weather helm??

jibes138 · May 12, 2009

Weather Helm

Many forces are at work here that sum up to a moment that is causing your boat to turn to winward. You note that you are sailing with a genoa and mainsail in greater than 35 knots of wind. This doesn't make any sense, What point of sail are you on? What is your angle of heel? If you are heading upwind the spreaders are likely in the water if the wind is over 35 knots and you have this much sail. Are the sails reefed?
If your boat is heeling over say 20 degrees you have too much sail, the boat is cruising along at hull speed and more sail makes the boat heel more but not go faster. This is because it is a displacement hull (assuming a monohull with keel). Excessive weather helm is a result of imbalances in your sail plan for the conditions. At these wind speeds you need your mainsail double reefed, a small jib like a storm jib (reefed roller furling stinks IMHO) and your main should be adjusted to a very flat shape using the outhaul, vang, and cunnugham.
Keep in mind as the boat heels the rudder is less effective as much of the rudder force is pushing up and down instead of in the direction to turn the boat. This is like dragging a drogue behind the boat. All kinds of forces putting stress on the boat but not making you go faster. Sails must be set for the conditions and since the conditions are always changing they constantly need adjusting. Read Don Guilette's sail trim guide available here for some great tips on adjusting your sails. He even has a handy laminated cheat sheet to keep at the helm.

Franklin · May 12, 2009

Speaking of weather helm, I noticed Sunday that I almost never have lee helm. Take Sunday: it was blowing 14-20 aparent with an AWA of 90 degrees. I only had my 105 jib out doing about an average of 5.3 knots with a heel of 5 degrees. I was wore out from working on the boat all day so just wanted to relax. I noticed though that the boat had just a tad bit of weather helm. I know that is good, but got me wondering. I figured my sail plan was actually un-balanced so I should have had lee helm.

Then I got to thinking that when I have the boat performing at it's best, I usually have quite a bit of weather helm, which goes against logical thinking too

I wonder if these are signs the boat is not balanced right (not the sails, but the boat).

Franklin · May 12, 2009

sand sailor said:
...i'm going to try moving the jib cars forward and see if that helps

No, you do not want to move the cars forward, if anything, backwards.

Mostlikely, your weather helm is a result of you healing the boat way too much. I don't know of any boat that is built to have full sails up in that kind of wind.

Witzend · May 12, 2009

Franklin, that is correct. When you move the cars back this allows the leach to twist off spilling wind off the top of the sail. Moving them forward will tighten the leach, not what you would want to do in an over powered situation. The other way to help de-power a head sail is to increase the halyard tension, or down haul if you have that adjustment at the tack of the sail. If you have an adjustable back stay tighten that and it has the same effect as increasing the head sail halyard if the front stay is tensioned correctly. The reason that flattens the sail and depowers it is because the sail should be cut so the warp and waft are diagonal to the luff. By pulling on a piece of cloth on the diagonal it stretches out and flattens. Try this with a cloth napkin; first pull it laterally and then longitudinally, no give. Now pull it diagonally, see how much is stretches!

RichH · May 12, 2009

When in boisterous conditions, this is RARELY a sail trim issue, and what you are experiencing is NOT weather helm !!!!!!

From what you describe, I 'think' what you have is a *skid to leeward* instead of 'weather helm'. HOW TIGHT IS YOUR FORESTAY/BACKSTAY ?????

Normal sail design and rigging tensions are based on the windstrength being somewhere near 15 kts. Well beyond 15kts. (>35kts) the very ELASTIC rigging will be well stretched (especially the forestay - sagging well off to leeward) and the DACRON sailcloth will be greatly stretched out of shape, as there is ~6-8 times the force of the wind at 35kts. as at 15kts.

When you go out again in such conditions notice how much CURVE there is to the luff of the headsail .... for you boat, perfect rig tension (and 'reasonable' winch tension on the jib sheets) should only have that FORESTAY sagging off to leeward by approx 8-12". This is so that the curved shape of the luff that the sailmaker cut into the luff 'matches' the sag in the forestay. Normally you want 12-15% of backstay tension; but sometimes in heavier winds, need to increase the backstay to 30%+ tension to compensate for the forestay sagging off to leeward. Occasionally you can adjust the backstay to greater than 30%; but at higher than 30% tension the LIFE of the backstay and other rigging components becomes VERY short (like to the tune of 1 milion load cycles).
With the boat over on its ear, the keel no longer is as deep as when sailing upright and the boat begins to make leeway (enhanced by the LARGE sag in the headstay). When overpowered, the first thing to do is estimate if the forestay is sagging off too much, then also look at your rudder wake/turbulence to see that its is coming 'straight off the stern' and not trailing off to WINDWARD. If the boat 'is' skidding (to leeward) due to excess sail pressure, etc. the rudder will get a LOT of side force ... and most sailors will blame 'weather helm' .... but if the boat is skidding this ISNT weather helm, you have to be sure the forestay isnt sagging and that the wake is coming out the stern in a straight line.

Rx for skidding to leeward:
Sail the boat more upright
REEF so that boat doesnt exceed 30 degrees of heel.
LOOSEN the jib sheet tension
TIGHTEN the backstay
Smaller headsail

If you want 'precision' for sailing in high winds and heavy weather see the attached:

higgs · May 12, 2009

Lots of good stuff here, but IMHO any reasonably designed boat carrying a genny in 35 kts BETTER have a lot of weather helm. If it doesn't I'm looking for a new boat. Some of us call this rounding up.

Witzend · May 12, 2009

Great article Rich. For all the years I have raced my J22 I have never had it explained any better. Unfortunately most cruising boats do not have an adjustable backstay. Rig tuning is so overlooked.

Joe · May 13, 2009

reef your main..... then get back to us. 35 knots... good grief! You should have maximum twist on the main.. this will spill air from the top so the tip of the mast doesn't act as a lever to spin the boat to windward.

sailaway78 · May 13, 2009

Heel

I agree with those who are talking about how much heel you have being the cause. The boat is trying to round up. My last boat, a 28' S2, would start wanting to round up at about 20 degrees of heel. Much more than that, and she was going to round up, no matter what you did. But all this being said, 35 knots is past time to start reducing sail, not to worry about sail trim.

RichH · May 14, 2009

Witzend said:
Great article Rich. For all the years I have raced my J22 I have never had it explained any better. Unfortunately most cruising boats do not have an adjustable backstay. Rig tuning is so overlooked.

Thanks for the acknowledgment.

Rig tension is just as important as sail trim and shape, as the shape of the sail (for the particular present sailing conditions) is very dependent on the rigging upon which it 'hangs'. Cruising sailors usually have their rigs too loose and racers are usually too tight .... and there is ONE proper tension for EACH wind strength, if you want anything close to optimum performance.

Morgan30 · May 14, 2009

I always have what I call a Weather helm, which is a wecolmed thing growing upon a lee helm boat. But, after reading these great posts, I am gonna really try to apply what I learned here. Even gonna print this thread. The Morgan 30 has quite a large Main and if there are white caps, or it is blowing say over say 18, the Genoa stays closed. If sailing with one sail, it is the Main on my boat, which has two jiffy points. So, again, thanks for the lessons.

weather helm??

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