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Discussion Starter · #1 ·
I have a Catalina 30T. 1990. Went aground early in this past season and chewed up the bottom of the rudder. Rudder also has some signs of delamination in a couple areas, so I am looking at an overall repair.

I have seen some information about a more optimal rudder shape, both cross section (NACA 0012 airfoil) and profile (leading edge curves aft towards the bottom of the rudder). This reportedly improves weather helm, pointing ability and ease of maneuvering under power.

Anyone have any thoughts on this? Anyone have any plans? I am not opposed to reshaping the rudder - I believe the most crucial tasks will be building a jig to hold the rudder in a proper position, and also aligning the rudder properly with the centerline of the shaft. I know I can also make a jig to use my router to create the NACA 0012 profile. And I can do it for a lot less $$ than a new rudder.

Or, I can just repair the rudder in its current shape.

Thanks in advance for any input/advice!
 

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George, have you tried the Catalina 30 owners association? They are a very active group and probably more than a few have replaced a rudder for one reason or another.

International Catalina 30 Association

The Yahoo email list is extremely active.
 

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I believe that your rudder was manufactured by Foss Foam which made rudders for numerous builders. They are a foam cored rudder which invariably leak and absorb water. Reshaping, it IMO, would be extremely difficult. I would simply repair the damage after draining the water and seal the rudder at the shaft entrance. I suspect the NACA foil rudder may be made by IDA Sailor and is not foam cored. I know they made one for the Hunter 285 and those that purchased it were very happy with it and it was guaranteed for life. By the way, the Hunter 285 is an excellent sailing boat, so if the NACA improved it, I would be very impressed.
 

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George, I had this link in my Catalina folder but I can't remember anyone actually buying this rudder and giving feedback in any of the Catalina forums.

You might try Googling it or posting a question on CatalinaOwners.com in the C30 forum or in the Catalina 30 Yahoo group to see if anyone has real world experience with it before dropping $2,500.

Catalina 30 High Performance HDPE Spade Rudder, Rudder Craft Inc.
 

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Assuming you have average boat repairing skills, if you only intend to sail short passages, daysailing and casual racing, then you might be able to repair the existing rudder satisfactorily. If you intend to make longer passages, in heavier weather and in isolated areas, then I would recommend you buy a commercially built replacement. Getting caught in an isolated area with a broken rudder is no fun.

There are pros and cons to a balanced rudder. With a balanced rudder, you will feel less weather helm, but there won't actually be less weather helm. IMO, you can achieve a light weather helm by tuning the rig correctly, and it will be just as light as if you had a balanced rudder. The balanced rudder uses a little energy to counteract the rudder pressure, and that is subtracted from the energy that could otherwise be used to drive the boat. The amount is probably inconsequential, unless you're an obsessive/compulsive racer, but it's a consideration nonetheless. If your objective is to reduce weather helm, the better alternative is to learn how to tune the rig correctly. It isn't as complicated as it seems, and it won't cost a dime.
 

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Discussion Starter · #7 ·
Thanks all for the feedback. Sailormon6 - not looking for the rudder to solely minimize weather helm. I agree that proper tuning of the rig and trimming of the sails to achieve a balanced helm are important. I'm working on those skills - I've been told of sailors who can steer by mostly trimming sails. That'd be a skill I'd aspire to!
 

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Discussion Starter · #8 ·
Likely going to repair with shape as is. However, my primary concern is sealing the area where the post enters the rudder body. It is clearly not sealed. Seems like I would need to clean out around post to sound material and rebuild up. My main concern is how to get the interface smooth, flat, and perpendicular to the shaft. Any ideas? If this interface was the highest point of the rudder body it would be reasonably easy.

I understand the high density plastic ring that sits atop the rudder should be adhered to the rudder (with 3M 5200 or similar) (it's loose), but I don't want to rely solely on the 5200 for the complete seal.
 

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There are pros and cons to a balanced rudder. With a balanced rudder, you will feel less weather helm, but there won't actually be less weather helm. IMO, you can achieve a light weather helm by tuning the rig correctly, and it will be just as light as if you had a balanced rudder. The balanced rudder uses a little energy to counteract the rudder pressure, and that is subtracted from the energy that could otherwise be used to drive the boat. The amount is probably inconsequential, unless you're an obsessive/compulsive racer, but it's a consideration nonetheless. If your objective is to reduce weather helm, the better alternative is to learn how to tune the rig correctly. It isn't as complicated as it seems, and it won't cost a dime.
Some of this is true, some is speculative, some is folklore. Rudder balance, tiller forces, weather helm, and boat balance is a very complicated subject. Complicated mechanics too. For example, the force (on the tiller) does not represent energy lost, it's just force. A light helm can be a benefit to the person steering, but is has little (nothing?) to do with performance. Odd, yes? Some of the folklore is probably a holdover from the keel hung barndoor rudders used a century or two ago.

I'd suggest that George copies what is there, repairs what is there, or uses some design already proven on the Catalina 30.
 

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I'd have to take issue with the comment about energy lost. If you're applying a lot of force to the rudder, that means it's doing a lot of work on the water flow, which in turn means a lot of drag.
 

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I'd have to take issue with the comment about energy lost. If you're applying a lot of force to the rudder, that means it's doing a lot of work on the water flow, which in turn means a lot of drag.
You would think, but force alone is not an indication of 'work'. For example, the mainsheet pulls on the boom and that is thought to be a good thing. The mainsheet force could, in theory, be reduced to zero by some clever placement of the gooseneck fitting. The main would then be balanced, there would be no mainsheet force, the drag would not change, there would be no difference in sailing performance. So nobody bothers.

Now since most spade-type or skeg-hung (non-barndoor) rudders are more or less well designed you are generally correct that a force on the tiller probably means the rudder is doing some work and therefore creating some drag. But that drag might be induced drag - drag with is beneficial. Again, sails create drag while producing forward force, so it's okay. More drag, more lift, more speed, to a point.

On a racing-inspired boat the rudder is part of the underwater balance. The rudder is wet (drag) so it might as well be doing something positive. A well shaped spade rudder is a very efficient hydrofoil. These rudders, when the boat is properly trimmed, add significantly to the force lifting the boat to weather. When racing (or attentive cruising), depending on many things, trimmers will trim the sails for some few degrees of rudder angle. 5 degrees, plus or minus. Whatever force on the tiller (or wheel) it take to achieve this angle in really immaterial. However, it works out that with well designed balanced rudders this angle can be held with very little force.

In short, the old-timers that judge sail and rig trim by tiller force, instead of rudder angle, are deluding themselves. I thing it's a holdover from the old keel-hung rudders which are bad in all conditions that are not straight ahead. And very good at that!

Note: Spade rudders are in the leeward flowing downwash of the keel foil. So some small angle is actually neutral rudder. My old Cal-36 with her then new fancy elliptical rudder would sail along to weather with the tiller up about 7 degrees, no hands.
 

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so if there is a slight force applied to the tiller there is drag caused by the rudder but also lift that can add to the lift of the keel and help lift the boat to weather which is opposing the forces to leeward. on some boats a slight weather helm is a good thing
 

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.....on some boats a slight weather helm is a good thing
I'd say on all boats a slight weather helm is a good thing for a number of reasons.. including a slight 'lift' to weather counteracting leeway, and the resulting tendency of the boat to 'round up' (possibly into irons) rather than 'round down' (into an accidental gybe) in the event of a tiller release.

That said, I think the major difference between a balanced and unbalanced rudder is the force required at the tiller to hold that slight rudder angle. On a 'barn door' unbalanced rudder the helmsperson has to resist the force of the water flow, all of which is behind the pivot point(rudder stock). A balanced rudder's area forward of that stock alleviates some of that pressure/force at the tiller.
 

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You're right Faster, as usual, but there are two ways that you can reduce the amount of force required at the tiller to hold that slight rudder angle. You can either tilt the rig forward, which will balance the whole sailplan and reduce the tiller pressure, or you can convert to a balanced rudder. Installing a balanced rudder will reduce the amount of force required at the tiller, but it won't do anything to reduce the imbalance in the sailplan, and that imbalance is what is causing the excessive weather helm. Tuning the rig eliminates the cause. Converting to a balanced rudder only reduces the symptom.
 

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Some of this is true, some is speculative, some is folklore. Rudder balance, tiller forces, weather helm, and boat balance is a very complicated subject. Complicated mechanics too. For example, the force (on the tiller) does not represent energy lost, it's just force. A light helm can be a benefit to the person steering, but is has little (nothing?) to do with performance. Odd, yes? Some of the folklore is probably a holdover from the keel hung barndoor rudders used a century or two ago.
In aerodynamics, lift-induced drag is a drag force which occurs whenever a lifting body or a wing of finite span generates lift. Lift is the force that enables the boat to drive to windward. A byproduct of that lift is drag. Generally, as the angle of attack of the sail(s) increases, induced drag increases.

Parasitic drag is drag caused by moving a solid object through a fluid. Parasitic drag is made up of many components, the most prominent being form drag. Skin friction and interference drag are also major components of parasitic drag.

Simply stated, the objective of a sail trimmer is to create an optimum balance between induced drag and parasitic drag.

If we start off with a full mainsail and genoa in moderate winds, and the windspeed increases, parasitic drag increases, so we flatten the sail shape to reduce lift-induced drag, which, in turn, reduces parasitic drag. If the windspeed increases further, we reduce sail area, which also reduces lift-induced drag, and which, in turn, reduces parasitic drag.

Sails are capable of generating more lift than the sailboat can use efficiently, so the sail trimmer's goal is to achieve an optimum balance between lift-induced drag and parasitic drag.

A good sail trimmer will be communicating frequently with the helmsman, to learn how much rudder pressure the helmsman is feeling. If it is excessive, that is an indication that there is a significant imbalance between induced drag and parasitic drag. If he can reduce that imbalance, through sail trimming, the boat will point higher and foot faster. Whether the boat has a light or heavy helm has a great deal to do with the boat's performance.
 

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...A good sail trimmer will be communicating frequently with the helmsman, to learn how much rudder pressure the helmsman is feeling. If it is excessive, that is an indication that there is a significant imbalance between induced drag and parasitic drag. If he can reduce that imbalance, through sail trimming, the boat will point higher and foot faster. Whether the boat has a light or heavy helm has a great deal to do with the boat's performance.
Yes and no. You missed my point. It's not the helm pressure. It's the rudder position. It is better if the trimmer looks at the wheel or tiller position than asking about helm force. You pointed out one more reason that this is true: Because the rudder is producing both induced (relatively good) drag and parasitic (bad) drag. How can the person holding know what proportion of the helm force is one or the other? They cannot. Plus helm pressure changes significantly with wind force, healing, boat speed, seas, etc. It's simply not a good indication. Especially with well-designed rudders with wheel steering where one may feel no force at all with both good sail trim and bad.

So, on the earlier subject. It's not really weather helm one is attempting to control, it's bow down rudder trim (or whatever one would call it).
 

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How can the [helmsman] know what proportion of the helm force is one or the other [i.e. induced (relatively good) drag and parasitic (bad) drag]? They cannot.
The helmsman can know that by the amount of rudder he has to use to hold the boat's heading. If he has to cant the rudder by more than a few degrees to hold course, then the combination of induced drag and parasitic drag is probably excessive. The trimmer can diagnose it by making sail trim changes to flatten or otherwise depower or balance the sails, and then watch the knot meter. If boat speed decreases as a result of the change in sail trim, then the change has reduced induced drag too much. If the boat speed increases, and the boat points a little higher and stops laboring, then the change has reduced parasitic drag, while maximizing induced drag.

You can't always be sure, in advance, if the sail trim change that you are thinking about making will be an improvement. Sometimes you have to try it and watch it's effect. More often than not, you'll be right. If you're wrong, you can always change it back. It is said that Ted Turner had a placard mounted in the cockpit of his boat that said, "The only sin worse than incest is cleating the sheets." :D If you aren't constantly searching for more speed and better sail trim, you aren't likely to find it.
 
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