Sage Marine - rig advice?

You were very helpful on our last questions so I thought I'd try again.

Jerry Montgomery is working on a new14'/15' pocket cruiser monohull design. One is a 3 stayed cat rig with a rotating mast. The other is a 3stayed sloop. 3/4 rig.

Can we get as good upwind performnance with the cat rig as with the sloop?

sal

 

Probably not, but the real question is, is it important? Unless you are racing pocket cruisers head to head, when would anyone notice a couple more degrees when tacking, or a 2% VMG improvement?

You are chasing a buying segment where features, space, stability and comfort are way more important than ultimate performance. I'd also pay a lot of attention to appearance and making sure your design looks the part - homely girls don't get asked to dance very often, even if they can dance a lot better.

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CutOnce

 

I think that will depend on the details of the design. You already have a rotating mast, with properly shaped mast cross section (which is the sail leading edge), and a good platform shape, full battens to help control the camber, it could perform as good or better.

The general consensus with conventional rigs is the sloop will point higher than a cat rig, but if you consider what the airflow "sees" at the leading edge of a conventional main sail, there is no surprise it does not perform as well. As much as 30 percent of a convetional mainsail has separated flow at mast, trailing edge and top.

Using a rotating mast is already a big improvement on a monohull over conventional design. traditionally rotating masts have been limited to multi-hull and not used on mono-hulls. There has been great advancement in sail designs in racing sailboats, sailboards and multihulls, for some reason they have not made their way into recreational mon0-hulls, likely due to tradition.

 

FWIW, I have a Venture 17 sailboat that I have converted to a rotating mast from a hobie cat and a full batten main sail and retains the original 3/4 jib. My experience has been that the rotating mast/full batten high roach main is much more efficient upwind. I've also found that I'm still able to point higher and have a much nicer boat balance with the jib unfurled than main sail alone. It's hard to say how it would handle with a different center of effort if it were cat rigged.

I have a roller furler up front, and I've found that I'm much happier going to wind with the a jib full or 30% furled and first reef in the main sail than I am with a full main and no jib. IMO I can lower the center of effort for the same amount of lift.

In either event, I would suggest a rotating wing shaped mast for either option. I would also suggest a fully battened main sail with slugs and lazy jacks and roller reefing standard. They seem kinda silly on a boat this small, but it makes sailing a breeze for one person and much more enjoyable when it takes only a few seconds to drop some sail if the wind picks up.

 

Hi Jetboy,

When you say "...slugs and lazy jacks and roller reefing standard". do you mean foller reefing on the main?

sal

 

Sorry. No I meant roller furling for the jib. I do "reef" my jib with the furler, but I certainly wouldn't call it true reefing.

The original setup for the Venture 17 was a roller reefing main where you would roll the sail around the boom. It was a very poorly functioning idea. Slab reefing with a battened main sail and simple lazy jacks is so much better. It's not even close. Better sail shape, easier, faster, and all probably just as simple to build.

My Lazy Jacks look like this: Very very simple. I trailer sail mostly and It's really nice to be able to just put the sail and boom on the jacks to hold the weight while I get the rest of the main sail control lines attached. I seldom see little boats with this type of set up, and for the $2 worth of rope it's really handy to have.

 

Thanx for the input Jetboy. So your advice would be to use the rotating mast with either the sloop or cat rig, but you would prefer to have the sloop given the option?

sal

 

I've often wondered why rotating masts are not found on monohulls when they are so common on multis. Tradition can certainly hamper forward motion. Thanx for the input.

sal

 

I would say yes absolutely go with the rotating mast in either configuration. I think the small cost difference is well worth the performance gains. Especially on a rig with a relatively small sail area. I also really like having a full battened main sail and would consider a boomless main. IMO a full battened sail is much easier for a casual sailor. There simply isn't that much you can do with it. The sail keeps a good shape over a much wider range of mistakes in sail trim. In fact it's pretty hard to get a bad sail shape. And I think it stacks a lot nicer and is easier to reef with battens. - Basically IMO compared to the traditional set up, I think a beach cat style rig is better performing, easier to trim, and easier to use.

I have a hard time saying that I'd prefer the sloop without having tried a cat-rig on my boat. If I had a good way to move the mast foot I'd certainly give it a try. On my boat it is poorly balanced without a jib. It could very well be that the difference in upwind performance between something like (a) full main no jib and (b) reefed main and full jib is that when I have the full main the lack of balance requires a lot of rudder input that causes a lot more drag. I find option (b) to be faster and point higher, but that may be primarily due to the nature of a boat that isn't balanced well with the main alone.

 

I think a likely explanation is the beam constraint on a monohull. With a wide cat or tri, you can have the stays lead to the top of the mast, with a decent angle, and have your spreaders, if you need them, rotate with the mast. Then, all you need is a thrust bearing at the mast head and another at the butt and your set.

With a narrower mono, the 'stays' must connect only partly up the mast, to get a decent angle, requiring a bearing that encircles the mast, if you want the mast to rotate. Then you can forget about spreaders, as they will foul the lower stays. Now you need a bigger bearing and a larger mast section to boot. Performance wise, it is probably found not to be worth the effort. Much easier to keep the mast fixed, add a jib, and sacrifice a bit of reaching performance. Remember, it's upwind performance that usually wins races. And winning races is one of his primary design goals.

I think the improvements in his ballast system will easily do that.

Personally, I rather sacrifice a little performance to have a shorter set up time. I would be daring and try a large balanced lug and forget all the fancy do dads. The mast can rotate, the spars can be carbon fiber, and the bearings can all be within easy reach. You also can have a sturdy tabernacle (which is part of the rotating mast), allowing you to raise and lower the mast quickly, with a minimum of cross wind drama.

Mike Storer has had considerable success with that type of sail, using low stretch halyards and other modern materials.

With the ever increasing cost and scarcity of slips, I think quick set up time for the rig is of vital importance. We can learn more from 19th century work boats than we can from 20th century racing dominated design, IMHO.

My goal would be to have a sailboat that can be kept on racks, like powerboats of that size range often are, and can be off sailing just five minutes after it's keel kisses the water.

 

I think you're right with respect to larger monohulls that require spreaders. That makes the rotating mast a lot more complex and difficult to design for proper use. On a larger boat, I think a mast with a wing profile would still be worthwhile even if it doesn't rotate. As you said, the upwind performance is where the mast profile is more important.

On a small boat like this, the rig will be practically indistinguishable from that of a similar length catamaran - other than generally being shorter due to the limited stability of a mono. The shroud angles are reasonably similar and there are no spreaders or diamond wires. Because of how small they are the setup is exactly the same - you just hand lift the mast and attach the forestay. The extrusion is roughly the same cost. The only additional cost is the foot/base assembly, but that's pretty easy to set up.

One argument I would see in favor of a sloop is that the mast will likely be shorter and therefore easier to raise. I can easily raise the 23' mast on my boat. I have a 30' mast for an 18' multi that I'm building and I'm pretty sure that I won't be able to raise that without some sort of mechanical advantage. I think the length of the mast and weight should be considered in terms of the ease of setup. If a longer mast is required for a cat rig, I'd make sure it's still easily managed. I suspect it would only be around 20' long either way for a 14/15' boat, so probably not an issue. Just another thing to think about.

 

Personally, I'm leaning more and more in favor of low tech. i.e. lug, either standing/balanced etc. But that's not the discussion. so. Can we consider freestanding cat rig? My experience with rotating rigs in F boats for example is that the rig is quite loose and the lee shroud is extremely loose. Mainsheet tension helps stabilize the rig. Also rotating rigs can be more efficient but they are less efficient when not rotated to advantage. i.e. a casual sailor may lose more performance than might be gained or lost with a fixed rig. Just some additional thoughts to throw in the conversation.

 

Examination of the most highly developed small boat classes may well indicate that tradition has nothing to do with it. As in many other issues, the reason that an "innovation" has not been adopted is because it's generally not worth the extra inconvenience and cost.

Bear in mind that at least one leading advocate of wing masts has admitted that he was not aware of the many, many experiments in such spars in small boats and boards. That indicates the way that many people are ignoring what it really happening out there on the waters of the world.

Some of the tests on which the claims for mast interference appear to be at odds with real-world experience. For example, Marchaj's tests (which are often used as the basis for remarks about the problems of mast interference) show round masts that are about 9-12% of foot length. For comparison, my own yacht has a spar 3% as long as the foot and 2.2% as wide as the foot. I have never in my life seen a boat with proportions such as Marchaj tested (i.e. a 10' mainsail foot and a 11-13" diameter round mast) therefore tests of such a rig appear to have little connection with reality.

Despite what theory says in practise rotating masts don't appear to have the enormous advantages that have been claimed by them. Recent studies by WB Sails etc are proving what reality has shown for years - that a conventional mast of modern construction is nowhere near as bad for airflow as formerly claimed.

Rotating masts have been tried by top-level players in the following classes;

International Canoe, 12 Foot Skiff, 18 Foot Skiff, NS14, MG14, Moth, Merlin Rocket, R Class, Z Klasse (I think), Suicides, Gwen 12s, Fireflies, Finns, Flying Ants, Cherubs, and the prototype for the 505.

These classes created many of the major developments in high-performance dinghy design, including racks/wings, foils, assymetric spinnakers, lightweight hulls, fully-battened mains, yada yada yada, so they are clearly NOT bound by conventional thinking. They have tried and dumped wishbones, cat rigs etc. And almost all of them have dumped rotating wing masts because they have found that in reality there is no speed improvement.

So either

1- the practical experience of world-class sailors in many of the major dinghy development classes is wrong; AND

2- the experience of world-class designers like Uffa Fox, Proctor and Bethwaite is wrong; or

3- the theoretical advantages are not borne out in practise, as demonstrated numerous times by experiments by top-class designers, sailers and sailmakers in some of the world's top classes.

This isn't saying that rotating masts don't work, as sometimes they clearly do (as in efficient small-rigged dinghies like NS14s, Moths, Finns and in cats). In the interest of openness, I have to say that I own a bunch of rotating masts and wing type sections. It's just that there is abundant proof that in typical small monos they either provide no advantage, or no advantage worth the issues as far as the typical sailor (even open-minded ones) is concerned.

Not all sailors are conservative - in some sectors of the sport they try many things and freely discard what does not work in favour of what does work. And of course every Laser proves that sailors are not scared of rotating masts, and that they are happy to use them if there is a reason. Most of the time, there isn't a reason worth the downsides.

 

Oh, and on the question of why rotating masts are founds on multis and not monos;

1- A mono's stability characteristics make gust response more important than on a multi, and gust response is better on a non-rotating rig.

2- A mono has fuller sails and needs more mast bend to flatten them, which is difficult or impossible on a normal wing mast. Multis have flatter sails and different gust response requirements due to stability and apparent wind ratios, and therefore need less mast bend to flatten them further IME.

3- Multi sailors are (IMHO) arguably more interested in top-end speeds (which can favour wing masts) and less interested in light-wind and fluky stuff when things like opening up the leach (which is often difficult in fully-battened sails and rotating wing masts) counts. Mono sailors are often the opposite. My gut feeling is that this is a difference caused by everything from social and geographical factors to hull resistance issues. For example, here in Australia cats have tended to be more popular (proportionately) on open waterways and monos are more popular on enclosed waters where the winds are lighter, flukier and gustier. This has significant effects on design.

This is very much just a personal gut feeling, but I don't think that mono sailors are any less open-minded than multi sailors. In fact in some very important ways, such as encouraging women into sailing, the more performance-minded sailors (in monos and multis) have been very conservative. It's just that more "conservative" rigs suit boats that move at lower speeds, as most monos do because of the inherent hydrodynamic restrictions on monohulls.

 

Agree with what you say, CT - but not on the gust response difference. If anything (and not just gut feeling but based on reality) on a multihull with wing mast and soft sail, the gust response is instantaneous, so much so that if you're not hanging on, you'll be rolling and bumping down the transom. Course I'm talking about light multihulls, not heavier versions.