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3rd generation rudder tracking questions

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Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Initially Posted - 06/21/2003 : 10:26:33

Looking for input from those with the 3rd generation rudder.

During my limiting testing of the rudder, I noticed a tracking issue that hadn’t been a previous problem. The boat wanted to wander rather than enjoy the previously very good tracking. It is yet too early to know why. There were some other variables like removing the most effective portion of a skeg to install the rudder, etc.

For those with a tiller, does the boat want to quickly wander off course when releasing the tiller?

For those with the wheel especially if there is some play or dead zone in the steering system, does the boat want to wander course a bit?

For those who have converted from the 2nd, do you notice any tracking changes?

Testing indicated very quickly that the rudder is very well balanced with little helm effort. However, it is possible to overbalance a control surface, which results in zooming, a flying term which can happen with either a tail heavy airplane or a control surface overbalanced. The effect is that the control surface doesn’t want to rest in a neutral position. Simply put, the forward offset that balances the surface is too great and the control surface wants to initiate a turn rather than trailing in the flow.

If there is an overbalance the fix would be simple. Remove the pintles, resin in the holes, and re-drill slightly forward.

Arlyn C-250 W/B #224
<img src="http://www.stewartfam.net/arlyn/rr.jpg" border=0>
N/E Texas and Great Lakes

[url="http://www.cox-internet.com/arlynstewart/"]Arlyn's C250 Mods n Cruisin Stories[/url]

Edited by - arlyn stewart on 06/21/2003 10:27:37

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G2CaptainB
Deckhand

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Response Posted - 06/21/2003 : 13:22:18

Hi Arlyn,
As a brand-new Catalina owner and Sailor's Forum participant, I thought I would throw my two cents in on the 3rd generation rudder. Ironically, we are on our second rudder after developing a vertical gelcoat crack just aft of the leading edge. Frank Butler and Catalina have been great about fixing the problem and apparently a production change is in the works.
Regardless, we have a C250 WK #684 (Red Red Whine)equipped with a tiller. Although we are still sorting out ballast, sail plan vs. conditions and other boat handling issues, we have been pretty happy with the way the rudder has handled. In light and steady wind (a rarity on Lake Mead), the rudder seems to track fairly well without the "wobble" I have felt in my hand on some other tiller equipped boats of similar size. Of course, rudder tracking issues aren't the primary concern when the wind comes up quick, strong, and gusty as it tends to do around here. Keeping the crew happy (i.e. flat boat) is.
I'm sure we'll get much pickier about rudder handling as our experience with the boat grows. If my thoughts on rudder handling change, I'll get back to you.
Meanwhile, thanks for all the interesting info from you, Bryan and the others are always posting. Sure helps a newbie like me.

Brad C-250WK #684
Red Red Whine
Lake Mead, NV

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DougA
1st Mate

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Response Posted - 06/21/2003 : 13:31:06

Arlyn

I found the same problem with the upgrade. If I let go of the wheel, the boat immediately turns to starboard. There is also a change in the total angle for turning, the rudder goes farther one way than the other.

Doug A., C250wb, San Franciscp Bay area

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Oscar
Master Marine Consultant

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2030 Posts

Response Posted - 06/21/2003 : 17:38:18

Arlyn,

I have the 3rd rudder with tiller....after sailing the boat for 5 minutes I said...."don't let go of this boat" so I immediately installed the tiller extension with lockbox so I can scratch my head with both hands once in a while <img src=icon_smile_wink.gif border=0 align=middle>.

I've been toying with the thought of extending the rudder a little (aft) this would:

1 Decrease the balance a little bit, which I think would improve tracking.
2 Increase the effectiveness of the rudder a little bit, which I think it could use. I'm only talking an inch or so along the bottom 12 inches of the trailing edge.

I don't want to seem disrespectful and arrogant second guessing the engineering team at Catalina, on the other hand, they've been messing with this thing for six years.....

<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>apparently a production change is in the works.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>

That would be the FOURTH generation rudder, heck they
have specified leaking cubbyholes for TWENTY TWO YEARS....so I guess I'm entitled to some skepticism.....

My rudder too has stress cracking and chipping along fiberglass mat pattern on the leading edge between the pintles. Gelcoat is very thin there, and apparently not resisting twisting forces. Frank is aware, haven't heard back from him yet.

When the barn is finished and the workshops set up, I might make a rudder and do some empirical research, maybe even come up with a variable surface design......<img src=icon_smile_cool.gif border=0 align=middle>

Oscar
250WB#618 Lady Kay on the Chesapeake:
<img src="http://www.woodenshoemusic.com/Images/familypics/Forumshots/chesapeake.jpg" border=0>

Edited by - Oscar on 06/21/2003 17:49:20

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zig zag
Deckhand

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16 Posts

Response Posted - 06/21/2003 : 23:20:16

I just installed a new 3rd gen rudder and found that it does wander a little bit more than the 2nd gen rudder. I have wheel steering and find the lighter helm is worth the anoyance of the wandering. I do sail solo most of the time so, this is a good excuse for me to buy that autopilot. My new rudder also cracked from hinge to hinge after the first use. Not a very good product if many of us are having this problem.
Keith

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bill bosworth
Navigator

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172 Posts

Response Posted - 06/22/2003 : 00:10:24

Arlyn;
I've been using the 3rd gen rudder quite a bit and have been biding my time to make any comment. I think that I like it better than the 2nd generation version. I can't say that I have any wandering. I have dropped my board much deeper as I was getting quite a bit of lee helm with the board raised. Even with the board down I still get some lee helm on close and broad reaches. The Boat has some weather helm on beats. I thik that the boat has less leeway as a result of the deeper board and seems to point as well or better. I find that the balance is generally quite good and that I can take my hand off the tiller for quite a while without going into a tail spin, using the hiking stick and lock box works well. The boat has always had a tendacy to go into a tail spin if I didn't keep an eye on the tiller, but this tendancy is less with the new rudder. I haven't seen any jell coat problems with the rudder but will look carefully. I expected the rudder to cavitate much more quickly and cause the boat to round out more easily, but that doesn't seem to be the case, I've sailed the boat in a variety of conditions and found that I have good rudder control. At some point this summer I'll probably put the second gen rudder back on just to see how it feels, but that will take some tiller midification.
By the way, I entered a "fun" race last weekend, most of the boats were much larger Hunters, I was very pleased with how my little cat250 competed with the larger Hunters, I think I'll rename the boat the "Hunter Killer" <img src=icon_smile_big.gif border=0 align=middle>
Bill c250wb Serendipity

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bren737
Captain

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291 Posts

Response Posted - 06/22/2003 : 12:18:52

Arlyn,

Having only experience with the third-generation on 'Ruah', I don't know how it compares with the second-generation 'beaching' rudder, however, I agree that the 3G rudder does tend to be a bit 'overtrimmed.' Until I installed the wheel-brake kit, in all but the lightest of airs, the boat would round up quickly when I let go of the wheel. Having the sails properly trimmed helped, but with the fluky winds at Canyon Lake, it wouldn't take long for things to change. Now, with the wheel brake, I turn a little tension on the wheel and that keeps her tracking, with the rudder 'locked' with no problem. Poor-man's autopilot.<img src=icon_smile_wink.gif border=0 align=middle>

Your comparison to an airplane is a good one. In order to 'balance' the boat's rudder to relieve turning resistance, the 3G rudder moved the hinge point aft of the leading edge of the blade so to use the natural assistance of the flowing water to help turn the blade. This is in effect the same thing a 'balance tab' does on many airplane control surfaces (aileron, rudder and elevator). The trade off, is that with control surfaces (airplane or boat), in order for them to be quick, light and responsive, they must be inherently unstable. When you build solid, positive stability into a surface, it's tendency will be to stay that way. That's why most of today's best, most manueverable fighter planes can turn, roll, etc in an instant, but if the flight control computer fails, the plane will just as instantly go out of control. . . for good! They have no natural stability designed into them.

As with all things, it's a trade off. It's all indvidual taste and desires. Obviously, changing the hige point of the rudder will reduce it's inherent instability, but it will also make it more like the 2G rudder, which some people complained about for it's too stiff feel.

Sorry to drone on about this, especially to YOU! I know you're already a physics guru of sorts.<img src=icon_smile.gif border=0 align=middle>

Oscar: As for second-guessing the engineers, that's the beauty of it. They are constricted by the need to sell boats so must engineer for the 'middle of the road'; that which will make the most number of potential buyers happy. Once it's our's, we can fine tune and 'garage engineer' to build the boat (car, bike, etc.) we really want. As you know, that's how many 'production run' innovations are made; after someone tinkering in their garage cam up with a better way.

Bren Peterson
C250WB, #642, "Ruah"
San Antonio, TX<img src=icon_smile.gif border=0 align=middle>

Edited by - bren737 on 06/22/2003 12:25:37

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Arlyn Stewart
Master Marine Consultant

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Response Posted - 06/22/2003 : 15:27:15

Good handling has always been a goal strived for with the three sailboats owned. Learned long ago, is that often a little tweaking will solve either design or production shortcomings.

Imagine a graph illustrating the relationship of rudder balance to helm torque (heavy helm). Somewhere on the line we would find for example that 80% of rudder effort needed comes from the helm and 20% from the balanced portion of the rudder.

Following the line, those percentages would grow closer together, cross and arrive at a point where no effort is needed from the helm. Farther on the line, the rudder would zoom, actually needing helm effort to avoid turning which would be very undesirable to boat handling… releasing the helm would have the balanced portion of the rudder constantly wanting to turn the boat. The smallest amount of play in the steering linkage would yield to the zooming.

This is the reason for desired input from those with wheel steering…especially those with some play.

Boat tracking can certainly be a problem however without having an overbalanced rudder as cause. My questions about the 3G rudder as Bren calls it are simply to gather evidence either way. Bill Bosworth’s comments go a long way to indicate that I may be barking up the wrong tree in looking for my tracking problems to be caused by an overbalanced rudder.

Very possible, is that the boat could inherently not want to track… and that the greater area of the 2nd generation rudder simply overcame that. Or, that the now lighter helm with the 3rd simply yields to those forces. Again, Bill’s comments were important as we both made the move from the 2nd.

In some ways, I can’t imagine Catalina not doing a tank test on the rudder to determine any overbalance… but I’ve also got the feeling that they wing it at times with their R&D and rely upon users to correct the problems.

I noticed the loss of tracking right away after installing the 3G. A deliberate attempt was made to hold the helm steady which offered no help. This is a clue that suggested that the cause was reduced lateral area aft and non tracking forces are now having their way.

What is not known is if any others have enjoyed the great tracking that I have the last few years perhaps made possible by the small skeg. As the saying goes, “if never had, it can’t be missed”.

Like Bill, I will be going back and forth between the two rudders… perhaps getting a better understanding. The one variable that also comes into play is the small skeg which had to be cut back (most significant portion) to fit the 3G. The primary purpose for a skeg is to aid tracking… and it could be that change is what is being felt.

As far as a tendency to veer off once helm is released, that could be caused by an overbalanced rudder or by the math on the curve of the graph. What I’m saying is that previously, if the rudder needed 10 lbs of effort to deflect it and the inherent non-tracking forces of the boat were 5 lbs…then the rudder would resist efforts to veer off. However, lets say with an 80% balanced rudder, the two pounds now needed to push the helm are overcome by the 5 lbs of non tracking forces.

This of course can be overcome by use of a skeg.

Arlyn C-250 W/B #224
<img src="http://www.stewartfam.net/arlyn/rr.jpg" border=0>
N/E Texas and Great Lakes

[url="http://www.cox-internet.com/arlynstewart/"]Arlyn's C250 Mods n Cruisin Stories[/url]

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bren737
Captain

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291 Posts

Response Posted - 06/22/2003 : 16:06:32

Arlyn,

As usual, sir, great thoughts and observations! I got to thinking, I wonder how much difference there is with the 2G and 3G rudders both in respect to the WK versus the centerboard of the WB and the rake angle of the centerboard under different conditions? I would think that the WK has a very different flow (turbulence, maybe) that would be striking the rudder than the centerboard at various angles of rake. Possibly not much difference at all, except for at higher hull speeds. It seems that those of us posted here with a WB have experienced this 'overtrim' but Brad, with a WK, hasn't.

The skeg definitely would add to the tracking stability of the boat. It's not unlike the vertical stabilizer in front of an airplane's rudder. Without it, the rudder would be so 'overtrimmed' that the plane would have no reasonable control about it's yaw axis.

Along those lines, with a skeg/2G set-up, I would think the boundary layer flow on the lee side of the rudder would be less disturbed and therefore more efficient. With the 3G, moving the hinge point aft effectively increases the angle-of-attack (to use an aviation description) for a given throw of the wheel. As the rudder turns, the balance tab at the leading edge of the rudder begins to break that laminar flow of lee side of the rudder (more so at higher AOAs) thereby actually reducing some of the rudder's efficiency. At high speeds, with a high AOA on the rudder, You can see cavitation both at the leading and trailing edge of the rudder when increasing the AOA at a quick rate. This loss of lift on the rudder would tend to cause the boat to round up, wouldn't it? Wouldn't this be even more pronounced when running with the centerboard up?

Just some thoughts. . . gives me something to ponder at work tonight!<img src=icon_smile_tongue.gif border=0 align=middle>

Bren Peterson
C250WB, #642, "Ruah"
San Antonio, TX

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Arlyn Stewart
Master Marine Consultant

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Response Posted - 06/22/2003 : 17:43:05

Bren, you nailed it about rudder efficiency...here is a quote, "It is a known fact that a rudder with a skeg will be more efficient at higher degrees of rudder angle than a rudder without a skeg." Perter Schmitt CSY Chief Designer.

I'm not sure differences between balanced and unbalanced have any play relative too the angle of attack other than how the rudder foil is presented to the various turbulence forces beneath the boat.

Bill is certainly right to lower the board when experiencing lee helm. His comments have me perplexed a bit however... in part because lee helm has been a rarity for me on the c250. However, that may be in part do to sailing waters differences. A boat sailed on reaches on a relatively smooth lake will behave differently than when sailed on the Great Lakes. The reason why is quite simple. Greater swell impacting a large rudder, has the effect of pushing the stern around as the swell slides under do to the side impact against the large rudder and if offwind this is accentuated by the momentary rudder stall. In fact, anticipatory helming very often is needed to vein the rudder as the swell slides under to keep the boat from wanting to broach. This is not much problem off wind on a small lake and lee helm might have more opportunity to manifest itself.

This has been a big problem with the 2nd generation rudder but would likely be less so with the 3rd as its area is considerably less.

I'm thinking the center board is forward enough even when raked back to not interfere significantly with flow at the rudder. My normal pull up for rake is about 2-3 feet of line out of the 8-10 feet or so required to bring the board fully up, which likely isn't more than Catalina now locks the rake at with the stop block. By running his fully down, Bill is actually running his a good bit forward of where later boats can, assuming his boat hasn't been retrofitted with the block.

I very quickly noticed a considerable difference in lift abililty between the 2nd and 3rd which Bill didn't. Having a 3 & 5 year old plus a dog on board may have been enough distraction from sail trim to leave my testing a poor comparison.

Arlyn C-250 W/B #224
<img src="http://www.stewartfam.net/arlyn/rr.jpg" border=0>
N/E Texas and Great Lakes

[url="http://www.cox-internet.com/arlynstewart/"]Arlyn's C250 Mods n Cruisin Stories[/url]

Edited by - arlyn stewart on 06/23/2003 07:25:17

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Bryan Beamer
Master Marine Consultant

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1038 Posts

Response Posted - 06/24/2003 : 01:08:32

My 2000wk came with the 2nd gen rudder. I used it for 1 year. I did not have many problems with it. I did not even know there was a 3rd until I got a letter from the dealer here in Colorado. My biggest complaint was I had trouble turn in reverse coming out of my slip. I got the 3rd gen rudder free due to the fact I helped at the Denver boat show a couple of times. The 3 things I did notice with the 3rd. backing out of the slip and turning was very easy and in a blow at a heal of 30 degrees or more I did not have to turn the wheel as far to bare off the wind and the weather helm with no changes in rig tuning was reduced some what. IMO with the wheel weather helm is harder to feel that with a tiller.

Turning in forward was close to the same. I have always been able to turn a tighter turn to starboard than to port but it not a problem with me.

I did a very hard inspection on all equipment especially the rudder before we left to Nationals. I do not have any gel coat cracks.

I can let go of the wheel in most conditions and it does not head up hard it will gradually head up over a short time I think that is a good thing incase you fall over board the boat will eventually head up.

I really have not noticed any difference in tracking ability of the 2 rudders but I have not sailed with the 2nd since May of 2001.

Bryan Beamer
<img src="http://im1.shutterfly.com/procserv/47b3da35b3127cce961d8ff3fd0b0000001010" border=0>
Daylight Again
C250wk #495
2003 National Champion

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Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 06/24/2003 : 14:55:03

One point about Bryan's response... a thicker foil generates more lift at slower speeds. His observation that the 3rd enhances control when entering and leaving the slip is likely for that reason.

Arlyn C-250 W/B #224
<img src="http://www.stewartfam.net/arlyn/rr.jpg" border=0>
N/E Texas and Great Lakes

[url="http://www.cox-internet.com/arlynstewart/"]Arlyn's C250 Mods n Cruisin Stories[/url]

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ssteakley
Captain

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USA
467 Posts

Response Posted - 06/24/2003 : 19:09:52

For what it is worth, I have the 3G rudder and wheel steering, if I am close hauled and sails balenced, the boat will sail itself, if there is a wind shift the boat falls off and goes close hauled on its own...but off the wind the boat tends to turn to the wind if I leave the Helm unattended.
Arlyn, I have about 3 inches of play in my wheel, can this be adjusted or am I stuck with it? I tried to find a way to adjust it this past weekend but did not see a way to do so..it is the push-pull single cable system,
Steve

<img src="http://im1.shutterfly.com/procserv/47b3dc32b3127cce94d57c8cff3b0000001010" border=0> Moon Chaser #385WK <img src="http://www.catalina25-250.org/forum/forum1.gif" border=0>

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Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 06/24/2003 : 22:41:19

Steve,

The good news is that there is an adjuster to deal with the play of the idler chain... the bad news is that it requires a significant effort to adjust. The innards of the pedestal have to be raised slightly which means obtaining a little slack in the cable. The worst of it is... the design of the idler chain and the single takeoff point on the chain is inherantly prone to some play. I'm not sure how much luck you would have. Mine always had some play. I hadn't had My boat long when Edson had an upgrade to the setscrews at the bottom of the pedestal... when performing that upgrade, I checked and adjusted the tension on the idler. Six years later... I had six inches of play. If I remember correctly... after adjusting, there was a couple of inches of play...

There are two bolts which fasten the inner aluminum frame to the pedestal. Those bolts have nuts that push the aluminum frame lower in the pedestal. First, unbolt the inner unit (upper pedestal assembly including wheel shaft) ...raise it for access to those nuts and adjust for an almost firm idler chain.

I'm tempted to tell you to inspect the set screws at the lower end of this frame that hold the sheath of the cable... but that requires a good bit of slack and unhooking at least the quarter mount on the stern. Significantly more effort.

Arlyn C-250 W/B #224
<img src="http://www.stewartfam.net/arlyn/rr.jpg" border=0>
N/E Texas and Great Lakes

[url="http://www.cox-internet.com/arlynstewart/"]Arlyn's C250 Mods n Cruisin Stories[/url]

Edited by - arlyn stewart on 06/24/2003 22:44:27

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