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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation > Weather Helm: Desirable or Dangerous
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Thread: Weather Helm: Desirable or Dangerous Reply to Thread
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Topic Review (Newest First)
02-02-2012 07:03 PM
smurphny
Quote:
Originally Posted by killarney_sailor View Post
One nice feature with our boat is that the centerboard allows us to control the amount of weather helm (I guess technically what we can do is move the center of lateral resistance when we drop the board). Absolutely essential to get maximum performance about of the Monitor windvane. I guess w/o the c/b we would have to do the things suggested here to reduce our helm when the wind pipes up.
Your Bristol 45 is a nice design. It seems to be similar to the P-40 which is on my shortlist of "next boats." If I had to choose one fault in my A-35, it would be the large main which requires constant attention to keep the windvane working. Being able to adjust the center of effort would be a godsend.
02-02-2012 06:47 PM
killarney_sailor One nice feature with our boat is that the centerboard allows us to control the amount of weather helm (I guess technically what we can do is move the center of lateral resistance when we drop the board). Absolutely essential to get maximum performance about of the Monitor windvane. I guess w/o the c/b we would have to do the things suggested here to reduce our helm when the wind pipes up.
02-02-2012 06:22 PM
AdamLein
Quote:
Originally Posted by jackdale View Post
How much does heel contribute to weather helm? Since the theoretical hull speed is based on water line, will the leeward side (with a longer longer line) not be able to generate more speed than the windward side; ending in a round up?
I think not, not until you're going fast enough that the leeward side can take advantage of the longer waterline. I have experienced weather helm when my boat speed was much lower than my theoretical hull speed.

Instead I think that weather helm due to heel is primarily a result of the fact that the COE of the sails is no longer over the centerline of the boat, adding a moment to the forces on the boat. This moment will always tend to turn the boat away from the side the rig is on.

This effect will be present regardless of boat speed.
02-02-2012 06:01 PM
jackdale Rich

Great discussion of sail shape. Many folks could benefit from proper sail shape and flattening their sails before they need to reef.

How much does heel contribute to weather helm? Since the theoretical hull speed is based on water line, will the leeward side (with a longer longer line) not be able to generate more speed than the windward side; ending in a round up? Shifting crew weight on a race boat is a common practice. In heavy air to windward, in lighter air to leeward. Race crew also tend to change foresails before reefing the main.

The "textbooks" use CLR and CE and tell us to reef the main first, then foresail, then main, etc.. But in my experience a foresail change will eliminate heel and reduce weather helm.
02-02-2012 05:44 PM
RichH Sail SHAPE is the predominant factor affecting 'weather helm', followed by rig tension ... and lastly mast rake.
In that vein, its simply amazing that most cruisers never bother with sail 'shaping' to affect a near neutral 'helm pressure', heeling effort, etc. ... even for 'safety concerns'. Yes, CLR vs. CE is important ... but that 'really' only applies when hove-to, not sailing with dynamic or aerodynamic effects acting on the sails.

To remove 'weather helm' one must use 'tell tales' (such as described in www.arvelgenty.com and other sources who use that work as their 'root source', etc.) and perform the 'sail shaping' (via monitoring the full set of tell-tales) needed to get good/efficient aero flow across the sails ....... instead of futzing-around with mast rake, etc.
When one begins to 'study' tell tales and their usage, one has to totally forget & discount the erroneous 'crap' that has been taught for nearly a full century in US high school science classes ... and simply adjust and 're-shape' to what the tell tales are indicating.

For the most part even the worst of sailboat designer will have the 'balance' already designed-in or close ... all it takes is correct sail 'shaping' and tell tales usage to tweak that helm balance for the boat to be 'safe and fast', etc.

So, how much 'weather helm' ... about 3° of rudder angle, so that also the keel can generate 'lift' when beating... otherwise youre dragging the rudder through the water.
02-02-2012 05:22 PM
St Anna
Quote:
Originally Posted by Faster View Post
I think your poll is missing a response, along the lines of "normal 5 degrees or so, easily held" which would be, I believe, a common response.

On our boat (frac, big main small jib) the amount of weather helm varies greatly with point of sail. Close to beam reaching in a breeze can load up pretty good whereas on the wind it's just about right.

I do think it's preferable to lee helm...
yup, ditto to what 'speedy' says

Not fractional though, but works effectively the same
02-01-2012 08:03 PM
Bene505 I adjusted our autopilot a few weeks back and the course didn't change. Then I noticed that I had it in standby. The boat just tracked along.

Of course, I've sometimes adjust the sails to find a good balance, but I don't think I did that time.

Regards,
Brad
02-01-2012 06:05 PM
pdqaltair
Quote:
Originally Posted by QuickMick View Post
I dont see how it could be desireable as you are just adding drag via rudder.
Good point. Very boat dependent.

Beach cats, for example really benefit from the lift of some helm angle, as their rudders are deep and efficient, but they have no other CB or keel. Other boats, less so.

But again, lee helm is always bad.
02-01-2012 04:04 PM
QuickMick The sail condition as mentioed above is (imho) huge. my buddy put new halsey canvas on and it erased it. then I promptly preformed an accidental gybe (with no time for ye ole 'gybe ho') while no one was knocked in the head or mob who know how much of a load i dropped on his brand new canvas!! I dont see how it could be desireable as you are just adding drag via rudder.
02-01-2012 03:30 PM
pdqaltair
Other factors:

a. Sail selection. Did you reef the jib first, or both together?
b. Are the sails blown-out? Has the point of maximum draft moved aft?
c. Trim. All sorts of possibilities.
d. There is a difference between helm feel and helm angle. 2-4 degrees of helm angle generally helps a boat get to weather by providing lift. For this reason (and others) lee helm is always bad; it drags you to leeward. However, feel is also very much about rudder balance;how does the shaft location relate to the COE on the blade? I've had boats with adjustable rake and I would always adjust for a light, finger tip feel. Personal preference.
e. Speed. On many high performance boats the helm goes light as the boat accelerates, if everything is trimmed correctly. This is generally over 10 knots and is a result of increased water flow.
f. Course. Some boats will have strong helm if close-hauled, very little beam reaching, and more broad reaching. Some of this is speed, some of this is COE sail location vs COE foil location (changes when the sails are eased).

So, it is many things, even on one boat.

One problem with heavy helm is what happens if the rudder ventilates in fast running; A boat with helm--either way--will be uncontrollable and will broach fast. Something to think about when going fast deep. If you're pushing hard, aim for reasonable neutral helm.
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