Steel Boats and Welding

[Matt sachs]

Originally Posted by Yachts66

Not all at. There are many advantages to keel cooling, just don't use water and keep in mind that unless you are going to go with a loud and hot dry exhaust system you'll still need to pump salt water into your wet exhaust system to keep it quiet and cool. 50/50 solution of antifreeze is what most use in the keel cooler. If you're headed south be mindful that all that hot water inside your boat will be a heat source you may not want. Be sure to give a few coats of epoxy paint to the interior and bilge as well.

Regards,

Thomas

Painting the inside of that thing may not be very easy. Its a foot wide and 13 feet long and three feet tall. What if I scale it, apply phosphoic acid then fill it with antifreeze that has a rust inhibitor? Im not going to start cutting corners, but it looks almost impossible to get clean enough for epoxy. And when I weld the plate back it it will burn it off anyway.
What do you think?
Matt

[haidan]

Originally Posted by Yachts66

Not all at. There are many advantages to keel cooling, just don't use water and keep in mind that unless you are going to go with a loud and hot dry exhaust system you'll still need to pump salt water into your wet exhaust system to keep it quiet and cool.



Regards,

Thomas

Every large work boat I've been on has keel cooling and a dry exhaust, as I do on my boat, on a steel boat you don't need to worry about where the exhaust pipe exit the hull, though weld a stainless plate 3-4" around cause the paint might not take the heat to well. Some of the main reasons for a dry exhaust is to limit the amount of holes in the hull, and to do away with having an impeller pump that will fail on you, which would melt you exhaust hose, best just do it right to begin with. My exhaust, which is a stainless 1 1/2" sched 40 pipe, goes through the transom and right into the water, maybe at some point I'll put a muffler in but so far it's not that bad for noise, worse inside the boat than outside, and the sched 40 pipe will take a long time to rust out if it does at all.
50/50 mis antifreeze will prevent rust in the keel cooler, mine just has the shop primming that the plate came with, but you could always scale it and spray the paint in, either that or use something like a mop to paint it with, it doesn't really need to be pretty.
That's a large area 13x1x3 feet you might be able to section of an area cause that's a lot of antifreeze to buy, mines about 15 gallons total for my 3 cylinder 20hp, though it's in the skeg which is a fairly long narrow fully immersed steel compartment, so make sure that there is adequate surface area surrounded by cold salt water. Also weld a stainless pipe down to the bottom of the tank for the pickup and put the return at the top to insure that you don't ever suck up any air which can block the system from circulating and overheat the engine, this is one problem with the whole keel cooling system getting the air lock out of the system but once you've got it figured out you shouldn't have any problems, unlike system Dependant on impeller pumps and heat exchangers salt water, no mre plastic bags killing your engine.

[Brent Swain]

Originally Posted by Yachts66

Not all at. There are many advantages to keel cooling, just don't use water and keep in mind that unless you are going to go with a loud and hot dry exhaust system you'll still need to pump salt water into your wet exhaust system to keep it quiet and cool. 50/50 solution of antifreeze is what most use in the keel cooler. If you're headed south be mindful that all that hot water inside your boat will be a heat source you may not want. Be sure to give a few coats of epoxy paint to the interior and bilge as well.

Regards,

Thomas

If you wrap a dry exhuast with fibreglass house insulation, 3 inch wide muffler tape then silicone the works, it will remain cool . If you run your dry exhuast thru the transom then underwater by about six inches, with an anti siphone hole( 1/4 inch ) above the waterline, it will remain quiet and cool. Adding water to an exhuast system invites a lot of troubles. Friends have had several engines corrode out by condensation on the valves. They now have dry exhausts.
One Mechanic in Port Townsend was quoted as saying"If everyone went dry exhuast and keel cooling, we mechainics would all be out of work."
A client ,today told me he went for the type of water soluble oil that machinists use , in his keel cooler. The results were impresive. If the top of the keel cooler dries out , the oil sloshed up there keeps things coated until it gets sloshed up again.

[boden36]

Matt, If the space in your keel takes 200 gallons, then if you fill it with water you will be adding approx 2000 lbs to your boat. There will be noticeable effects from this.
Keel coolers work from surface area rather than huge capacity so that would be a pretty lazy 2000 lbs.
To get the best cooling result for the weight involved, you could weld a plate between the tank ends about 2 inches from your keel side, and plumb it top and bottom and use it as a heat exchanger. There are tables available which give an indication of surface area required per horsepower.
Another use for the rest of that space would be to use it as a fuel tank as diesel is not that heavy but you would want to be sure that the welds are 100% as diesel will find its way out of any little pinhole.
We have had a 90 gallon diesel tank in an unpainted section of our keel for 25 yrs with no ill effects.
Regards, Richard.

[Boracay]

Keel cooling with a dry exhaust is a good way to manage the exhaust from your engine. However it is easy to ignore the drawbacks of this method and the advantages of a wet exhaust.

What is an advantage in a cruising yacht is a decent amount of fuel storage.

How difficult would it be to make up a fuel tank of triangular cross section and to insert it into your space?

It would be necessary to put some effort into rust proofing any steel that would become inaccessible.

I have aluminium tanks on Boracay and these seem (with polyurethane foam under them) to have held up well.

[Matt sachs]

Thanks again. I see your point about surface area v/s large volume and I agree an extra 2000 pounds of dead weight dosent sound like a good Idea.
I spent a few hours last night scaling and cleaning the bilge. and its not going to be that tough to divide it up and use the forward section for fuel and the aft section (that is considerably more narrow) for cooling.

Im a long way from engine plumbing but I do like to plan in advance. Since the engine is below the water line, I assume I need to run the exhaust up above the water line then back down to prevent flooding?? Can I run the exhaust back below the water line to vent it underwater?

[Matt sachs]

sorry I see my exhaust question was addressed already, thanks Brian

I have a CNC shop and I was going to ask about the souable oil instead of antifreeze in the keel. Its ton cheaper and one gallon makes 50 gallons of coolent.

[Matt sachs]

Finally, the deck is finished, inside hull is painted, and I'm starting on the aft keel convertion to a diesel tank. ....fun fun. :-)

[Laidback]

Hello Matt,
Here is pic of some fun - additional fuel tankage in corten steel , 8 days ago. Boat back in the water.
Richard

[haidan]

Originally Posted by boden36

Matt, If the space in your keel takes 200 gallons, then if you fill it with water you will be adding approx 2000 lbs to your boat. There will be noticeable effects from this.

How much of a difference would it make, the coolent would be under the water line right?

[Laidback]

It depends on the sectional shape of the hull - a thin hull would sink more than a fat hull. Call 2 thousand pounds a ton of ballast - good. What happens when the tank/s are empty??

[Yachts66]

Laidback, I'm curious why you would go to the added expense of Corten steel?

[Laidback]

Originally Posted by Yachts66

Laidback, I'm curious why you would go to the added expense of Corten steel?

Hi,
3 reasons :- a) because the rest of the boat is Corten steel
b) because in this part of the world, for the similar strength in steel plate the difference in cost is not that great.
and c) The welders wanted to use Corten because of a) above
Richard
P.S. have grounded few times, as a result have additional faith in Corten - although much stronger that ordinary steel plate or mild steel it is subject to corrosion - but modern day epoxies and epoxy primers give good protection.

[hpeer]

Interesting project and construction. I have two steel boats (stupid) and both of them have hollow hulls with a "shoe" on the bottom. 1/2 inch IIRC. The shoe is extra ballast and helps in a grounding. I wacked a submerged piling at 6 knots earlier this year and lifted the boat a foot out of the water. No problem.

How did you manage to get the internal baffles, if that is what those transverse plates are, welded?

[Laidback]

Originally Posted by hpeer

How did you manage to get the internal baffles, if that is what those transverse plates are, welded?

They are baffles - the welders tell me that they were inserted with great difficulty.