Association Forum - Catalina Balanced Rudder

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

Catalina 250 Specific Forum

Catalina Balanced Rudder

New Topic

Topic Locked

Printer Friendly

Author

Topic

Page: of 2

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 01/16/2010 : 08:09:23

Don, I see where your coming from. Steve Colgate is a respected sailing figure and I'm sure his words should have some weight but I doubt his words are the authority on fluid dynamics.

And, the "exactly 1/4" you offer, is a theory proposed in 1920 for thin wing foils. I suspect the science of fluid dynamics has added a great deal of understanding since then. For example, until the last thirty years, lift of foils was ascribed primarily in terms of Bernoulli's principle but that is no longer true. The greater factor in foil lift is now understood to be vector lift with very complicated if not impossible mathematical explanations, in part because they are forever dynamic and applicable to a great amount of the wing surface in a variety of fashions.

For example, the vector force of the laminar flow off the trailing edge of a foil is a prime lift force and is dependent upon speed and angle of attack of the foil. It is not hard to imagine that such a dynamic force fully aft on the foil has a huge influence on the center of lift making the center of lift shift.

Again, going back to the boat world, not that long ago, CLR was defined as the center of lateral resistance of hull and its underwater appendages and such a definition can still be found during a search but modern science has proven such a definition is wholly inadequate of describing or understanding boat balance.

I once again say that 1/4 back is a good reference point for describing about where the center of lift might be but it ain't written in stone that it is the center of lift and because the center of lift is dynamic and because a balanced control foil dare not stray aft of lift center, a conservative discipline has to be applied to producing a balanced rudder design.

A good read is the 'Boat Mechanical Systems Handbook'

[url="http://books.google.com/books?id=euQZ16elT5kC&pg=PT216&lpg=PT216&dq=percentage+of+balance+to+boat+rudders&source=bl&ots=dmWxFNtmMo&sig=sn8G5r-yRVG7y8V3oUd5X_lyH6A&hl=en&ei=dM9RS4qoPM2ZlAeG4syzCg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAYQ6AEwAA#v=onepage&q=percentage of balance to boat rudders&f=false"]link[/url]

It can be seen that 17% is the established norm for rudder balance and that 20% is considered the absolute maximum and then a warning of what happens when going over that.

Sorry, I would have cut and pasted those words but it is a pdf that wont allow cut and paste from the overview article from the handbook.

btw, several years ago I wrote an article about cause of monster weather helm. In that article, I quote a theory by Steve Colgate that he had proffered that the cause of monster weather helm was water packing up on the bow... he was wrong then too.

Edited by - Arlyn Stewart on 01/16/2010 08:51:06

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 01/16/2010 : 10:10:06

OK, I'll jump in with you geniuses.

My research indicates that the sweet spot is about 15% - 17% of chord length. Yes, 25% of chord length is the "truest balance" but at 25% the rudder is too neutral and does not give good feedback to the skipper and results in the boat over-turning. The 15% mark lessens the force required by the skipper to make the turn but still provides the needed feedback through the tiller or wheel.

Here is a good article on rudder design:

[url="http://books.google.com/books?id=GliCdk2exrgC&pg=PT123&lpg=PT123&dq=balanced+rudder&source=bl&ots=NIirVL_kxv&sig=rBW6iiz_HgWI9uUSiWc5RgCRwmw&hl=en&ei=de9RS6G3OYOKsgPesuCHCA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAcQ6AEwADgy#v=onepage&q=balanced%20rudder&f=false"]Yacht Design Explained[/url]

Edited by - Nautiduck on 01/16/2010 10:12:01

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 01/16/2010 : 12:47:46

Randy, your link was a wonderful read. It is rainy here today and I'm house locked and read the section about rudder balance and then enjoyed other areas as well... thanks.

Edited by - on

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 01/16/2010 : 18:10:33

Arlyn, glad you enjoyed it. I'm tempted to buy the book. It seems well done and has lots of good reviews.

Edited by - on

PDXSteve
Deckhand

Members Avatar

20 Posts

Response Posted - 01/17/2010 : 13:43:42

I just ordered it! Takes two weeks to build (built to order) and another two to get it from Florida to Oregon. Still plenty of time to get it on the boat for a late March launch.

I have to say the fellow at Catalina (Warren Paddy) was very helpful.

<hr height="1" noshade id="quote"></blockquote id="quote">

Way To Go Randy! Looking forward to seeing the installed photos!
I was going to buy at IDA rudder with part of my tax return this year, but Im liking that Catalina rudder..
Now my Questions ---- Your boat is a Tiller model right? Forsee any problems with this mod? And all inportantly, Cost??
Thanks

Edited by - PDXSteve on 01/17/2010 13:46:55

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 01/17/2010 : 16:42:19

Steve, my C250 has wheel steering. I think the hardest part is going to be mounting the Edson steering arm bracket.

I note that you have a water ballast 250. For the water ballast, Catalina makes the same balanced rudder but 12" shorter (59" vs 71" for the wing keel version). I believe the rudder is shortened to facilitate launching/retrieving off the trailer without having the rudder strike the ramp. The shortened rudder is reported by some to have less grip when the boat is heeling which makes sense. The result is a higher likelihood that the boat will round up in strong wind. Also, I think the 59" rudder will not allow you to beach the boat if you like to do that - although that seems less important to us PNW sailors than those in Florida for instance. Catalina no longer makes a kick-up rudder. IDA does and that model has been popular with some C250 water ballast owners because it is said to offer good control and swings up to allow beaching.

Another good option for you - assuming that you don't need to beach, would be to get the 71" rudder and mount it after you launch. If you have a tiller boat that would be easy to do. Then you get the latest Catalina balanced rudder with the extra length.

The 71" Catalina balanced rudder is $660.

Choices, choices.

Edited by - Nautiduck on 01/17/2010 16:47:04

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 01/18/2010 : 10:01:35

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Nautiduck
 Here is a good article on rudder design:

[url="http://books.google.com/books?id=GliCdk2exrgC&pg=PT123&lpg=PT123&dq=balanced+rudder&source=bl&ots=NIirVL_kxv&sig=rBW6iiz_HgWI9uUSiWc5RgCRwmw&hl=en&ei=de9RS6G3OYOKsgPesuCHCA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAcQ6AEwADgy#v=onepage&q=balanced%20rudder&f=false"]Yacht Design Explained[/url]<hr height="1" noshade id="quote"></blockquote id="quote">The "Transom-hung rudder" graphic (figure 4.10) doesn't illustrate the Catalina "balanced" design, however. The Catalina "step" puts perhaps 15% of the blade surface forward of the pintles so it works like the graphic in Figure 4.9.

Edited by - on

PDXSteve
Deckhand

Members Avatar

20 Posts

Response Posted - 01/18/2010 : 12:20:54

Thanks Randy..
My boat is in the water 24/7 and i dont have a trailer, so no worries about installation and removal.
Im looking to change out my rudder (unbalanaced) for the rounding up issue and to just plain have better control of the boat. I was looking at the IDA due to the Kick up factor, might still be the better choice for me..I currently have a kick up rudder and it is a tiller model, and the whole thing comes off with ease! I do, on occasion, get into some places that are nice to beach it and stay a while.
Ive still got some time to think about it..Thanks for the info and sugestions

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 01/18/2010 : 15:33:46

Steve, which rudder do you have now? From your comment that your issue is rounding up rather than excess torque, I'm guessing you have the original release rudder.

Crunching the numbers. The 1st beaching was 61", the second beaching 76" and the 3rd was released only in a blade, which is 59" for the water ballast and 71" for wing keel.

Rangy gives you the stuff to consider... the intent of my post is only to take note if by chance you have the 2nd beaching as it is in my opinion the finest rudder available for the 250 water ballast and would be a shame to give up on when its issues can be cured with some rudder head mods.

Edited by - on

PDXSteve
Deckhand

Members Avatar

20 Posts

Response Posted - 01/18/2010 : 16:59:56

Yes, I have the original kick up rudder and its un-balanced. Been living with it for 5 years now and this is the year to replace it! Though about doing your rudder mod after i bought the boat, Bookmaked your page a long time ago! I also figured there was a better rudder out there that i could just replace mine with.
The IDA Rudder might be the best fit for me..

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 01/19/2010 : 06:28:04

Steve, actually the original rudder had a forward offset in it and wasn't that bad as to balance unless it positioned aft in the rudder head due to the wear of the rivet/detent hold down system.

But, I don't think I'd waste energy modding the rudder head to hold the rudder in proper position as that rudder just doesn't have enough control.

Let us know how the upgrade goes.

Edited by - on

britinusa
Web Editor

Members Avatar

USA
5404 Posts

Response Posted - 01/19/2010 : 08:35:50

FYI, my 2005 Swing has a rudder 56"tall and max of 17" wide. It looks pretty much exactly like the one shown in the first post.
Randy, is that your boat? I thought the pic was a swinger!

Paul

Edited by - on

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 01/19/2010 : 13:32:14

Paul, those photos are from Catalina Yachts. They sent them to me as we were discussing rudders. That is the current rudder being put on 2010 models. The water ballast version is 59" and the wing keel version is 71".

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 01/19/2010 : 16:33:43

My water ballast version is 59".

Edited by - on

TakeFive
Master Marine Consultant

Members Avatar

2272 Posts

Response Posted - 01/27/2010 : 16:33:48

Hi everyone. I am new here. I may place an offer on a 1998 WK with Edson pedestal in the very near future. I am trying to figure out which rudder it has. The original owner has been described as "extremely meticulous" so it's possible it was upgraded from the 1998 OEM version. It is 71" tall. It looks exactly like the 3rd generation one that the OP shows, but does not have the indents for the pintles and steering arm mount.Actually, I think I figured out how to attach a pic, so here goes:

<center>

</center>

Is this the 3rd generation one, or some earlier one? Was there an "original" 3rd gen that is balanced but thinner? Any performance issues with this one? Perhaps the flutter due to eddies off the tip?

By the way, not to nit-pick, but when applying Newton's third law "equal and opposite reaction yada yada" you have to include the acceleration from Newton's second law. Acceleration is any change of the velocity vector - speed or direction. So, by definition, turning the boat is an acceleration. You need to include the force represented by this in addition to the forces on the rudder, keel, and the rest of the boat. You have to do the full vector calculation in 3 dimensions, not just scalar multiplication.

Edited by - on

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 01/27/2010 : 17:30:39

Doc, welcome to the forum! You'll find lots of good information and helpful people here.

Your rudder looks like the 3rd generation rudder that was put on C250 WKs beginning with the 2001 model. My 2000 WK had the 2nd generation rudder. Your previous owner upgraded from his 2nd generation rudder - lucky you!

I believe (will verify when I get it) that the newest rudder is a "4th generation." How much it varies from the 3rd (just the indents for the pintles or more?) will be determined when I can measure it and compare it with my friend's 2001 WK and it's 3rd generation rudder.

Edited by - Nautiduck on 01/27/2010 17:47:20

richardnsmith@verizon.net
Deckhand

Members Avatar

USA
2 Posts

Response Posted - 10/25/2010 : 17:38:23

I have a 250 wk 2002 version. The rudder was badly cracked so I bought an IDA rudder. The boat seems to round up sooner. I wonder if the new catalina rudder would perform better?

Edited by - on

bear
Admiral

Members Avatar

USA
909 Posts

Response Posted - 10/25/2010 : 19:18:26

I upgraded from the 1st generation rudder to the IDA kickup rudder 5 years ago. I have been thru some "good times" with this rudder haven't even come close to rounding up. The only questionable issue I have is the weight. Being 68 it's kinda a jerk and pull up the stair opening.

Edited by - on

richardnsmith@verizon.net
Deckhand

Members Avatar

USA
2 Posts

Response Posted - 10/26/2010 : 06:10:35

I'm 62 and find the rudder hard to handel also. Thanks for the reply!

Edited by - on

Page: of 2

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.