Troubleshooting a rounding-up problem

[DaveC426913]

Is adding a Cunningham a helpful mod? Does that extra two inches or so of hardening the luff help?

Reading suggests it help to flatten the sail in breezy conditions. I suppose that would be good, since I'm often over-powered. The harbour I sail on has some wind tunnels. It can vary between 0 knots and 10 knots over the space of a mile. Short of going out reefed, it's hard to depower the sails when I get in one of those slots. (Cuurrently, I have to completely flog the main to recover from these gusts.)



Is it a feasible mod with the slug/slot/lock system of an ?
I guess as long as the lowermost slug is above the slot lock by a few inches, the cunningham should able to do its job, right?


And now that I think of it, will a cunningham interfere with me being able to flog the main in an instant when I need to?

[Be Free]

I can't see any harm in a Cunningham on an X but I don't see a whole lot of benefit either.

Do you have any wrinkles in your luff now? If it's already tight then a Cunningham will not have much effect.

You should not have to make any extraordinary adjustments to the main (like allowing it to flog) to safely and comfortably sail in a 10 knot wind. That is pretty much the "sweet spot" for an X.

Are there other issues with the main that need to be addressed?

[DaveC426913]

Do you have any wrinkles in your luff now? If it's already tight then a Cunningham will not have much effect.

Not a lot. I can usually get the halyard al the the way up.

You should not have to make any extraordinary adjustments to the main (like allowing it to flog) to safely and comfortably sail in a 10 knot wind. That is pretty much the "sweet spot" for an X.

A 10 knot wind will invariably cause SeaSaw to round up on a close reach or close haul. (Yes, I have my ballast in and blades down.) Often, I can luff it a little and it's OK, but sometimes I have no choice but to flog it or I just round up. This can happen even when reefed. OK< thi might be more of a 15+ knot apparent wind. I do fly a 150 genoa, though if it's really blowing I'll furl that to 50% or 30%.

It's also possible I am dreadful at knowing my wind speeds. It's my estimation that whitecaps start to appear above 9 knots, so if I see enough of them, I assume I'm in a 10-knot wind. (And, of course, 10-knot true wind will be a 14-15 knot apparent wind on a close haul).

Next to my depth-sounder, an accurate wind speed indicator is my next most desired piece of nav equipment. I have never had much luck with hand-held wind-meters. I wonder if there is a less expensive wind-meter option. Something that I could mount on the bimini, say. (Maybe I should just get a windsock...)

Are there other issues with the main that need to be addressed?

Quite possibly. I just bought a new main sail. It's used but still in great condition. It was still very 'crinkly'. If there's any 'issues' with it, they be at the bitter end of the main sheet, operating the steering wheel.

I do wonder if my skillset has gaps. I've been sailing for at least 15 years, and I did take Beginner and Intermediate Sailing courses (on a Beneteau 38) and raced on 32' cruisers for two years. But these"real" sailboats aren't the best at learning what works on a Mac. (For example, when you point a sailboat on a heading, it tends to stay pointing on that heading longer than three seconds ... )

[PSNA]

There may be a little confusion here between a downhaul and cunningham.

A cunningham attaches to the sail and changes its actual shape to increase performance. A downhaul attaches to the spar and applies a downward force to the boom. You will also find downhaul's on poled spinnakers and jibs.

[Be Free]

If you don't have slack in the luff then the Cunningham will be of limited (or no) use.

For the purists, I'm not going to use the technical terms for the forces involved. I'm going to describe this in terms of how the forces work together (or in opposition).

Taking your other points in order:

If you are rounding up in a 10 knot wind then something is wrong. In 10 knots you should be able to sail for extended periods with about a 10-15 degree heel without touching the wheel.

The wind hitting the main is going to turn the boat to windward (round up). The wind hitting the jib is going to turn the boat to lee. When those forces are balanced (or maybe just little bit in favor of the main), then everything is right in the world.

Since you have a furling fore sail I'd suspect that you are making it too small and the main is overpowering it. Sailing upwind in 10 knots you need at least 100% fore sail if your main is not reefed.

Another possibility is that your mast is raked too far aft. This will increase the force that the main contributes by giving it a longer "lever" to push with.

You will see the beginnings of white caps around 10 knots but keep in mind that on the Beufort scale 10 knots is still described as "gentle breeze".

If you are seeing a lot of white caps then you may be in the upper teens. That would call for 100% fore sail (maybe a bit less) and the first reef on your main.

Remember, it is a balancing act. The main and the fore sail need to be balanced to keep from rounding up (or down). The main and the wind need to be balanced to keep the heel at an efficient point.

It is true that 10 knots true may be 14-15 knots apparent, but not until you have the boat moving 4-5 knots to windward.

You wind speed should be measured at the top of the mast. Anywhere else you will get turbulence and inaccurate readings.

The main reason that the boats in your sailing course kept going in the same direction was because their sail plans were balanced (and they were much heavier with longer keels so they were less sensitive to an imbalance).

You have an imbalance in your sail plan and we're going to find it.

Questions to follow...

[Be Free]

Dave,
I'm going to ignore the actual wind speed for now and just concentrate on the reaction of your boat to the wind.

Assumptions: Full ballast, all boards down, boat (mostly) sits on her lines at rest (level for-aft and port-starboard), rounding up occurs on both port and starboard tacks under similar conditions.

When you round up:

How much is the boat heeling? (Measured or estimated?)

How much main do you have up?

How much fore sail do you have out?

[Jimmyt]

I’ll second the “mast rake” comment.

Also, balancing the sail plan is excellent advice. In combination with sail trim, you should be able to get the helm almost neutral (where you apply very little pressure on the wheel to hold your course).

The comment that your boat won’t sail straight for more than a few seconds is a symptom that can be caused by either of the above concerns.

The problem could be either, or a combination of both.

Anxious to see the responses to the questions posted above.

Agree that a Cunningham is not the answer to this problem..

[DaveC426913]

If you don't have slack in the luff then the Cunningham will be of limited (or no) use.

Good to know. It was just an idea. I have much bigger fish to fry.

If you are rounding up in a 10 knot wind then something is wrong. In 10 knots you should be able to sail for extended periods with about a 10-15 degree heel without touching the wheel.

Alas, since I do not have a quick disconnect on my Honda BF50, there are precious few circumstances where I don't need to have a hand on the wheel.

The wind hitting the main is going to turn the boat to windward (round up). The wind hitting the jib is going to turn the boat to lee. When those forces are balanced (or maybe just little bit in favor of the main), then everything is right in the world.

Yes. It is the main that's pushing me over. This doesn't happen until I get up to 4 or 5 knots on a haul. As I pick up speed, the boat heels more and more and I have to turn the wheel to keel from rounding up. Under the right conditions, I can manage to keep it on a 30+ degree heel if am quick on the mainsheet and on the wheel.

Since you have a furling fore sail I'd suspect that you are making it too small and the main is overpowering it.

No. Reefing the main is always before furling the genny. I only really furl the genny if the wind is so high that I'm overpowered. Maybe upwards of 15 knots.

I have never been in a circumstance where the genny gets furled while the main is full.

Another possibility is that your mast is raked too far aft. This will increase the force that the main contributes by giving it a longer "lever" to push with.

This is very possible. I've never really understood the opertational consequences of a raked mast. I tried to measure it once - took apic and used Photoshop, and it seemed to be about 4 degrees, so I moved on. Of course, it likely changes every year when I step the mast. Attaching the forestay is by far the most back-breaking step on my boat. (Partly because that 150 genny weighs so much.) I have spent a lot of time and energy trying to figure out ways to ge the forestay that laaaaasst inch to the tang. I have no idea how correct rake could be anything but a lucky shot.

You will see the beginnings of white caps around 10 knots but keep in mind that on the Beufort scale 10 knots is still described as "gentle breeze". If you are seeing a lot of white caps then you may be in the upper teens.

Sounds right to me.

That would call for 100% fore sail (maybe a bit less) and the first reef on your main.

Again, I rarely need to pull in the genny unless it's a gale.

Remember, it is a balancing act. The main and the fore sail need to be balanced to keep from rounding up (or down). The main and the wind need to be balanced to keep the heel at an efficient point.

Never come even close to rounding down.

You wind speed should be measured at the top of the mast. Anywhere else you will get turbulence and inaccurate readings.

Yes but it may still be better than nothing at all. Knowing me, I will use it until I get good at knowing wind speeds by feel and then I'll go with my gut. But till then, I could be way off, for all I know.

The main reason that the boats in your sailing course kept going in the same direction was because their sail plans were balanced

I suppose that makes sense.

(and they were much heavier with longer keels so they were less sensitive to an imbalance).

Definitely.

[DaveC426913]

When you round up:
How much is the boat heeling? (Measured or estimated?)

It tends to build as I pick up speed. Maybe 25-30 degrees, and then I reach a tipping point where no amount of steering will stop from rounding up unless I am super quick on the main.

So what happens is I do this kind of scalloping path: Pick up speed, heel, start rounding up, ease or flog the main, drop back, rinse repeat. My top speed is severely limited by the imminent rounding up just when I'm getting up a good steam o' steam.

I have had it over at 35 and stable (at least for a short time) - so I know it can be done - but that was a long time ago.

[DaveC426913]

Oh and before anyone asks: yes, my aft stay is loose.

I’ll second the “mast rake” comment.

I'll take a pic next time I'm down at the dock.

Also, balancing the sail plan is excellent advice. In combination with sail trim, you should be able to get the helm almost neutral (where you apply very little pressure on the wheel to hold your course).

If excessive mast rake causes too much power in the main, then that will be great, because I can fix that. I don't want to have to reef habitually just to keep from rounding up!

Agree that a Cunningham is not the answer to this problem..

No, that's wasn't the intent. But it opened this rounding up can-o-worms, so this is good.

[DaveC426913]

Because we don't have enough irons in the fire, I'll add another one or two that might or might not be part of my problem.

How do I know when my jib luff is too curved? In a good wind the centrepoint of my jib luff can be a foot and a half or more from centre line.

I've tried to harden my shrouds but I never found any specs for proper tension. I'll check next time I go out if my leeward shrouds go slack.

[Be Free]

If you are heeled 25-30 (or more) degrees then you should expect to have to work to keep the boat from rounding up. Your windward rudder will be almost out of the water and the lee rudder will have reduced efficiency. With practice you can you can do it but it is not an efficient way to sail.

If you don't have to fight to keep from rounding up with no more than 20 degrees heel then your sails are pretty close to balanced.

For reference, running between a close haul and a close reach (a very good point of sail for an X going upwind), you should expect to see about 15 degrees of heel in a 10 knot wind and about 20 degrees at 15 knots. Above 15 knots you will (probably) need to reef your main to stay under 20 degrees of heel.

Above 20 degrees of heel you are wasting wind, increasing your wetted area, and decreasing the efficiency of all of your foils (boards). I'm not saying it's not fun (occasionally) but it is not efficient. The sweet spot for an X is around 15 to 20 degrees of heel.

Since you asked, I'm going to get a little technical to explain why too much mast rake makes the boat more likely to round up.

If you combine all of the forces acting on the hull of the boat (the shape of the hull, the rudders, and the keel) you will find that they will average out to a theoretical point under the boat called the Center of Lateral Resistance (CLR). This will usually be somewhere in the aft part of the keel and it does not change significantly no matter how you sail.

If you do the same for all of the forces above the water (mostly the sails), you end up with another theoretical point called the Center of Effort. On our boats that point is ideally a little aft of the mast, in the lower portion of the main. Changes in the sails (size, or position) regularly change the location of the CE.

When the CE is directly over the CLR, all is right in the world and the boat will keep going in the same direction without you having to steer it.

If the CE is in front of the CLR, you have lee helm and will tend to round down.

If the CE is aft of the CLR you will have weather helm and tend to round up.

Too much mast rake moves the main (and the CE) closer to the stern which puts it behind the CLR resulting in a tendency to round up.

[Be Free]

I forgot to mention...
I have a BF40 which is exactly the same weight as the BF50. I have (but very seldom use) a quick disconnect. The engine does not appreciably interfere with steering or holding a course.

[NiceAft]

The engine does not appreciably interfere with steering or holding a course

.
Ditto with my Honda DF50.

[DaveC426913]

Since you asked, I'm going to get a little technical to explain why too much mast rake makes the boat more likely to round up.

If you combine all of the forces acting on the hull of the boat (the shape of the hull, the rudders, and the keel) you will find that they will average out to a theoretical point under the boat called the Center of Lateral Resistance (CLR). This will usually be somewhere in the aft part of the keel and it does not change significantly no matter how you sail.

If you do the same for all of the forces above the water (mostly the sails), you end up with another theoretical point called the Center of Effort. On our boats that point is ideally a little aft of the mast, in the lower portion of the main. Changes in the sails (size, or position) regularly change the location of the CE.

When the CE is directly over the CLR, all is right in the world and the boat will keep going in the same direction without you having to steer it.

If the CE is in front of the CLR, you have lee helm and will tend to round down.

If the CE is aft of the CLR you will have weather helm and tend to round up.

Too much mast rake moves the main (and the CE) closer to the stern which puts it behind the CLR resulting in a tendency to round up.

Ah! Got it now. I have read about CE and CLR, but yours was the most informative and succinct explanation I've read. Until now, I never really thought about separating them into 'the forces below the waterline' and 'the forces above the waterline'.

And now I understand mast rake too. In a simplistic nutshell, more rake literally moves the bulk of the main sail aft, giving it a longer moment arm.

Why couldn't they all have just said that, like you did!