Extra large roach mainsail

klubko · #1 11-11-2010

Hello,
we are thinking about extra large roach (overlapping the backstay) mainsail to expand our sail area (not that it would be bad now).
I want this for a our 31' HR Monsun.
My main sources of information about these sails are two: Cruising Encyclopedia by S. Dashew and a cruiser we met in Malaysia, who had such a sail himself.
I've previously asked for comments here and here and here.
I am wondering if there are people who could share their experience with such a sail on a monohull with fixed backstay.
Many thanks

BubbleheadMd · #2 11-11-2010

I've done it. My main is about 9 months old, and just barely twangs the backstay on it's way by. I've noticed no wear patterns on the sail where it touches. Is that what you're concerned about?

As you commented on one of the other forums, the sail is bent enough in a breeze, that it doesn't actually touch the backstay. Mine only touches when the breeze is too light to bend the batten. In that case, I just hop on the transom and and "snap" the backstay and the sail slips through.

I did not require roller bearing cars, but my boat is only 25' so the sail is smaller than yours would be.

Unfortunately, I cannot provide you with any data on performance vs. the regular main because my original main was 40 years old, blown-out and very tired. I didn't sail with it long enough to make a valid comparison. The main is powerful, and I suspect that I'm reefing a bit earlier than with the normal main to reduce weather helm, but the reefed shape is wonderful and I get great speed and balance out of it with my 100% jib.

I guess the bottom line is: Don't make the extra roach so big that it's slapping the backstay, even in a breeze or you WILL experience chafe and that'll be expensive later on.

I'm not a sailmaker, and I didn't stay at a Holiday Inn Express last night, so my opinion is worth exactly what you paid for it.

capecodda · #3 11-11-2010

I'm wondering what this does to balance.

On a lot of new boats, designers are opting for smaller jibs (often fractional) and bigger large roached mains. Amongst the arguments for this, at least for cruisers is the ease of tacking a smaller jib. On many of these boats, the mast is located further forward so that the center of effort remains correctly placed for the "right" amount of weather helm.

I'm wondering if you add a bigger large roached main, effectively expanding the area of your main sail and particularly the aft most part of your main sail, what do you do to balance? Wouldn't this increase weather helm? Would you counter this with a bigger Genoa?

capecodda · #4 11-11-2010

Oh, and I didn't stay in the same place as BubbleheadMD, also not a sailmaker, and likely have no idea what I'm talking about.

BubbleheadMd · #5 11-11-2010

Well, as I said, I don't really have good comparative data because I barely used my original main, but I don't get bad weather helm until about 20kts, and by then, I'm reefing anyway. I don't like to reduce weather helm by easing the main way out in high winds, because it flogs.

You mentioned newer boats, mine's 42 years old, so not a high aspect main. I'm also a full forestay, not fractional.

It's probably safe to assume that more cloth on the main, moves the center of effort aft, which would increase weather helm, but it's probably not drastic. I'm guessing that I step down to my smaller jib a bit sooner, and reefing a bit earlier than I would with a normal cut main.

tommays · #6 11-11-2010

Are biggest race main on the 35' (1970) boat is a PITA to tack in light air

Is it faster

Yes a bit

Is it worth it in anything other than a serious race effort

NO

Sailormon6 · #7 11-11-2010

I bought a North dacron racing mainsail with a big roach (and with partial battens) in 1981, and used it for 22 years, and, at first it was a minor pita when I tacked, until the fabric softened a bit. After the first or second season, it stopped hanging up on the backstay when I tacked. After the first two seasons, it was as easy to use as a standard cut mainsail, but it was considerably faster. I liked it, won a lot of races with it, and would recommend it to anyone except perhaps a long distance cruiser. After 22 years, mine ripped in high winds, and I decided to replace it rather than repair it. Chafe didn't seem to be a problem with my sail. A bigger, more powerful mainsail improves a boat's performance in lighter air by increasing speed, and consequently by improving pointing ability. As the windspeed increases, it can be reshaped accordingly. A big roach doesn't move the center of effort so much that it can't be balanced out by rig tuning.

klubko · #8 11-11-2010

Thanks guys (again, if you have already replied to the same at the different forum). We will probably go for a little overlap, but try not to go too far over. Hopefully, backstay protection and extra chafe patches on the battens will protect the leech. I am also hoping for a 1st reef that would still provide lots of sail area and allow tacks that would clear the backstay all together even in light air.
to capecodda: the theory (and it's seem to be supported by experience of several people -- but not all) is that more sail area at the top of the sail actually reduces both heel and weather helm, because it reduces drag and provides more lift. From what I gathered so far, the effect seems to be more prominent on lower aspect rigs.

JimsCAL · #9 11-11-2010

i assume you are going with one or two full-length battens to support the extended roach. Went with one on the club race main I bought from North 10 years ago.

Hudsonian · #10 11-11-2010

The standard roach on my boat overlaps the backstay. To keep the roach from hanging up when tacking I installed two rollers on the backstay where the mainsail meets the backstay. This has worked well.