Jib versus no jib on A Class, M32... which would be faster ?

[MRS OCTOPUS]

Windrush 14 cat rig , one up, VYC yardstick 95. 

Windrush 14 sloop rig, two up, VYC yardstick 90.

Note:

Around a course the sloop is faster with this design.

cat rig points real high upwind, but is glacial downwind.

 

[ex18er]

Am guessing that the deal is, if you hoist a jib, you have to take the extra weight of a passenger too.  Does not really prove anything in this context.  Except that maybe Hobie 17's are overweight and lack the buoyancy to carry 2 humans efficiently.  And that Americans can't do PY.

Except the PN doesn't clarify if the boat has 1 or 2 crew on it.  Agreed that 2 crew with a jib might be slower than 1 crew without a jib.  But shouldn't PN allow for 1 person with jib if it made a difference ?

 

[ex18er]

Windrush 14 cat rig , one up, VYC yardstick 95. 

Windrush 14 sloop rig, two up, VYC yardstick 90.

Note: Around a course the sloop is faster with this design.  cat rig points real high upwind, but is glacial downwind.

That is what a gennaker is for.  Fast unarig upwind.  Fast main + gennaker for downwind.  Best of both worlds and better than a jib in both situations.

 

[Waynemarlow]

Guys the Portsmouth handicap system is so out dated for catamarans and is so subject to error through it being a reporting system where individual club reports can skew a handicap simply by having at one club top end sailors and at another bottom end racing against boats of other classes in specific site conditions which equally have few results, you are much better to use a calculated mathematically honed over the years to actual cat on cat racing such as https://schrs.com/downloads.html

The SCHRS calculator has now gotten its act together on the 1 crew v 2 crew that we are finding it pretty good on over the water racing of cats that are quite different. The only downside is they haven't yet worked out the PY conversion number is way wrong.

 

[SimonN]

I think there are a number of issues that stop a jib working on an A, and in particular, on a foiling A. To start with, self tacking does not equal self trimming. I think there would be real issues when trying to get up on foils with the need to trim the jib and main to get the rig to work as one. If you ease the main a long way, which is needed to get up on foils, then an untrimmed job would simply backwind the main and hurt performance.

On the F50's, the jibs perform a very specific job of sorting out flow over the wing that makes the wing less sensitive to trimming. One of the big problems with a wing is to get flow over the wing and it is an art to be able to read the wing and know what to do without the usual mainsail tell tales. The jib directs flow so that during and after tacks and gybes, airflow stays attached or reattaches to the wing quicker. The jib also helps in lighter conditions.

Another major issue is that even if a jib might be better, the current A rig is very highly developed and it would take a lot of work to develop a sloop rig that works as well or better, particularly over a wide range of conditions. 

++++++++++

 

[Groucho Marx]

C Class cats started off with jib/main setups way back in the 1950s early '60s, then when the wingmast una rigs arrived that was the end of the double sail designs. If you're talking of the world's highest performance sailing designs and rigs from the last 3 or 4 decades and which set world speed records .... no heasails.

 

[Sidecar]

The real benefit in foresail(s) and mainsail combinations comes from reduced rig height for the same sail area, from which flows reduced mast weight and rig drag, reduced pitching, reduced centre of effort/heeling moment, and greater flexibility with regard to balance, shortening sail and manoeuvrability.

In A class and M32’s, where you can carry a una rig without undue detriment from these factors, why wouldn’t you use a una rig?

Far simpler, especially if short/single handed and preoccupied with the complexities of foiling……

 

[Amati]

Because on the faster catamarans they are not really spinnakers anymore. Mine are down to 65% mid girth, the latest handicap rules allow it with a calculation. They are getting flatter and flatter and in light air can on occassions be used both upwind and downwind successfully if you are prepared to move the clew inboard. I would like to go even smaller on the mid girth.

Theres long been an argument that on the likes of the F16's where sailing solo is just mainsail and dual is with jib, that even though the jib is relatively small, the efficiency of the jib working together with the main is such that it will out advantage the extra weight of the crew over a typical small race course. Actual top speed would be slower but faster at the bottom end wind speeds and in manouevres.

You can forget the Smythe experiment on the A, he chose to go to quite a large jib and loose quite a bit of main for a specific events conditions, it didn't work out as the wind gods didn't play ball. Now if he had gone to a very small blade jib my guess with modern materials a solo sailor sailing a classic A would be faster around the course mainly because we now have better sail laminates and the advantage of easier sail setting on the main ( you only have to look at how the jib streams and smooths the wind onto the lower part of the main ) + easier tacking and the usual race conditions where its not all about top speed.

As to foiling A's, that a whole different story but my guess a jib would give better grunt to get up onto foils with less top speed. For an average sailor it would be probably faster in total overall as that ease of transition onto the foils is the difference between the top guns and the average sailor and once up onto foils you need a smaller main.

If you could furl the jib tightly enough once you’re foiling?  Or furl it into a head stay foil? That would have it's AoA controlled automatically by a tail plane, of course. (Class legal?). Getting into Waterworld or Chris White land. .  How much would jib sheets hanging around a furled jib mess with main performance?  How much difference to the foils would the change in rig CoE make when the jib was furled? Although I suppose if the jib was just used in the light, and the sheets were like 1/8” dyneema or something, maybe the Reynolds number would be small enough so the difference was negligible- goodbye simplicity.  The next thing you know somebody will rediscover the advantages of hiking planks, if those are still class legal. (let’s see, weight to windward & if shaped correctly, smoothing out flow around the helm, getting rid of trapeze wire parasitic drag and making it physically easier to maintain full helm extension?)  It’s always something….

 

[maxstaylock]

Wouldn't it be great if there was a place you could bring what you thought was the bestest catamaran in the world, and race it against what others thought was the bestest catamaran in the world?  You would need some basic limits, so you were comparing apples to apples.  Lets say, maximum 18 foot long, just because it'll fit in a boat park?  2.3m wide, so you can tow it behind a car, without taking it apart?  We would have to limit the amount of sail you can have, to keep a level playing field, we could say, 150 square foot?  Maybe say minimum weight 75kg, pretty light, but not impossible?  We would have to all agree to use the same sail/mast/foils etc for a whole regatta, to avoid pointless expense of needing to rock up with 10 of everything.  This will also mean the equipment would be well rounded, and work across the wind band, but there is a limit to anything, lets say we'll race between 5 and 23 knots of wind.  Then we can settle all these arguments on what works best, empirically.  We should just do that.  Who's in?

 

[Sidecar]

^^^^^ How many crew?

 

[Amati]

^^^^^ How many crew?

Weight limit.

Trapeze?  Sliding seats?  Feet on hulls?

This would make an excellent AC.  Owner drivers….. B)

 

[Jethrow]

Weight limit.

Trapeze?  Sliding seats?  Feet on hulls?

This would make an excellent AC.  Owner drivers….. B)

I think @maxstaylock was describing the A class cat...

 

[WetnWild]

Some excellent suggestions above to improve the A cat. Let’s not stop at adding a jib. I particularly like the hiking plank idea and it should be made from natural timber so we can get away from that nasty petrochemical carbon fibre. And let’s get back to timber masts with maybe a good gaff rig. I also like the snap of a fresh calico sail. Good times ahead. 

 

[Sidecar]

I think @maxstaylock was describing the A class cat...

He clearly was. Forget the M32.

The reality is that for a given set of parameters, one type of rig will be optimal. For a trapezing single hander, I am not surprised that a una rig is best. Add a crew member and a little more sail in the mix, especially downwind sails, and you could end up with a different optimal rig. If an M32 was only allowed to have 3 crew with a corresponding total crew weight reduction, I would expect an evolution to smaller mains on shorter masts with a jib in front.

 

[Waynemarlow]

You guys are forgetting that to get an Uni rig dialled into optimum shape for optimum performance, only about 10% of sailors are savvy enough. On the other hand with a jib smoothing the flow over the main, 50% find it relatively easy most of the time. 
 

So what it’s to be, 50% enjoying racing all relatively close enough for rules to come into play or just the top 10% sailing off into the distance with the other 90% in the bar or playing golf ?

 

[maxstaylock]

You guys are forgetting that to get an Uni rig dialled into optimum shape for optimum performance, only about 10% of sailors are savvy enough. On the other hand with a jib smoothing the flow over the main, 50% find it relatively easy most of the time. 
 

So what it’s to be, 50% enjoying racing all relatively close enough for rules to come into play or just the top 10% sailing off into the distance with the other 90% in the bar or playing golf ?

We should do more class training, the A Cat rig is simplicity itself when you get the right sail on the right mast, and dial in the base settings. Come to Clacton for the nationals this year and we'll have a sail trim tutorial on the Friday, if there's interest.  It doesn't need any more savy than any other development class, but it does take a little more effort than buying a Laser sail.  It is easy to stall in light winds, but it's so responsive that it shouts at you when it does stall, but when it finds it's happy place, its a rig that takes your breath away, and makes every other rig on any other boat seem like hanging washing on a line by comparison.