of views. Will the fathead sail really add anything to the class?.

Change for athetics or to keep up with the Jones's is not a very good basis for change.

Mossie's are Mossie's, not Tornadoes or Taipans.

That's a curious story you have about the beams Darryn. It just doesn't match with what I've seen. My boat is nearly 10 years old, has been raced hard all it's life, as a sloop for the first 5 or 6 years, then with a spinnaker for the last 4 years, one of those as a sloop with spinnaker. The old beams are still going fine!

Oh yes, and the edges are rounded!

My previous boat broke a front beam, but that was very badly corroded (and did not have rounded corners). Where it broke it was eaten right through, so it had to break.

Are the SA beams coming from a different source to the Victorian ones? I'm amazed you are breaking new ones.

Hell, Bob Wilson even takes the centre beam off his boat and it still hangs together !!!!!!!

Not sure what you mean about "badgering". I'm not aware there's any moves afoot to change anything at all right now. There's a big difference between talking about stuff and actually putting in a rule change proposal (which, by the way, any member can do).