Since I've had the boat on the water (bought this year) I've always noticed a bit of Weather Helm on a Starboard Tack (Port Tack has no issues at all, completely hands off).
Lately, and especially yesterday when it was howling on the ocean, the effect has gotten more severe and I have to fight a fair bit to keep the boat from heading upwind.
I've read through the forums, caught this post, and plan on doing some serious work over the off-season. It's an 84' and certainly due for a complete rudder/crossbar rebuild.
viewtopic.php?f=3&t=662&p=2429&hilit=ru ... ther#p2423
Till that time, any thoughts? I'm curious on why it's only on Starboard, and if this is a clue to an obvious place to start in order to make it through the season without a rebuild ... there are only so many days left and I'd like to spend them on the water.
Weather Helm (Starboard Tack)
-
falseicon
- Novice
- Posts: 6
- Joined: February 6th, 2013, 10:37 pm
- Boat Make/Model: SuperCat 17 '84 Vintage
Weather Helm (Starboard Tack)
SuperCat 17 '84 Vintage
-
Bill Roberts
- Expert
- Posts: 515
- Joined: November 17th, 2003, 9:13 pm
- Location: Stuart, Florida
Re: Weather Helm (Starboard Tack)
Novice,
It sounds to me like one of your rudders is not symmetrical. One of your rudders is generating side fore when it is at zero angle of attack, like straight ahead. A slight change in leading edge rake angle will not cause weather helm on one tack. One of your rudders is generating a side force toward the starboard side of the boat on starboard tack. This adds to the normal slight weather helm built into your boat. The result is a strong weather helm on starboard tack. On port tack this non symmetrical rudder is still generating a side force toward the starboard side of your boat when it is at zero angle of attack. This would be leehelm except for the fact that your boat has a slight weather helm designed into it on both tacks. Evidently this leehelm caused by the non symetrical rudder balances the normal weather helm built into the boat and the result is a very neutral helm on port tack.
This has always been my experience with a helm situation, strong helm on one tack and neutral helm on the other tack, like you described. After you have exhausted all possible other fixes, I suggest you send your rudders to Tom and he can check for symmetry and fix if there is a problem.
I just thought of a test: Sail the boat with one rudder at a time; the other rudder up. Mark a hull/deck centerline on the aft deck from the rear beam going aft. Sail the boat on starboard tack. Note how far off hull centerline the front end of the tiller is. It will be 2 or 3 inches or so. Then raise that rudder and sail the boat on the other tach. If the ruddder is non symmetrical, the end of the tiller location will be significantly different from the other tiller/rudder. If the port rudder rudder is generating starboard side force at zero angle of attack, you will have to move the tiller further off center to make the boat go stratght. If the starboard ruddder is not symmetrical, the end of the tiller will be significantly less distance off hull center line than on the other tack. Good Luck.
It sounds to me like one of your rudders is not symmetrical. One of your rudders is generating side fore when it is at zero angle of attack, like straight ahead. A slight change in leading edge rake angle will not cause weather helm on one tack. One of your rudders is generating a side force toward the starboard side of the boat on starboard tack. This adds to the normal slight weather helm built into your boat. The result is a strong weather helm on starboard tack. On port tack this non symmetrical rudder is still generating a side force toward the starboard side of your boat when it is at zero angle of attack. This would be leehelm except for the fact that your boat has a slight weather helm designed into it on both tacks. Evidently this leehelm caused by the non symetrical rudder balances the normal weather helm built into the boat and the result is a very neutral helm on port tack.
This has always been my experience with a helm situation, strong helm on one tack and neutral helm on the other tack, like you described. After you have exhausted all possible other fixes, I suggest you send your rudders to Tom and he can check for symmetry and fix if there is a problem.
I just thought of a test: Sail the boat with one rudder at a time; the other rudder up. Mark a hull/deck centerline on the aft deck from the rear beam going aft. Sail the boat on starboard tack. Note how far off hull centerline the front end of the tiller is. It will be 2 or 3 inches or so. Then raise that rudder and sail the boat on the other tach. If the ruddder is non symmetrical, the end of the tiller location will be significantly different from the other tiller/rudder. If the port rudder rudder is generating starboard side force at zero angle of attack, you will have to move the tiller further off center to make the boat go stratght. If the starboard ruddder is not symmetrical, the end of the tiller will be significantly less distance off hull center line than on the other tack. Good Luck.
-
Bill Roberts
- Expert
- Posts: 515
- Joined: November 17th, 2003, 9:13 pm
- Location: Stuart, Florida
Re: Weather Helm (Starboard Tack)
Novice,
I've thought of another test. Tow your boat with a power boat in a straight line at an easy sailing speed, 3mph is plenty. Disconnect the tiller crossbar on the side of the boat where you are sitting. The rudder will go to a minimum drag position with equal pressure on the sides. This should place the end of the tiller off hull/deck center line about 3 inches, whatever the Ackerman Steering Compensation is, check with Tom. Put a mark on the deck under the end of the tiller. Go to the other side and repeat. If one of the rudders in not symmetrical. The end of the tiller will be out of place, probably much closer to hull/deck centerlime than the normal rudder.
Basically this test is showing/saying that if the rudders are symmetrical, the ends of the tillers will be the same distance off hull/deck centerline in a straight line tow test.
I've thought of another test. Tow your boat with a power boat in a straight line at an easy sailing speed, 3mph is plenty. Disconnect the tiller crossbar on the side of the boat where you are sitting. The rudder will go to a minimum drag position with equal pressure on the sides. This should place the end of the tiller off hull/deck center line about 3 inches, whatever the Ackerman Steering Compensation is, check with Tom. Put a mark on the deck under the end of the tiller. Go to the other side and repeat. If one of the rudders in not symmetrical. The end of the tiller will be out of place, probably much closer to hull/deck centerlime than the normal rudder.
Basically this test is showing/saying that if the rudders are symmetrical, the ends of the tillers will be the same distance off hull/deck centerline in a straight line tow test.