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Catalina/Capri 25/250 Sailor's Forums

Catalina 250 Specific Forum

Building a rudder

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shemp
Deckhand

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USA
19 Posts

Initially Posted - 01/21/2010 : 13:00:24

Im thinking about building a new rudder for my 250WB. Has anyone out there done this or can lend some suggestions? I posted this on the general forum, hopefully its not duplicated.

Thanks
Shemp

Jeff Dowling
Chicago
203

Edited by - on

Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 01/21/2010 : 13:43:22

Can't help you with the building of a rudder but Catalina does sell a balanced blade rudder for the C250 WB now and IdaSailor sells a kick-up rudder for the 250 WB. Either would be a major improvement.

Edited by - on

bear
Admiral

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USA
909 Posts

Response Posted - 01/21/2010 : 19:32:28

My suggestion, Get your checkbook out and buy one of the later designed rudders

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 01/22/2010 : 12:52:12

Making a rudder blade and using the existing rudder head is not a difficult or expensive thing to do...

In our case we needed, in order to make the 2006/7 380 km passage through the Trent/Severn waterway system in Ontario, a rudder with maximum 5ft draft. Just in case we made two rudder blades, one from a pine board and one from a solid seasoned oak plank as per illustration below.

The outline, location of holes etc. were copied, cut and fabricated. The full length oak blade was reinforced and shaped somewhat similar to the existing rudder. The shorter pine blade although it had been reinforced horizontally, was apparently not strong enough since it broke later during the trip.

We stow the oak blade as spare.

A possible cause for breaking could be that we deviated from the original blade and angled it much further forward creating, what could be, a lot of force on the bottom of the blade...(I'm not an expert) People on this forum will be able to advice the best design

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 01/22/2010 : 13:27:55

If I were going to do this, I'd probably make the rudder from laminated plywood, which will give you greater strength than a solid piece of wood. You should be able to make it from a single sheet of 3/4" marine ply, and if you get a BS 1088 rated sheet, you won't have to worry much about water intrusion, although I'd still seal it in epoxy, and then probably three coats of Cetol over that. I haven't looked recently, but you used to be able to get a sheet for around $100.

Henk, how did your pine rudder fail? Did it snap along the grain, or across it?

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 01/22/2010 : 16:57:41

The solid pine blade snapped just below the aluminum head more or less horizontally as per illustration

Johanna holds, using the Honda outboard, the boat in reverse, against the current and off the rocks while I dive below and quickly mount the new oak blade. Even at slow speed it's impossible to steer the boat forward by motor only without a rudder.

As back-up to the back-up blade we have on board a long "one sided", paddle that could be tied to the aluminum rudder head or, if everything fails, the gudgeons. (removed most of one side of the paddles blade)

BTW: I would support using plywood to make a blade

Edited by - zeil on 01/22/2010 17:28:06

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 01/23/2010 : 08:09:46

A high aspect rudder encounters a great deal of stress so no surprise the pine wasn't up to the task.

While oak has the strength, it is likely a good choice only for a back up rudder as oak is not tolerant of moisture and will suffer wet rot easily.

Marine ply is a good choice and especially when accompanied by generous amounts of resin when laminating and sealing. If replacing my rudder, I'd go that route but in part because my boat doesn't live in the water otherwise a composite will endure longer.

The construction method would likely be three layers of marine ply, laminated with epoxy resin with a layer of carbon fiber between laminations in the area around the bottom of the rudder head.

Be very careful however when using carbon fiber because producing dust from it can cause a serious health issue. Even using a respirator, I'd not make the risk. I'd only use it in those areas where it was certain that there would be no shaping. It would only be needed in the upper section about six inches either side of the bottom edge of the rudder head and keeping it in the middle third so as not to be involved in shaping. Carbon film is very strong and would add a lot of strength.

Edited by - Arlyn Stewart on 01/23/2010 08:11:09

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 01/23/2010 : 11:07:30

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by zeil
 ...Johanna holds, using the Honda outboard, the boat in reverse, against the current and off the rocks while I dive below and quickly mount the new oak blade.<hr height="1" noshade id="quote"></blockquote id="quote">

Henk--glad you still have all your arms and legs! The power of the suction through that propeller is pretty fearsome!

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 01/23/2010 : 11:17:34

That was my first thought too, Dave, but I think (I hope)he meant that he dove below(decks) to retrieve his spare and then hang it on the stern. You shouldn't have to go in the water to replace the rudder on a 250 although stepping down the swim ladder might make it easier to reach the cotter pin in the pintle.

Edited by - on

shemp
Deckhand

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USA
19 Posts

Response Posted - 01/25/2010 : 10:36:12

Ive built model airplane wings with foam core and balsa sheeting. Arent some rudders built using foam cores??

Edited by - on

farrison
Navigator

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USA
166 Posts

Response Posted - 01/25/2010 : 11:49:24

Jeff;

Yes, some of the newer rudders are built using foam cores with fiberglass skins. There are a lot of foam/glass or foam/carbon wings used with great success in the experimental aircraft industry, like the Rutan aircraft. Parts of our hulls are foam/glass/epoxy, like the transom (I discovered this when we ripped the lower gudgeon out of our 25').
I am currently building a balanced rudder for my 25' (see my post in the 'General' section). Arlyn is correct in that laminated plywood will be stronger than solid wood. I am using 4 plys of 3/8" marine mahogany ply because finding the right kind of foam that can be bonded with epoxy is tough/expensive. I didn't want to put this much effort into the rudder using foam from home depot and have it delaminate. I will be using carbon fiber on the outside surface, but not in the interior plies. Carbon fiber is very strong, and doesn't stretch or fatigue. I am using carbon because I am in the composites business and have access to it, but you could get away with fiberglass only. Both carbon/epoxy and glass/epoxy can be inhalation hazards if you sand it, so a respirator is manditory. I will put a layer of fiberglass cloth on the surface for sanding and fairing before I paint.

Paul

Edited by - on

Jack Schafer
Navigator

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USA
112 Posts

Response Posted - 01/26/2010 : 16:00:55

OK, You have my curiosity up. I have a 1st generation rudder in my attic. would it be reasonably possible to redesign it into a balanced rudder? I currently have a 2nd Generation and happy with it, but thought it may be a good back up if I could do it easy enough.They are not beaching rudders

Edited by - on

shemp
Deckhand

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USA
19 Posts

Response Posted - 01/26/2010 : 17:10:29

Hey Jack, is there a fleet of 250's in Lake Geneva? I would love to race mine once the rudder is fixed. I cant imaging racing it like it is. I have to reef in 8 kts!

Edited by - on

shemp
Deckhand

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USA
19 Posts

Response Posted - 01/26/2010 : 17:11:25

Farrison, are you going to take the time to sand the rudder into an airfoil or is that a waste of time?

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 01/26/2010 : 17:30:42

Thank you guys for caring for me...

Of course I meant diving below "decks" to retrieve the spare blade... the C250 rudder assembly allows for easy removal from the cockpit, by just pulling the retaining clip out-of-the-way and up floats the rudder... no need to go in the water!!

The snapped off part of the wood blade was still attached by way of the up-haul line and was easily pulled into the cockpit. Loosing rudder control and having your world swirling around you in the subsequent rounding up happened in an instant

... fortunately we had enough sea room... could've been a lot worse!!

Edited by - on

Jack Schafer
Navigator

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USA
112 Posts

Response Posted - 01/26/2010 : 18:24:28

Shemp, There are only 2 250's on the lake and I am the only one racing. We have a PHRF club that sails Wed and Sat. We have 4 classes ranging from Melges 24 to Catalina 25's etc.,about 20 boats..
Check out the web site WWW.glkcsail.org

Edited by - on

farrison
Navigator

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USA
166 Posts

Response Posted - 01/27/2010 : 09:58:17

Jeff;

No, It is not a waste of time to shape the rudder. Yes, I have planed down the plywood laminate into an airfoil shape with a hand and a power plane. I found a spreadsheet on line that calculates the thickness of the blade along the wing cord and based the thickness and shape from that. If you want more details and a picture or two, send me an e-mail.

Paul

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 01/27/2010 : 10:37:10

Farrison,
Could I talk you into posting your calculations, plans & photos here?

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farrison
Navigator

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USA
166 Posts

Response Posted - 01/27/2010 : 13:11:50

David;

I designed my rudder for my '82 Catalina 25' SR/WK. The original rudder is too long and touches the lake bed first, so the new rudder is shorter. The specific plans for my rudder are for a shorter (2"), but wider rudder, so the specific measurements wouldn't do too many owners much good, unless they were to use them to re-design their own, based on their specific keel type, etc. Since mine is loosely based (but not exactly) on the 25' balanced shape in the 25 tech tips section, it is unproven, so I would not like to make any claims on it being the "best" design. The excel spreadsheet I used to calculate the measurements for the NACA 12 airfoil shape I found on-line, in another forum. I drew it to scale and made a template for shaping the wood. The pivot point for the pintals I determined from other articles I had read about balanced rudders (about 13% of cord).
I'd be happy to share the few photos I have so far, and had planned on submitting it to the Tech tips when it's all complete. At this point the plywood is shaped, but the carbon and glass still need to be applied when the weather here warms up. Send me an e-mail if you have any more questions, I'd be happy to answer what I can.

Paul

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