So walk me through the in-mast furling mainsail

[C420sailor]

Originally Posted by James M B

So I have a Beneteau 373 since 2008 with in mast furling and here are a few tips.
When unfurling, pointed into the wind (mostly) everything should be loose, mainsheet, vang, topping lift. This gives the best chance for the sail to find its way out.

When furling again have everything loose, except a little tension on the outhaul to make sure the sail furls tight and even. If not then when trying to unfurl next time the loose sail can bunch up and bulge out the slot, causing a jam, pulling harder makes it worse to the point you can no longer furl or unfurl. Resolution is to go up the mast to the point the sail is bulging out and stuff it back in, unfurl, then furl with proper tension.
Mine came with vertical battens which seem to add unwanted weight at the top of the sail causing a sag in light winds.
I have new sails coming without vertical battens and hope it is a better design.

B361 without battens. Same exact issue.

Combine a sliiiiight aft bend in the mast with a sail that isn’t perfectly flat, and you have extra material in the middle that doesn’t furl tightly.

In my experience, furling almost always goes well. Unfurling is a dice roll. I even installed the recommended ball bearing car/track kit. Didn’t change anything.

I stopped using the cockpit controls to unfurl. The angle of the outhaul is slightly down, and that pulls the loose sail in the middle out of the slot, and jams it all up. Instead, I simply uncleat everything, go on deck, and pull the sail out manually, straight back. Works 90% of the time.

Never had to go up the mast though. If you catch the jam early (NEVER WINCH IT) you can do a series of in/outs and it’ll sort itself out.

The days it works, I’m happy I have it. The days it doesn’t, I wish I had a conventional main. Both have their drawbacks. With lazyjacks, a normal main isn’t bad. Without them? The WORST.

[Cheechako]

In mast furling is easier to put the boat away.
I find no other benefit.
-They lack a roach, a huge deficit, but ok for daysailing with a big genoa.
-they can work fine in a perfect world ..until .. they dont.
-"You just have to keep the tension etc etc" Translated as "In a perfect world they work fine" Try that when the boat is wallowing with the main flopping around.
-Squall coming? "start the engine etc etc "? Nah, Just slip in a reef with slab reefing and carry on as a sailor should!
-Slab reefing is actually faster and bulletproof if you ask me.
JMHO

[Rallyguy]

We're four years into ownership of a Beneteau 351 with original (1995) in-mast furling. It was a bit of a learning curve - just like all of sailing. If you do a bit of research and understand the system (like you should be doing for every system on your boat, IMHO) it becomes easy and reliable to use. We had problems at first - until we learned the tricks. Everything loose, as noted above - a bit of outhaul tension on furling - AND have the boom a bit on one tack or the other (depending on your system) to allow the sail a clean, smooth path into the mast. Do that and you're golden. You should be reefing LONG before there's any urgency, so I don't really get this "how do I drop the sail in a hurry" concern. Sheet out to instantly de-power the boat if needed. If the wind is really catching someone so unawares that they have to drop the whole sail suddenly - I'm scared of where or how they're sailing. : )

As for "convenience" - I don't regard avoiding the need to go up on deck to struggle with putting a reef in as the weather is building as a convenience. It's a profoundly safer way to do things.

RK

[Muaddib1116]

Originally Posted by S/V Illusion

Why you categorize as "ridiculous" a perspective with which you apparently disagree is interesting. Presumably, pride of ownership????


Regardless, the message is true even when you attack the messenger. These are problematic in many cases and only a few people can claim to have never had a problem. They have them as a matter of convenience and consequently that convenience brings the attendant problems. Stated differently, the problems are self-inflicted simply because some prefer convenience over reliability.

You're going to have to point out how I "attacked" you. What I said was that one, the claim that using in-mast furling is wrong is an absolute statement that I don't think is reasonable to make, and two, that accepting additional risk for convenience is something that everyone does everyday in a number of different ways.

[Rallyguy]

And I'll make the case for the inverse - I contend that set up and used correctly, IMF can be 100% reliable - and therefore is actually SAFER than going up on deck in building seas. With a nice side helping of convenience too. : )

[Muaddib1116]

I don't know if I'd go as far as to say 100% reliability, in regards to pretty much anything, but I think it's certainly possible to use reliably enough to justify the downsides. I can say that I definitely tailor my sail area to wind conditions far more with my in-mast furling than I ever did with slab reefing. It takes very little effort for me to reduce sail, and since I don't have battens I can choose how much sail to take in, and I can do it without coming up into the wind.

[CheekyGirl]

We have had the boat for 12 months now and the IMF is one of the best things ever. There are 2 of us on board nearly all of the time so staying in the cockpit is the preferred way.
Want to reef - ease the mainsheet & outhaul tighten up the furler - job done.
Coming into marina boat bouncing all over the place just roll it in no holding onto boom trying to do zip on stack pack up

Would I ever go back - No
Would SWMBO allow music to go back no way

[waterman46]

Originally Posted by Cheechako

In mast furling is easier to put the boat away.
I find no other benefit.
-They lack a roach, a huge deficit, but ok for daysailing with a big genoa.
-they can work fine in a perfect world ..until .. they dont.
-"You just have to keep the tension etc etc" Translated as "In a perfect world they work fine" Try that when the boat is wallowing with the main flopping around.
-Squall coming? "start the engine etc etc "? Nah, Just slip in a reef with slab reefing and carry on as a sailor should!
-Slab reefing is actually faster and bulletproof if you ask me.
JMHO

I came to the same conclusion. In-mast or in-boom is nice for stowage, but not so reliable.

I really value reliability in being able to reduce sail quickly, and I'm willing to spend more time after anchoring or in the marina, to put on my sail cover.

Regarding quick sail reduction combined with control, I prefer the Dutchman system with full battens. To reduce sail all you do is head up, release the main halyard, then go back to the helm. The sail will drop instantly to less than 20% of it's area, and remain in control just above the boom. No possibility of jamming in the mast or hanging up in lazy jacks.

[Rallyguy]

Oh sorry - "100%" in boat-speak means it always works when it's not broken. : )

RK

[wnischt]

So I have owned a 41 Hunter with in mast furling for 5 years and for the first 4 years I had a lot of problems with the in mast furling system. All of these problems turned out to be attributable to be self inflicted/operator error. The system now works flawlessly. Pull in and pull out on a slight starboard tack (always). Pull the sail out with the outhaul keeping tension on the furler. When pulling in the sail, keep tension on the outhaul. Works flawlessly on my boat!

[S/V Illusion]

Originally Posted by Rallyguy

And I'll make the case for the inverse - I contend that set up and used correctly, IMF can be 100% reliable - and therefore is actually SAFER than going up on deck in building seas. With a nice side helping of convenience too. : )

To state the obvious, any slab reefing or dousing a traditional mainsail can easily be done from the cockpit when properly designed to do so. The argument that it’s more convenient to reef an in-mast furler applies only when the owner allows a rigging arrangement to necessitate going on deck. Kind of ironic in a debate about convenience.

[Muaddib1116]

This thread seems to be following the same rubric as most IMF/BF threads I've read. The people that have used IMF and have figured out how to use it properly more often than not have good things to say. The people who haven't used one cite the many popular arguments against, many of which are factual but avoidable, in favor of slab reefing. In my case, I like it so far, and don't regret buying a boat with it, but I'm not yet sure I would hinge my decision to buy a boat upon it.

Another argument that might come up is that it isn't suitable for any long distance sailing, only for coastal sailing. It's interesting then, that most of the big name cruising boat manufacturers choose to equip IMF. Amels all have it, using Amel's in-house design. Boats like Oyster, HR, Najad, Discovery, etc. all offer slab reefing or IMF over in-boom-furling systems. Boom furling has been around for a long time now and has a distinct theoretical advantage over IMF, but is much less common to see. I don't know why this is, but it does suggest that IMF has had better real-world user experiences that justify it's market share.

Plenty of people sail production boats around the world with IMF. It is clearly a very viable choice, and not at all an absolute. Does it have inherent risks? Yes. So does every other thing in life. Evaluate the risks, try to cut through the hyperbole, and decide how much risk you are willing to accept.

I've now typed IMF too many times and have gotten the Mission Impossible theme song stuck in my head.

[Hoodsail]

Never had in mast furling, but assuming no battens to speak of for sail shape?
I have lazy jacks to assist dousing the main and go to the mast to hoist the main, no lines running aft. Just like to keep things simple so if something does break, I can effectively fix or jury rig it. I could potentially see an advantage when reeving, but is it really that much work to flake the main on the boom???

[Muaddib1116]

As far as I know, mast furling sails can have full length vertical battens, partial vertical battens, or no battens. The battens help with sail shape and also allow some positive roach, although not to the extent of a horizontally battened slab reefing sail. The in-mast volume still limits the amount of sail that can fit inside. The downsides of battened sails, is that you need to more carefully control the sail shape as you furl it, so that the battens enter the mast slot vertically and also wrap around the spindle vertically. They are also more prone to getting stuck going in and out. As I've mentioned, I have no battens, which at this point, I am happy about. It makes the system easier and I don't find myself wishing I had them.

[mglonnro]

Originally Posted by Muaddib1116

Boom furling has been around for a long time now and has a distinct theoretical advantage over IMF, but is much less common to see. I don't know why this is, but it does suggest that IMF has had better real-world user experiences that justify it's market share.

I don't know either, but I recall VHS vs Betamax where the supposedly better system lost.

When I check the new Hanse price lists, the in-mast furling upgrades are surprisingly affordable (+2500 eur to a Hanse 458).

The boom furlers, on the other hand, are ridiculously expensive, so there's that working in the favor of IMF.