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Thread: rudder discussions

  1. #286
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    Looks like a 3-plank rudder there! Wonder if it's original?
    Does indeed look good, except for 'incidentals' on the bottom edge.
    Third plank out might have been attached with lags.

    Copper (pink) color on a supposed bronze (gold) shaft would not be a good sign.
    It would mean the alloy was high zinc and the zinc has leached leaving a porous copper behind. Leaching is INTERNAL alloy galvanic action. Does not require anothedissimular alloy nearby. In the case of a copper alloy - too much zinc for salt water immersion.
    If you get serious about making a new rudder, I strongly suggest you go with silicon bronze. So you can keep the alloys in the rudder all the same. High zinc manganese bronze should NOT be used underwater. Nor stainless. I think this is beyond 'my opinion'.
    Prepare for a nosebleed on the price!!! ($53.31 a foot +s&h for 1" S.B. rod from Onlinemetals)

    Impressive action there!
    __________________________________________________ __________________________________________
    Getting bronze for a boat is a big problem these days. Nearly all marine sources are orientated to stainless steel. Silicon rod is still available usually, along with a range of fasteners from SOME marine catalogers. S.B. sheet and bar is impossible to find in small quantity off-the-street sales. As the woodenboat forum says: you have to find fabricators in your area. They may have left-overs from a job because they too have to order 'minimum quantities'.
    Here are three non-ferrous suppliers that show phone numbers on their net pages, it may be a friendly sign.
    Rancocas Metals in New Jersey - 800-762-6382
    Atlas Metals in Denver - 800-662-0143
    Busby Metals Hauppauge NY 800-552-8729. / 631-434-3400 (sometimes get better action with a local number)
    There is no indication from woodenboat forum experience that these suppliers with internet sites will send you a 1 foot piece of bronze in the mail.

    BUT TRY Phil at Metal Service Center*, 7743 Bell Rd, Windsor CA, 707-838-8088. The estate metal and wood shop here where I work buys small quantitys and custom pieces of all kinds of metals constantly from them. No problem. Maybe they UPS. Remember you are in the boat repair business.

    * from whom I ordered my original Everdur from. I got NO break in the price. (gold)
    One metal fabricator in my area is Lux Metals in Santa Rosa CA. They, or actually Dean, welded my silicon bronze rudder shaft and strap armature together. Beautiful piece of work. (platinum)
    They never returned to me some S.B. sheet I had to quantity buy for the job.
    I mention these to show that every metro area has some sort of access to specialty materials.
    Always E X P E N S I V E .
    Last edited by ebb; 03-10-2008 at 12:48 PM.

  2. #287
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    A three planker indeed! Looks old as dirt so I figure the real Mackoy. Thanks for the shout about the bronze. I guess if I convert to Si bronze then I'll have to change my shoe. The shaft is in sad shape but I think it will hold for a bit.

    Well start to scout out options.


    Andrew

  3. #288
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    shaft and shoe

    There is a 'rudder shoe discussion' on the board here about the manganese question.

    The official designation of manganese bronze is that is is a BRASS. It is a pig in a poke.* There is a bit of manganese added to the copper and zinc that makes it quite strong. For example: 58% copper/38% zinc/ 4% manganese. It's as if the M. was a catalyst for two soft metals, like polyester resin, resulting in a much harder material.

    I had a conversation once with Roger Winiarski the owner of Bristol Bronze.
    Most of their castings are done in M.B. Most of their castings NOW are one off above the waterline casting for mega yachts, and mega retros last I heard. They do have a number of castings in their catalog that they must get calls on. And they do have a few silicon bronze fittings.

    Roger said that Bristol supplied all the original bronze for the Pearson Ariels.
    I just cannot believe that Bristol supplied a brass for the underwater rudder parts on the Ariel. He did some casting for me and in the two part cast gudgeon he said he used manganese. And I called him on it. And he started changing the subject. I will probably not use the fitting.
    [and you know, I keep saying who am I to take issue with THIS guy...]

    I had a new rudder shoe cast locally in silicon bronze and I will be inserting a S.B. rudder shaft into it.

    There is no real way you can stop an alloy that wants to destroy itself from the inside out like a brass will do IN sea water. I believe mounting a zinc on the shoe is only a palliative.
    I also believe that the proper bronze has to have been originally used. There are evidently plenty of Ariels that have their shoes in perfect condition after 45 years in brine. Only silicon bronze or some other high percentage copper alloy could have survived that long unchanged.

    Winiarski could be wrong and it is other early Pearson classes that have had problems with their shoes.

    However, 338 did show corrosion on its shoe, but the Ariel came to me with a bastard rudder with a stainless shaft. I assumed the combination caused the problem with the shoe. There was a zinc attached to the shoe with one longer through bolt. The side the zinc was on was most corroded with a whitish coating on the bronze pitting (when dry) that I assumed was zinc. Logically it should have been the other way around, with the stainless shaft being eaten away - but it was perfect. How long the rudder had been there is unknown. SO somehow Winiarski could be right - that BRASS was used for the rudder shoe in the Ariel.


    But that has to be one of the most unfortunate admissions by a professional purveyor of bronze fittings that I'll ever hear.

    *Alberg might have said (had he known!) "Kopa grisen i sacken!"
    There's a cat in the sack - what you think is a fat suckling pig is a stray cat.
    What kind of pig is in your shoe? What kind of 'bronze' is in your fitting?
    Last edited by ebb; 03-11-2008 at 07:28 AM.

  4. #289
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  5. #290
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    Galvanic Corrosion guessing game

    Here is a very short paper by Prof Stephen C. Dexter from the University of Delaware Sea Grant Program. Short but compact with implications. Obviously I'm fascinated by the subject - and there are many commonly held misconceptions this read might start to unravel. Including my own!

    This paper has a revealing galvanic series table referenced 'in flowing seawater'.
    Which is exactly where we want to be when discussing the problem.
    Manganese bronze and silicon bronze are cheek by jowl with each other in the table having a close voltage range. Here I discover the 300 s.s. are closer to the cathodic or noble end of the series.

    So my assumption that copper alloys are more noble than stainless is WRONG.
    Stainless has more problems than bronze like crevice corrosion and changing voltages when covered with slime.
    And I might add, that while the voltage range is amazingly close with M.B. and S.B., the one overloaded with zinc is more prone to falling apart than the nearly pure copper alloy.

    This table shows why we do not want 300 steel in our bronze shoe. And it explains the phenomena I saw on my Ariel's rudder shoe.

    It also shows the surprising over-lapping voltage range between manganese bronze and silicon bronze. Either one can be anode or cathode in a galvanic couple "depending on exact exposure conditions." So that's a good reason to add a third more anodic metal in the form of zinc - if you have that going with those two..... M. bronze shoe and S. bronze shaft, or......

    Galvanic Corrosion Final
    www.ocean.udel.edu/mas/masnotes/corrosion.pdf
    Last edited by ebb; 03-11-2008 at 08:34 AM.

  6. #291
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    Worked on the rudder a bit more this w-end. Dug out all the bad wormy wood and backfilled with thickened epoxy. Decided to give her a few coats of epoxy. I don't intend to "seal" it but rather using the resin to beef up the punky wood, smooth the surface and fill some of the cracks.

    Two more coats and this baby is done. At least for the time being!

    Andrew
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    Last edited by Westgate; 03-16-2008 at 06:10 PM.

  7. #292
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    just as a belt and suspenders measure, i you might want to smear some 3M 5200 along the joint between the resin and the rudder shaft. The dissimilar material may leave you with a path for water intrusion into the rudder core. While the rudder is out, for an afternoon worth of fiberglass and sanding, you could fix it for good....

    cheers,
    bill@ariel231


    By the way you are really close to having a long term solution here (mine has been in service about 11 years now with no sign of splitting or water entry, take a look at posts #259-#263 in this thread).
    Last edited by bill@ariel231; 03-17-2008 at 12:44 PM.

  8. #293
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    plasticizing an old rudder

    gotta listen to bill on this.
    5200 in the metal to wood seams if you are launching now is a good call.

    Depending on how much water is still 'logged' in the wood of a rudder, it could conceivably be successful to GLASS a rudder with a few layers of CLOTH and EPOXY. Arguably the wood is still swelled throughout most of its interior and is 'equalized'. If the water content in the wood was close to 20%, but the surface dry enough for regular epoxy laminations, who's to say it wouldn't work?
    If your rudder there in the photos has been very dry, back in the water the swelling of the wood WILL crack the thickened epoxy. There is always the exception, the stuff may not crack because the rudder is old enough to be almost inert. The blade is also well shaped and thin enough to be successfully subdued with frp but not gelled epoxy.
    Baking the planks in the sun would, could shrink and loosen it up and open up the surface radically. And immersion in water will tighten it up. Swell seams closed again. And reduce the wobble of the planks on their bolts. Wood is amazing.

    In my book the only certain useful epoxy on an old plank rudder is to dress the wood in penetrating epoxy. No more than two coats, loading creates a gummy mess. Goes for a brand new one also. The commercial stuff is very flexible and would not contest the movement of the wood. It would be a sealer and provide a better base for epoxy primer and bottom paint. And add worm protection. You can make a credible penetrating sealer by thinning combined two-part laminating epoxy with xylene.

    If you are going to use the present rudder as is - as a core for fiberglassing - you will have to put many layers of cloth to defeat the core's swelling. It may be nearly impossible.
    If you strip the old mahogany from the shafts, you could replace it with plywood. The method is described here in this thread. (see pg 11, 153>) But does not describe the glassing step.
    You'd rout in coves where the bolts are and sandwich them between two layers of meranti-aguaply. You may not need even to remove the bolts from the shaft. Then apply glass cloth around well prepared bronze rod and
    shaped ply. Ply is not going to swell like planks.

    [What countless skippers (well, maybe they could be counted) have discovered is that both polyester and epoxy allow moisture and or water vapor to enter what the plastics are covering. Depending on how thorough the glass job, it's only a matter of time.
    The rudder with the least future problems has a closed cell pvc foam core.]

    What's good about this plywood method is that you can use what you have - if the metal is in good condition - and end up with another 40year rudder. Your investment is in the plywood, epoxy and cloth.
    imco, ebb
    Last edited by ebb; 03-17-2008 at 07:57 PM.

  9. #294
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    Bill@Ariel231 HAS SUCCESSFULLY COVERED A PLANK RUDDER.

    I would go ahead NOW and do the deed exactly as he describes.

  10. #295
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    OK will do!

    What purpose does the underlay of matt serve in Bill's method? Why not use just 3 x cloth?

    Andrew

  11. #296
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    the mat just builds up thickness faster than an equivalent amount of cloth and it handles irregular surfaces pretty well. given you have covered the surface with resin, the cloth alone may be a good approach. i went with 1 layer of 1.5oz mat and two layers of 6oz cloth. 5 to 6 layers of 6oz cloth may be the equivalent for depth of the whole laminate.

    the area that will need particular attention will be where the shaft enters and exits the rudder. the topmost joint is the one most likely to twist. This area in particular got attention on A-231 with the core cut back a bit replaced with thickened epoxy, 'glass and a bit o'3m5200 added for good measure

    good luck
    bill@ariel231

    p.s. we of course look forward to pictures, unfortunately i failed to photograph my rudder as a work in progress.
    Last edited by bill@ariel231; 03-18-2008 at 12:24 PM.

  12. #297
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    The great cover up!

    I applied a few layers of glass to my rudder this w-end. Following Bill's how to guide first dug out then backfilled problem locations with thickened. Next applied 3 layers of cloth to each side. Then I added 2 layers to each edge. Still to come one more layer on the side and then a final wrap around on the edge. That will give a four layer side and a three layer edge. Of course I sanded each layer smooth before laying on the next. Didn't take as many pics as I should have but the epoxy was flying!!!

    Andrew
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  13. #298
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    Andrew

    looks great... am i missing something. where is the hole for the rudder strap (maybe it's just the resolution of the picture)?

    mean while.. i've opened the top of my rudder (A-231) for a look around after a 11 years of service. yup, as expected the core was moist around the entry point for the rudder shaft. and mostly dry again about a hand span away. I'll post some pictures this weekend.

    cheers,
    bill@ariel231
    Last edited by bill@ariel231; 03-24-2008 at 06:15 AM.

  14. #299
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    No nothing missing. I plan to rout out a new slot for the grungeon strap. This will be done in the region of thickened epoxy you see in the picture.

    One thing that I'm a bit unclear about is the whole issue of water in the rudder. Now a "naked" rudder must be saturated with water. I know mine was even with all that bottom paint. An encapsulated rudder may also get a bit wet. So what's the difference between these scenarios. Does the encapsulation provide a better environment for rot (lack of fresh seawater exchange, low O2 gradient, darkness?).

    I am hoping that this rudder glass job will provide me with service until at least the next haulout. Maybe, if I'm lucky, longer than that. I feel good about the rudder itself now but the bronze is is fairly poor condition.

    Will post finished product pics shortly.

    Andrew

  15. #300
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    Andrew

    for me, skinning the rudder it was a chance to bind together a loose collection of parts with a mix of prior repairs into a solid whole. A side benefit is a smooth skin. it's actually pretty dry in there since the skin has not delaminated. i make a habit to check this every season by sounding the rudder with a mallet or screw driver handle. if it were really soaked, i'd strip the glass back, dry it out and start again.

    not too worried about rot, it takes both water AND air to be an issue. This is the first season i've seen any change on A-231, and the repair is a small region where the rudder shaft enters the blade. I opened the rudder out of curiosity as much as any other reason.

    cheers,
    bill@ariel231

    ps. Now i understand what you are doing with the slot for the rudder strap (i did the same thing with a dremel).

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