Why does a cutter rig point higher & sail faster?

Perhaps the added performance may have just the tiniest amount to do with the fact that the gennaker adds an extra 25 square metre to the 24 sq me main and jib?

Oddly enough, more than doubling the sail area often increases speed.

Goran Marstrom and A Class designers are not complete idiots when they choose cat rigs for other boats, nor are the AC and conventional guys like Farr fools when they choose fractional sloops.

 

You and I and Farr and Melvin and the rest of the world simply don't understand the theoretical world.

We get too caught up in the real world issues like weight location and how it influences pitch, abnormally high loading due to reduced backstay angle (even requiring a backstay spreader arrangement), the alarming problems associated with lack of headstay tension (causing the sails to become fuller at just the time you want them to be flatter), headstay angle, aspect ratios, etc.

Let's face it, no one, well, almost no one, is pursuing the aft mast cutter configuration simply because we, the establishment, are all wed to the status quo. If we could open our minds we could see just how wrong we all are.

 

Tornado Code Headsail

Don't get too upset guys, I'm not going to use this Tornado double headsail configuration in support of my aftmast concept, but rather in support of the 'slot effect' that has come under attack again.

Since it was a 'double headsail', I thought it might raise some ardor if I put it in the cutter subject thread. Granted, it is not being utilized in the conventional cutter scheme, and I'm sure they might wish to douse that jib when flying the flat code sail so they wouldn't have to play that delicate balance with that jib inserted so close between the other two sails. But then again, if they douse that jib, they just might not be able to fly the 'flat spinnaker' so close to upwind.

Very true...even upwind somtimes

Might be too much a distraction to fool with this step. Besides that jib might just be allowing the code sail to point a little higher (slot effect)

But masthead rigs are not as good as fractional ones....

Hull flying could be attainable in light airs by crewing on the lee side. This code sail is providing more power to go to windward.

I agree here. I'm not arguing here for my aft mast cutter, but rather the slot effect making that big headsail more productive.

Here is an interesting comparision....the Code 0 spinnaker John Lovell and Charlie Ogletree have developed and are considering using in the Olympic Regatta and the one they used in 2004 to win the silver medal.

Tornado Code 0: Imaginative Innovation or Unscrupulous Advantage

Yesterday Dutch Tornado sailor Mitch Booth (who won two Olympic medals for Australia in the 1990s, but that's another story) submitted for measurement for the 2008 Olympic Regatta a spinnaker that is significantly smaller and flatter than the ones traditionally used on the Olympic catamaran, which of course is most likely enjoying it's last Olympic regatta as it's been removed from the docket for 2012. The big advantage of this spinnaker is that in under 8 or 9 knots of breeze it can be used upwind as well as downwind. Winds for this time of year in Qingdao are predominantly under 10 knots and often very light. The American team of John Lovell and Charlie Ogletree worked with Booth and crew Pim Nieuwenhuis to develop the sail and may measure in one as well. The Australian team of Darren Bundock and Glenn Ashby have created one on their own at the last minute.

Because the class doesn't have any minimum measurements for the spinnaker, it should be declared legal for class competition. However, it could well mean the Tornado medals are awarded based on breeze strength. A light-air regatta and the boats sailing with this Code 0, for lack of a better term, will dominate. In more moderate conditions, the traditionally rigged boats will dominate.

Not surprisingly, class favorite Roman Hagara of Austria is steamed about the development and has said he is considering boycotting the event if the Code 0s are used.

 

Hmmm ... 100% more area in a masthead rig that is only 80% effcient as the same area in a fractional rig, is still an 80% gain.

Crewing on the leeward side to fly a hull does not increase the available power. Doubling the sail area improves the SA/D.

... what slot effect?

Is this the sail that they used to power their way from 1st to 15th when the breeze filled in and they were very under powered on the downwind legs?

... what slot effect?

 

Actually it was a marvellous brain**** on their competitors and a route to the back of the fleet for the one who was silly enough to try it...

 

I love 4 years of activity on a thread about Cutters sailing faster and pointing higher.

The simple answer is: They Don't, They don't point higher and they are not faster.

No doubt that new sail and paying more attention to trim will make any boat faster and more weatherly than the same boat with old sails. But that was not the question.

 

Arvel Gentry's aerodynamic study on cutter rigs

Very interesting article here by a man who did lots of experimenting and practical explaining of how sails work. Here is a list of some of his articles.
#7 addresses cutter rigs in particular.

http://arvelgentry.jimdo.com/articles/



Oh, and BTW there are at least three other papers of his that help explain the 'slot effect'
#1, #4, #5

http://arvelgentry.jimdo.com/articles/

 

3 sails is harder to get right for upwind efficiency, but if you have a sailboat that is otherwise underpowered for the conditions, 3 sails with the same total area can theoretically give you more power than 2, and even if the sails are a little less efficient in terms of lift to drag ratio if they have more power they can make the boat go faster and until you reach hull speed, as in light air and light/medium air, going faster will also allow you to point higher. Part of the reason for this is you will have less induced drag on the hull, keel, and rudder for the same amount of lift, and less leeway also. As a general rule when going to windward; first go fast, then go high.

 

With due respect to Gentry, the double headed rigs he writes about died out within a year or two of that article- because it was found that they just did not go fast enough.

The world's best racing sailors and designers are NOT fools or ******. When the typical racing boat finally got rid of the double headed system, they did it because it was not as fast as the alternatives.

 

I think you are correct with respect to those older, relatively small staysails on cutters.

I also found this article of his interesting as I personal experienced this 'questionable' performance advantage of a small staysail on my original wood ketch. It was a tough sail to trim, and of questionable benefit in light air upwind. I always thought it was a question of being in too close proximity to both the bigger foresail and the mainsail.

That is one reason I chose to make a significant greater separation of my two headsails on the aft-mast rig,...and of course I do not have that 3rd sail (the mainsail) on my rig. So my 'staysail' is acting as a 'mainsail',...the reason I chose to call it my 'mainstaysail'.

I also took note of this quote from that article:

That definitely told me I needed to have the leech of my 'staysail' well behind the leech of the headsail, which was not always true with a lot of early cutters.

 

Many sailboats are underpowered. This results in poor upwind performance particularly in light air, going slow and going low. Even some old IOR racing boats are under-powered. like a Mirage 24 designed by C&C for MORC. This can be corrected by getting a taller rig, or 'somewhat' cheaper going to an oversized Genoa, like 165% or 170%. A taller rig works because it provides more sail area and is more efficient. An oversized genoa will also allow you to go higher and faster, not because it is more efficient, but simply because it has more sail area, so you can point higher and still have enough drive to keep moving. Similarly cutter rigs can do the same. More power can enable you to go higher and faster even though they are not neccessarily more efficient in terms of lift-drag ratio under idea conditions. A raked cutter rig can also add more sail area by adding a bowsprit or moving the forestay all the way to the stem. You might have to rake the mast a bit. This can be a cheaper solution than getting a new mast, and can look really cool.

As an experiment, reef your main and use a smaller jib in light air, and you will see that you will go not just slower, but also lower. With this lower rig two jibs would be better than one in light air, to get the boat moving, but with a taller rig, one jib is better than two, because once you are moving well you need to focus more on efficiency to go higher. So the bottom line is that cutter rigs can be higher and faster upwind in light air, but only if your mast is too short to begin with.

 

A modern boat race built with tissue paper and a 17 ft deep leel will surely go faster without the cutter rig.

A cruiser of any sort is helped by the extra drive and when it comes to sail handling the second foresail helps keep the boat balanced and easily steerable during the transition

Not as useful with the plain to windward on the spinnaker crowd with 15 crew aboard.

 

Many of the boats that discarded the cutter rig were those what would be called short rigged and under-powered in light winds like some IOR boats. Classic examples from my part of the world were the S&S 49 Ragamuffin #1 (winner of the '71 Fastnet) and the Miller and Whitworth boats (Gingko, Apollo II, Ceil III, etc).

These boats came out at the tail-end, or within months of, a phase where there was a rebirth in the use of cutter rigs in heavy air in Australian offshore racing. This was a well documented phase and the top crews were extremely familiar with the use of cutter rig. Despite this experience with the cutter rig, it was dropped very, very quickly, probably as improvements in sailcloth and design lead to the arrival of the "blade" or "Solent" jib for heavy air.

As I write this, I'm flicking through some early '70s books, which show what was almost a mania for the use of staysails (both upwind staysail and tallboys, cheaters etc) - a mania which died out within the next three years. Going back a bit further, one of the books shows the sailplan of a 1965 32 foot cutter that had no less than 11 headsails, not counting spinnakers!

So there's lots and lots of evidence that in the days of underpowered small-rigged boats, people were extremely familiar with cutter rigs - and yet almost all of them dumped them as soon as they could, when technology improved. And, where the specific situation allowed, as on Stienlager II in the 89/90 Whitbread, the cutter rig would return quickly which indicates that there was no particular bias against them.

So the facts are that racing sailors of earlier days were very familiar with cutters, and yet despite the fact that they gave "free" sail area under the rating rules, they were dumped very quickly (even in the days of short rigged racing boats) when technology allowed them to do so. It all seems to point to the fact that (as my memory serves, and as Brian E indicates) the problem was that while they could work at times, it was very difficult to get them to operate efficiently, and therefore most of the time we continue the 85 year old process of reducing the number of headsails we use.

Of course, cutter rigs remain great for cruising and Open 60 style boats, but in those applications they are not evidence that they provide superior aerodynamics as the OP claimed.

 

CT. I must pay you a big compliment. :!:

Your knowledge and recall capabilities of these numerous vessels, both big and small, from our past and present is amazing. It's good to have such a knowledgeable source/participant on these forums.
Regards, Brian

 

ponting upwind

Google "Arvil Gentry".
Passed away recently but lots of his work available for download.