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Lee/weather Helm

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John Russell
Master Marine Consultant

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USA
3444 Posts

Initially Posted - 11/11/2008 : 17:55:03

Here we revisit this topic yet again.

I was reading another post about a collapsible water tank and a comment was made about weather helm. That made me wonder the following.

I had a problem with lee helm earlier this year when I first started using my new 135%. I made a few adjustments (mast rake, etc.) and it was mostly corrected. I still have a little issue with lee helm at very low wind speeds. My question for this august body is this: Should I remove some of the ballast rocks in the bow since I went from a 110% to a 135%? Do you think that will make a difference?

John Russell
1999 C250 SR/WK #410
Bay Village, Ohio
Sailing Lake Erie
Don't Postpone Joy!

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 11/11/2008 : 20:10:25

I'm gonna guess NO. Your hull (below the waterline) contributes to your overall center of lateral resistance, which you want a little further forward (or your center of effort further aft). Also, the more of your bow that's in the water, the more of what I call "wedge effect" (created by heel) you have contributing toward weather helm. How much rake do you have?

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 11/11/2008 : 20:15:15

Now, about 90 degrees.

since I'm on the hard with the mast down.

I had about 6-8".

Edited by - on

Russ.Johnson
Commodore

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USA
855 Posts

Response Posted - 11/12/2008 : 13:24:15

John,
I have the extra water tank you mentioned.
My water-ballast model with a 110-jib had weatherhelm that was reduced by the water tank.
If you changed to a 135-jib and have lee helm, I would say yes remove the ballast.
If you don't like the results, then you can always put it back.
Russ

Edited by - on

Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 11/12/2008 : 13:53:19

Can someone define Lee Helm for me please? With the wind in my back I think its when the tiller wants to move away from me (in the direction of the wind).

On windy days and if heeled over much then I have lot's of lee helm (as per my description above). Apart from the bow ballast, what is the concensus on rake? I currently have about 4-6" of rake, would more rake or less rake be my solution? And what is normal, is it possible to rid lee helm on all point of sails at any wind speed with the proper adjustments?

PS: I have a 110% jib but going to a 135-150% soon.

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 11/12/2008 : 15:49:26

Lee Helm
The tendency, if any, for a sailboat to want to steer away from the direction of the wind (bow to leeward). The opposite condition is known as weather helm.

This causes the helmsman to push the tiller to leeward in order to correct the condition. The problem with this is, it becomes more difficult to put the bow into the wind (round up) in the event of an overpowering gust. That can result in an increased possibility of knock down. It can also make tacking more difficult since the helm is already alee prior to making the maneuver. Lee helm is undesirable for that reason. Slight weather helm is preferred in that it tends to put the boat into a "safer" position in the event of gusts. I think that it is even preferred over neutral helm (if such a phrase exists) because it gives the helmsman a better "feel" for the boat.

As far as rake is concerned, the Owner's Manual that came with the boat suggests 4"-6" of mast rake. (Going on memory here, don't quote me) I had at least that and still had minimal lee helm. I pulled it back farther (~ 8")and it corrected the problem --mostly. As 've said, I still had some lee helm at lower wind speeds.

I did not have this issue with my 110% jib in 2007. I had it this year after switching to the 135% genoa. Since I made no other alterations to the boat, my conclusion was that the larger sail was the cause. This winter, I've take the mast down and will start all over in the spring. My plan is to hire a professional rigger to come and adjust my rigging in the spring(and teach me at the same time).

Edited by - John Russell on 11/12/2008 15:55:51

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 11/12/2008 : 17:10:04

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Steve Blackburn
 Can someone define Lee Helm for me please? With the wind in my back I think its when the tiller wants to move away from me (in the direction of the wind).<hr height="1" noshade id="quote"></blockquote id="quote">That's weather helm--the tendency of the boat to turn to weather (into the wind). Some is desirable, if for no other reason than safety. You want the boat to luff up if you release the tiller (for example, when falling overboard). Weather helm can be reduced by reducing the aft rake of the mast. On a WB 250, you can also reduce it by pulling the centerboard up (and thereby back) a little, thus moving your "center of lateral resistance" aft. I believe several WB owners have tried this successfully, and it's certainly easier than messing with the rigging to move the mast.

I can't speak to how ballast affects it in a C-250--John will be able to next year. (Although he's trying to solve the opposite problem.) If I were you, I'd experiment with the centerboard.

Edited by - on

Steve Milby
Past Commodore

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USA
5904 Posts

Response Posted - 11/13/2008 : 07:31:20

John, you said you have a little concern about lee helm at very low wind speeds. The tiller on my C25 used to have enough friction in the gudgeons and pintles so that it didn't move perfectly freely in lighter winds, and sometimes it acted as if it had lee helm, when it really didn't. When the wind becomes so light that those small factors, such as friction, come into play, then weather helm, as a safety factor, isn't very important, because the boat won't go anywhere very fast. What is important is that the boat has slight weather helm when there is enough air moving to overcome any factors such as friction.

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 11/13/2008 : 08:19:13

Good point Steve!

Paul

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 11/13/2008 : 10:18:19

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by John Russell
 I still have a little issue with lee helm at very low wind speeds...<hr height="1" noshade id="quote"></blockquote id="quote">I think that's common. When the keel is barely moving through the water and the sails are not drawing fully, the forces on the boat are different. And at very low speeds, a balanced rudder can feel a little squirrelly. I wouldn't be concerned with the helm balance in 5 knots or less.

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 11/13/2008 : 11:49:04

I agree, I haven't been worried about it per se, it just feels strange. At the wind speeds at which it occurs, I'm don't even move very much let alone risk a knock down. It does go away if I reduce the headsail a little, but then, that defeats the purpose of the bigger headsail.

Edited by - on

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 11/13/2008 : 15:28:36

Hi all... one more point.

A slight bit of weather helm also makes the boat weather better as it provides a positive angle of attack for the rudder which then lifts to weather. The most efficient numbers are 3-4 degrees of rudder. When we raced Hobie Cats, this was easy to accomplish by crew position trim.

Another interesting factor regarding crew positioning is the drag curve... as boat speed goes up when sail plan powers up, hull drag of course increases and with sailplan power up, an increasing couple between the two pushes the bow down. The leeward bow on the cat would actually go submarine if not careful to move crew aft and on some cats like the Hobie 16 would actually produce a pitch pole. My Hobie 18 would simply dive and come up almost completely stopped.

If you have crew that can move, move them aft in heavy air and forward in light air. In very light air on the cats, skipper and crew would both be on the forward amas and helming done by a twist lock extension hot stick.

Edited by - on

Tom Potter
Master Marine Consultant

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USA
1913 Posts

Response Posted - 11/13/2008 : 20:09:52

Good to hear from you again Arlyn!

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 11/13/2008 : 21:43:29

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Arlyn Stewart
 ...

If you have crew that can move, move them aft in heavy air and forward in light air. In very light air on the cats, skipper and crew would both be on the forward amas and helming done by a twist lock extension hot stick.

<hr height="1" noshade id="quote"></blockquote id="quote">Kinda argues against the extra ballast in the bow. Maybe this is what Frank was thinking when he designed the 250 to ride bow high. Don't know, just thinkin' out loud.

Edited by - on

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 11/16/2008 : 08:20:11

John... I confess to throwing something into the mix that I shouldn't have. I might can explain it this way. All theory about boat balance says that trimming the bow down, increases weather helm because it reduces wetted surface aft and therefore also lateral resistance aft.

However, we know from experience that the 250 suffers an anomaly to this law and I've in the past offered my theory to why that is.

Nonetheless, the 250 anomaly only applies when heeling excessively (perhaps more than 15 deg)... so while the boat is fairly well upright, normal laws apply and trimming the weight aft is a proper action to reduce weather helm.

I also admit, that I've never sailed with enough crew on a 250 to make application of what I suggested.

Edited by - on

Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 11/16/2008 : 13:53:03

I feel successful if I can get the crew to change sides when we tack. Asking them to move fore and aft ("honey would you put down your book and move to the bow?") would create a mutiny.

For our sailing and cruising the added bow weight has been a plus and the boat handles very nicely in a variety of conditions. This year I also spent considerable time on tuning the rig. I found our mast had far too much rake and fixing that also improved performance.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 11/16/2008 : 14:07:52

On our boats I think we can get away with letting our spouses/SO's continue reading their book/snoozing, etc. I know Rita's quite content to let me drive while she sight sees, reads, or snoozes. If it were a cat as Arlyn says, there's no choice, the crew has to move as you tack, or you put the boat into places you don't want to be. I've never pitchpoled my cat, but have a friend who broke his arm on his Hobie 16 doing so. I have managed to get a sponson underwater though, in weather I probably shouldn't have been sailing in, but man it was a ball!. My golden retriever bailed on me and swam to shore, I'm pretty sure he thought I was insane to be out there. We got within about 10 yards of a seawall at one point, and that was close enough for him, he jumped ship in his PFD and got on shore to watch. That was an exhilarating day.

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