Lots of "weather helm"?

[davesisk]

Did a few hours of sailing on the Cape Fear river today! The wind was blowing around 15-20 knots I believe, with some occasional gusts of more. I probably averaged about 4 knots up the river (presumably against the current), and hit 7.5 knots a few times on the way back (presumably with the current).

Now, maybe something on mine isn't quite "tuned" right (or maybe it's the operator! ) but sure seems like the 26X has a LOT of weather helm (ie. when the wind blows hard and the boat heels hard, it automagically points itself into the wind). A small daysailor passed me easily because I kept turning into the wind unintentionally. Now, this is not necessarily bad I think...for instance, in an accidental overboard at least the boat would point itself into the wind and stall. So, I think a little bit weather helm is probably good. Maybe it was designed to do this to keep us from getting too stupid?

The "weather helm" response seems to happen very quickly though...the boat heels hard, and next thing you know it has pointed itself into the wind. Steering against it to correct doesn't seem to have any effect either. It seems it happens a little too fast for comfort though...I could see accidentally hitting something that you didn't intend!

Is this just me, or do other folks get the same behavior?

Cheers,
Dave

[Hamin' X]

What you describe is the typical response to too much rake of the mast aft. It should be 2º - 4º aft.

~Rich

[davesisk]

Ah...too much rake meaning the angle aft is too much?

So, how do I adjust this? Let the backstay out some, of course. With the roller furler, I'm not sure how I'd shorten the front stay?

Dave

[bartmac]

This topic has been covered many times..... but I found even with the front stay as short as adjustment would allow...still not right....so moved the upper fitting on the mast up about 75mm /3" and now I have adjustability back and our Mac is much easier to keep in a straight line...so much so our autopilot even keeps up unless its a real blow.Of course the other stays will need adjusting!!!

[seahouse]

A brief summary...weather helm can be controlled in a number of ways. Reducing mast rake is one of them.

Excessive heeling causes weather helm (the resulting asymmetric hull shape in the water “plows” the boat sideways) so the same techniques you use to reduce heeling will also reduce weather helm (WH).

So to do that with an “X”, and to move the position of the forces to act more favourably on the boat, you can-- reef the main; flatten the main; increase mast bend; ease the mainsheets; use a larger headsail (say, go from jib to genoa); ease the headsail, tighten the boom vang; move weight (people) to the windward side and/or aft. Also on an “X”, you can swing the centreboard up part way to reduce weatherhelm.

These are the most obvious ones, I don't have an “X”, so other posters can fill in whatever I missed.

-Brian.

[mastreb]

Brian's recommendations all work. They move the center of effort forward, creating more lead which causes the boat to track straighter.

Think of CE (the midpoint of wind pressure) and CLR (the mid point of water pressure) as two points of rotation. Now consider rake on a bicycle, which also has two balanced pivot points, the handlebar stem and the center of the front wheel. The rake, or angle of the front forks, causes the center of wheel rotation to lead the center of handlebar rotation by a specific amount. Too little makes it too easy to pivot, and too much prevents easy. As with rake, there's a perfect lead for sailboats for the exact same reason: Too little makes rotation (weather helm) too easy, and too much causes the boat blown downwind because the rudder can't overcome the inertia created by the excessive lead. This is called Lee helm.

Too much lead will cause lee helm, which is both dangerous (far more likely to blow down) and lower performing than weather helm because it requires the rudder to be turned to downwind, which causes additional leeway.

An ideal balance for the Mac will have slight weather helm at 20 degrees heel, and increased weather helm as the boat heels further.

The closer the CE is to the CLR, the more the boat is likely to round up to the wind, because there's less lead preventing it. This is why raking the mast correctly moves the CE forward and balances the helm.

In the winds you're talking about (15..20 knots) you have enough wind to consider the points of effort on both the main and the jib separately. Reef your roller furling genoa until the heel is correct for the boat. You can think of this as pushing two separate centers of effort on both sides of the CLR, allowing you to precisely balance them both. You can either reef or dump the main a bit to move the aft CE forward, and then manage the roller furler to precisely balance the helm.

[Catigale]

...and 15-20 knots is too much for a genoa. Furled in, the shape will be lousy compared to a jib.

[davesisk]

Great post!

A brief summary...weather helm can be controlled in a number of ways. Reducing mast rake is one of them.

Excessive heeling causes weather helm (the resulting asymmetric hull shape in the water “plows” the boat sideways) so the same techniques you use to reduce heeling will also reduce weather helm (WH).

So to do that with an “X”, and to move the position of the forces to act more favourably on the boat, you can--


reef the main;

Understood. I'm not sure how to most easily do that on a 26X (climbing up on the cabin top in heavier winds with the boat tossing around isn't much fun), but I'll look for existing posts on it.

flatten the main;

How would you do this?

increase mast bend;

Which direction? How would you do this?

ease the mainsheets;

Did this...there was still WH with each gust that came along though.

use a larger headsail (say, go from jib to genoa);

I have a 150% genoa already, but it was too much wind to have that mostly unfurled. I prob had it about half furled most of the time. Q: Would I have been better off to maybe drop the main and just use the genoa? Just curious.

ease the headsail,

Did this, just short of it flapping.

tighten the boom vang;

How would this help?

move weight (people) to the windward side and/or aft.

It was just me this time, but definitely shifted my own weight to the other side.

Also on an “X”, you can swing the centreboard up part way to reduce weatherhelm.

Now that's an idea I didn't think of! That would shift the fulcrum that it wants to pivot around back a little...makes sense, I may try that next time.

These are the most obvious ones, I don't have an “X”, so other posters can fill in whatever I missed.

-Brian.

Cheers!
Dave

[DaveC426913]

Brian's recommendations all work. They move the center of effort forward, creating more lead which causes the boat to track straighter.

Think of CE (the midpoint of wind pressure) and CLR (the mid point of water pressure) as two points of rotation. Now consider rake on a bicycle, which also has two balanced pivot points, the handlebar stem and the center of the front wheel. The rake, or angle of the front forks, causes the center of wheel rotation to lead the center of handlebar rotation by a specific amount. Too little makes it too easy to pivot, and too much prevents easy. As with rake, there's a perfect lead for sailboats for the exact same reason: Too little makes rotation (weather helm) too easy, and too much causes the boat blown downwind because the rudder can't overcome the inertia created by the excessive lead. This is called Lee helm.

Too much lead will cause lee helm, which is both dangerous (far more likely to blow down) and lower performing than weather helm because it requires the rudder to be turned to downwind, which causes additional leeway.

An ideal balance for the Mac will have slight weather helm at 20 degrees heel, and increased weather helm as the boat heels further.

The closer the CE is to the CLR, the more the boat is likely to round up to the wind, because there's less lead preventing it. This is why raking the mast correctly moves the CE forward and balances the helm.

In the winds you're talking about (15..20 knots) you have enough wind to consider the points of effort on both the main and the jib separately. Reef your roller furling genoa until the heel is correct for the boat. You can think of this as pushing two separate centers of effort on both sides of the CLR, allowing you to precisely balance them both. You can either reef or dump the main a bit to move the aft CE forward, and then manage the roller furler to precisely balance the helm.

Thnaks masteb! This is the first time I've understood CLR and CE! The bike forks analogy is excellent!

[BOAT]

Weather helm on the M boat (well, on 'boat') does not happen until we exceed 30 degrees - if it is a real fast gust - hard, strong, it will indeed knock ANY boat into an upwind turn pretty fast. If your at 20 knot wind the boat is already right on the edge, and the slightest puff above that is gonna kick you over. On our old A23 we could make 25 to 30 knot winds but again, once your at the limit, anything will knock you into a turn. On the old A23 we would pull up the centerboard about half way. This made two things happen: The "pivot" point on which the boat turned moved to the rear and with less board in the water she tended to slide a bit and heel less.

Reefing the headsail on the M boat seems to just make things worse if it's a hard blow -

My take on the vang would be to loosen up the vang all the way or just remove it in a hard blow - the idea is to let the wind spill out of the main early.

Unfortunately, I have found on 'boat' that the only way to wrangle in the bucking bronco when the wind blows over 20 knots is to reef the main, or sail on the genny only, but what's the point of sailing on the genny only if it means you need to handle the main to get it down anyways!!??!! It's just another lesson learned - if your going to bother taking down the main, why not just reef it instead? It's the same amount of work.

I understand the feeling of not wanting to go forward to reef the main, and I too often forgo it in heavy wind if I'm on my way in and I only need to endure it for an hour or two. I will just let out the sails and take a more broad or beam tack to my destination, (which is slower). But, if your out there and you need to travel, the best bet is to reef the main. You need to get the wind off the top of the mast - you need to stop heeling over.

[DaveC426913]

I'll add: another way of reducing heel in fresh winds is to not have your bimini up!

I think I figured out why my boat rounds up every time a gust comes. I've got a 32ft sail on the stern that kicks in whenever the boat heels.

[vkmaynard]

Try this (vkmaynard 3rd post from top) http://www.macgregorsailors.com/forum/v ... loos+gauge

Worked great on our boat and several others we adjusted.

When we first sailed our X in heavy winds the boat would heel and vigorously round up in a large scooping maneuver due to the center of pressure pushing the aft end of the boat away from the wind and down into the water, creating a positive angle of attack on the centerboard causing further heeling. This was mainly due to too much rake angle on the mast. Now no problems; the boat just heels.

Victor

[EZ]

On reefing the main in heavy weather...

I usually just 'heave to' which puts the boat in a semi-stationary position. Semi-stationary b/c the boat drifts slightly at 45 degrees. But this keeps the boat position stable enough that you can go up on deck and lower the main. It also puts some heal on the boat so it is less tender against waves.

http://en.wikipedia.org/wiki/Heaving_to

[Johnacuda]

Yesterday, was a little erratic. I was beating into the a 10-15kt. wind and after a few minutes on a tack, the boat would develop a lot of lee-helm and heel heavily. I kept flattening the sails, and letting them out and luff to depower even though I wasn't making much speed, 2.5 maybe 3 kts. It turns out I'd left the ballast gate open, and the longer I'd be on a tack (port was worse) the more ballast I'd drain. Luffing off, would level the boat enough to start filling again.

Standard op is to leave the dock with a full ballast tank, but I had been powering to clear some debris (and the centerboard) from the centerboard trunk. I opened the gate to fill the tank while I was preparing to raise sail and forgot to close it. It took me an hour or so to figure out what I'd forgotten. Luckily, the consequences were limited to poor performance. Check everything ,and start simple when things are not working as expected.

[WASP18]

Suggest you type up a checklist, get it laminated at Staples for $1.00, punch a hole in the plastic and attach it to your console using a large twist-tie. It's so easy to forget something especially when you become briefly distracted.