Traditional Main vs In-mast Furling

[jtsailjt]

Technically, DH is correct that weight aloft doesn't decrease rolling because, while it does decrease the frequency, it increases the amplitude of the roll. But what is being left out is the perception of humans aboard is what counts the most and a slower, though somewhat larger amplitude roll seems less unpleasant to those aboard the boat and is less likely to cause seasickness.

The direction this discussion has taken seems pretty silly to me because the stability and rolling characteristics differences we are discussing are so trivial that I bet 95% (including some of the most adamant on both sides) of those posting/reading would not notice the difference and I include myself in that number.

I don't have a dog on either side of this fight because I've grown to become comfortable with either option but I think it's not helpful for either side to exaggerate the "other" options negatives and I've seen some of that here. Both options can be very good or very bad, depending on the details of how they are set up and how the boat is used. Roller furling is super convenient but there's no doubt that sail shape suffers a bit so performance will be slightly (on a cruising sailboat) degraded in some wind conditions and some points of sail. But in most conditions, there will be no discernible performance degradation in a cruising sailboat. The hanked on option doesn't have to be all that inconvenient if there's a low friction way to drop the sail and easily reef it and there's an electric winch (for larger boats) available to raise it and it's equipped with a well designed stack pack or sail cover that's easy to secure.

I'm reminded of my days as an Air Force pilot when I would hear a Navy pilot expounding on how the "Navy way" of doing something was superior because "you Air Force guys do it this way," which almost always was a ridiculous way of doing things that neither I or any other Air Force pilot I knew had ever heard of. But among his Navy peers, it was accepted as fact that all Air Force pilots had been doing things this ridiculous way forever. I'm sure that those of us on the Air Force side were equally guilty of similar faulty assumptions about Navy pilots. But eventually I figured out that our differences were actually very small and most of negative things I'd heard about how the Navy did things were either not true or only applied to a very small group or were necessary to avoid another, worse problem that was unique to their mission but not ours.

Similarly, many of the shortcomings or problems that have been discussed were true for early versions or poorly designed or incorrectly set up systems but almost all can be avoided now because the technology is mature. Furling sails can have reasonable shape and good furlers very rarely jam and hanked on sail handling doesn't have to be as problematic as some make it sound. Make whatever choice you prefer, then study everything about it so you can maximize its advantages and minimize its shortcomings, then enjoy! ⛵️

[UNCIVILIZED]

Guys I was using plug in numbers only in my math, & wasn't trying to instigate anything. What I seemingly failed to mention is that with an in mast furling main that extra weight is always up there unless you strike the sail. Something rarely done at sea. Whereas with a conventional main, if a storm gets bad enough, the sail is lowered & lashed to the boom. So that then you gain the advantage of significantly less weight aloft, when you least want it up there.

[Dockhead]

Originally Posted by UNCIVILIZED

Guys I was using plug in numbers only in my math, & wasn't trying to instigate anything. What I seemingly failed to mention is that with an in mast furling main that extra weight is always up there unless you strike the sail. Something rarely done at sea. Whereas with a conventional main, if a storm gets bad enough, the sail is lowered & lashed to the boom. So that then you gain the advantage of significantly less weight aloft, when you least want it up there.

Not just the weight of the sail -- but the weight of the thicker and heavier mast and foil.

[jtsailjt]

Originally Posted by UNCIVILIZED

Guys I was using plug in numbers only in my math, & wasn't trying to instigate anything. What I seemingly failed to mention is that with an in mast furling main that extra weight is always up there unless you strike the sail. Something rarely done at sea. Whereas with a conventional main, if a storm gets bad enough, the sail is lowered & lashed to the boom. So that then you gain the advantage of significantly less weight aloft, when you least want it up there.

That's true but I have to quibble with your use of the term "significant." For example, my boat weighs 46,000 lbs and, though I've never weighed the mainsail, I have no trouble carrying it up the dock on my back and I'm not a weightlifter. Yes, I'm familiar with CG and moment arms, and ultimate stability, etc. but for a cruising boat like mine I don't think it's much of an "advantage" to eliminate that weight. If the conditions are so bad that they necessitate striking or completely furling the mainsail, in those conditions would you rather be stuck with that relatively small amount of weight up high but securely stowed where it can do you no harm and cause no windage, or confronted with going out on deck and possibly climbing up on your dodger to securely lash that mainsail to your boom? Which choice yields the bigger advantage or potential disadvantage?

[Dockhead]

Originally Posted by jtsailjt

That's true but I have to quibble with your use of the term "significant." For example, my boat weighs 46,000 lbs and, though I've never weighed the mainsail, I have no trouble carrying it up the dock on my back and I'm not a weightlifter. Yes, I'm familiar with CG and moment arms, and ultimate stability, etc. but for a cruising boat like mine I don't think it's much of an "advantage" to eliminate that weight. If the conditions are so bad that they necessitate striking or completely furling the mainsail, in those conditions would you rather be stuck with that relatively small amount of weight up high but securely stowed where it can do you no harm and cause no windage, or confronted with going out on deck and possibly climbing up on your dodger to securely lash that mainsail to your boom? Which choice yields the bigger advantage or potential disadvantage?

I would have to agree with this -- a good example of theory vs. practice.

My mainsail is heavier than yours (or else you are much stronger than I am ). I would sure as heck not want to be wrestling with it in a storm. Having it rolled up inside the mast is just about the best place you can imagine for it, in storm conditions.

I've said it before -- in-mast furling is very attractive in heavy weather.

It won't be doing stability any good, but it's far safer, more secure, and less windage, than a mainsail flaked on the boom.

[UNCIVILIZED]

Point taken about stowing the main for a storm. Typically I'll usually tighten up the main sheet as much as possible, so that the boom is fixed in place vertically by the vang, & also use a preventer to oppose the traveler in order to fix it in place horizontally. So that it's positon is pretty rock solid. And I'm a big fan of grab rails on the boom for exactly this scenario. So that there's plenty to hold onto, & lash things too, in addition to my wrapping one leg around the vang to steady myself, hands free. Ditto on using a short harness tether to secure my positon, again so that I have both of my hands free to tidy up the sail.

As to climbing onto the dodger, I can't see trying that one. If for no other reasons than; most of the aft 1/3 - 1/2 is already well secured to the boom via having taken reefs as the wind has built, and that the bulk of the sail which needs to be corraled is the forward half of it anyway.

So, yeah, being able to put it safely to bed simply by pulling a line would be convenient. Though as to how often one runs into conditons where the entire main needs to be struck, depends on where you sail I reckon.

[CharlesFCook]

Originally Posted by Pete O Static

In mast furling, air conditioning, bow thrusters, electric winches, etc etc etc....This seems to be an all too common theme on modern boats today. After 40 years of sailing, I bow to the K.I.S.S philosophy.

These things are convenient when they work. However they always add to the endless job list and inevitably let you down at the worst possible time.

I don't own a boat and only crew on deliveries. So I am only on the boat for a month at a time max. And I crew almost exclusively on Hylas yachts. So you can take this with a big grain of salt.

You can get pretty spoiled with "mast furling, air conditioning, bow thrusters, electric winches, etc etc etc...."

On one boat we had hydraulic furling (main and head sails) and winches. Worked great but I bet you could pull the rigging down with all of that power. The slot on the main mast where the sail entered was very large and with all of that power furling was a breeze.

All of the other boats had electric furling in mast or in boom and head sails and winches.

The electric in mast furling was more touchy and the boom topping lift and main sheet had to be set just right for it to work well. But it always worked good weather, bad weather or squall. We are pretty proactive when it comes to reefing because you don't want to beat the crap out of a boat when doing a delivery.

The in boom furling was very fussy. Someone had to go on deck and ease the halyard. If you did not do this job perfect the sail would need to go back up and then down. If you wrap the sail too tight in the boom you could run out of reefing line (downhaul) and some sail would still be up.

It kind of boils down to timing and crew size etc. On the big boats I have worked on we had lazy jacks and 3 reef points. We would reef super early and shake it out late because it was a big job. With the in boom it was in later out earlier. With the In mast it was pull some in sort of last minute.

[jtsailjt]

Originally Posted by UNCIVILIZED

As to climbing onto the dodger, I can't see trying that one. If for no other reasons than; most of the aft 1/3 - 1/2 is already well secured to the boom via having taken reefs as the wind has built, and that the bulk of the sail which needs to be corraled is the forward half of it anyway.

So, yeah, being able to put it safely to bed simply by pulling a line would be convenient. Though as to how often one runs into conditons where the entire main needs to be struck, depends on where you sail I reckon.

My boat has a center cockpit so the midpoint of the boom is actually aft of the dodger and the only way to access it is to climb up on something, but for aft cockpit boats I agree that you can usually access the mid boom area without climbing up on the dodger.

The worst weather I've even encountered was gusting between 45-65 knots (and I was in the Gulf Stream and yes, it scared the crap out of me) but I felt it was important to keep my double reefed main up so I could keep sailing and dodge the worse breakers to avoid getting rolled. I'm going to do my best to avoid sailing in those conditions ever again. How often and where do you find yourself in conditions where it's necessary or even advisable to completely strike your mainsail?

[minaret]

For the record I don't find it any harder to strike my furling main than a traditional set up. Of course what you do with the giant sails after striking them is another issue, as roller furling boats tend to have much less interior space dedicated to sail stowage, as it's just not needed and can be put to other uses.


There's not a hatch on my boat that a full sail bag will fit through. It's either bag wet sails below deck, have a huge hatch and accompanying locker, or furl. Past a certain size, anyhow.

[Jim Cate]

ne point emphasized is the importance of DAMPING:

"Damping may be caused by three things:

* Friction between the water and the yacht
* Generation of waves on the water surface
* Generation of vortices from the keel, rudder, sharp bilges and sails."

Note that more polar moment of inertia does NOT dampen rolling. It merely reduces the acceleration and natural frequency of oscillation, but at the expense of increasing the amplitude. Damping is dissipating the energy to kill the roll -- inertia merely repackages the energy.

At anchor, the underwater foils do much less to dampen rolling, which is why rolling is more of a problem at anchor.

DH, these are important points, and the emphasis on damping is crucial in understanding rolling. But I think you've misinterpreted some of the quoted factors.

At anchor, the damping from appendages is pretty important... and is not "much less than" while sailing. The lift generated is near zero, of course, but the vortice generation mentioned is significant. The reason that rolling at anchor is more of a problem at anchor is that there are no SAILS providing damping... a huge factor!

Another big factor is hull shape. Boats with slack bilges and near circular cross sections tend to roll more than boats with flat bilges and great form stability, as this changes the friction between water and yacht as mentioned in the quote, and likely changes the wave making factor as well.

There is no question about the influence of polar moment, and its effect upon frequency and amplitude of roll, but these various factors in damping are, I think, what determines how comfortable you are at anchor.

Jim

[Pete7]

Originally Posted by jtsailjt

My boat has a center cockpit so the midpoint of the boom is actually aft of the dodger and the only way to access it is to climb up on something, but for aft cockpit boats I agree that you can usually access the mid boom area without climbing up on the dodger.

Good point about the different cockpits, hopefully there is a rule on the boat that the saloon hatch is shut before folk start walking around on the cabin roof.

Originally Posted by jtsailjt

How often and where do you find yourself in conditions where it's necessary or even advisable to completely strike your mainsail?

Actually, very rarely and I can only think of a couple of occasions in a decade. However, slightly different is being able to roll away the main when arriving in a marina in strong and probably gusty winds which we do have to deal with on a regular basis. The wifey isn't as nimble as me so I just couldn't see her standing on the cabin roof flaking or even scrunching the main away even with a boom sack.

The marina is in an extremely busy harbour with lots of commercial shipping and home to the Royal Navy which just adds to the fun, the wash and congestion after a long trip.

[Dockhead]

Originally Posted by Jim Cate

DH, these are important points, and the emphasis on damping is crucial in understanding rolling. But I think you've misinterpreted some of the quoted factors.

At anchor, the damping from appendages is pretty important... and is not "much less than" while sailing. The lift generated is near zero, of course, but the vortice generation mentioned is significant. The reason that rolling at anchor is more of a problem at anchor is that there are no SAILS providing damping... a huge factor!

Another big factor is hull shape. Boats with slack bilges and near circular cross sections tend to roll more than boats with flat bilges and great form stability, as this changes the friction between water and yacht as mentioned in the quote, and likely changes the wave making factor as well.

There is no question about the influence of polar moment, and its effect upon frequency and amplitude of roll, but these various factors in damping are, I think, what determines how comfortable you are at anchor.

Jim

I think, no question, all of this is exactly correct, and I did not intend to say anything different. We didn't talk about the damping effect from sails, but this should be obvious to all sailors -- it's why we keep a tightly sheeted mainsail up when motoring in a calm. It's why sailboats under sail are so much more comfortable in a seaway than motorboats.

As far as my own boat is concerned -- I think that the main factor which makes her less comfortable than my old boat was, is the size of the keel. The old boat had a very long fin keel, almost a full keel. This I am sure did a lot of damping even with no water flowing over it. My present boat has a much thinner bulb keel which doesn't do much unless it is working with water flowing over it.

But the extra weight aloft also plays a role, I am sure. It means the boat rolls over further. That is when the roll becomes uncomfortable at anchor -- when the amplitude of the roll gets to that point. Furthermore, with that much weight aloft and such a tall mast, the natural frequency of the roll is far lower than that of my old boat. It's low enough to sometimes match up with the short frequency small waves we sometimes get in anchorages around here, and sometimes this sets up a resonance which can actually throw glasses off the salon table. I would not be getting this with a lighter and/or shorter mast -- I am sure.

[Jim Cate]

Do remember, DH, that while your emphasis of greater polar moment and its effect on roll amplitude has merit, that with higher PM it takes a larger force to induce roll to a given deflection. I think that for roll induced by wind the roll will be reduced by higher PM, while roll induced by wave action it might well be increased, especially if there is frequency matching between the roll period and the exciting force.

It is a more complicated issue than first appearance suggests!

Jim

[Kenomac]

Originally Posted by Dockhead

I think, no question, all of this is exactly correct, and I did not intend to say anything different. We didn't talk about the damping effect from sails, but this should be obvious to all sailors -- it's why we keep a tightly sheeted mainsail up when motoring in a calm. It's why sailboats under sail are so much more comfortable in a seaway than motorboats.

As far as my own boat is concerned -- I think that the main factor which makes her less comfortable than my old boat was, is the size of the keel. The old boat had a very long fin keel, almost a full keel. This I am sure did a lot of damping even with no water flowing over it. My present boat has a much thinner bulb keel which doesn't do much unless it is working with water flowing over it.

But the extra weight aloft also plays a role, I am sure. It means the boat rolls over further. That is when the roll becomes uncomfortable at anchor -- when the amplitude of the roll gets to that point. Furthermore, with that much weight aloft and such a tall mast, the natural frequency of the roll is far lower than that of my old boat. It's low enough to sometimes match up with the short frequency small waves we sometimes get in anchorages around here, and sometimes this sets up a resonance which can actually throw glasses off the salon table. I would not be getting this with a lighter and/or shorter mast -- I am sure.

You keep writing the same stuff over and over again, but that doesn't make it more and more factual.

Our Oyster 53 has a slightly taller mast, keel the same depth and one ton more ballast than your "present boat," so how do you explain the fact that we don't experience a rolling issue in anchorages or while underway in relatively calm seas without our main sail deployed? We never deploy the main to lessen roll.

We also have a furling main, but unlike your "present boat," we've never experienced an anchorage roll that can "throw glasses off the salon table." Not even close, in fact... when we prepare to get underway, there's really very little if any preparation needed to prevent things being tossed around. Basically, our narrow Brita water pitcher gets placed, into the galley sink.. just in case, then we're off. Our boat really doesn't heel or roll much at all, and is never uncomfortable. Actually, it's very peaceful down below, and I'm sure CF member poiu can verify this.

Now with stabilizers deployed occasionally, we actually roll and move around less than a catamaran in anchorages. How can this be?

[Pete7]

With a lighter or shorter mast I suspect your roll frequency will increase. With the present set up you would need to deploy the spinnaker pole and a large plastic bin over the side.

We have in the past abandoned a mooring ball in Alderney near the breakwater when the small waves and the reflected returning wave combined to make life on board really quite unpleasant, even with a British stiff upper lip. The solution was to go and anchor 1/2 a mile away and have the bow meet the first wave and be far enough away not to be affected by the reflected wave.

Perhaps the solution is not a riding sail which isn't going to be big enough, but to use some of the main to dampen the roll just as a ketch might use the mizzen.

Pete