rudder discussions

[C-164]

Thanks for the replies, guys. Since I don't have a manuel yet, everyones posts on the rudder threads gave me all the information I needed. Got my rudder off today at anchor. Went at it with a mask and snorkel and a 7/16 open end wrench tied around my neck with some twine and a vice grip.The bronze strap holding the rudder shaft to the keel was attached with 2 stainless steel bolts with 7/16" nuts. They came off easily as did the tiller head. I appreciate someones comment about opening the slot on the tillerhead by banging in a large screwdriver. Worked for me and came off with just a little prying.
Oh yea, of course I tied the rudder with line, then I yanked the tiller up as far as it could go, went back down, pushed the rudder shaft off of the shoe came back to the cockpit and removed the tillerhead then dropped the rudder.
Anyone need half a rudder?

Barry

[Tim Mertinooke]

We need some pix of the rudder being extracted when yer beached

Oh don't you worry about that. I just hope you guys aren't working off of dial-up.

Rudder neutral buoyancy?.

As I understand it the shaft should not be taken into account when figuring the density which in turn determines the buoyancy of the rudder as it acts as a pivot point and rests in the shoe, therefore it's weight is insignificant. The blade of the rudder however is allowed to move side to side and can do so either by sinking or floating, but the shaft cannot.
I have read that a well constructed rudder should have the same density as the water it is in. If the rudder is more dense than the water it is in and you are healing 10 degrees lets say, the rudder will have a tendancy to want to sink. This can affect the feel in the tiller and possibly the handling of the boat. There is of course a force against the rudder as the boat is moving through the water which could negate the sinking rudder, but on a light day I think it may be noticable and I see the logic in the argument even if it is a negligible amount of pressure caused by it wanting to sink. If the rudder is less dense than water, then it will have a tendancy to want to float. In that case as you were traveling in the same situation mentioned earlier heeled over, you would be compensating against it's buoyancy. If however the rudder is the same density as the water it is in, then it should not sink or float, but stay where you put it. Of course this isn't taking into account weather-helm, etc. which could make this a moot point, but nontheless it seems like a good argument to me that a well balanced boat has a rudder with the same density as the water it is in even if it takes an America's Cup skipper to notice.

How do you weigh an immersed rudder? Might be good to know.

You can get the density of the rudder through water displacement if rudder is removed and then find its mass by weighing it then converting. With the mass and volume you can get the density. Compare that to water which is about 1g/cc. More it sinks, less it floats. You would have to subtract the mass of the shaft, but include the "bar stock" that extends into the rudder which might make for a tricky situation. To get the mass of the just the shaft I supppose you could submerge just the shaft end of the rudder into a kiddie pool and measure the amount of overflow somehow and that would give you a pretty accurate volume reading. Then you could find the density of that particular bronze and simply multiply the volume with the ?g/cc to get the mass of the shaft. You could then subtract that from the overall mass of the rudder and shaft and that would give you the mass of the blade and bronze located within the blade.

Thing is, neutral buoyancy isn't really possible if you're going to use 6' of 1" bronze rod for your rudder post! Or have I got it wrong?

I have a habit of being wrong more than right and I have no ego to harbor, so if I am wrong or my logic doesn't jive with others, someone chime in.

How did Carl Alberg figure it?

Good question, but I know my Typhoon rudder is made of two pieces of plastic that foam was injected into, then the whole thing was covered in FRP. I wonder how much Alberg called for specific construction methods and materials to be used, and how much of that went to the wayside in the search for a cheaper product to produce by the manufacturer. Cape Dory infamously used regular steel backing plates welded to bent steel rebar for its chain plates on the CD-28. These backing plates have been the achiles heel of a world cruiser now that these boats have hung out in salt water environments for the past 20-35 years and have begun (or have) to disinigrate. I don't think Carl would have ordered that up, do you? Someone was looking to save a buck. My boat has no seacocks, surely a stubborn swede with an eye for seaworthiness would not have specified that.

[ebb]

Tim,
OK, basicly if you disregard the weight of the rudder post, it could be figured that in the traditionally designed Alberg rudder of wood, a couple long bolts and a few screws... you have a neutral buoyant rudder there. Wood floats, add some metal and you got neutral. By definition.

On the Foss Foam rudder site they suggest that if you have a n.b. rudder it would be a breeze to remove it in the water. This is where my understanding breaks down - it seems you'd have to leave the rudder post in place for that benefit. I would guess the preponderance of Foss Foam rudders are spade in shape and not keel attached. They have a short ss pipe for the shaft with a couple short welded fins to keep the foam from turning inside the skin. Maybe yer Cape has one of these? Anyway the rudder unit in a modern foam design would be significantly lighter and perhaps easier to remove in water. Remember though, they have to skimp on the plastic and glass which is 3 times heavier than wood and only displaces water.

An Ariel rudder could be removed that way, but its weight will be significant.

On the Foss site they say that a n.b. rudder would reduce "the moment of inertia in the stern." But it would not, if traditional constructed, reduce the weight added to the stern by metal.

Could somebody make an arguement FOR our original rudder in that its metalic weight creates some welcome inertia to ease steering? Dampen steering movement? Would a lighter rudder make for easier steering?

With a thin blade and a 1" diameter bronze rudder shaft it isn't obvious how a lighter rudder could be fashioned.

Still, a neutral buoyancy rudder is a matter of function, not weight, and that kind of thing is what engineer's brains are made of. (To me this urethane foam rudder is "compromise design." The term neutral buoyancy is a quasitech term invented to sell questionable skin and foam and s.s. rudders to the consumer. )
Thanks for making it clearer. IF I got it?

[commanderpete]

Good job on the rudder Barry.

Sounds like your rudder has been off before, since you found stainless bolts.

You guys who have taken the rudder off....how was the rudder strap held on?

[Tim Mertinooke]

My strap which had been on since at least 1974 making it most likely original was held on with two pins with a carraige bolt type head on one side and peened ends on the other. I knew that I was going to replace the strap as it was well worn and slightly corroded so I decided to take the destructive route and drill out peened ends until they could be tapped out. Removing the strap was easy once the pins were removed. Then I overdrilled the holes and allowed them to dry out for a while and gave healthy doses of acetone to speed the process up. Once it was completely dry I filled with epoxy, then redrilled the holes to accept the 1/4 bronze bolts I put in to hold the new strap.

More details here.








The new strap fabricated from a 1/8 inch sheet of bronze provided by Ebb.




After the epoxy cured and I redrilled the holes, I set the strap in 5200. I used bronze carraige bolts and nuts from Jamestown to hold it in place.




Hopefully I will not have to remove the strap when I make my temporary rudder repair as I plan to sandwhich plywood to either side of what's remaining. This winter however, I will be removing the strap to remove what is left of the rudder and will start from scratch. The shoe will stay on as it is bedded in 5200 and I epoxed the bronze pins in place to ensure a watertight, strong bond as I only peened the ends of the pins on the shoe. I hope to fashion a new rudder to Albergs modified design and use a full length bronze shaft ($$$). I also want to make it so that it can be put on and removed without removing the shoe so that I can do repairs in the water. Right now the rudder cannot be lifted high enough to remove it without removing the shoe. This will require a nifty modification to the top of the rudder so that the shaft will clear the shoe, possibly a bolted on piece that is strong, but removable when desired to do so. I'm thinking of epoxying with cloth over marine plywood for the rudder construction, but I still have time to work those details out.

The Contessa 26 and the Flicka were also on my list when I was looking for a bigger boat earlier this year. I always saw the value of the transom hung rudders in terms of simplicity and repair potential. Our rudders are annoyingly less so, but hey, we have overhang and that is sweet!

[ebb]

imho The rudder shoe is a permanent fitting. There should never be a reason to remove it.
The gudgeon is a maintenance fitting if it can be called that. It is what is removed or merely bent out of the way to allow the rudder to be raised out of the shoe and removed.
The gudgeon's main use is to limit the rise of the rudder out of the shoe.
But it is possible to argue that if the gudgeon is substantial, it could allow the rudder to rise above the seat in the shoe. That is it could allow the rudder to rise and still guide it right back down into the seat.

Arguements for this would be that there is more rise available in case of grounding. Depends on what the top limit is. Also if you were persuaded that a delrin or some ultra HDPE washer between the bottom of the shaft and the shoe was an improvement, it could be slipped in and replaced easy. An arguement against is that you could get mud in yer shoe.

Depending on the galvanics of similar and different alloys present, there may be a need for zincs to be incorporated on longer bolts - and easily replaced.

[Tim Mertinooke]

imho The rudder shoe is a permanent fitting. There should never be a reason to remove it.

I have only removed my rudder by removing the shoe, but I like the idea of being able to do so without removing the shoe. How much would one have to bend the shaft in order to remove rudder if the shoe were to stay on. Or is there enough play in the rudder tube to take it off without bending?

Arguements for this would be that there is more rise available in case of grounding. Depends on what the top limit is.

These rudders I'm afraid are not setup well to a grounding as the tube itself travels into the hull at or just above the waterline. If the rudder got punched into the bottom of the hull or if the lateral force was too great within the tube, the consequence could be the loss of steering, but also a hole in the hull where the tube is. I think an upgrade like yours where you reinforce the tube with epoxy and cloth is a well thought out plan and I think should be standard protocol for anyone seriously cruising with an ariel. The transom hung rudders on the other hand would allow the pintles to pop out of the gudgeon if the cotter pins holdng them in place were of lesser strength. If the rudder was attached to the hull via a short cable, the rudder would still be attached to the boat, all mounting hardware would be intact and your rudder would still be with you. Great setup for repair.

Depending on the galvanics of similar and different alloys present, there may be a need for zincs to be incorporated on longer bolts - and easily replaced.

I am going over this in my mind as I make a list of things to get for my replacement. I found a 1" rod 6 feet long for $250 at onlinemetals.com . It is silcon bronze, but I'm not sure if it would play well with the rudder shoe. A zinc is certainly a possiblility for this new setup, but exact materials is ideal to prevent making a battery at the expense of an expensive piece of hardware.

[ebb]

Tim, The reason we don't have a bearing where the shaft enters the boat is to have room to move the rudder over to drop it once it's lifted out of the shoe. (And the TOP bearing removed.) That seems to be the main reason. There is plenty of room in that 1 1/2" tube (maybe its bigger, can't remember) for a 1" shaft to be skooched over. But the gudgeon has to be removed or opened enough.
Couldn't bend the rudder but on 338 there was only glass and plastic around the hole the shaft goes in. Take a rat tail to file it open enough to get it over.

Gudgeon.
Have to make it easy to un-nut the bolt and bend the 'U' open.
Or knock the bolts thru and drop the rudder with the gudgeon in place. til you get it away from the keel. Imco I would not glue this fitting on but use bedding compound. It doesn't need to be adheesed! Doesn't do hardly any work. It's a back-up. Important back-up.

A tired Ariel came into the yard once that had no rudder shoe! It was plain gone! The rudder was hanging there and held in place with what looked like copper plumber's tape in the gudgeon position. It went back in without getting fixed. But this illustrates how important the gudgeon is.

Keel hung rudders that go into the boat have a generic problem with going aground and jamming the rudder up into the boat. Somebody did just that here and posted. Find it? Guess you have to live with this danger. Can't know how extensive damage will be so it's not really possible to prepare for it. I think the rudder looses, not the boat.

Silicon bronze is essentially inert in seawater. It's 98% copper. This doesn't mean your rudder shoe is silicon. Many bronzes like manganese are actually brass, they can have 40% zinc in them.

Bristol Bronze once said that they supplied Pearson with these castings. Manganese bronze underwater is bad news. Who knows what bronze was actually used for the shoes in our A/C's.
The shoe on 338 was heavily pitted on one side as if being eaten or leached away. The eaten side was greyish, it may have been the alloyed zinc in the fitting leaving home.
The rudder shaft was a refit s.s. propeller shaft that showed no corrosion at all. Hard to know what that alloy was or whether it was responsible for the corrosion in the shoe. Obviously the metal mix was BAD.
The zinc was threaded onto a longer bolt thru the shoe. But was not up to the job. Course you never know the whole story.

It is possible to get fancy and make a rudder blade with pvc foam (NOT urethane) and maybe design in a breakaway top or even a bottom breakawy piece that will leave the mid section of the blade usable in a dramatic grounding.

[Tim Mertinooke]

Tim, The reason we don't have a bearing where the shaft enters the boat is to have room to move the rudder over to drop it once it's lifted out of the shoe. That seems to be the main reason. There is plenty of room in that 1 1/2" tube (maybe its bigger, can't remember) for a 1" shaft to be skooched over. But the gudgeon has to be removed or opened enough.

Makes perfect sense, thank you for clarifying that. I must say I am a bit relieved, because the thought of removing the shoe after welding it on with 5200 and epoxy was a bit daunting.

Imco I would not glue this fitting on but use bedding compound. It doesn't need to be adheesed! Doesn't do hardly any work. It's a back-up. Important back-up.

Good point. I used 5200 because I did the strap and shoe at the same time and had it on hand. I think I'll use a polysulfide on the strap when I remount my new rudder this winter.

[bill@ariel231]

FYI: The summer issue of "Boatworks" magazine has a short article on fabrication of a transom mounted rudder using epoxy, redwood and carbon fiber. While the style of the rudder doesn't include a bronze shaft like ours, the choice of materials may be applicable...http://www.sailmag.com/boatworks/

[ebb]

One great idea I've seen - if I recall, from a singlehand race boat prep site -
is a rudder blade that you make up yourself out of foam and glass, whatever, rather like a surfboard -
that slips into a stainless steel rod cage you have hanging on your transom.
The cage, of course, doesn't have to live there, but that may not be a bad idea, it could hook on with gudgeons and pintles. Or that as a unit of hinges and cassette could slip down some huge sail track like system permanently attached to the stern.
The idea was that if you suddenly needed the backup rudder you attach the cage without trailing the rudderblade which would make it impossible to attach while hanging over the transom
- and then slip the blade in.

I would imagine the blade unit would have to be minimum 6 feet. Probably more like 7 or 8 for a well-heeled Ariel.
I believe that rudder blade would be narrow, no more than a foot front to back, and not very thin, for beef.
This page had formulas for calculating torque forces on such a rudder, plans and foil formulas. Those forces would be huge, much more than the forces on a keel hung.

You'd have to split the backstay.
It could be that an offshore Ariel would not handle well with a faraft rudder. Never know - has it been done? It would take some spirited invention and development. Both as a backup rudder and as a possible replacement for the original. And what would you do with the original, lock it into place?

Might have to move the mast.

[bill@ariel231]

There's an old 1980 vintage BOC transatlantic boat at my marina with this sort of setup. The box is on the centerline with a single back stay. I believe the setup used either a wishbone shaped tiller or control lines to get around the backstay. I'll tack on a picture of the mount when I get a chance....

even better... here's a link to the boat with the rudder installed:
http://www.nike4.com/

[Tim Mertinooke]

You'd have to split the backstay.

Nimble 20's or 24's which I think are really cool boats have a mizzen mast that gets in the way of a tiller the way a backstay would on our boats. They get around this by using a triangle shaped piece of hardware made out of stainless tubing that is attached to a fitting on the rudder and on the other end the tiller. It allows free movement side to side without hitting the mizzen. It's a neat idea and could imagine this setup working with an emergency tiller hung on the stern of our boat.

[Orca]

Hi:

I"m interested if anybody has used oak as a material in the rudder. A family friend is a boat builder and I asked him to build me a new rudder after mine recently ripped apart after catching on a lobster pot at speed. He said we could use oak if the wider gaps in the planks over the winter don't bother me. Growing up around wooden boats I know that oak was widely used on rudders here in Maine but I'm not entirely convinced.

Also, I read about taking the rudder off in the water and my brother is a diver who said he could do the job but he asked me to find out if an Ariel can be beached on its side and refloat without flooding through the sink or cockpit drains. We were considering beaching her in the soft mud letting the side rest on a couple of large pieces of styrofoam. Has anybody beached an Ariel before on its side? We have a local wharf that has a tie up for beaching boats in the upright position but this time of the year it would be a pain in the but with all the tourists.

Best,

Ed

[bill@ariel231]

Ed

Yikes! I don't know if anyone has voluntarily done this on a flat surface. Mr. Tim (A-24) has talked about hauling out on a mud berth for his rudder repair.

I'd suggest thinking about finding a place to haul out that has some slope to it... Or... maybe drying out on with some jack stands or a cradle positioned in the water before the tide runs out. The attached cartoon shows some possible waterlines. It looks like the boat should recover just fine, but wave action may put water in the cockpit/icebox/lockers... (Are there any Naval Architects in the house??)

cheers, and good luck
Bill