Rudder stock material ?

[PeterSibley]

On page 218 of Bud MacIntosh's "How to Build a Wooden Boat" there is a drawing of a metal rudder stock being heated so that it will bend from its own weight.The text doesn't say what alloy of bronze or what grade of stainless would be suitable.Any suggestions re a heat bendable bronze
alloy available in round stock ?

I will probably be using a bronze casting to carry the stock through the counter timber,what casting alloy would be best in combination with the rudder stock...my foundry likes gunmetal whenever possible , so thats what it would be unless otherwisw specified.

[Wooden Boat Fittings]

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Someone will probably chime in with the right alloy composition Peter, but I've just come in from heat-bending some small-diameter bronze rod for a pennant staff, and as far as I know it's the hard-drawn silicon bronze routinely supplied as gunmetal by White's (or Brass & Copper in your neck of the woods.)

B&C's phone number is 9624 2355.

And yes, it does bend under its own weight once you get it to red heat. Metal spaghetti.

Mike

[PeterSibley]

Thanks Mike smile.gif Is that B&C number Melbourne....03 prefix? and they sell hard drawn silicon bronze rod as gunmetal ?? OK.. I'll ring them ,as long as it bends! I've had some very unsatisfactory experiences trying to bend brass rod..no idea what kind of brass it was.It left me with a lot of brass punchs in very short lengths !

More comments please on the best alloys.

[ 07-13-2004, 06:19 AM: Message edited by: PeterSibley ]

[Wooden Boat Fittings]

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No, B&C's number is 02 Peter. They're at 14 Stanton Road, Seven Hills. (They and George White here in Melbourne are somehow related, but I don't know the connection.)

I'm by no means sure of their terminology you understand, but if you tell them you're after hard-drawn bronze that's heat-bendable you should be fine. If they're anything like GW they're very helpful people anyway, and they'll let you pick their brains to your heart's desire.

Mike
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[PeterSibley]

Mike...the material they supply is LG 2, leaded gunmetal.Not silicon bronze ,they said they don't stock that ,but I think LG2 will suffice.A bit more checking to do.
Peter

[John E Hardiman]

You want bronze (copper-tin) not brass (copper-zinc) Some bronze is hot workable, most brass is not hot workable. Anything with more than (really bad edit...It should have said 10% or red brass not 1%...sorry)~10% zinc or lead will give problems. LG 2 is a Copper(85)-tin(5)-zinc(5)-lead(5) alloy somewhere between bronze and brass which is recommended for friction surfaces (hence the lead always for lubrication),castings and bushings, not for hot working.

You want aluminum bronze (http://www.suppliersonline.com/propertypages/C64200.asp) (alloy C64200).

[ 07-14-2004, 11:45 PM: Message edited by: John E Hardiman ]

[PeterSibley]

Thank you John...very much appreciated !

[PeterSibley]

John, how would LG 2 be for a cast stuffing box/bearing in conjection wth the Al.bronze C64200 ?

[John E Hardiman]

Corrosion should not be a problem (they're right next to each other in potential). Aluminum bronze is harder than LG 2 (~180 vice ~60 HB), so shaft wear is not a problem and LG 2 is for bearings (web page) (http://www.sarucopper.com/leadedbronze-alloy.html) . Tensile and yeild for Al bronze is ~twice LG2 so plan the casting accordingly.

[PeterSibley]

Again....thank you!

[Wooden Boat Fittings]

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Thanks John.

Maybe the two companies don't carry identical stock, Peter. I didn't specificially ask GW for silicon bronze for the rods, but I don't think it can be LG2. Whatever it is, it's certainly heat-bendable anyway --

http://www.woodenboatfittings.com.au/public/p-staff-rod-s.jpg

As I said, metal spaghetti.

Mike

[PeterSibley]

That certainly bendable Mike ! I'm impressed. Next time you're speaking to them perhaps you could ask exactly what it is they're selling you smile.gif

I followed up on John's advice and priced the aluminium bronze and it's just a little bit expensive ! redface.gif Now my local steel merchant has 316 stainless in 1 1/2"round bar at a much more reasonable price......how do you think it would fare with the LG 2 casting ?( bearing in mind that the whole hull is copper fastened ) Strength should be no problem.I can also have it cold bent at the same establishment which would be a major advantage bearing in mind the amount of heat required to hot bend the bronze.

[Wooden Boat Fittings]

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Well, if you stayed with any sort of bronze for both, there'd be less room for electro-potential-difference problems.

But on the other hand, similar metals in situations like this can tend to "stick" together (at the molecular level,) which you wouldn't really want happening.

But on the first hand again, maybe the lead in LG2 would prevent that developing -- as John says, it "lubricates" the metal a bit, like graphite powder in a padlock.

And on the first hand still, if you have a stainless stock, and if corrosion does occur, it'll either happen in the casting -- which would presumably be harder to replace than the stock itself -- or in the rivets, in which case I suppose you might need to replace stock, bearing, rudder, boat, and all....

So I'd stick with the LG2.
smile.gif

Mike

[John E Hardiman]

If you do use 316 here are some guidelines.
A 316 SS spec page (http://www.askzn.co.za/tech/tech_grade_316.htm)

1) Use 316L because the lower impurties reduce corrosion problems

2) All 300 series stainless is suceptable to crevice corrosion (316/317 are the best of the lot) so insure that the bearing surfaces are not tight and flooded with stagnat seawater.

3)Anneal after all forming and welding to passivate the surface.

4) USE NO FERRIC TOOLS OR FERRIC CONTAMINATED ABRASIVES ON STAINLESS. You'll get pitting.

As for using LG2 as a bearing material, I think as a structural casting it will do fine, but I'd use a non-metalic bushing (with a fair amount of clearence to reduce the chance of crevice corrosion) between it and a stainless shaft.

[PeterSibley]

Thank you both John and Mike, more food for thought.

[PeterSibley]

John, the alloy you kindly specified is not available in Australia...I'm doing a search here by phone for a corresponding alloy.

Available here are Aluminium Bronze 95400, 95800 =(AB2),and AB1 .These codes are Australian I understand and problably don't appear in your handbooks.If they do ...perhaps you could recommend one .

[PeterSibley]

Bump

[John E Hardiman]

Peter; both the alloys you listed are casting alloys, not wrought alloys. You need wrought aluminum bronze rod something like CW 304G, CW 305G, or CW 307G (NI-AL bronze) to use the BS EN codes. You want a wrought alloy with the following composition

Aluminum (Al) ~9%
Nickel (Ni) 0-4%
Iron (Fe) 0-4%
Copper (Cu) remainder

In ISO code it should look something like this:

CuAl7Si2 =C64200 aluminum bronze
CuAl9Mn4Ni4Fe4 =C63200 nickel aluminum bronze
CuAl9Ni3Fe2 =CW 304G nickel? aluminum bronze
CuAl10Fe1 =CW 305G aluminum bronze
CuAl10Ni5Fe4 =CW 307G nickel aluminum bronze

Edit: Try www.copper.org (http://www.copper.org) for the Copper Development Assn. who are the guys that make up the CXXXXX numbers. They have a fairly good reasearch site and spec cross reference.

[ 07-21-2004, 12:05 PM: Message edited by: John E Hardiman ]

[PeterSibley]

John, I know the alloys mentioned are not suitable, I'll keep looking and thank you for the composition figures .At least I can now give the composition of the alloy I need .Much appreciated.
Peter