Paradoxical Lee Helm Puzzle

[Ex-Calif]

So basically where do you think the wind is coming from?

I agree that he is at great risk of an accidental and uncontrolled gybe. I don't see anyone tending the main...

[cal40john]

Originally Posted by Ex-Calif

CalJohn - I corrected the boom position in my post (turned myself around for a minute).

However this isn't a colregs exercise.

This boat is on starboard tack and the wind is coming from the port quarter.

Skipper needs to steer to starboard - #1 rule, stay under the spinnaker - if anything he is rounding up - down in this case is towards the spinnaker.

Everyone I've ever sailed or raced with does not switch which direction is heading up everytime you're by the lee. This would be very confusing, the wind indicator momentarily indicates you're by the lee and people shout at the helmsman head down? I think most people are going to determine which way is heading up based on which side of the boat the sails are set on, even if by the lee. So I would tell the skipper to head up, in this case to starboard and in reality more downwind.

John

[Ex-Calif]

Originally Posted by cal40john

Everyone I've ever sailed or raced with does not switch which direction is heading up everytime you're by the lee. This would be very confusing, the wind indicator momentarily indicates you're by the lee and people shout at the helmsman head down? I think most people are going to determine which way is heading up based on which side of the boat the sails are set on, even if by the lee. So I would tell the skipper to head up, in this case to starboard and in reality more downwind.

John

Everyone is gonna see what they see I guess...

I will say that contrary to what you posted I have never heard anyone in the position photographed say "head up"

"Go downwind" seems pretty clear...

[cal40john]

Originally Posted by Ex-Calif

Everyone is gonna see what they see I guess...

I will say that contrary to what you posted I have never heard anyone in the position photographed say "head up"

"Go downwind" seems pretty clear...

I don't think we're "seeing" things differently, it's a matter of convention. As long as everyone on your boat knows that if you're by the lee and you say head up it means you're going to jibe all's good. The people I've sailed with use a different convention.

JOhn

[Ex-Calif]

Originally Posted by cal40john

I don't think we're "seeing" things differently, it's a matter of convention. As long as everyone on your boat knows that if you're by the lee and you say head up it means you're going to jibe all's good. The people I've sailed with use a different convention.

JOhn

Sorry John - The "everyone's gonna see" comment is a boring, pedantic and incomplete thought around whether this is a "momentary" situation or if they have been sailing by the lee - not important.

If I gave a command to turn to port on my boat it would likely be "gybe-ho" although in this case clearly no one is ready - LOL...

I'm still wondering if there must be someone hidden by the skipper tending the spin sheet. And who might be tending the main - I tracked down the picture based on it's filename to a blogger site but couldn't find any story about this picture - oh well...

[savoir]

Originally Posted by Andrew Troup

Anyone else care to come up with an alternative explanation, or to toss around ideas on the ones already suggested?

The boat doesn't have enough power meaning the keel can't do its thing leaving the bow at the mercy of the waves so it is pushed down.

[markpierce]

Originally Posted by Ex-Calif

A simpler explanation perhaps - We can all agree basic spinnaker handling is pole square to the wind and boom square to the wind.

No, if the mainsail boom is square (perpendicular) to the wind going down wind, the top of a cloth sail will "fall off," spilling wind or even wrapped over the stays.

[gjordan]

What I see in post 5 looks like a normal summer afternoon on San Francisco Bay. Probably just before the Death Roll. I wonder if the gooseneck (or rig) will survive the gybe that might come along? Lots of fun!____Grant.

[delmarrey]

Then conditions deteriorate further. The wind picks up.
A killer gust comes through. The wind strength is enough that you're no longer fighting to stop the boat rounding up, in fact (still on the same heading relative to the wind) it's all you can do to stop it bearing away.

W/o reading all these replies I'm thinking you heeled over far enough that your rudder was mostly out of the water and had very little steering.

[markpierce]

Originally Posted by gjordan

What I see in post 5 looks like a normal summer afternoon on San Francisco Bay. Probably just before the Death Roll. I wonder if the gooseneck (or rig) will survive the gybe that might come along? Lots of fun!____Grant.

Not normal, but done that there (speaking as a fellow on the foredeck.)

[savoir]

Originally Posted by delmarrey

W/o reading all these replies I'm thinking you heeled over far enough that your rudder was mostly out of the water and had very little steering.

Could well be right but if it was the result would be a roundup.

[Ex-Calif]

Originally Posted by markpierce

No, if the mainsail boom is square (perpendicular) to the wind going down wind, the top of a cloth sail will "fall off," spilling wind or even wrapped over the stays.

Point taken. I did say basic to illustate that the boom and pole in the photo are nowhere near correct.

WhT's funny about this place is if I had started with, "that is perfect downwind sailing" everyone would get on the other side of the argument just for sport.

Call it how you want. No new sailor should think that boat is in good shape.

They should seriously be stering to starboard.

All the rest is just a pissing contest.

[Bash]

Originally Posted by Andrew Troup

There's a bit of a tendency to round up – as you'd expect – but it's not unmanageable if you feather the sail, in a measured way, in the puffs.

I'm sorry, but this doesn't make any sense. Any tendency to round up is caused by weather helm, not lee helm. Lee helm is the tendency of a boat to turn away from the wind. This is caused when the center of effort moves ahead of the center of resistance. A solo storm jib might cause lee helm, but a solo triple-reefed main would cause weather helm.

The only way you'd get lee helm from the sails in the OP's scenario would be if a genoa was furled on the headstay and the wind resistance on the furled sail overcame the main's effort, if for example the main was completely luffing during the gust. Was this the case? If not, what am I missing in this little brain teaser?

[Andrew Troup]

Original post excerpt:

"You're close reaching in strong conditions....There's a bit of a tendency to round up – as you'd expect – but it's not unmanageable if you feather the sail... "

Originally Posted by Bash

I'm sorry, but this doesn't make any sense. Any tendency to round up is caused by weather helm, not lee helm....

I think my title might have mis-led you. Lee helm is the paradoxical late-comer to the party.

Up until the point in the story quoted by you, everything is trucking along as you would expect from that sailplan in those conditions, ie moderate weather helm in the lulls, strong weather helm in the gusts.

The lee helm comes later in the story, and it is this which represents the surprise, and the paradox ....

which I nevertheless think I can explain - if no-one else is going to put their oar in? (or launch a red herring )

[Andrew Troup]

Seems to me there are two animals in this room, a red herring and an elephant.

I'll address the red herring in this post:

I'm referring to the photo of a boat rolling heavily while sailing downwind under spinnaker in moderate conditions. I'm not sure that it helps illuminate the situation of a boat close reaching, bareheaded, under conditions which have become too strong for a triple reefed main.

I personally think the fights which broke out among contributors regarding the wind direction arose from chasing an embedded red herring: I don't personally think the wind direction is a controversial aspect of the photo.

When a suitable (ie old school) boat sailing dead downwind gets the death rolls in moderate conditions as in the photo, the APPARENT wind direction at the masthead swings through a total of forty degrees or more with each roll, without any change in heading needed. This is because the masthead is effectively tacking downwind.

The spinnaker swings through a similarly radical angle, not just because the apparent wind is swinging, but also due to the influence of gravity. It's relatively free to swing, not being attached to a stay. (Modern, flatter spinnakers, coupled with modern hull forms and underbodies are much less prone to these vices, which might help explain why people here are so perplexed by what they see.)

Most crucially, the sail swings because it is getting a good old rhythmical "one – two" from the vortex shedding series, coming to it from around the luff and leech of the main alternately.

It's this rhythmical shedding which is the root cause of the death roll sequence.

Things get truly unmanageable when the frequency of the vortex shedding happens to match the natural roll frequency of the hull.

So my interpretation (having spent many happy hours on and around boats with this propensity) is that the boat is probably sailing Dead Down Wind.
Boats of this vintage tended to hold their heading pretty well even under this syndrome, and for the death rolls to initiate, the course has to be DDW or close to it.
(Otherwise all the vortices come off the leech (or the luff, if sailing by the lee)

Unfortunately the boats which can be steered actively so as to kill the rolls are also the boats which are least likely to get them in the first place. It takes a deep spade rudder, well aft, and a short-chord keel. And someone on the helm who has the knack (probably a gifted dinghy sailor) and bravery to burn ... It's much easier to make it worse than it is to cure it. You have to do something very specific and perfectly timed, but which is almost (but not exactly) opposite to what instinct suggests.