So walk me through the in-mast furling mainsail

[Dockhead]

Originally Posted by Rohan

My boat is in mast furling. It wasn't my first choice, since I was trained on a traditional main, but it's what the boat had.

The downside is a little less sail area than a standard main, and I can't drop it so quickly if I really need to. But it's less work and maintenance and works fine. Some of the problems described here I think are on older systems. The way mine is designed (Selden circa 2006) there's no way I could pull out the clew or wind it so tight that I wouldn't be able to get it out later.

A few people have mentioned in boom furling. I haven't tried it, but it seems to make a hell of a lot more sense, putting the weight lower where it belongs. But not many boats have that, I don't know why. I believe it's standard on Tartans and Seaward, I don't know who else.

You make a good point. Not all in-mast furling is created equal. I have the Selden system.

Concerning in-boom -- I haven't tried it, but in-boom has some obvious advantages and some obvious disadvantages. Big advantage is roach and normal battens. Huge advantage. Shared with slab reefing. But the drawbacks of in-boom seem pretty serious, too -- no outhaul is the biggest one. That's a sail control I can hardly imagine living without. Another is the massive heavy boom, the idea of which I really don't like (even much more than the massive heavy mast which comes with in-mast furling). I think I would prefer normal slab reefing to that.

By the way, another drawback to in-mast furling is weight aloft, and heavy almost un-bendable mast, which takes away one sail control, less serious than outhaul, but something I do miss from time to time.

[rslifkin]

I don't see why you couldn't have an outhaul with in boom furling. Just might take some creative design and it might only be usable with the full sail up, not when reefed.

[Rohan]

Originally Posted by Dockhead

But the drawbacks of in-boom seem pretty serious, too -- no outhaul is the biggest one. That's a sail control I can hardly imagine living without.

There is still an outhaul, right? It just goes vertical instead of horizontal.

[Dockhead]

Originally Posted by rslifkin

I don't see why you couldn't have an outhaul with in boom furling. Just might take some creative design and it might only be usable with the full sail up, not when reefed.

Whether it's possible in theory, I can't say. But in practice, those systems which really exist, like LeisureFurl, do not have any kind of outhaul.

[Muaddib1116]

I've never paid too much attention to what was causing the howling at my winter boatyard when the wind picked up, but it does seem like it may be some IMF masts. There are a few little harbors which I assume have Hood masts and an Amel 50 which has their in-house design. Those seem to make a lot of noise when the wind hits them right. My Selden mast doesn't seem affected. It does appear like the Hood and Amel mast slots are noticeably wider than the Selden mast slot, perhaps that's why.

[MultiCountryDon]

I have had IMF on a 48 ft, a 36 ft, and a 34 ft . No issues with any.
I have had a 42 ft and a 45 ft with IBF. No issues.
Both give you the benefit of infinite reefing % vs 1,2 or 3 positions.
I have had numerous boats from beach cats to 45 crusiers with slab, stack pack, dutchmen,etc. No issues.
Just have the rigger teach you how to best use the system, listen, practice and get on with it. Most problems are operator error or poor maint.Of all ofthem, I prefer the IBF system, but they are expensive!

[nortonscove]

First unfurl it and then attempt to walk through it. If it's really old you may succeed.

[nortonscove]

Originally Posted by Markb250

There seems to be little discussion here about the substantial compromise to sailing performance that comes with the substantially compromised sail shape inherent in the in mast furler concept.
Just look at an in mast furler and a fully battened slab reef main sailing side by side, and ask yourself why you would want to completely stuff up the most important asset you have, when slab reefing just couldn't be any easier and reliable than what it is.

This might matter to some but if it mattered so much to me I'd have bought a power boat. I go out to be on the water and the destination is simply a place to get fuel and food. Getting there faster isn't much of a consideration. I also do 99% of the work on my boat and in mast just works better for me than the traditional. My 40 is easier to singlehand than my 27 was.

[Dockhead]

Originally Posted by Muaddib1116

I've never paid too much attention to what was causing the howling at my winter boatyard when the wind picked up, but it does seem like it may be some IMF masts. There are a few little harbors which I assume have Hood masts and an Amel 50 which has their in-house design. Those seem to make a lot of noise when the wind hits them right. My Selden mast doesn't seem affected. It does appear like the Hood and Amel mast slots are noticeably wider than the Selden mast slot, perhaps that's why.

I've never heard in-mast furling masts making noise. The Selden ones are silent. Others I don't know about; in these parts the Selden system is pretty much universal.

[Dockhead]

Originally Posted by Markb250

There seems to be little discussion here about the substantial compromise to sailing performance that comes with the substantially compromised sail shape inherent in the in mast furler concept.
Just look at an in mast furler and a fully battened slab reef main sailing side by side, and ask yourself why you would want to completely stuff up the most important asset you have, when slab reefing just couldn't be any easier and reliable than what it is.

There was plenty of discussion about it. There is no doubt, that in-mast furling mains give up performance compared to roachy full batten ones.

However, there are a few nuances to the question.

First of all, not all in-mast furling mains are the same. The dacron ones with hollow leech are pretty awful. But a laminate in-mast furling main with vertical battens and straight luff is a whole nother thing. This gets pretty close to the performance of all but really roachy performance mainsails.

And in higher latitudes with a lot of wind (like where I sail), where you are often reefed, there are some advantages to in-mast furling mains. First of all, once you start reefing, the performance difference goes away. In-mast mains get flatter when you roll them in; they are very efficient when reefed compared to a normal one. Also you have so much control over sail area, that you are more likely to have the right amount of sail out, and that is good for performance. This also allows you to control sail area with the main and leave the headsail alone, which can be a BIG performance advantage. So in windy weather and higher latitudes I think I might prefer in-mast. I have raced my boat and I'm reasonably competitive.

But for moderate latitudes, especially for coastal sailing, I think I would prefer a nice roachy full batten main. I like to sail fast.

So each system has its own pluses and minuses, like in so many things connected to sailing.

[Dockhead]

Originally Posted by Rohan

There is still an outhaul, right? It just goes vertical instead of horizontal.

We call vertical outhauls "halyards"


Halyards will control your luff tension, but do nothing for foot tension or shape of the sail in that dimension.

[mglonnro]

Here's a video with some IMF challenges on a new Hanse 418. Elvstrøm sail, Seldén furler.

https://www.youtube.com/watch?v=ATP7roZXj_U&t=952s

[Muaddib1116]

That definitely is the biggest risk/fear with IMF, but he did a lot of things wrong. Aside from having a crazy boom angle and letting the sail flap around when furling, he indicates that at some point he accidentally released the halyard tension. What's also crazy to me, is that he turned into the wind to furl the main (this is something a few people in this thread have also mentioned doing). I don't know if that's wrong, per se, but it seems to me that it's much easier and you get a much tighter wrap, if you furl the sail with some wind in it to control it's shape and tension as it enters the slot. This is something I came to well before I even took ownership of my boat, after reading a lot about IMF. Even when furling a genoa, using the sheet to maintain some wind in the sail makes it easier to furl, compared to pointing up wind and letting the genoa flap about. It only ever seemed to make sense to point into the wind to reef/drop a slab reefed main. It even seems like it would be advantageous to have some wind in the sail when furling an IBF sail, but I don't know enough about that.

This makes me really glad that my boat came with a batten-less mainsail as my first IMF system. It is surely much more forgiving. Perhaps after a few years of experience, when it's time to replace my main, I'll go for a vertically battened laminated main. Perhaps not.

[Hoodsail]

Somewhat still on topic - with in mast furling do you still carrry a try-sail for heavy weather? Or is it redundant given the ability to shorten sail into the mast? Thinking to qualify for offshore races, Newport to Bermuda or Marion to Bermuda. thnks

[rslifkin]

Originally Posted by Hoodsail

Somewhat still on topic - with in mast furling do you still carrry a try-sail for heavy weather? Or is it redundant given the ability to shorten sail into the mast? Thinking to qualify for offshore races, Newport to Bermuda or Marion to Bermuda. thnks

You'd only need to if you're worried about the strength of the mainsail material. With IMF, you don't have defined reef points, you just keep rolling up more sail until you've decided it's small enough.