Bilge of flat bottom barge

I'm designing a dutch barge. It's a 70x16 footer with a keel plate about 12 feet wide and about 40 feet long of 3/4 ah36 plate. As I'm putting the frames in, I'm thinking about the bilge. Typically I would angle the plates inward to the centerline slightly and put in a bilge box but I'm already having a hard time meeting my max draft.

Until I find a better idea, my plan is to put pumps in for the normal safety and about triple the normal venting airflow thru the bilge. That way flooding is handled by the pump and typical condensation moisture is dried up by the fans.

I'm planning on an air gap of about two inches between my hull insulation and my interior panels so I can vent the bilge right thru the deck

Anyone have a better idea?

 

I don't think I could qualify how good an idea it is, but, what about something like a number of bead channels formed into the bottom a foot or three apart (I don't know if you're familiar with beading machines for sheet metal, you probably are, and they provide the "inspiration" for this "idea" ... such as it is) to provide a localized low spot for water to gather? It can't be much of an improvement save for having fewer places to think about pumping from.

Naturally, putting a bead in heavy steel plate isn't something I'd consider easy....

 

I can bead it with a welder I suppose. Same effect.

Interesting. Thanks

 

I'm thinking 3/4 plate is way too thick, but I'm not a designer.
http://www.boatdesign.net/forums/me...arrow-boat-project-plate-thickness-49002.html

 

I did not want to look too hard in my files. The first thing I found is a container ship of 118 m in length, with an keel plate 13 mm thick.
I know that the thickness depends on many things but to get a keel 3/4 thick, must have done many things wrong.

 

Like the other responders said, 3/4" plate is way too thick for such a small barge.

What most barge builders do is limit the use of these thick plates to areas which are going to see a lot of wear, like in the corners of the barge, or just along the bilges. The rest of the plating is much thinner, usually about 3/8" in a 200-foot barge. For a barge 70x16, you can use thinner than 3/8", depending on your framing arrangement.

Also, ABS AH36 is a high tensile steel, which means that special procedures have to be followed when welding, otherwise you wind up with ordinary (or worse) steel because the heat of welding has destroyed the metal's strength.

 

My barge is 60' by 13', with a flat bottom, and came out at about 15 tons for the hull and superstructure. I used 1/4 mild steel for the hull, and 4mm for the superstructure and roof because I got a cheap batch of plate.

I've used about 15 tons concrete blocks as ballast to give a draft of 2'6".

The simple solution is to notch the frames with a little 'v' at the centre, and at each corner, and then any water that gets into the bilge will flow back to rear because of the stationary trim angle which is about 3 or 4 deg down at the back; the water will collect under the engine in front of the uplift for the Skeg and prop.

What ever you do or don't do, spay foam onto the inside of the roof to stop condensation drips; pushing insulation between the frames does not work.

 

I'm using such heavy plate for two reasons, one, this boat is going to live on the Mississippi which is notorious for changing depths overnight and causing groundings, nasty surprises sticking up under eyesight just outside the main channel, and the like. So I don't want a keel as much as an underwater torpedo belt. Two, with increasing the mass of the keel plate that much, that means that much less space I have to dedicate to fixed ballast. I actually havnt taken going even thicker off the table if it means I need that much less fixed ballast. (Most likely precast concrete block, similar to you it sounds)

Not sure if the ideas will pan out yet, I still have a ton of calculations to do for this and various other systems, but that's the thinking.

And for insulation, I havnt made the final choice yet, but seeing as a section of this boat is going to be a mobile biodiesel refinery, spray foam isn't coming within a half mile of this thing. Most likely the condensation layer is going to be an armaflex or clone, then the temp control layer is going to be rockwool attached to the back of my interior panels, leaving about a 1-2 inch gap between the two systems for airflow from the bilge

 

Instead of "leaving about 1-2 inch gap between the two systems for airflow from the bilge," why do not you remove the insulation and you'll see how well and how air flows away moisture.?

 

If commercial barge operators can live with 3/8" plate on a 200-foot hopper barge, I think you could live with 3/8" thick or less for your small vessel. It takes a lot to punch thru 3/8" plate, let alone 3/4" plate.

The bottom of a 70'x16' barge made out of 3/4" steel plate will weigh:

70 ft. x 16 ft. x 40.8 lbs/sq.ft. x 0.75 in. = 34,300 lbs give or take,
less any framing. (a 1" thick steel plate weighs 40.8 lbs/sq.ft.)

I don't know if you plan on building this vessel next to the water where you'll launch it, but you better.

It's not easy to weld such thick plates together without edge prep, multiple passes and the like, all of which means that paying attention to proper welding procedures is even more important.

Unless you plan on navigating in ice, there's also no reason to use high-tensile steel. You'll pay more for the AH36 material than regular A36, and it's harder to weld it without the proper procedures and preparation.

 

Home port is Pittsburgh. Our rivers freeze over every few years up to about 2-3 inches. This past season we had 20 inch ice drifts going down the river when it broke up. I found out this past weekend the drifts ripped the hell out of many cargo barges that were moored at the sides of the river at the huge commercial moorings. Apparently slammed one against the dock at a power station up river so hard it tore thru the hull and sunk it right there. This past year is extreme, but obviously happens. That's what made me choose AH36. That and my welder typically works at a fab shop building bridge sections, he welds this class of steel all day every day up to several inches thick and knows it well

For location, I'm in negotiation with a steel mill a few miles from here, they have an unused section of their yard with the rail line still intact. The rail line goes right to their barge dock. And as luck would have it, the business next door builds large cranes. So I can build it, put it on a rail car, roll it a mile or so to the dock with one of the mills mules, and lower it in

 

An addendum to my bead comment.

If you are going into cold areas you need to be sure to design these so there is not, as much as it may be possible, welding around all four corners of a plate as this has in the past resulted in some rather dramatic brittleness crack propagation failures -- in one instance (per my old materials class professor) an improperly welded plate on a deck caused an oil barge to split in half one very cold day. Your welder probably knows a number of horror stories and what could have been done to prevent them as well.

 

yea, i already know i need to get all kinds of equipment to preheat and cool the plates, and a few other things.

And im likely not going to do the keel plate in AH36 if i don't need to. When im done with the design, if my welder says he can make it work using cold rolled, or hot rolled, ill go that route and save a few bucks. but thats up to him really.

 

Just to throw it out there here are a few canal boat designs I really like....include with a quote from another subject thread:

Interesting. I will be interested to see what design options you come up with.

My personal favorite canal boat is Roi Soleil. I made this posting on a long subject thread about canal boats:
http://www.boatdesign.net/forums/boat-design/dutch-barge-long-distance-cruisers-11316-20.html#post455644


This is another one I like:
http://www.boatdesign.net/forums/boat-design/dutch-barge-long-distance-cruisers-11316-20.html#post455651


PS:
BTW, are you planning on building in St Augustine area? I just bought a place down there, and expect to move down in several months. I'd like to follow your progress.
Brian

 

Condensation & Insulation Subjects

Long subject thread on 'condensation'
http://www.boatdesign.net/forums/metal-boat-building/steel-hull-isolation-alternatives-foam-26839.html