21 replies to this topic

[Tom the rower]

So, Ross Lillistone recently posted the following:  My question is would this work on the CS20 with the Cat-ketch and make it better (I have hardly any sailing experience, so I don't know)   Spritsail with Jib Set Flying

When I posted about the Sailing Pilot Boat-inspired design that I have started for Geoff Leedham, I was reminded about how much I like the Spritsail rig with a jib set flying.
 

Bertil Andersson's drawing of Lotsbat Skum

Back in about 1998, I think, I was working over what I thought would be the optimum-sized boat for solo and two-up beach-cruising (see post here). The whole process became an obsession, and one of the things that I worked over in minute detail was the choice of rig. Over many decades I had sailed my existing boat with a range of different rigs, and had gathered a worthwhile amount of general daysailing and cruising experience using un-conventional rigs.
 

After much head-scratching, I settled on the spritsail with a flying jib (i.e. a headsail not hanked onto a stay), having been influenced by the writing of a number of people, of whom Phil Bolger was the most influential. 

Why the spritsail? Here are my reasons: -

• I wanted the shortest practical spars, and in particular, I want to be able to store the spars inside the boat. Several reputable authorities had written that the spritsail sets the maximum sail area on the minimum length mast;
• A jib or staysail would be nice when sailing to windward - particularly a flying jib on an un-stayed mast;
• The rigging needed to be very simple, and preferably easy to make and repair by hand using wood and line;
• It was important to me that the centre-of-areas in the sail-plan be as low as possible to reduce the heeling moment;
• The possibility of using the mainsail as a boomless sail as well as being usable with a boom was desirable. In really tough conditions, a boomless sail is a safety feature, as there is no boom to trip during a knockdown - you can always ease a boomless sail but not so a boomed one;
• A spritsail can be brailed if properly set-up.

The above list made lots of sense to me, but the overwhelming advantage seemed to be that the spritsail is one of the very few rigs which can carry a jib without any shrouds or back-stays. Any headsail needs plenty of tension in the luff or else it will sag off to leeward, drastically damaging windward performance. Usually the rig with a headsail of any sort needs shrouds with plenty of drift, and/or backstays in order to keep the luff taught.  A friend of mine who sails a Bolger Folding Schooner finds that it is necessary to drop his jib when going to windward, because the boat goes faster without it! This is because there are no stays and the jib sags badly when on the wind.

In the case of the spritsail, the sprit is placed under considerable compression by the snotter at the lower end (the heel end of the sprit). This compression is required to hold the head of the mainsail up and out and to keep the head of the mainsail taut.

Here you can see how the sprit pushes the head of the mainsail upwards and outwards

  The above photo illustrates how the sprit tensions the head of the mainsail. The tension in the head of the sail is transmitted to the masthead, where it pulls aft strongly (somewhat like stays) and that, in turn, puts tension in the luff of the jib. A wonderful side effect is that as the wind gets stronger, the tension in the head of the sail gets greater, with the result that the tension in the luff of the jib increases just when it is needed - all in a rig which can be made by hand from a few bits of wood and some line!

Phoenix III getting to windward in fresh conditions with the jib standing very well, despite the lack of stays. In most other free-standing rigs the luff of the jib would be sagging badly.

 

Here is the same boat in even windier conditions, with a reef in the mainsail. Despite the reefed main and the blustery wind, the jib is standing very well once again. Note how the sprit snotter has been stretched by the stong wind and consequent high tension on the snotter - the crease from throat to clew highlights the problem - but the jib is fine.  

In the photo above, the winds are lighter, but the boat is being sailed without the jib. Despite the lighter winds, the head of the mast is bending aft because there is no jib providing support. The mast bend has reduced head tension in the mainsail, allowing the unwanted throat to clew crease to form. Phoenix III was designed to balance well with or without the jib. Note how the tiller is pretty much centred, indicating that there is very little weatherhelm despite having only the mainsail set.

No rig is perfect, but the sprit rig offers simplicity, drive, low centre-of-area, short spars, and the ability to set a jib effectively without any stays. Perhaps the Scandinavians, Melanesians, Chinese, Dorymen, and Thames Bargemen, to name just a few, were several steps ahead of us.

Ross Lillistone, Bayside Wooden Boats, Australia.

[Ken_Potts]

That's a pretty rig. I'd love to take that boat for a sail.
On A CS20, though, I'd stick with the rig Graham drew - It works very well. If you get bored with the rig as-drawn go ahead and add a mizzen staysail. That'll keep you smiling for a long time too.

[Hirilonde]

Sail shape has evolved since the first fore'n'aft rigged boats.  But it is surprisingly recent that it was learned that a sail is a foil.  The sprit rig you picture is beautiful Tom, and practical at the time.  But when it comes to power for the size, the ability to sail to weather. healing forces, etc., it is no improvement on the trangle sails and cat/ketch rig Graham specs out for his boats.  If you want a classic era boat, build one.  They are beautiful, and that alone is reason enough to do it.  But I see nothing to gain by trying to rig a CS like a boat of the past.

[Tom the rower]

Shows how little I know.  What I thought was that  I do GB's cat ketch rig and add a jib up front.  I thought that was what he was talking about in the article and that the main sail was the same main sail we use (ie the one GB designed).  Is the main in the article not the same as the main for the CS20? (I don't mean the red sail). Thanks

[Howard]

Tom:

 

Have you seen this narrative about the cat ketch rig on the B&B site?

 

http://www.bandbyach...om/catketch.htm

 

Sailboats may look simple, but are deceiving in that the sails that power them represent a complex and precise combination of size, shape and position relative to the boat. Sails have to balance with the boat shape, rudder and centerboard. Get that right and they work surprisingly well.......get it out of whack and out of balance and it doesn't. To give you an idea of how important this is, even if you build the boat to exact design specs, if you get sloppy with sail shape and trim, in a fleet of identical boats sailed by people who know what they are doing, you (and about everyone else in sight) will be left far, far behind.

 

If you build a CS20, I'd suggest to start out by sticking to the plans as drawn, and that includes the sails and cat ketch rig as designed. With that, you can establish a baseline of performance to measure anything else against. If later on, you wanted to experiment with other sail options, with some research, you might be able to pull it off and get something to work.  There is no harm in that, and if you are of the curious type and that is what interests you, it can be a fun (and expensive) hobby. You might even find you prefer sculling to rowing.

[Howard]

One additional thing that I don't think is mentioned on the cat ketch narrative and that is the ability of the cat ketch to hove to. That is an important safety feature, not to mention it can be an awfully convenient way to "park" the boat while on the water.

 

Basically, the mizzen of aft most sail is raised first, then the main or forward sail. Sheet in the mizzen, sheet in the main and you are off! If you want to hove to, let the mainsheet go and the only sail with drive left will be the mizzen. With all the drive aft of the CB, the boat will weathercock around and face the wind at an angle, and essentially come to a stop and sit there like a duck. A boat with main and jib, may....or may not......do that, and certainly not as easy. Unless you build a jib boom, the jib is also not going to be self tacking as the main and mizzen on the cat ketch are.

 

Yet another nice feature of the cat ketch is it's ability to self steer. In steady winds, it should be possible to trim the sails relative to the CB and the boat will jog along nicely without someone at the helm steering. That may not sound like much of a benefit, but if you have ever been stuck back there for hours on end.......unable to leave the helm for even a moment......it will.

[Oyster]

Sprit rig and Graham and company???? I can personally say that he told me that he likes toothaches more.  [howdy Ken, check in offline and lets catch up.] Better remove this thread before he sees it.HEHE!

[MisterMoon]

Once you try a cat ketch, you'll wonder why you thought about changing. It's a very versatile rig and oh so handy. Banish the thought of 'improving' your boat. You will very likely compromise it in some way. 

[Tom the rower]

Yes, I have read that and just popped over to confirm that the cat ketch has sprits....  The article by Ross Lillistone uses a sprit.  He just does not have 2 unstayed masts, but adds a jib.  I am just saying that I do want the cat ketch rig, for all the reasons stated, hove to and self steer.  Since the cat ketch has sprits and Ross Lillistone's article has sprits and then he seems to say that adding a jib in front of the sail that has a sprit instead of a boom seems to improve the whole shebang , that is what I am asking.....keep the two masts as GB has designed, just add the jib.  (not do away with the mizzen) 

 

So, does the addition of a jib help or hurt?

[Tom Lathrop]

There is a ton of difference in a traditional sprit sail like the one in the photos and a sprit-BOOM like the CS boats.  I would also prefer a toothache to a large boomless mainsail to fight with, especially if it also has the topsail rigged.  Nothing wrong with the rectangular sprit rig that a boom would not fix.  I will duck behind my workbench while erster grabs some scraps to throw at me. 

[Howard]

Tom:

 

I think you are looking for a solution to a problem that doesn't exist. Grafting a jib onto a cat ketch......with the main mast set forward.......would certainly mess up the balance, unless you then dropped the size of the main to match. If you were to do that, all you would have accomplished would be to add a great deal of complexity for no real benefit. Certainly both have sprits to tension the sails, but that is where the similarity ends.

 

As far as the additional jib is concerned, think of any sailboat in the context of a weathervane. It pivots on it's center of balance, which is generally going to be the keel or in this case, CB. The sails have a center of effort that is positioned in a particular place, relative to the center of balance. Put too much drive in front of or behind the center of balance and the boat will want to turn. Too much forward and it will turn away (lee helm).....a really bad thing. Too much aft and it will try to turn into the wind (weather helm).....better, but still not good. You would have to apply a steering correction at the helm, which leads to drag and that slows you down......in addition to being tiresome.

 

By messing around with sail shapes and sizes, you might be able to set a four sided sprit sail main in the center mast position, and add a jib forward of that to duplicate the rig in the article. They did that from the beginning on the boat in your article and sized it all to balance. That rig has it's touted advantages, but in comparison to a cat ketch, a number of disadvantages. In boats, everything is a tradeoff.

 

The rig you appear to be thinking of would technically be referred to as a ketch rig, or even a yawl if you moved the mizzen mast aft of the steering position. There are a number of boats built with those rigs and plenty of people swear by them. Others, swear at them. Again, all a matter of preference and taste. None of the more right or wrong, just different.

 

But again, to answer your question, there would be no advantage I can think of in trying to add a jib onto the CS20 designed rig.

[Tom the rower]

Ok... that settles it then.   as a new sailor, who has only used a roller furling main on my TRIAK trimaran, I am trying to learn about the other aspects of sailing as quick as I can.  The article sounded good to my untrained ear, so I thought I would run it up the flagpole and see who saluted.  Now I know.  Even with the small mast and sail on the TRIAK, I have been out in wind that was big and scary and wished for the ability to heave to.  That was a real seller for me on the cat ketch. Plus the planing hull.  I think my daughter is coming for a visit in a couple of weeks and she will presumably stop by B&B to pick up my cnc cut CS 20 mk2 and I can get started building.

[Howard]

No harm in asking. Most everyone has asked questions along the way (or failed to and learned the hard way on our own). 

 

But it also sounds like you have had enough time on the water to start formulating some well founded opinions. A few near death experiences will do that.

[176inches]

Adding a jib would definitely upset the helm balance, plus the whole point of the cat ketch rig is not to have to worry about jib sheets and bringing the jib across, but just putting the helm-a-lee for a leisurely tack.

 

If you like the spritsail's low center of effort and gravity and short spars, but perhaps want to avoid some of its disadvantages, I would suggest you go the way I did with my self-designed cat ketch: use two standing lugs with sprit booms.  AFAIK it may be the only one of its type, but it's stable, low center of gravity and effort, traditional, nicely short wooden spars, easy tacking, not too difficult to reef.  Initial rigging up is a little tricky, though.  More details on http://176inches.blogspot.com.

 

But I would not mess with the sail plan of a professionally-designed boat without very careful analysis of Center of Effort and Center of Lateral Resistance.

.

 

[Tom the rower]

Thanks for the advice guys.  I will tell you that sailing in moderate to higher winds scares me.  Sometimes I will bring some cold beer out on my little trimaran and I will wait till the gps says that I have gone 1 mile before I crack the first one, so that I have to "man up" to the big scary wind and waves.  I honestly don't know how more experienced sailors aren't more apprehensive.  Once, on my way home, a storm blew in between me and home, with big wind.  I rolled my sail down till it was snuffed and thought I was going to paddle back, but was getting blown backwards, so I let out enough sail to be the size of a hanky.  I was going 5 kts before I knew it on such a little bit of sail.  Obviously made it, but, the wind and waves gets my respect.

[Terry Dunn]

Perhaps you need to check out periwinkle's lug ketch rig.

[Charlie Jones]

Ross also has an interesting article on lug rigs on Duckworks at the moment-

 

http://www.duckworksmagazine.com

[MisterMoon]

Core Sounds do great in big winds. There's no need to think about reefing my CS17 until it's solidly blowing 15 knots. And the second reef comes in around 19 or 20. I would not think about making any changes to the rig until you've sailed it as designed. 

[Howard]

Ross also has an interesting article on lug rigs on Duckworks at the moment-

 

http://www.duckworksmagazine.com

 

Hmmmm..........what goes around, comes around:

 

http://messing-about...lanced-lug-rig/

 

I don't know if the concept ever got past the conceptual phase.

 

I maintain a curiosity about the balanced lug (and only the balanced lug.......not lugs or dipping lugs) that may only be sated by trying one, and I intend to do that on my Spindrift. Best information I've found for rigging one comes from Storer:

 

http://www.storerboa...GISRigging.html

[Charlie Jones]

Storer did an excellent presentation on balanced lugs at Sail Oklahoma earlier this year. They were video taping and I expect the vid is available from Mike Monies. I don't have his contact info, but I think Travis does.