Hi Matt,
Like your
project. I'm doing a similar one, 42'
steel double ended
cutter. Much of my detailing is similar to yours. So I've been looking at a lot of the same questions.
Regards engines, with a metal
boat I far prefer
keel cooling to the usual
heat exchanger.
Keel cooled and a dry
exhaust eliminate the most common failure areas on
marine diesels. And they eliminate the need to buy a
marine diesel. With this setup you can buy an industrial
diesel for about half the cost. On my
boat I have a Cummins 3.3L. They are available from 65 to 85 hp, with or without turbo. I bought mine for $3995 brand new from a dealer. They are compact, extremely reliable, and run at lower
RPM than the typical
Yanmar type.
If your
hull type is what I
recall it has a
rudder skeg. This, if it is large enough, can be used as your
heat exchanger. This can be a a very clean setup.
Dry stacks can be run out of the
hull, just above the waterline, just like a wet
exhaust. This is done by cutting a hole in your hull about 1 foot in diameter where your exhaust exits and welding in a circle of 316L stainless, 1/8" thick, into the hole. The exhaust is 316L also and is welded to the center of the stainless plate. The stainless does 2 things: one it allows you to have a bare, non-painted area around the exhaust exit to eliminate heat damage to the
paint, and two the stainless has very low thermal conductivity so it severely restricts the heat which is transmitted to the hull.
There is now an American company which manufactures, in the US, galvanized 1x19 wire. I'd suggest you consider this as an alternative to the usual stainless. If the galvanized is painted with coal tar
epoxy (which has about 10 time the flexibility of standard epoxies and is more resistant to
water permeation) and then has a cover of closely fitting, thin walled UV resistant plastic tubing slipped over it (for UV protection) you will have a rig which is probably good for a lifetime. So long as it is protected from rust, galvanized is far longer lasting and long term reliable than stainless wire. It's also much cheaper. Another benefit to this is that the plastic tube covering is very slick and it reduces chafe significantly.
In the same vein, galvanized rig fittings have much to recommend them. I like to weld them up from 4130 or 4140
steel. Up the
mast corrosion is not much of an issue, and these will be stronger and longer lasting than they typical stainless fittings.
Where you do need stainless for hi stress areas like
rigging I highly recommend you look at duplex stainless. I use 2205. Rolled Alloys is a good vendor. Much higher strength than the 300 series stainless and much higher
corrosion resistance. This is a far superior metal.
Regards, Paul