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Old 05-01-2011, 23:40   #46
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Originally Posted by SailFastTri

Is this true even when the boat is being overpowered? I'm very skeptical, as the loads would be huge and the friction of the mast being pushed (and bent) around the slot edge would be quite significant. Please describe how this is achieved.

BTW -- I have no doubt you could furl it under light load. There can be a big difference between reefing and furling circumstance.
Well we were reefing the main in squalls approaching 50 knots. All we did was lift it off the spreaders and ground it in. Good chafe protection on this mast no problems all the way across.

Sometimes in my experience there's a lot of friction in some systems. This needs to tracked down and eliminated. It should be as easy as headsail furling.

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Old 05-01-2011, 23:45   #47
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Originally Posted by goboatingnow View Post
Well we were reefing the main in squalls approaching 50 knots.

It should be as easy as headsail furling.

Dave
What sort of boat and furler?

There is a substantial difference in a reefed IMF and slab-reefed sail. As you reef down a traditional sail you still have a properly shaped draft and battens on the remaining bits. On the IMF sail you quickly bury what draft there is after the first reef which is probably acceptable for reaching but bad going to windward.
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Old 06-01-2011, 00:03   #48
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Originally Posted by tsmwebb

Nice post Dave. I like your philosophy. However, I'm not sure I totally grok two points you're making. It seems to me that too little clew tension when furling will result in a loose roll that can fill the mast and jam before the sail is completely furled. I seen problems with mis-cut and imperfectly installed sails jamming. I've also seen a bushing on a top swivel disintegrate and result in a bad jam. And, as mentioned before, I've got some friends who managed to get a their top shackle jammed in the slot. I'm not a rigger or anything, these are just problems I've come across in passing. Your point that folks don't understand how to unjam the sails when they do jam doesn't comfort me somehow. Now, it seems to me that virtually all of these problems are caused by having the roller system inside the mast. So, please help me out, what are the benefits of in-the-mast-roller-furling versus behind the mast? I've tried and I can't think of any serious benefits of in the mast furling over behind the mast. I suspect that people chose in the mast because it looks nicer. But the cost in potentially serious problems seems like a high price to pay for style. I'm sure I'm missing some important benefits. What are they?

Tom.
Tom. My experience with jams ( I'm an instructor so I see lots of near newbies ) is that they have a very slack clew ( often from a mistaken concern over ripping the main). This as you say generates firstly a bulkly roll and secondly a turn on the sail inside the mast, this tends to be followed by enthusiastic ! Grinding , at this stage ( with a fairly generous mast profile), most of the sail is in the mast, then the fun starts !!

Problems with mis-cut sails should be fixed at the outset, failing swivels etc , all problems associated with lack of maintenance and too few trips up the mast ( the out of site out of mind problem).

Off all the boats I've delivered or sailed on the in-masts gave the least problems !! It's interesting to note that Tom cunliffe the noted English writer reviewed about 18 months ago three reefing system on sister boats , in mast, battened single line, in boom , he surprised himself by finding the in mast was the best all rounder.

Behind the mast is a very inefficient setup. Firstly you can still get jams between the furled and the mast body, secondly it's very aerodynamically inefficient , and there's a massive offset bending force on the mast.

Benefits ; no battens ! , simple one man reefing. , reef on all points of sailing with a proper setup . little string, infinite reefing points provides good boat balance " , sail uv protection. Extended roach possible with add ons

I'm completely not sold on in- boom systems ( a) they're very expensive, they require very accurate positioning of the boom angle

To answer the other posts , on a battened main with single line reefing I always find that friction in the system ( ands there's a lot of friction) causes the clew end to come down and leave the foot end not fully down., even though to the winch man it feels down, at night etc when the boom is out on a reach you can't see the foot end clearly from the cockpit to verify a proper reef it's always seems to require a trip to the mast with a torch. ( that's my experience)


I really do think in-mast suffers like other innovations in that early issues became fixated in people minds. There are still people arguing against headsail furling !!. Proper designed-in in-mast systems have been around a long time now. The bugs have been worked put in general. Both like all mechanical systems. They require inspection and maintenance and importantly user training.


Other minor issues like whistling have all been solved by various means.


Dave
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Old 06-01-2011, 00:18   #49
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Originally Posted by muskoka
.......Though you couldn't reef downwind in a serious blow.

Ask any sailmaker for their opinion. The key failing lies in the poor cut of the sail: There is no roach, no battens, the fabric needs to be lighter which leads to a shorter lifespan, the draft is usually not optimal and you really can't fine tune the sail. A mainsail provides the majority of the power in a cat.

Stating that in-mast furling has an inferior sail isn't a dogmatic opinion: It's a fact based upon the physics governing sail performance. You need to weigh that against the marginal convenience gained when furling the sail.
Well properly setup I've always been able to reef downwind, it requires a bit of grinding but it can be done. It's only mainly a problem if you have full sail out and you suddenly need a big reef , ands that's bad practice , in-mast encourages early reefing. The downwind reefing of any sail is problematic, it's impossible with ordinary sail slide mains and even with cars requires a downhaul, which very few boats fit. At least with in-mast you can wince and grind


Your comments 're sal weight longevity and sail shape are only true to a point. Firstly vertical battens in mast can support substantial roaches and modern laminates ( like cruising 3DLs etc). can fix sail weight. ( and there's other solutions as well). The point being these issues can be designed out)

That aside nobodies arguing that a full battened main isn't more efficient , noire then a rigid wing sail isn't even better. Efficiency is an angels on a head of a pin thing.

I'm not a cat fan so I'm not drawing conclusions 're cats, in any main driven boat, battened mains will always be favoured, but like lots of things is really a preference thing , Botha systems can be setup ( with enough money ) to do what you require.

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Old 06-01-2011, 00:29   #50
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Originally Posted by muskoka

What sort of boat and furler?

There is a substantial difference in a reefed IMF and slab-reefed sail. As you reef down a traditional sail you still have a properly shaped draft and battens on the remaining bits. On the IMF sail you quickly bury what draft there is after the first reef which is probably acceptable for reaching but bad going to windward.
The boat was halbert rassy 42 with a hood mast mast and reckmann im mast furling , very good furling system with a generous mast profile. Worked a dream.

I agree with all the issues 're draft and sail shape. , but and it's a big but. Sail shape on a heavily furled main in a big blow os not really a big issue. Racing it is as you are trying to extract max speed for a given wind speed, in the real world most modern boats sail too damm fast in a blow and often especially battened mains are too efficient and I find I have a damm time slowing the g' damned boat down. At least with in -mast I can continue to furl until the drive is gone. I've taken some in-masts through some big winds and seas and in real life the argument somewhat redundant. ( my comments are aimed at Monos as I said before)
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Old 06-01-2011, 01:05   #51
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Originally Posted by goboatingnow View Post
( my comments are aimed at Monos as I said before)
Well, the OP did ask about in-mast furling on cats...

In any event, IMHO opinion too much of this discussion ends up looking at the extremes - like will it reef in a 200 knot wind against a lee shore. Or suggesting that if you want performance then logically you must drop a small fortune on a wing sail...

Assuming we're all looking at getting the most pleasure out of sailing, the reality is that for the majority, there will be some cruising, lots of day sails and some racing. I sail in a lot of light winds, do some offshore racing, and am prepping our boat for extended cruising.

I've sailed the same boats with and without IMF (Beneteau Oceanis vs First). The poor shape makes for really bad performance in light winds which I think is the real litmus test of a good sail. The only time I preferred the IMF is when sailing solo - it's a worthwhile compromise for that purpose.

It may simply come down to whether there's some racer in your blood or whether you're happy motor-sailing. But frankly, there is no situation in which the performance of the IMF is superior except getting you to the bar quickly whilst the other guys are busy bagging their sails.
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Old 06-01-2011, 01:21   #52
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Originally Posted by muskoka
In any event, IMHO opinion too much of this discussion ends up looking at the extremes - like will it reef in a 200 knot wind against a lee shore. Or suggesting that if you want performance then logically you must drop a small fortune on a wing sail......

I've sailed the same boats with and without IMF (Beneteau Oceanis vs First). The poor shape makes for really bad performance in light winds which I think is the real litmus test of a good sail. The only time I preferred the IMF is when sailing solo - it's a worthwhile compromise for that purpose.

It may simply come down to whether there's some racer in your blood or whether you're happy motor-sailing. But frankly, there is no situation in which the performance of the IMF is superior except getting you to the bar quickly whilst the other guys are busy bagging their sails.
That's in itself a rather pejorative statement you've decending into the absolutes you initially criticise. Every sailer has a little bit of a racer in them.

Good in mast systems with proper sails can be more then adequate in all winds. The answer is that in mast is a good all rounder but necessarily master of anything

Ultimately these systems boil down to personal preferences and ones specific experiences and expectations. Many sailers for example can't abide not having the latest efficient systems even when the boat most of the time can't use it.

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Old 06-01-2011, 03:34   #53
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Originally Posted by goboatingnow View Post
Good in mast systems with proper sails can be more then adequate in all winds. The answer is that in mast is a good all rounder but necessarily master of anything

Dave
Performance issues aside, I'm not sure I've ever seen IMF on a large cat. Has it been done?

It seems as though it would be a challenge: I was down at my boat this afternoon and the boom/sail measures about 5.5 meters long. Plus, cats use much heavier material for the sails because energy isn't naturally dissipated through heeling. My main is 55 sm and has a massive roach. And many of the newer cats have a square topped main.

That is an awful lot of sail to roll up.
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Old 08-01-2011, 04:10   #54
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Stacy... Our system sounds very similar to Colemj just with the addition of a 12mm line taken to the top car on the mainsail. If we are off the wind when we want to bring the main down we just put the line on the electric winch in the cockpit and pull it down.
Mike re downwind reefing in strong winds
It took me a lot of dscussion with the Admiral before she would agree to practising downwind reefing on our 47 ft cat. Once I explained the dangers of going from sailing downwind and attempting to turn into the wind across the swell and with the increase in apparent wind and hence the risk of broken gear & capsize, she grudgingly gave in.

HOWEVER, we seem to strike problems half the time. The battens become caught on the lazy jacks of the boom bag. I have attached a downhaul on the main head board but it is rarely necessary as we have good batten cars. I centre the boom then to put in the #1 reef I get the admiral to ease the main halyard slowly while I tighten the #2 reef in an attempt to keep the leech of the main away from the leeward lazy jacks. But sometimes the battens still get caught up BADLY

Any suggestions would be gladly accepted.

Both sets of lazy jacks are tightened by the same rope so easing that might not be helpful, but I am considering it.

I guess it just needs more practice. Maybe reefing downwind on less windy days is the way to iron out the process. Unfortunately the boss does not like doing things that don't always go well. It took me 12 months to get her to agree to hoist the assymetrical on our last boat.
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Old 08-01-2011, 04:48   #55
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Other than a Hobie Cat, I have all my time on Monos...... My current boat has a Stow Boom and I love it. I could care less if I'm missing a knot because my sail is not PERFECT, and that knot is well offset by convenience. I guess you cat sailors like to go FAST!
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Old 08-01-2011, 05:53   #56
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.

Both sets of lazy jacks are tightened by the same rope so easing that might not be helpful, but I am considering it.

.
Thats it I reckon, - ease the lazy jacks - right off and then pull them back on.
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Old 08-01-2011, 07:03   #57
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Other than a Hobie Cat, I have all my time on Monos...... My current boat has a Stow Boom and I love it. I could care less if I'm missing a knot because my sail is not PERFECT, and that knot is well offset by convenience. I guess you cat sailors like to go FAST!
Nobody has questioned in-boom furling on a cat. In fact, there are a lot of cats equipped with them. I doubt those cats (or you) are missing much of your speed potential using them.

The discussion has been about in-mast furling on a cat. Here, there are potential problems with sail area, balance, etc. These are larger issues on cats compared to monos because cats gain almost all of their drive from a very large main on a highly fractional rig (think 2/3), and the mast is mounted further forward to accommodate this sail plan.

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Old 08-01-2011, 13:07   #58
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[QUOTE=muskoka;591674]Performance issues aside, I'm not sure I've ever seen IMF on a large cat. Has it been done?

I've seen once.. This was a FP Belize 43 catamaran. I don't know whether she was delivered this way from the factory or was it changed later. From what I've seen, the guy was not sailing much anyway..

Again, whether it is mast or boom furler, on a cat, not a good idea.. On mono, it could work somewhat better, if you are not racing or not keen sailor..

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Old 17-01-2011, 16:41   #59
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Here's a documented fact: in-boom furling is bad for resale of a cat. Two sellers had to go so far as to replace them (at considerable expense) to get a reasonable offer. In-mast-furling is likely to be worse.

With roughly equal construction quality, a forty foot cat costs as much as a fifty foot monohull. Loaded with the same luxury features, their performance is equal because the cat is more weight sensitive. If anything, the monohull is more weatherly.

There are two levels of sophistication in new cat buyers; there are two sides of the performance question. Imagine a four square grid with unsophisticated performance shoppers in the upper right, sophisticated performance advocates on the left, then in the lower boxes an unsophisticated luxury buyer and a sophisticated cruiser with comfort formost in his dream boat. The unsophistcated buyer will be influenced by what he hears from the Broker and reads in the full page ads in boating magazines. The experienced buyer has formed his own opinions based on experience, understanding of design and construction issues, bar talk, hearsay and old wives tales (just to be fair!)

The performance enthusiasts will hear about bad sail shape and avoid in-mast OR in-boom furling. They are cat shoppers for the performance advantage, and do not want to compromise that. The experienced performance-minded buyer will even go so far as to take stuff off a used boat.

The sophisticated cruising-only buyer is looking at cats for the size of the salon and cockpit, perhaps the fuel efficiency from doing without a heavy keel, and he will consider either IMF or IBF with a clear understanding of the implications.

The untested cruiser will, uh, have a chance to learn a lot!
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Old 17-01-2011, 18:50   #60
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Here's a documented fact: in-boom furling is bad for resale of a cat. Two sellers had to go so far as to replace them (at considerable expense) to get a reasonable offer. In-mast-furling is likely to be worse.

...

The untested cruiser will, uh, have a chance to learn a lot!
Interesting. I hadn't realized that in-booms were problematic for resale.

I'm not sure why they'd need to replace the furling boom though - you could simply rig a conventional non-furling mainsail at considerably less expense. Though you'd be carrying more weight/windage in the boom which would drive the racing set mental.

Hell, I removed an aircon unit to offset the weight of some stuff I added to my boat. And I don't even race it.
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