Marine aluminum vs marine steel for ship hull. What to choose?

I really count on it))

I looked at the table of the analogue AlMg5 to make it easier to understand what kind of aluminum is used and these brands came up. But it was probably more correct to indicate 5083
I now see that there is some confusion in the standards.

Aluminum with a similar composition to 5083 aluminum do you think is preferable?

 

We are in Moscow. Operating shipyards in St. Petersburg, Yaroslavl and other cities, but the Moscow shipyard is not working, it is now a land plot built up with residential buildings ...
And our budget will not allow us to build a ship in a shipyard.
It is very difficult to find specialists.
Could you give us the contacts you can contact in Russia, maybe they will help you find specialists in aluminum welding?

 

Edem,

I think you need women welders. Buy the high end machines and have them trained by the manufacturer.
All the best.
Jeff.

 

I don't know a lot about the differences between steel and aluminum. Reading this thread has been quite interesting. I have been reading a bit about corrosion lately and, again, reading this thread has been quite interesting.

Steel is the more noble metal and of two boats are moored in close proximity to each other and one is steel and one is aluminum and the happens to be some stray current in the water, the steel boat will eat the aluminum. However, I admit that I was being a but cheeky, because stay current is not as common as people believe and several feet apart is a large distance for galvanic action.

My preference for steel comes from a Cruising World article I read when I was a kid dreaming of World cruising in the 70s. It talked about a sailor who, having been caught in a crush between two work boats while moored in a marina in Europe, was sailing home to NY to get repairs done on her bent hull. The point the article made was, only because the boat was made of steel, could the owner have even considered crossing an ocean after an accident like that. Any other building material that suffered the hull bending damage this boat had suffered, would have needed to get repairs in the foreign port where the damage had been done.

-Will (Dragonfly)

 

Don't get me wrong now, but your questions indicate that you need to get someone with professional boatbuilding experience involved here. You say you are building yourself; what qualifications do you have in your team, and what conditions are there at your building site?

A good steel welder is NOT automatically even a decent aluminiumwelder (and vice versa); alu is different, not necessarily difficult, but you MUST know the differences! Also, the hull is less than 1/3 of the total cost, that is not where you can cut expenses to stay within a budget.

I suggest that you contact Mr Leonid Boychenko at Metallocenter in "Piter", mail: info@metcenter.ru. He is a very decent and skilled guy, take his advice seriously (and don't waste his time with nonsense.......).

 

The way to find a good welder, aluminium or steel, is to ask the welding consumables dealers. They know exactly how much each company/individual buys from them in a month, and usually also what they normally weld. Once you get the names, you go to those places and explain that you want to hire a pro welder, for an after hours job, good pay, cash in hand.
Once you find the man, you buy/rent the machine he wants, and he only comes in to weld. Prepwork and tabbing to position can be done by others, beforehand.
Moscow is a big city, it's impossible that you can't find a pro welder, and if you offer money they will work.

 

For the length of boat you are considering, aluminum would be the best way to go and you will find many articles on the net to support this statement. If you search under
Aluminum Boat Design, you will find that many of the worldwide aluminum boat manufacturers will discuss this very topic, Steel vs Aluminum to help guide your decision.

Of extreme importance are two points
1) proper design to limit future problems
2) competent fabrication processes to ensure a long lasting boat

Look at a current thread running right now, "Cracks ion (on) Aluminum Hull: Reinforce or Not" to see an example of a poorly designed and poorly welded/fabricated hull and
the problems the owner is having now. Had the original boat builder followed proper design and fabrication procedures, the owner would not be looking at a sketchy fix at this time. The actual cost of doing the job correctly, (besides hiring a welder who was capable) in material might have been under $1000.
Aluminum boat building is strong in the Pacific Northwest area of North America and there are thousands of aluminum boat that are standing the test of time without issues.

If you decide to purchase a hull, ensure that the hull is of proven design with a high quantity of boats in existence for many years. You risk a higher expense later if you purchase a boat
hull that is unproven

A few other considerations are fitting out the boat. Contact with dissimilar metals, you cannot just attach bronze/brass attachments to the hull due to corrosion issues. At high latitudes,
you will need to insulate the boat and there are ways of doing this properly. As AH mentioned above, twice, the boat has to be designed properly for corrosion issues and fatigue resistance

A couple of books worth reading Boat Building in Aluminum Stephen Pollard and Aluminum Boat Building Eric Sims. While their focus is design/fabrication they have references to other aspects of finishing and mechanical installations. Additionally there are several fine books on fitting out boats.

http://www.kastenmarine.com/_pdf/notes_on_metal_boats.pdf

Aluminum and Steel, one designer's view - Ocean Navigator - July/August 2007 http://www.oceannavigator.com/July-August-2007/Aluminum-and-Steel-one-designers-view/

Some links to some discussion on this topic can also be found in this Forum as noted below "Similar Threads"

A fitting out process on a boat is a complex process. The mechanical systems that we take for granted in our homes, and at comparable low cost, need more elaborate mechanization in a boat. Pumps to provide water for a head, sealed discharge and inlet valves, holding tanks, discharge pumps. Freshwater holding tanks, black water holding tanks, the list goes on.

The set of regulations or standards for small craft in North America is consolidated in the ABYC manual, that discusses the various components and the proper standards.
At over 2 inches thick it is thorough but it provides the most comprehensive look at any of the systems . For example the section on even the construction
and installation of a fuel tank, an important boat component, is several pages long but discusses types of acceptable fittings, fuel line routing standards, grounding, corrosion considerations etc. You might find someone who has a used set to save some bucks


Certainly in Sweden there will be another set of standards. I would check out a library to at least view either of these books.

The high price of these books might make you omit purchasing them so consider this:

1) If you want to insure the boat, you may need a survey. If you have incorrectly installed a system or two or even say used the incorrect type of wire, different in a boat than say an automotive application, you may not meet the requirements to insure your hull or have to redo, at great expense, some aspect of your installation


2) Without this type of technical information, you might use non-marine techniques in your mechanical systems that could lead to expensive fixes down the road or life threatening failures
or at the least major trip failures

3) Having such a set of standards will answer probably 90% of questions that you will need answered and ensure if followed that you will have a reliable boat

Saving several hundreds of dollars on such a text or set of standards and not buying one, WILL cost you much more money than just writing the cheque. Additionally, they will save you much frustration in trying to figure out the best way to move forward.

"Pay me now or pay me later"

PAY 400 plus US dollars equivalent NOW (and maybe in Sweden they are cheaper) or perhaps PAY several thousands of dollars LATER



THE ABOVE COMMENTS WERE pulled from a similar thread from awhile back.

 

Gentlemen, I am frequently amazed at the quality and quantity of good solid advice available on this forum. My own tiny project has benefited immeasurably from your generous assistance.

 

I believe I would hire such an obviously qualified person.

 

But would such an obviously qualified person hire-on with someone who aims to misbehave?

 

What confusion is that?

No.

5083 has been created for the marine industry. Other alloys may appear better but are more piecemeal items, rather than for major structure.

 

Per GOST 4784-97:
AMG4,5 = 5083
AMG4 = 5086
AD35 = 6082

 

Russia's best welder probably only works for the best.. For her it is a passion.

 

My choice would be aluminum. Steel would be heavier and affect performance, plus, if operating & maintenance costs were amortized over 10 years, the savings in steel might amount to about 5%....... not much.
Years ago (1990) a client came to me about designing a 66' (20m)tour boat to carry 225 persons. We looked at several options, monohull/cat/steel/ aluminum & decided on an aluminum catamaran of 20m x 8.5m with a 9 kn. cruise. Boat was built & still in service.

 

Most would choose aluminum as the material for the hull but since the OP says he cannot weld aluminum, there are only two options left :
- steel
- aluminum with rivets.