Hello, I recently purchased a 1987 Hunter 31. I am very happy with the boat and have been sailing her in the San Francisco Bay for the last few weeks. I noticed this past weekend that I am experiencing some weather helm when the winds started to pick tuo aroubnd 10-15 knots. Is this something common on the Hunter 31? A friend of mine that was out with me said that the rudder on the Hunter might be a little small and that could be the cause. Any one ever experience this problem? Thanks, Casey Las Lunas
Weather helm on my Hunter 31?
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Weather helm is common to most boats
Excessive weather helm can be a symptom of a larger problem (mis-aligned or bent components, out-of-tune rigging, etc.). Moderate weather helm is present in almost all sloops (maybe all) to some extent. Adjusting sail trim can help reduce it. Ease the main (or drop the traveler) and trim the headsail. Weather helm is caused by the forces acting on your hull and your sails. The way I understand it, wind blowing against and around your sails creates lift, like an airplane wing. This lift is spread out over the surface of your sails but creates what they call a "center of effort" which is the spot on your sails where the average of this force is. Imagine an X at the center of effort (CoE). The CoE is probably about half way up your main and closer to the luff than the leach. Sail trim will move the CoE to different spots. Think of your fin keel as a pivot point. If the CoE is behind your fin keel the stern is being "pivoted" away from weather and your bow is being turned into it, weather helm. Moving the CoE forward with sail trim reduces these "pivoting" forces thus reducing weather helm. The other thing that happens, particularly in gusts, is your boat will heel. When your boat heels the CoE can move past your leeward rail and now be over water instead of over your deck. The CoE is now pushing your leeward side harder than your weather side, turning you into the wind, rounding up in a gust. Racers drop the traveler in gusts to prevent rounding up and making it easier to hold course. Once the gust has past they pull the traveler back into position. Think of weather helm as a safety feature built into your boat. If you are overpowered by a gust you automatically turn into the wind, reducing it's effect on you. If you are beating to weather and got hit with a gust and your boat didn't have this built in feature the gust could turn you off of the wind, putting you on a beam reach and making you much more vulnerable. OK guys, did I get this right? Tom s/v Orion's Child
Excessive weather helm can be a symptom of a larger problem (mis-aligned or bent components, out-of-tune rigging, etc.). Moderate weather helm is present in almost all sloops (maybe all) to some extent. Adjusting sail trim can help reduce it. Ease the main (or drop the traveler) and trim the headsail. Weather helm is caused by the forces acting on your hull and your sails. The way I understand it, wind blowing against and around your sails creates lift, like an airplane wing. This lift is spread out over the surface of your sails but creates what they call a "center of effort" which is the spot on your sails where the average of this force is. Imagine an X at the center of effort (CoE). The CoE is probably about half way up your main and closer to the luff than the leach. Sail trim will move the CoE to different spots. Think of your fin keel as a pivot point. If the CoE is behind your fin keel the stern is being "pivoted" away from weather and your bow is being turned into it, weather helm. Moving the CoE forward with sail trim reduces these "pivoting" forces thus reducing weather helm. The other thing that happens, particularly in gusts, is your boat will heel. When your boat heels the CoE can move past your leeward rail and now be over water instead of over your deck. The CoE is now pushing your leeward side harder than your weather side, turning you into the wind, rounding up in a gust. Racers drop the traveler in gusts to prevent rounding up and making it easier to hold course. Once the gust has past they pull the traveler back into position. Think of weather helm as a safety feature built into your boat. If you are overpowered by a gust you automatically turn into the wind, reducing it's effect on you. If you are beating to weather and got hit with a gust and your boat didn't have this built in feature the gust could turn you off of the wind, putting you on a beam reach and making you much more vulnerable. OK guys, did I get this right? Tom s/v Orion's Child
tcbro
Yes, you got it right. Sail shape is a huge factor in weather helm and old baggy sails are extremely prone to this problem. A nice flat main will minimize this and playing the traveler is the best way to deal with sudden gusts. The amount of weather helm should be about 5 degrees of helm at 10 to 15 kts. Mast rake, prop type, and rig tuning are some of the factors in weather helm.
Yes, you got it right. Sail shape is a huge factor in weather helm and old baggy sails are extremely prone to this problem. A nice flat main will minimize this and playing the traveler is the best way to deal with sudden gusts. The amount of weather helm should be about 5 degrees of helm at 10 to 15 kts. Mast rake, prop type, and rig tuning are some of the factors in weather helm.
weather helm
Casey, Tom and Alan are certainly right on. My 1988 Hunter 26.5 also had a lot of weather helm. After working on all trim options, I finally shortened the fore stay 2.0 inches. It took an amazing amount of helm out of her, leaving a more tolerable amount, and I gained a bunch of boat speed with winds at 10 knots plus. However, I now can also bend the mast easier, flattening the main more. Have I moved the center of effort forward, or am I trimming the main better? Probably both. Now, if I ever get up the bucks for the new sails I want, I could be back to the longer fore stay, maybe. And yes, I think one should always have a touch of weather helm. My 2 cents worth. Chaos
Casey, Tom and Alan are certainly right on. My 1988 Hunter 26.5 also had a lot of weather helm. After working on all trim options, I finally shortened the fore stay 2.0 inches. It took an amazing amount of helm out of her, leaving a more tolerable amount, and I gained a bunch of boat speed with winds at 10 knots plus. However, I now can also bend the mast easier, flattening the main more. Have I moved the center of effort forward, or am I trimming the main better? Probably both. Now, if I ever get up the bucks for the new sails I want, I could be back to the longer fore stay, maybe. And yes, I think one should always have a touch of weather helm. My 2 cents worth. Chaos
To the Experts...
So, if we had the exact same mast set-up, rake, pre-bend, etc and the exact same sails on a deep draft 31 and on a shoal draft 31....(the forward edge of Hunter keels are in the same location, and the trailing edge varies).... I'd guess the center of resistance of the shoal draft keel being further aft of the center of resistance of a deep keel... the deep keel would seem to have more weather helm? Seems intuitively backwards, or at least we seem to hear more complaints about weather helm on the shoal draft boats.
So, if we had the exact same mast set-up, rake, pre-bend, etc and the exact same sails on a deep draft 31 and on a shoal draft 31....(the forward edge of Hunter keels are in the same location, and the trailing edge varies).... I'd guess the center of resistance of the shoal draft keel being further aft of the center of resistance of a deep keel... the deep keel would seem to have more weather helm? Seems intuitively backwards, or at least we seem to hear more complaints about weather helm on the shoal draft boats.
S. Sauer
I'm no expert but deep draft keels generate more lift than shoal keels. More lift means less weather helm. I would think that this is the single largest factor in the difference. Also the righting moment on deep keels are higher which also reduces weather helm. I would have guessed that the CR (center of lateral resistance) would be about the same in the two keel types.
I'm no expert but deep draft keels generate more lift than shoal keels. More lift means less weather helm. I would think that this is the single largest factor in the difference. Also the righting moment on deep keels are higher which also reduces weather helm. I would have guessed that the CR (center of lateral resistance) would be about the same in the two keel types.
Try reefing
I would suggest that you try reefing to the first reef point and see if you experience any difference. Once the wind hits 18-20 you should be on the second reef. Sail condition & rig tuning are also good things to check.
I would suggest that you try reefing to the first reef point and see if you experience any difference. Once the wind hits 18-20 you should be on the second reef. Sail condition & rig tuning are also good things to check.
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