Swept spreaders and mainsail shape

[dustoff]

I have a question if it is normal for the swept spreaders on my M to often disrupt a perfect mainsail shape.
I still have my original stock sails, which are now 5 years old. I've used them an average amount in that time, and very few times in winds over 15 kts. I believe I've maintained the main well, folding it up in the cover when stowed.
I've added sail sliders to the main, the BWY stack-pack lazy jack system, and an outhaul block with cam cleat.

What I've noticed is that on any wind position more aft than a close reach, the mainsail drafts out to the point that the spreader bar touches it, and starts to interfere with the shape at that point. I can't remember if it's always done this from day one, but certainly for at least the last few years.

I've cranked down on the main halyard and the outhaul as much as I can. I also have tried to crank down on the boom vang when on a beam or broad reach or running.

My sailing performance is still good. I can regularly get my boat speed to 50% of ground wind velocity in all but close hauled.

Is this normal, or is my main blown out?

[kadet]

Swept spreaders will always interfere with the main on a run. The original Doyle factory main was rubbish and would be blow out after one or two seasons in anything over 10 knots.

So to answer your question yes they are probably blown in the belly but if it is still working use it until it falls apart or keep as a spare.

[sailboatmike]

Depending on cost you could always get the original recut to take out the stretch, you would need to get a quote from a sail maker to see if thats worth doing.

Reading the BWY web site, they recon the originals are good for 5 years at best

[dlandersson]

I'm impressed. My best is about 40% of wind speed.

IMy sailing performance is still good. I can regularly get my boat speed to 50% of ground wind velocity in all but close hauled.

Is this normal, or is my main blown out?

[dustoff]

Thanks guys,
that's what I figured. I guess the stretch in the main has been gradual, so I didn't really notice it until this year.
I guess I'll add a new main to the top of the wish list for this offseason.
As far as the 50% goes, I would have to add that it takes a lot of trimming, effort, and concentration, and winds over 8kts to do it consistently.

Dustoff,

[Judy B]

I have a question if it is normal for the swept spreaders on my M to often disrupt a perfect mainsail shape.
I still have my original stock sails, which are now 5 years old. I've used them an average amount in that time, and very few times in winds over 15 kts. I believe I've maintained the main well, folding it up in the cover when stowed.
I've added sail sliders to the main, the BWY stack-pack lazy jack system, and an outhaul block with cam cleat.

What I've noticed is that on any wind position more aft than a close reach, the mainsail drafts out to the point that the spreader bar touches it, and starts to interfere with the shape at that point. I can't remember if it's always done this from day one, but certainly for at least the last few years.

I've cranked down on the main halyard and the outhaul as much as I can. I also have tried to crank down on the boom vang when on a beam or broad reach or running.

My sailing performance is still good. I can regularly get my boat speed to 50% of ground wind velocity in all but close hauled.

Is this normal, or is my main blown out?

If you can post a picture taken looking up from underneath the boom looking up, showing the top of the sail and from luff to leech, I can tell you definitively what shape your mainsail is in. And if it's being trimmed correctly (See the examples below)

The spreader shouldn't be hitting the mainsail on a beam reach to the true wind. If I recall correctly, the 26x spreaders are swept aft about 25-30 deegrees (which is a lot compared to other brands), so I'd expect the main to hit the spreader a bit on a broad reach. But not a beam reach.

One thing to check before you replace the mainsail:Maybe the boom is rising up so far that the upper section of the main is falling/twisting off to leeward excessively? The upper batten should be parallel to the boom in moderate winds (4-15 kts), when properly trimmed. If the boom is allowed to rise up too high, the leech will loose tension and twist off to leeward too much, putting the mainsail onto the spreaders. To reduce leech twist when you sail lower angles, use the vang.

People have a tendency to let the main out more when it's baggy, because they are getting overpowered. If that's the case, it's time to replace it, for sure.

Fair winds,
Judy B
Hyde Sails Direct.

Below: This is what a blown out 26M mainsail looks like. There are 3 obvious problems with the sail:

1) Notice how deep the draft is! Draw a line from the luff to the leech and look at the curve between the two points. The draft on this sail is nearly twice as deep as it should be.
2) Notice how sharp curve is at the luff, near the mast. It's got a "knuckle in it. Maybe the skipper could have eased the halyard tension a bit to reduce the knuckle at the luff but this sail is so elastic-bandy that it's going to change shape drastically with every slight change in wind strength.
3) Notice how "rounded" the back half of the sail is. It should be flat from the middle to the back edge. This sail is using half the power it develops to heel rather than go forward! Ugh. It's going to heel alot, so you will need to turn the rudder too much to go straight, and round up with no warning

This boat will heel a lot, round up unexpectely, won't point, won't tack easily, be slow.... ugh....

Unfortunately, as a sailmaker, I get to sail on boats like this occassionally ... and even I can't get them to point, tack or stay flat. I wouldn't even keep this sail as a spare because sails like this, IMO, aren't good for anything except sailing downwind in light winds.

Click the picture to see an enlargment


Below: Here are a few pics, showing what a well-designed Mac 26x mainsail (from Hyde Sails Direct, of course!) looks like. Notice the masthead windex.
.
Based on the masthead windex, this boat is on a beam reach or lower.
Click the picture to see an enlargment

.
.
.
BAsed on the masthead windex, this boat is in pointing mode -- and doing very well!!!
Click the picture to see an enlargment

[dustoff]

Thanks Judy
I was out this weekend, and made some observations, but I forgot to take some pics. But based on what I saw, my mainsail looks exactly like the blown out M sail in your picture.
Also, all the symptoms you are describing are also affecting my sailing performance. Probably my biggest problem is that the boat makes quick and uncomfortable(to my crew) heeling motions when hit by gusts, and the only way to reduce the overpowering effect is to let out the mainsheet. I'm pretty confident that my trimming process is getting the best I can out of what I have, as I've taken a couple of sailing courses, and have acted as crew on several other boats.
In order to keep my crew from mutiny, I have to put in at least one reef, and constantly be ready to let out the main to counteract the gusts, even in winds as light as 10-12 knots. This, of course, takes a lot of the fun out of sailing for both them and me, as I'm always inclined to try to get the most out of the available wind. (at least until I reach the 6kt hull speed of the M)
I would add that my Genoa is probably blown too. I have to keep it reefed to about 2/3rds (with the clew about at jib length) even with the genoa blocks all the way aft, to keep it from creating a really twitchy and almost overpowering weather helm.
Thanks very much for the post, and I'm sure I'll be talking to you this off-season about some sails.
v/r
Dustoff

[Tomfoolery]

Below: Here are a few pics, showing what a well-designed Mac 26x mainsail (from Hyde Sails Direct, of course!) looks like. Notice the masthead windex.
.
Based on the masthead windex, this boat is on a beam reach or lower.
Click the picture to see an enlargment

I recognize that sail. It and its matching genoa partner were kicking our collective butts a couple of years ago.

Of course, it didn't help that mine look like the first picture.

[bobbob]

I have a CDI Main Furler on my , and there is no doubt in my mind the sail is blown out. However, because the sail is loose footed and cannot have horizontal battens, I am not sure how much a new sail will really benefit me. I'm getting close to 40% efficiency in stronger winds (10-12 knots) but in lighter winds I'll barely break 2 knots SOG.

I have seen pictures of sails with vertical battens but I have no idea if they are compatible with the CDI Main Furler. I love the convenience of the further too much to give it up though

Any thoughts?

[bobflshmn]

Thanks Judy B that was the best example and explanation I have ever seen. I will be putting this to action this weekend to check my sail trimming, and boat handling .

[Judy B]

I have a CDI Main Furler on my , and there is no doubt in my mind the sail is blown out. However, because the sail is loose footed and cannot have horizontal battens, I am not sure how much a new sail will really benefit me. I'm getting close to 40% efficiency in stronger winds (10-12 knots) but in lighter winds I'll barely break 2 knots SOG.

I have seen pictures of sails with vertical battens but I have no idea if they are compatible with the CDI Main Furler. I love the convenience of the further too much to give it up though

Any thoughts?

I've done vertical battens on furling mainsails before for various furling masts, but never one for a CDI mast furler.

I don't see any reason why we can't do it for a CDI, except that the manufacturer doesn't have any gulde for the sailmaker, the way other furling mast makers do. The plastic extrusion will deflect when you power the mainsail up, and that leading edge of the mainsail will be unlike any other mainsail furling system out there. I suspect the luff curve would have to be hollow, because the CDI extrusion would bend the opposite way a mast would be bent.

Figuring out how much the extrusion flexes under load is critical for getting the luff curve right. Getting you to measure the "reverse bend" fairly accurately would be key to getting a good flying shape. If there is too much cloth on the luff, the draft of the sail will be too deep and may have a "knuckle" (deep curve) very close to the mast. That would be bad.

I estimate that it would require several hours of extra design work and measuring to be sure the flying shape of the mainsail on a CDI furler would be right.

[bobbob]

Thanks Judy. here's a pic that illustrates what your talking about I think (as well as the spreader impacting the sail)



I'm always wondering what the effect is of the sail foot curving horizontally (as opposed to a sail that was footed by the boom and therefore held straight). It seems to me vertical battens would do nothing to correct this?

[grady]

Thanks Judy. here's a pic that illustrates what your talking about I think:

Ewwwwwwww!

[sailboatmike]

OK, I will bite, isnt that a genoa or jib that someone is using as a main???

Notice the UV strips on the foot and leech and no sail slugs or for that matter bolt ropes into the sail slot on the mast, its just held at the head and the tack.

Someone has got it VERY wrong here

[Judy B]

Thanks Judy. here's a pic that illustrates what your talking about I think (as well as the spreader impacting the sail)



I'm always wondering what the effect is of the sail foot curving horizontally (as opposed to a sail that was footed by the boom and therefore held straight). It seems to me vertical battens would do nothing to correct this?

There's a big problem with the way the CDI extrusion is sagging away from the mast.
Looks to me like the luff is sagging more than a foot away from the back face of the mast. That's a huge distortion in the shape of the sail. That's most of the reason the sail is rubbing on the spreader.

There's not much anyone can do to improve mainsail shape until you eliminate the all (or most of) the sagging.
Sorry, but I don't have a clue how to fix how the CDI mainsail furler is operating.

Judy B