You will have a very hard time finding malleable iron bolts these days. 99%
of what we call "wrought iron" these days is actually mild steel. You can
find aluminum bronze which is much better but it will cost you more than the
rest of the boat.

Because of all the talk about crevasse corrosion I did a lot of research
before settling on 316 stainless. Crevasse corrosion requires an oxygen
depleted environment AND an electrolyte like seawater. If the hull to keel
joint is reasonably well sealed there will be no electrolyte. Stainless is
a compromise but 99% of production boats are built with stainless keel
bolts. If it were as bad as a lot of people think we would have keels
falling off all over the place.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"pete" wrote in message
...
Thanks, where I live there are loads of these guys. You have confirmed
what I thought about the stainless problem, but do I need to use
larger diameter iron bolts in lieu of a given diameter for the
stainless ones?

The hull is wood strip composite, so no problems for anything there.

On Tue, 14 Feb 2006 20:24:17 +0100, "Steve Lusardi"
wrote:

Pete,
The best choice is maleable iron, but finding them is difficult. Find a
guy
that makes wrought iron gates. It is best to have them made by a
blacksmith.
The second best is manganese bronze. The absolute last material to use is
stainless. The explanation is long and tortuous, but here is a short
version. Stainless is susceptable to crevise corrosion and when it occurs,
it is very fast. Stainless is rust free only in the presence of oxygen. If
the bolt is subjected to rubbing, even a little bit, the oxide coating is
removed and must replentish. When the water around the bolt is oxygen
depleted (stagnent water), the corrosion begins. Iron is non-homogenous
and
is not susceptible to internal electrolosis like steel, because steel is
an
alloy (homogenous). Bronze is also good, but it is suceptable to
dissimilar
metal electrolosis, especially with steel alloys and requires extensive
galvanic protection.(sacrificial anodes) In making your choice, you need
to
consider hull material and underwater metal. When using iron, use old
fashion red lead packing for protection outside and tar inside.
Steve

"pete" wrote in message
news

Hi, I am pretty sure this question has been covered before, but I
thinking now about casting my lead fin keel.
The architects drawings show the keelbolts bent over inside the keel
to lock them in, but I have always been told to draw a keel bolt every
few years to check their condition.

Any thoughts on this? It would be simple enough to fit a frame with
nuts to screw the keelbolts into before pouring the lead around, so
that they stay unscrewble, but is this the best solution?

And is there a better material to use than stainless steel? - Within
reason that is.

The keel weight is 2 tons

Pete