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Old 19-08-2008, 19:54   #1
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builing a rudder

Hi everyone,

Those who saw my previous post know I sailed a 1990 Catalina 22 from Fukuoka, Japan to Busan, Korea. Unfortunately, along the way, the rudder snapped. It's a standard kick up rudder and it broke clean where the blade meets the aluminum housing.

So I tried to order a new rudder blade at catalinadirect, but it's back order with a lead time of 4 to 6 weeks. I don't want to wait that long so I decided to take the advice of a couple of sailing friends and build one.

My plan is to use marine grade plywood to cut out the basic shape. Then use a plane to create a rought foil shape. Then sand it until it's very smooth. After that I'll glass it with epoxy. Once that's done, I'll put the pin (bolt) in that's used to keep the rudder down. Finally, I'll paint it with a UV protective paint. I know it's not that detailed, but I want to start working on it this weekend.

I haven't build anything since middle school shop class, but I've got some people around me who do have a bit of woodwork experience.

I would love to get you input on the idea. I'll be doing mostly coastal sailing and may just rig it so it doesn't kick-up anymore. I personally feelt the original rudder isn't stong enough for the conditions of the Korean East Sea, so maybe a more solid wood core will do the trick.

Any and all advice... especially the techy stuff would be much appreciated.

Mark
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Old 19-08-2008, 21:02   #2
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What was the original material?

Weight would be my concern.

Our rudder is cored and sheathed in ply.
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Old 19-08-2008, 21:05   #3
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Hey Mark,

You might want to pick the brains of the fellas over at www.boatdesign.net/forums/

That being said, your plan sounds a lot like what I have in mind when I haul out. You might want to beef up around the pivot point, and spend some time studying where the next weak link might be.

Cheers,

Zach
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Old 19-08-2008, 21:33   #4
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I built a rudder for a 20 footer once. Never again. That said, try Minneys Yacht Surplus. They have some used rudders laying around. It cn be done, and If I recall, I sent Wheels a magazine article on it a few years back, but if you have the option, used and ready to go is the better option.
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Old 19-08-2008, 21:48   #5
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Go for it! You're not going to get into too much trouble with a rudder for a 22' Catalina. Besides, think of the bragging rights you'll have when the new, replacement comes and it's not much faster than your first effort at being a partially fledged shipwright. Plus, you'll be back on the water in a short time.
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Old 19-08-2008, 22:24   #6
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Hi Mark,

I see no problem with your plan. You don't need to sand it all that smooth, as long as it is fair. A rough surface will only let the epoxy adhere better. If you arre looking for some extra strength in the laminate you might consider unidirectional and biaxial fabrics. As I have recently learned, you do not need to have a razor sharp trailing edge on your foil. Shouldn't take you much more than a long weekend. Best of luck!

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Old 20-08-2008, 00:18   #7
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Ply is not the best choice. It does not like repeated side loading and unloading and will eventually break. Solid timber cut into 1x1 or 2x2 (depending on rudder size) laminated together is better. Then shape and glass. I don't think the wee catalina had much of a specific shape. But if you want to shape it specifically, use the NACA0012 formula. Actually if you do uses it, it helps you shape evenly by giving you points of reference to shape to.
http://www.ppart.de/programming/java...les/NACA4.html
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Old 20-08-2008, 00:35   #8
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Alignment at 30 degrees

If I remember correctly the plans for the Hartley ROTC 32 that I built specified a marine grade wood (able to withstand continuous submersion) with two layers of planks at a 30 degree angle to each other and epoxied together.

The bronze fittings were riveted on with 3/8" copper rivets.

Given the difficulty of getting bronze these days I would put my faith in stainless strip through bolted ahead of a layer of fibreglass. Both would be better.
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Old 20-08-2008, 00:38   #9
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I agree with the laminated wood vs ply. That is what I used. I created a laminated board, then shaped it with a plane and grinder, then glassed over. Getting it fair, and getting the shape I wanted was quite a chore, but, it did turn out nice. I suppose hat turned me off was the fact I found a rudder for $50 after I was done, and it looked just as good as the $50+ in materials I had put hours of my labor into.
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Old 20-08-2008, 01:57   #10
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Hey Guys,

Great stuff. Your advice has been very usefull. I'll look into using the laminated wood. Buying a used rudder blade would be okay, but it would still probably cost me around $300 to $400 to ship it here to Korea.

Anyway, I still think the original rudder design isn't strong enough. It has a very thin plywood core, maybe a quarter inch, surrounded by hard foam and finally a layer of glass with a paint finish. I think a more solid core would make a difference in the open seas.

As far as weight goes. I'm not sure, but after the blade broke off (the piece was about 80% of the entire blade), It floated on the water so my guess is the rudders would be about the same weight in the water.

While the blade broke, the rest of the rudder and tiller is intact. I can take the fittings off the old rudder since I was able to recover the whole thing.
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Old 20-08-2008, 02:03   #11
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Use a good glue, what ever you do. And re-inforce the load points with extra thickness if you laminate or metal overstraps. If the back edge f the rudder falls off that's live able, if the front edge falls off you got no rudder.
Half round on the front edge, 6" (3 will do) at the back edge.
This is only a spare until the catalina replacement arrives? and will make a nice saloon table top until it'd needed again. 'Multi' Tasking!
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Old 21-08-2008, 06:59   #12
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Okay. After some good advice here and doing some extensive research, I've decided to laminate to sheets of some kind of solid hard wood, probably oak, together using epoxy. I'm going to try and creat a foil and then I'll put a couple layers of glass and one final coat of epoxy. After that I'll sand it down and put on a finishing coat of paint. Hopefully I finish most of the work this weekend. I'll post some pics when I get a chance.
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Old 21-08-2008, 09:30   #13
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Sounds like a good plan. You might consider some alternatives to oak such as spruce or clear douglas fir. Oak (particularly red oak) is susceptable to rot and is a little harder to work and heavier. You will find that the strength (though not hardness) is similar with the softer woods. Check this link to consider your options.

http://http://www.fpl.fs.fed.us/docu...tr113/ch04.pdf

Best of luck and keep us posted.
Mike
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Old 21-08-2008, 11:26   #14
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OK, So, I missed the fact you are in Korea. You are correct about the shipping cost from the US. I also would advise against Oak. A hard wood is not necessary, but rot resistance is a must. You need something that will flex such as Cedar, or Spruce. I would talk to some of your local wood suppliers to see what local wood has those properties (Rot resistance, and flex).
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Old 22-08-2008, 02:38   #15
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Every site I've checked has said to use hard wood. And as far as I know, fiberglass doesn't flex that well. Is it possible to have the wood be more flexible than the glass and have the skin rupture because of too much flex?

I'm looking into the wood rot thing now. If cedar is okay, I may use that. The place I checked yesterday didn't have African Mohogany or Oak but they did have red cedar.
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