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RT MAN
09-02-2009, 10:28 AM
Which type of bronze for keel bolts,. The plans call for Tobin Bronze but nobody seems to sell Tobin. I'm going to use bronze rod and thread both ends.

Tobin Bronze
Silicone bronze
Phosfur Bronze
Maganeeze Brone

Robert

Don Kurylko
09-02-2009, 01:00 PM
Tobin Bronze is generally referred to as Naval Brass. It is available through Alaskan Copper and Brass http://www.alaskancopper.com/

It is cheaper than the other alloys on your list, but is considered less corrosion resistant. However, it is also the closest to lead on the galvanic scale, so the interaction between these metals shouldn't be an issue. Naval Brass does contain a large amount of zinc and that could be a problem in the long term with de-zincification. This could render the bolts porous and weak unless they are well insulated from the leaching properties of the surrounding salt water.

Candyfloss
09-02-2009, 02:29 PM
Des Townson uses solid copper for all his keelbolts.

RT MAN
09-02-2009, 02:53 PM
Don thanks for Alaskan contact
GaryE plans are 1912 Herreshoff Alerion 111

Canoeyawl
09-02-2009, 04:13 PM
Naval brass is 75,000 psi
Silicon bronze (commonly available) is 85,000 psi

RT MAN
09-02-2009, 05:05 PM
Slicone Bronze it is. quote from Alaskan Copper was $360 for 36' of 1/2" plus shipping seems pricey.

Jay Greer
09-02-2009, 05:23 PM
Dont you think there are better materials today?
No. Tobin "Naval Brass" machines well and is extremely strong. It can also be headed.
Jay

Vinny&Shawn
09-02-2009, 05:40 PM
Not to get off the subject but, we have an iron keel on Acacia, she is 26 years old. If one were to change the bolts,could you use stainless or someone mentioned copper. She is copper riveted.??
Also the boat is very dry just weeps inside hear and there,doesn't seem to work open when sailing hard. In fact she seems to get tighter(when sailed hard),is this my imagination, or the cumulative effect of 6 years in the water year round?

Don Kurylko
09-02-2009, 10:38 PM
Naval Bronze (ex Tobin) UNS C46400 has a tensile strength of 70,000 psi. Silicon Bronze C655 is rated at 85,000 psi. I am using Naval Bronze 1" dia. keel bolts on my cutter. No qualms - they will outlast me.

Vinny&Shawn
09-03-2009, 04:25 AM
Naval Bronze (ex Tobin) UNS C46400 has a tensile strength of 70,000 psi. Silicon Bronze C655 is rated at 85,000 psi. I am using Naval Bronze 1" dia. keel bolts on my cutter. No qualms - they will outlast me.

Is this an iron or lead keel? What is best with iron?

PeterSibley
09-03-2009, 05:42 AM
Des Townson uses solid copper for all his keelbolts.

Standard in Oz too .

and before anyone tell's me it's no good , my 1945 copy of the American Machinist's Handbook gives 60,000psi as the tensile for hard drawn ( unannealed ) copper .36000 psi for soft .

Vinny&Shawn
09-03-2009, 06:20 AM
Standard in Oz too .

and before anyone tell's me it's no good , my 1945 copy of the American Machinist's Handbook gives 60,000psi as the tensile for hard drawn ( unannealed ) copper .36000 psi for soft .

Once again can you use copper in an iron keel?

PeterSibley
09-03-2009, 06:36 AM
I don't think so ,but iron is generally not used as a keel in Australia.I'd seek advice from a Brit ...they also have cold water as against our warm ,I think the last is relevant .

Canoeyawl
09-03-2009, 09:58 AM
Tobin Bronze tensile strength is 35,000 psi
Silicon bronze (commonly available) is 85,000 psi

Sorry, this is in error and I will edit (Thanks Don)

From "Marks"
Naval Brass - rod, hard - 75kpsi
High Silicon Bronze - rod, hard - 92kpsi


(Silicon Bronze has 0% zinc - This would indicate they are very similar in strength, but probably not in corrosion resistance.
Note that Marks qualifies the specs, stating the values shown are typical... ).

Candyfloss
09-03-2009, 02:09 PM
Don't know about iron. All Townson keels are lead.

zertgold
09-03-2009, 06:03 PM
Hmm, my Iron keel is held on with galvanized bolts. They are over 40 years old; I might one day be in trouble. Is switching out those bolts an expensive thing to do?

Ian McColgin
09-03-2009, 06:12 PM
If in doubt hit the keel. You'll know if it's iron. Also, you'll usually have some rust and such unless the iron is very well protected.

An iron keel must be insulated by something from the bottom paint. Red lead is traditional. Epoxy is often used.

Fasten with black iron bolts, best. Galvanized iron second. Galvanized steel if you must. Not stainless and certainly not any non-ferrous unless you can get monel, I think.

G'luck

Ian McColgin
09-03-2009, 06:14 PM
Second thought on keel bolts for iron keel. Huge pain to remove the old. If you really have cause to doubt, like the head is totally exploded, consider sistering in new bolts on some reasonable patter between existing bolts. The only good news is that you'll only have to thread into the iron keel at great depth for a bit over the bolt's diameter.

G'luck

PeterSibley
09-03-2009, 06:35 PM
Second thought on keel bolts for iron keel. Huge pain to remove the old. If you really have cause to doubt, like the head is totally exploded, consider sistering in new bolts on some reasonable patter between existing bolts. The only good news is that you'll only have to thread into the iron keel at great depth for a bit over the bolt's diameter.

G'luck

I don't quite understand you Ian .Are you suggesting boring and tapping a hole to the depth of the bolt's diameter only ?

Ian McColgin
09-03-2009, 08:28 PM
In iron. There's a proper formula but it's a bit over a diameter, maybe diameter and a half. One of our engineers will get this right. Think about it - how many threads, how deep is a nut? The iron keel is just a very very large nut.

This applies to iron, not lead, keels.

PeterSibley
09-03-2009, 09:22 PM
I was thinking of the shear of iron versus steel Ian .25 K psi versus roughly 60K for steel .

It's easy to bore and tap ,I'd go x 3 at least .....I mean why not ?

PeterSibley
09-04-2009, 01:23 AM
Mine are 7/8 " :D , but then I don't mind an hour or two extra work to make me happy with the job .I assume nothing with castings , faults and inclusions are very hard to see .

peter radclyffe
09-04-2009, 01:34 AM
this is not an engine block, its safer to put a bolt thru a keel, or a gallery bolt, as you then have full diameter where it may work & try to sheer at the top of the keel, especially if you run aground,
also when a tapped bolt seizes, its harder to tighten it up if its weeping, whereas if the nut is above , you have greater control

PeterSibley
09-04-2009, 01:51 AM
Mine will be gallery , mainly because turning over a 5600 # keel is verging on serious work without a crane .

I'll have to get the crane in once at least but with travelling it will be $200 a pop .

RFNK
09-04-2009, 02:00 AM
Peter. are you putting iron ballast on this boat you're building? Why? Rick PS The Twister has iron ballast

PeterSibley
09-04-2009, 02:09 AM
No Rick ,lead .It's already cast and sitting beside the keel assembly .

RFNK
09-04-2009, 02:12 AM
Right, I thought it'd be lead. Good for you - I'd have lead over iron any day. Rick

PeterSibley
09-04-2009, 03:09 AM
I don't have a big enough cupola to cast 2.5 ton of iron .Lead was easy .

RT MAN
09-04-2009, 07:56 AM
Mine will be gallery , mainly because turning over a 5600 # keel is verging on serious work without a crane .

I'll have to get the crane in once at least but with travelling it will be $200 a pop .

What is a gallery bolt?

D Happ
09-04-2009, 09:04 AM
Because tapping that deep is a pain and even if you do, it gains you and the connection NOTHING...
no additional strength and no brownie points.


I would agree in steel, but this is cast iron.

willmarsh3
09-04-2009, 09:34 AM
I'd drill the hole at least 3x the diameter deep to allow room for the tap. Breaking a tap in a hole is no fun. DAMHIK.

Canoeyawl
09-04-2009, 09:41 AM
Cast iron thread depth for studs is Thread dia x 1-1/2
(Marks mechanical engineers handbook)
That spec is for a standard steel bolt, what we call a grade two. High tensile studs/bolts will require more thread depth.
For example threads on an iron automotive engine are typically tapped at least two and more normally three diameters into the block.

peter radclyffe
09-04-2009, 12:01 PM
What is a gallery bolt?
a gallery or pocket bolt does not go right the way thru a keel or deadwood, but is stopped, & a pocket is either cast or carved out to put a nut & washer on, it is used also where you want to pull the outrigger tight to the deadwood, but theres not enough wood either side of the sterntube to run a bolt

willmarsh3
09-04-2009, 12:19 PM
amatures do a lot of foolish things... your allowed :D
What I mean is drill the hole extra depth for the chips and room for the tap. Then you can get the required 1 1/2x threads.

Canoeyawl
09-04-2009, 01:33 PM
You want to make your own calculations?
have at it...

It's much faster to just crank the tap in a few more turns...