| Re: Mast rake back more weather helm?
[Re: warbird]
#101079 03/21/07 08:52 AM 03/21/07 08:52 AM |
Joined: Jun 2001 Posts: 778 Houston carlbohannon
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Posts: 778 Houston | From what I can see the 14sq is based on the 4.5, a skeg not a dagger board hull.
In extremely simple terms, to get rid of weather helm, you want to match the center of effort(Ce) to the center of force(Cf) of the sails. The Ce is the point along the hulls where the average effect of the rudders, skeg, sides of the hulls to resist lateral movement is located. If the Cf is aft of the Ce you get weather helm.
With skeg hulls the Ce moves around a lot. The side of the hulls, especially the sides of the bow on NACRA's, act like keels. With the bow down the Ce moves WAY forward. When you rake the mast back and move your weight back, the Ce moves back faster than the Cf.
If I am right, the weather helm should come back if you move your weight forward, at least this is my theory.
I don't know if the theory is true but I have found that on Waves and my 14, get the bows up and the weather helm goes away. On my 14 I found if I hiked really hard on the back corner, I could pull the bow up and sometimes even have lee helm for a few scary seconds. | | | Re: Mast rake back more weather helm?
[Re: ncik]
#101087 03/22/07 03:27 AM 03/22/07 03:27 AM |
Joined: Jun 2006 Posts: 177 Sydney/Northern Beaches Bandit
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Posts: 177 Sydney/Northern Beaches | I cant say my 16 sq works that way as I found I had more weather helm the further back I rake my mast.
However I would recomend checking you toe in and out of your rudders and also see if your hulls are aligned corectly its possible one has shifted or is set incorrectly. Once forward pressure pushes the bow down it may be digging in on a bad angle and pushing the boat upwind... As to the correct setting for the toe in and out I can't help you but perhaps someone else may help answer this?
Sail 1635
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| | | Re: Mast rake back more weather helm?
[Re: warbird]
#101088 03/22/07 06:30 AM 03/22/07 06:30 AM |
Joined: Nov 2005 Posts: 1,203 uk TEAMVMG
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Posts: 1,203 uk | Generaly, more mast rake does give more weather helm IF all other things stay equal.... Dont forget that by changing the rake of the mast, you are changing the sheeting angle of the mainsail. with an upright mast, the sheet is pulling down more and inducing leech tension which will be a factor in giving weather helm. By raking the rig, the sheet is flattening the sail more and letting the leech open up = less weather helm. It is always a problem in boomless cats that as you hit a gust, you become overpowered and sheet off, this lets the sail get fuller and more powerful and also gives weather helm. so what you need to do in a gust is sheet IN !
Paul
teamvmg.weebly.com
| | | Re: Mast rake back more weather helm?
[Re: TEAMVMG]
#101089 03/22/07 07:50 AM 03/22/07 07:50 AM |
Joined: Jun 2001 Posts: 890 Dunedin Causeway, FL David Parker
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Posts: 890 Dunedin Causeway, FL | a problem in boomless cats that as you hit a gust, you become overpowered and sheet off, this lets the sail get fuller and more powerful and also gives weather helm. [color:"red"] so what you need to do in a gust is sheet IN ! [/color] YES! You are the first I've heard say this (except for me). It took me about 3 years to realize this. There is a rapid bad sequence of gust, sheet out, fat main, excess heel,rounding up (like weather helm), sheet out more to depower which slows you down, then foot off to regain speed, often driving bows under. This often repeated sequence is low, slow, and the boat hobby-horses causing weather helm and/or a bow stuff. It also makes people hate boomless boats. Instead, if you sheet IN (or just hold it) and move weight forward, the bows don't stuff, the boat doesn't heel, and you point higher and increase speed. This is NOT pinching. It's faster and the weather helm and tendency to stuff a bow eases off. Steady speed, no excess steering, higher pointing. Eases pucker factor in high wind gusts as well! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> However, it takes balls of steel to NOT sheet out the first few times you try it in a gust. | | | Re: Mast rake back more weather helm?
[Re: David Parker]
#101090 03/22/07 07:53 AM 03/22/07 07:53 AM |
Joined: Jun 2001 Posts: 12,310 South Carolina Jake
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Posts: 12,310 South Carolina | working the downhaul on and off in the gusts helps greatly too.
Jake Kohl | | | Re: Mast rake back more weather helm?
[Re: Jake]
#101091 03/22/07 07:57 AM 03/22/07 07:57 AM |
Joined: Jun 2001 Posts: 890 Dunedin Causeway, FL David Parker
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Posts: 890 Dunedin Causeway, FL | working the downhaul on and off in the gusts helps greatly too. Little solo boat, remember. Can't be done solo. Two hands, 3 jobs. No can do. | | | Re: Mast rake back more weather helm?
[Re: David Parker]
#101093 03/22/07 08:48 AM 03/22/07 08:48 AM |
Joined: Jun 2001 Posts: 1,459 Annapolis,MD Keith
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Posts: 1,459 Annapolis,MD | a problem in boomless cats that as you hit a gust, you become overpowered and sheet off, this lets the sail get fuller and more powerful and also gives weather helm. [color:"red"] so what you need to do in a gust is sheet IN ! [/color] YES! You are the first I've heard say this (except for me). It took me about 3 years to realize this. There is a rapid bad sequence of gust, sheet out, fat main, excess heel,rounding up (like weather helm), sheet out more to depower which slows you down, then foot off to regain speed, often driving bows under. This often repeated sequence is low, slow, and the boat hobby-horses causing weather helm and/or a bow stuff. It also makes people hate boomless boats. Instead, if you sheet IN (or just hold it) and move weight forward, the bows don't stuff, the boat doesn't heel, and you point higher and increase speed. This is NOT pinching. It's faster and the weather helm and tendency to stuff a bow eases off. Steady speed, no excess steering, higher pointing. Eases pucker factor in high wind gusts as well! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> However, it takes balls of steel to NOT sheet out the first few times you try it in a gust. Hmmm, don't ever recall that type of action on my 6.0. If over powered letting the main off opened up the top of the sail dumping wind and depowering very nicely. I suspect if dumping the main powers and rounds you up that maybe you weren't trimmed properly to start (over trimmed a bit maybe, or maybe the sheeting angle wasn't set right). Also, the only time I've experienced a boat rounding up like that was either in a monohull or on my H-18 with the molded rudders. On the monohull the rounded shape of the hull itself lends to weather helm when you heel excessively. On the 18 the rudders deflected and boat would skid the stern. If you're getting excessive weather helm helm when overpowered perhaps the rudders are loosing bite, for a variety of reasons. At least upwind. Downwind sheeting can stall the back of the sail and depower things well, and over sheeting the jib can give the same effect - closing the slot and stalling both sails. I guess nobody has asked whether this is an upwind or downwind problem, or a problem all the time. But just to make sure the terminology is correct here - weather helm is when the boat wants to turn into the wind on its own. Lee helm is when the boat wants to turn away from the wind on its own. It has everything to do with the balance between the center of effort on the sailplan versus the center of effort of the underwater portion of the boat. Line up the centers of effort and the boat is neutral (my H-20 was this way, downwind it would transition to lee helm if a wave got you just right), sail effort behind the wet effort and the boat will tend to round up giving weather helm, the other way results in lee helm. But again, it's the balance between the hull center of effort and the sailplan's. What's going on with the boat at a particular time can affect that balance. Sail trim definitely affects this - we know it's easier to turn down if the main is eased, easier to turn up if the main is trimmed. You should be able to steer the boat with sail trim alone. So, given all that, is it possible raking forward is sinking the bows a bit, effectively moving the wet center of effort forward as well as the center of effort of the sail plan? Maybe, I'd have to see what your boat looks like and how you're sailing it. It could be just that your boat likes the mast forward more and is more powered up, giving you the feeling that helm has increased when maybe you just need to get your rudders raked right. Again, my 18 was like this - mast forward meant more power, and it emphasized the weaknesses in the rudder system. So many variables... Improperly raked rudders can give the feeling of horrible weather helm, when in reality it's not affecting the balance of the boat that much, but is affecting the effort required on the helm, again giving the feeling that weather helm is bad. | | | Re: Mast rake back more weather helm?
[Re: Keith]
#101094 03/22/07 02:41 PM 03/22/07 02:41 PM |
Joined: Nov 2005 Posts: 1,203 uk TEAMVMG
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Posts: 1,203 uk |
"Hmmm, don't ever recall that type of action on my 6.0. If over powered letting the main off opened up the top of the sail dumping wind and depowering very nicely. I suspect if dumping the main powers and rounds you up that maybe you weren't trimmed properly to start (over trimmed a bit maybe, or maybe the sheeting angle wasn't set right)."
Keith It is not a case of my trimming method stops rounding up - it just makes the boat GO faster.
I agree with Jake that the downhaul has to come it to play aswell
This does make sailing the 6.0 to windward a bit like working on a chain gang, but its pretty satisfying when it comes together
Paul
teamvmg.weebly.com
| | | Re: Mast rake back more weather helm?
[Re: Bandit]
#101095 03/22/07 03:42 PM 03/22/07 03:42 PM |
Joined: Jun 2002 Posts: 1,658 Florida Suncoast, Dunedin Caus... catman
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Posts: 1,658 Florida Suncoast, Dunedin Caus... | I cant say my 16 sq works that way as I found I had more weather helm the further back I rake my mast.
However I would recomend checking you toe in and out of your rudders and also see if your hulls are aligned corectly its possible one has shifted or is set incorrectly. Once forward pressure pushes the bow down it may be digging in on a bad angle and pushing the boat upwind... As to the correct setting for the toe in and out I can't help you but perhaps someone else may help answer this? I agree with you. Rudder systems that are sloppy or not toed in enough will cause this problem. Make sure the system is tight and try 3/8" toe in at least and see what happens. The weather rudder should not be toed out when going up wind with the weather hull light.
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