[Public-list] bronze rudder post replacement
mainstay at csolve.net
mainstay at csolve.net
Wed Oct 18 06:00:38 PDT 2006
Hi there -
I agree with John - there are a myriad of varieties of bronze, as I
learned the hard way making lifeline stanchions. Some are soft, some
are brittle, some will rust! Silicon Bronze is hard and stiff, has
terrific strength and endurance. Aluminium Bronze is even better but
costs a lot.
We had a shipment of Alum. Bronze stanchions made; I gave the maker
precise information about the alloy I needed. Regardless, they used
another alloy (1/3 the price). First I knew of the switch was a
concerned call from the schooner's skipper in Bermuda saying that the
new stanchions were 'bleeding red rust'. How could this be?
I went on a crash course on alloys and chemistry. Aluminium needs a
bit of iron in the mix to help it do its thing with the copper... and
5% Nickle to bind the iron. Cheap alloys don't have any nickle.
Without the nickle the iron rusts... expensive lesson! We had a new
set of 18 stanchions made and rushed out to the ship...the sat down
and had a talk with the foundry about 'saving money' and following
instructions...
Gord
Quoting John Birch <Sunstone at cogeco.ca>:
> Try to get silicon bronze, easier said than done - there is a lot of stuff
> out there called bronze which is closer to brass ... some "bronze" even has
> zinc in it - you don't want that. Also I would suggest you want forged,
> rolled or extruded bronze not cast - plain castings are not nearly as
> strong.
>
> Same with bolts and screws - silicon bronze. A "great deal" usually isn't,
> its often crap bronze - use a reputable specialist supplier - up here I go
> to Pacific Fasteners off Chauncey Drive off Islington in Toronto.
>
> Just a suggestion
>
> Cheers,
> John
>
> ----- Original Message -----
> From: <brooks.glenn at comcast.net>
> To: "Alberg 30 Public List -- open to all" <public-list at alberg30.org>;
> "Alberg 30 Public List -- open to all" <public-list at alberg30.org>
> Sent: Tuesday, October 17, 2006 11:51 PM
> Subject: Re: [Public-list] bronze rudder post replacement
>
>
>> Hello Chris,
>>
>> I would definitely replace with bronze, except probably all the metal in
>> the rudder should be replaced bronze. I just took my 30 yr old bronze
>> shafts ( and rudder from which they recently were attached) to a
>> commercial boat yard/machine shop. The shop owner said his experience is
>> that short gudeon shafts are very common on sailboats, particularly if
>> located just below the prop aperture, ala A-30's... Two small pins run
>> into the rudder centerline are all that are needed to hold the shaft from
>> turning. B
>> ronze shaft material is commonly available in many sizes. Any good
>> machine shop could turn the grudens/(pintels??) out of bronze stock, +
>> there are several foundries on the internet who sell cast pieces...
>>
>> Here's what I discovered when I removed both upper and lower shafts, plus
>> the 6" mid rudder grudeon shaft... Found out
>> the upper shaft runs from the tiller assembly, down through the stop water
>> in the hull, then down the leading edge of the rudder, then bends rearward
>> around the inside of the prop aperture to about 2/3d's of the way to the
>> bottom leading edge of the rudder. The shaft sort of zig zags ( picture
>> half a carton ligthing bolt)to get around the back side of the prop
>> aperture, and runs behind the grudeon shaft about 4-5 inches. The machine
>> shop guy says this design gives terrific additional strength and tranmits
>> a great deal of torque down through the rudder, Thus helping prevent the
>> shaft from twisting in the F/G and foam rudder body.
>>
>> I am goling to have the shop extend the new shaft anothor 18" or so down
>> to the bottom of the rudder- replacaing the origianl 8" lower stock wikth
>> this all new, full length piece. I cut through about 4 ea 5/16" pins
>> bedded laterally through the rudder center line and seated in the shaft
>> itself. The pins also stop the shaft from torquing out of position.
>> Will put 4 or 5 pins through the new full length shaftin to the rudder
>> body to prevent twist.
>>
>> My existing upper and lower shaft is 1" bronze. Gudeon shaft origanlly
>> 3/4" bronze, but now 5/8 and crumbling rapidly, with 2 1/2" 5/16th bronze
>> pins holding it from twisting.
>>
>> Bronze shaft stock is still commonly available, so I am going to stay with
>> all bronze shafts. I wouldn't worry about casting the gudeon shaft. you
>> should be able to buy a piece of 3/4, 7/8 1", 1/18 and up, as you need.
>>
>> Also am thinking about having the shop make up a second set of
>> gudeon/pintels ( still havent figured out which is which), ie to add an
>> additional pivotpoint/support either at the top of the shaft just below
>> where the fairing leads into the full or above the rudder shoe... this
>> is probably overkill, but am going to Hawaii and Alaska in next couple of
>> years, so its just extra small insurance.
>>
>> BTW, the easiest way I found to cut out the FG material around the shaft
>> was to use a thin, high speed composite metal cutting wheel on my 4"
>> grinder. This cut a nice clean, vertical 3/16 slot through the FG layers,
>> just like butter. Then hung up a bit on the shaft material, making a nice
>> depth gauge for cleaning out just enough material to chisel out a channel
>> where the shaft was embedded in the original mold.
>>
>> I will grind out the top half of the rudder and reglass and pin everything
>> back into place once the shop returns my proud and shiny, NEW full length
>> bronze shaft assembly, and I fit it into the existing channel.
>>
>>
>> Also, I intend to have them machine a 5/8 or possibly 3/4" pin directly
>> out on the end of the new full length shaft assembly, and ream out the
>> rudder shoe to accept the new pin dimension. Will give lots more strength
>> and longer life. Also might go with 1 1/8th" stock instead of existing
>> 1", and have then turn the top part down to 1" to fit the packing gland in
>> the full. Again, small difference, but a lot of added strength and larger
>> pin size for the next 30 years wear and tear.
>>
>> I spent a lot of time very tentatively cutting into the rudder to remove
>> the two lower pieces-- maybe 4 hours. Once the shape of the upper took
>> form, it went quicker. Now I wouldn't hesitate to whack the thing right
>> from the beginning, top to bottom in an hour or two, if I had to. Which I
>> won't , because in 30 years the boat will be 60 years old and I'll be 90,
>> so probably will just sell it and buy another which already has the work
>> done.
>>
>> So, probably more info than you wanted to know, but it wasn't nearly the
>> fema disaster I was expecting. Iam very confident ( now) the whole thing
>> will go back together in short order, probably by end of the week, except
>> for curing time...
>>
>> PS. George, thanks Very Much for the followup info you sent. Very
>> helpfull anticipating how to do this thing!
>>
>> Glenn
>> Dolce #318
>>
>>
>> -------------- Original message ----------------------
>> From: "Chris Blain" <chris.blain at gmail.com>
>>> I have another question regarding this whole assembly- the mid rudder
>>> strap/gudeon - has anyone fabricated one from bronze strip, or is there a
>>> source for a cast one? My boat (an A35, but identical in rudder
>>> contruction,
>>> had a stainless strap which showed classical corrosion patterns and was
>>> almost gone, and I'd prefer to replace it with less prone to corrosion -
>>> bronze.
>>>
>>> Thanks,
>>> Chris
>>>
>>>
>>> On 10/17/06, brooks.glenn at comcast.net <brooks.glenn at comcast.net> wrote:
>>> >
>>> > Hi George,
>>> >
>>> > I would like to ask an additional question regarding your rudder stock,
>>> > if
>>> > I may?
>>> >
>>> > Is your lower rudder shaft all one piece or two short pieces?
>>> >
>>> > I just opened up my lower rudder and found two short pieces 6-8" long:
>>> > one
>>> > at the bottom with the pin fitting into rudder shoe, the other at
>>> > mid-rudder
>>> > where it can be grabbed by the pintel/grudgeon assembly...Both have two
>>> > 5/16" round pins several inches long bored into the rudder to keep
>>> > everything from spinning. The design seems a little light weight for
>>> > off
>>> > shore sailing...( but it has lasted 30 years now...)??
>>> >
>>> > Do you have any thoughts about replacing these two short ones with one
>>> > long shaft- aside from cost?
>>> >
>>> > Thanks much,
>>> >
>>> > Glenn
>>> > dolce #318
>>> > -------------- Original message ----------------------
>>> > From: George Dinwiddie <gdinwiddie at alberg30.org>
>>> > > brooks.glenn at comcast.net wrote:
>>> > > [snip]
>>> > > > Can anyone suggest the best way to do this?
>>> > >
>>> > > I don't know if it's best, but my approach is included in the
>>> > > Maintenance Manual. Basically I chiseled out the foam and removed
>>> > > the
>>> > > lower post, which was in a condition similar to yours. I had it cut
>>> > > off, drilled and tapped. I then put it back in the rudder with glass
>>> > > and epoxy and filled the voids with thickened epoxy.
>>> > >
>>> > > > PS, I really don't want to go stainless as the pintels and shoe
>>> > > > are
>>> > > > in excellent condition, and the rudder post mounted in the hull is
>>> > > > bronze.
>>> > >
>>> > > You really don't want to use stainless below the waterline. See
>>> > > http://alberg30.org/maintenance/Steering/CreviceCorrosion/
>>> > >
>>> > > --
>>> >
>>> > >
>>> ----------------------------------------------------------------------
>>> > > When I remember bygone days George
>>> > > Dinwiddie
>>> > > I think how evening follows morn;
>>> > > gdinwiddie at alberg30.org
>>> > > So many I loved were not yet dead,
>>> > > http://www.Alberg30.org
>>> > > So many I love were not yet born.
>>> > > 'The Middle' by Ogden Nash
>>> >
>>> > >
>>> ----------------------------------------------------------------------
>>> > >
>>> > >
>>> > >
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>>
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