Behind Mast Mainsail Furler Experience?

[barnakiel]

I have been on boats with mains furled:
-inmast,
-behind the mast (add-on),
-behind the mast (witha a gap).

All solutions sucked and jammed or fell apart.

Slab reefing.

I think the furling main is only for very light use and weekend cruising, etc. I like it as an idea and think it is OK if you have the time and know-how to pamper it and do the maintenance, but not the thing you want on a squally rainy night.

b.

[Pete7]

Having reefed single handed on a wet and squally night I think it is just the thing you need rather than dancing about on a cabin roof. They are very popular with Moodys owners but most will have been specified and fitted whe the boat was built rather than "add on". Certainly many are used for blue water cruising and the ease of reefing single handed a major advantage.

The actual maintenance is minimal.

The problem though is evaluating an "add on" inmast reefing system. Did someone just pop rivet it on or has someone done the job properly and taken into account the extra weight, strength of the original mast and rigging and fitted a new main or just chopped the old one down.

Everyone will have there own opinions just as we have on anchors or batteries. It certainly wouldn't put me off indeed I would look for inmast again if we ever changed.

Pete

[jim_thomsen]

I agree with Pete. We also have original equipment in mast furling. It did take some practice to remember to get the boom at 90 degrees and also make sure the mast was staight. We have vertical battens and they give a good sail shape (again, not for racing, but cruising).
But the ease of reefing is fantastic. When crossing the Atlantic either my wife or I, whoever was on watch, could reef or enlarge the main without waking the other.

[KatKokomo]

I have an erly style behind the mast Pro Furl reefer which I like. I have never had problems with jams. Exactly the same principles apply for my headsail reefing. The behind the mast system is very simple and works well for me. I am aware that I lose some performance but I am cruising and not racing.

[s/v Jedi]

So, why is it that you guys think more heel is good for cruising? I assume you know that increased heel is one of the consequences of a furling main. The vertical battens make good part of that but those come with other possible disasters.

My biggest objection for in/behind-mast furling is the possibility for jams while partly reefed so that the sail can't be lowered either. I don't understand the cruisers who take that risk for ocean passages but I agree it makes sense for coastal sailing.

I would opt for in-boom reefing if I had anything against my current slab reefing system. But I prefer the slab reefing over anything else.

cheers,
Nick.

[Pete7]

Nick,

How do you get from inmast reefing to increased heeling

Yachts heel because the wind blows them over (okay pulls them over to be exact). If you have a modern boat with too much heel then put a reef in and sail it upright, it will go faster too.

We probably have a smaller main over an identical yacht with slab reefing because we don't have batterns, something else to break and wear holes in sails during a long trip, so no huge roach. Therefore less likely to lean over, more reasons for considering it for water sailing">blue water sailing.

Why would it jam after winding it in half way?

Pete

[s/v Jedi]

Originally Posted by Pete7

How do you get from inmast reefing to increased heeling

That is easy: a sail cut for in-mast furling is a compromise on sail shape... leading to more drag... leading to more heel. For slab reefing, you can go to the other side: full battens + big roach approaching the perfect wing shape... resulting in less drag, less heel and more speed.

Reefing to decrease heel on a hollow-leech sail means going slower (when under wind-design-speed) while the roached sail gives less heel with more speed.

Yachts heel because the wind blows them over (okay pulls them over to be exact). If you have a modern boat with too much heel then put a reef in and sail it upright, it will go faster too.

That is correct when you go over the design wind speed of the boat. But a regular main can be reefed too and will still give more speed and less heel.

We probably have a smaller main over an identical yacht with slab reefing because we don't have batterns, something else to break and wear holes in sails during a long trip, so no huge roach. Therefore less likely to lean over, more reasons for considering it for blue water sailing.

I know it's hard to believe, but a big roach mainsail, with more surface area than the in-mast-furled sail, will heel your boat less while giving it more speed. Drag is the keyword.

Why would it jam after winding it in half way?

You tell me (operator error, bad weather conditions?) but it does happen, we have seen it more than once every year. It means putting the knife to it to make port.... a very dangerous thing, incl. going up in bosuns chair in bad weather.

Let's turn it around, in your opinion:

- why is in-mast better than in-boom?
and
- why is in-mast better than slab reefing?

Some links:

WB-Sails Ltd
WB-Sails Ltd
Theory of Sail Shape | Tacktician

cheers,
Nick.

[Pete7]

Nick, you haven't convinced me, I am struggling to see how the bigger sail can have less friction, but let me have a good read of the links first.

Its too late this side of the pond tonight.

Pete

[s/v Jedi]

Pete,

You quickly end up in aerodynamics and foils etc. and I am quickly confused with all this myself, with all those vortexes trailing behind the sails etc. But what I do know is that the goal is to create a foil that delivers the required lift (drive) while minimizing the induced drag (drag leads to heel). So, where you talk about lift and drag for an airplane wing, you can translate that to drive and heel for a sailboat.

The shape of the sail is a very important factor for that relationship between lift and drag. An elliptical shape is very good and a triangle is not good at all. Let me quote someone from a boatdesign.net forum:

Triangles are poor foils, rectangles, trapezoids, and elipses all generate much more lift for their drag than triangles. You've probably already noticed that there are no triangular keels. You can see on many modern rigs that mainsails are growing more eliptical or rectangular. Fat headed rigs, and rigs with fully battened mains and huge roaches are examples of this trend.

The reasons that modern sails tend to be triangular is that they are a natural shape to fit on our tall masts with standing backstays. The gaff main is at least in theory not a terrible shape for a sail. Don't let anyone tell you that the gaff disappeared because it was less efficient than the marconi sail. The gaff rig disappeared because the International and Universal rules only measured the amount of sail area a boat could set, and this doesn't take account for the shorter gaff rigs ability to carry more sail. Steve Dashew's Beowulf shows the potential of shorter more efficiently shaped sails. The masts on Beowulf are stubby and short but they carry full-battened mains with a practically eliptical, she is quite fast.

cheers,
Nick.

[Pete7]

Originally Posted by s/v Jedi

That is easy: a sail cut for in-mast furling is a compromise on sail shape... leading to more drag... leading to more heel. For slab reefing, you can go to the other side: full battens + big roach approaching the perfect wing shape... resulting in less drag, less heel and more speed. Reefing to decrease heel on a hollow-leech sail means going slower (when under wind-design-speed) while the roached sail gives less heel with more speed. cheers, Nick.

Nick having thought about what you have said this is my take on the matter, the boat btw is a late 80s masthead rig with large 140% genoa and small main.

In wind speeds of F1/2/3 we do loose a little due to the smaller sail area of the main. However remember we live on a little soggy island of the NW coast of Europe which is also windy. In the unlikely event we have F1/2/3 then we put the cruising chute up or switch on the engine.

However once we are in F4/5 then there is little difference. A larger main sail would have to be reefed just as our inmast main has to be reefed. In calm water we might hold on to 19 knots of wind, whilst offshore normally reef about 16 knots and keep the wife happy. We reach hull speed with about 15 knots of wind quite easily just can't quite break the 7 knot barrier.

Whilst I agree with you that a triangle may not be the best shape for a main sail, I will say that it isn't critrical. Why? because it is a masthead sloop with the 140% genoa providing the main driving force not the main sail (although yes they do have to work together). The loose footed main is easy to adjust with the outhaul and kicker to achieve a good sail shape. Remember the outhaul also pulls down as well as out for inmast reefing. Adjusting the outhaul alters the main sail shape from full for light winds to flat for strong winds easily and provides a good sail shape. Loose footed means we don't have 2 foot of baggy sail doing nothing next to the boom. I happen to believe in the saying if it looks right then it probably is right.

So inmast reefing, easy to launch, reef and put away no batterns to worry about wear and cheaper to make whilst loosing a little peforamance in light winds. Those are trade offs I am more than happy to accept.

Pete

[s/v Jedi]

Pete,

Let me start with saying that for your boat, a big roach main would not work without other modifications which might include moving chainplates, angling spreaders and probably even mast position. The reason is that the sail-balance would be disturbed otherwise. Also, I don't know your displacement but I think a Moody would be light enough for the big main approach. Heavy displacement is not really compatible with big main and small jib configurations.

But there are still some things to be discussed ;-)

- your main is a triangle but it isn't really: you have a hollow-cut leech because you have no battens. If you would measure up the rectangle formed by mast and boom, your sail is well under 50% of that surface. A triangle is 50% and as roach is added you go over 50%. We are at well over 70% and our big sister Beowulf is at 85%, see attached photo.

- your genoa is the main driving force and it will probably provide 90% of that.... when you main is up. You should start thinking differently and consider your genoa+main combination as one single airfoil, because that is how it really works.

- comparing surface area is not the right approach: you should compare lift and induced drag of the two different shaped sails. The lift is what gives speed and the drag translates to heel. So, an elliptical shaped main needs to be reefed when it's drag reaches the same level as the other main when that needs to be reefed. This means that the elliptical can have more surface area up without heeling more.

- loose footed: of course, there's no other way.

- flattening sails: full batten mains can be flattened much more than a batten-less hollow-cut main. If you can reduce the draft of the sail 20% extra, it means you reduce both lift and drag 20% extra. This is another factor why you can have more surface area up with full battens without heeling more, or, in other words: a full batten main has a much wider range of trim resulting in a much wider wind-range it can be used without the need for reefing. This is why a "baggy" main is so bad. Most big roach mains are tri-radial cut with stiff round battens (ours are 3/4" round!) and that is another big step to widen this range.

- batten trouble: yes, I know many experience this. The only solution is to throw money at it by using metal batten hardware/tensioners at the luff, connecting to cars and special pocket-ends at the leech (spectra webbing reinforced). Every decent sailmaker can do that now because all the cats and racers have this system and the problems have been dealt with.

- you could improve your system with full vertical battens. It would give you more speed at every wind-speed (so also high winds) while heeling less.

- you still have the risk of a jammed system and you have much more weight aloft. Like I said before, I would be fine with that except for coastal sailing.

cheers,
Nick.

[s/v Jedi]

I would like to write some more here in this thread with the risk of straying off topic a bit but it is all related and I think many sailors are confused with these points:

- Heel and weather helm: I hear so often that the way to counter act the weather helm is by reefing the main, putting more percentage sail area at the bow and less aft. This is mostly wrong. You can find that out yourself by reefing the jib instead which will drastically reduce weather helm. The reason is that it is the heeling that causes most of the weather helm and the reason for that is the change of shape of the part of the hull that is submerged. It is symmetrical when upright but asymmetrical when heeled. This is why narrow boats have much less weather helm trouble. So the trick is to heel less while keeping the sail plan balanced (reef main and jib on a sloop; cutters and ketches have more options).

- weight and windage aloft: every one know that it's bad and it's good to think about it more. When you heel 30 degrees, imagine what a 10 kilo weight at the masthead would do... heel you much more. There are many things that add weight aloft and the most important one is often skipped: a deck-stepped mast adds a lot of weight aloft because it must be much stiffer (heavier) than a keel stepped mast, plus it needs heavier rigging for support (keel stepped is partly self-supporting). In-mast furling leads to bigger diameter masts that weigh more and have more windage. Behind-mast furling is even worse (more windage, about same weight). When it becomes time to reef, an in/behindmast furled main keeps the same weight aloft while a boat with slab reefing reduces weight aloft. Don't under estimate the difference.

- aft-swept spreaders and boom vangs: they come together. If you sail downwind, the main can put too much force on the spreaders and you must tension the boom vang to reduce that. A wide traveler helps too, or putting up a temp sheet arrangement on the toe-rail.

- center of effort: so many sailors change the boom position by bringing it higher up the mast. Reasons are the bimini's etc. They forget to call the rigger to design a new rigging setup to deal with the change. Also, it will drive many to in-mast or in-boom furling because they can't reach the boom anymore or close the sail cover etc. Basically, it's all bad for sailing and handling.

cheers,
Nick.

[Talbot]

It always amuses me that some people get all evangelical about any form of reefing other than slab.

We all know that Jedi worships at the god of performance, and that his preferred compromise is biased towards extracting every scrap of speed regardless of effort to achieve it. I have no problem with that, but I am a much lazier person, and prefer to work at a system that allows me to sail singlehanded and enjoy that sailing without worrying about acres of sailcloth.

Similar verbal fisticuffs used to happen about hanked on sails versus roller reefing.

I respect anyone else's right to enjoy their sailing in whatever manner they want to do it - I wish others would do the same. Just because one person has been unsuccessful at doing something, does not mean that others have the same problem. in mast sails (and presumably in-boom systems as well) need slightly different techniques. If you try to operate them without learning those techniques you will have difficulties.

If you can be bothered to learn those techniques, that is fine and is your decision, but dont rant about systems that you self-evidently dont actually have any expertise with.

Discussions about the difference in triming and techniques and advantages and disadvantages are always usefull, but biblical bible thumping bores me.

[James S]

I do appreciate Nicks view and detail.

[s/v Jedi]

Talbot,

I can understand why you think I would do anything to go faster but the situation is a bit different. I try to go as fast as I can with what I have (many many sailors do that I think) but speed is not on top of the list when I select and buy sails, rigs or systems.

At the top of our list is safety, ease of handling and comfort in that order, followed by speed in some cases.

The truth about it is that in many cases, speed and comfort or safety go hand in hand. Like less heel means more speed and more comfort.

So when you read what I wrote in this (and other) threads, you must understand that I have safety, ease of handling and comfort in mind before speed while writing that. So yes, IMO slab reefing can be safer, easier to handle and more comfortable than in-mast furling, even though you find that hard to believe. Note that I highlighted the word "can" in that sentence because it's not just about slab reefing: you need the complete sail handling system with properly rigged lazy jacks, integrated sail cover, loose footed main, maybe an extra (powered) winch, granny bars, low-enough boom, full battens etc. to make it work really good. Many boats come with all that while older boats have just a few of these items or none at all.

For boats that have all these items/features, there is no better system. For all others, it depends on what is available and what can be changed (technically and financially).

I am not biblical about it at all and even wrote that I think in-mast reefing is fine for a large group of boats that do coastal cruising. But I will always react to someone stating that it's just the surface area that counts and sail shape is a minor detail which isn't relevant for cruising.... because that isn't true.

ciao!
Nick.