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Old 29-08-2006, 19:45   #1
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Automated Main Sail

I'm fairly new to sailing but I find that raising, lowering and especially reefing the main sail can be a dangerous affair. So I got to wondering why the main sail is not motorized. I invision a rolling affair in the boom, such that when the main sail is lowered, it is all contained in the boom and rolled up on a shaft. This would act to protect the sails from the sun too. When its time to raise the sails an electic hoist on the main halyard raises the rolled sail into position. To reef the sail, you roll it up until you get the size you want. Perhaps the issue is keeping tension on the every changing effective tack and clew of the sail
I'm sure such a system must already exist. If so, what is it called?

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Old 29-08-2006, 20:08   #2
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Mainsail Furling

There are 2 main types of furling/stowing systems presently available for mainsails;
1. In mast
2. In or on boom

I have used neither and cannot comment on the operation of such, however, from what I have read, both are similar in that the sail is rolled onto a core or axle - a little like a roller blind in your home, or a pull down projection screen. The in mast type actually rolls up into the mast.

The common boom type I have seen is the sail rolling onto the boom that rotates on the gooseneck fitting.

I am not aware of a motorised version, but I'm sure if you want this feature, someone can engineer and build it for you.

As with all such items, they have advantages and disadvantages.

The biggest drawback with any type of furling system is that to get it to work well and easily, the shape (therefore performance) of the sail is often compromised. The mainsail is not a flat piece of cloth, it is cut and sewn to have a curve in it that when filled with wind, drives the boat.

Sailing should be an enjoyable experience, and if having such an item aboard makes your sailing easier and more enjoyable, get one. Many will of course dissagree.

Fair winds


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Old 29-08-2006, 20:10   #3
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Its called "in-boom roller furling", and yes, it does exist. In fact, it exists in almost exactly the configuration you described...
Schaeffer makes one, Leisure Furl is electric winch certainly makes things easier. An added benefit (over in-mast furling) is you get to retain those nice full horizontal battens, and the more-efficient sail shape they provide. All in all, its a fairly elegant solution for main-sail control, specially on larger boats.
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Old 29-08-2006, 20:25   #4
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Standard equipment on my boat

All newer Amels have electric in mast furling, electric genoa furling, electric staysail furling, and electric primary and main sheet winches
fair winds,
Amel Super Maramu
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Old 29-08-2006, 20:27   #5
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One more disadvantage

is the cost vs. performance. Neither the in-boom or in-mast will perform as well as a standard hoisted sail $ for $ due to it's aerodynamic shape and the cost of manufacturing, which is what helps propel the boat. For every convenience there will be a sacrifice be it performance or electrical.

BTW the in-boom is the worst of the two for performance.............................._/)
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Old 29-08-2006, 20:30   #6
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some say in mast is the lesser of the two

The difference is that if you have to blow the sail you can not drop the halyard if the sail is furled on an in mast furled sail.
Fair winds,
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Old 29-08-2006, 21:32   #7
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I found these:

Just needed the right search terms
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Old 29-08-2006, 23:12   #8
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There are numerous sollutions to raising, lowering and reefing your main that do not have the well-publicised problems inherent in the "in-mast roller furling" of many of the pretty "floating bungalows" that pass for yachts these days (lousy sail shape, no battens, prone to jam, weakened mast section, etc)

If you use a decent batt-carr system, and run your main halyard back to the cockpit, you don't need to go forward to raise / lower the main. There are also some quite reasonable single line reefing systems available these days, so you souldn't even need to leave the cockpit to reef. If you really want the easy life, you can always install a motorised winch for raising your main more easily too, not to mention lazy jacks / flat packs for dropping.
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Old 30-08-2006, 03:30   #9
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As an aside, I believe in the boom is call roller reefing, and in the mast is roller furling.

Roller reefing is usually cheaper to add to an existing rig than roller furling.

A manual system with a power windlass should give you what you want.

Ditto to all the above about trading effeciency for convenience.

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Old 30-08-2006, 05:21   #10
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I haven't used either system, but why is the in-boom the worst for performance? The in-mast system can't have battens and the sail has to be cut with a hollow roach. I would think that the in-boom would have fewer compromises on the sail shape and area.

So (in the absence of experience) I always thought the opposite regarding performance of the two.

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Old 30-08-2006, 06:43   #11
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You said,

"BTW the in-boom is the worst of the two for performance" and
Neither the in-boom or in-mast will perform as well as a standard hoisted sail"

I believe just the opposite to be true, after installing an in-boom furler system 3 years ago.

First, the in-boom mainsail solution performs BETTER than the in-mast roller furling solution because the mainsail may have a large roach and full-length horizontal battens. Also, when reefed or fully furled the weight is carried lower down where you want it. And, in the event of a malfunction, the sail can simply be lowered just as you would a "regular" main; this is not the case with in-mast furlers which can get you into a lot of trouble if/when they jam.

You're right, though, that this is a costly solution, both because of the hardware involved and the need to have a purpose-built mainsail for in-boom furling. I've had a LeisureFurl in-boom furler with a North main for three years and love it. It's easy to handle and sets well on all points of sail.

The LeisureFurl almost approaches the "motorized" model mentioned in the original post, having a Lewmar electric self-tailing winch for raising and lowering. You DO have to pay attention and maintain the proper tension with the reefing line when raising and the halyard when lowering...just takes a bit of practice.

Second, re: the comparison between in-boom furling and a "regular" main's performance, I've found there is little or no difference when under full sail. With its large roach and full battens, my new main may have a slight edge over the old one. However, when furled -- and the in-boom furler can reduce the mainsail area by any desired amount -- the sail retains a beautiful shape and I believe is more efficient than my old "regular" mainsail with slab reefing.

You can see pix of this setup here:

S/V Born Free
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Old 31-08-2006, 00:01   #12
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I have in-mast furling. It works fine. It is a bit tedious to put the sail away, but not as bad as flaking it. Like Bill says, you have to keep tension on the outhaul as you roll it up, or it bunches up and jams. When it jams, you just have to roll it back out a little and try again.

If you work hard enough, you can roll it up messily, and then it will be hard to unroll later. I find it works best to always keep some wind on the sail when rolling it up; it helps keep the tension high enough so it will roll up smoothly. By "some wind", I mean pointing 5 or 10 degrees off dead upwind, not reaching.

I haven't noticed any performance problem w.r.t. a conventional main (like on my last boat), but then maybe I wouldn't. I hear that "racers can cruise, but cruisers can't race" because a cruiser gets out there and says "hey, the boat is going the right way, why don't you quit fussing with all those lines and relax".
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Old 31-08-2006, 06:45   #13
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Great pictures... thanks for sharing that gallery!

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Old 21-10-2006, 00:57   #14
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Inmast furling

There are pros and cons to inmast/inboom furling vs slab reefing. The typical cons are the reduced roach area of because of lack of battens and the cost. The cost is a big consideration for a retrofit -- but is not such a difference when buying new. As for the battens, Selden offers a vertical batten sail with positive roach that has now been in use for several years and has proven reliable.

The major and I mean major benefit for us (being a two person cruising boat) is that my spouse can easily (even at night) furl or reef the mainsail by herself. And she can accomplish this even if it is blowing F8+. A side benefit is that inmast furling allows you infinite control on the amount of reef. You are not just limited to a typical 20% or 40% reef option.

Finally, I like the inmast furling option over the boom furling because you still wind up with a usuable vang. To me the vang is an important sail control line that I would hate to loose, which happens with the boom furling systems.


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Old 21-10-2006, 07:31   #15
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I really like my conventional, full-batten main. I have three reefs that give me a lot of flexability. The Selden RCB system (there are lots of batt-car alternatives) makes the effort to raise the main reasonable. My not-very-big girlfriend gets the main within four feet of full hoist before moving to the winch for the last bit.

Keeping the track and cars clean, lubricated, and in good shape makes all the difference in the world.

If the effort wears on us I'll put an electric halyard winch on.

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