What is the best material for a hull?

Good ol' Ronald. He's Everywhere.

Durango, Mex

 

The Professionals use steel hulls with alloy topsides and superstructures.
For a home build it's easy to build the underwater sections in steel, install a flash bonded steel to alloy strip, then maybe rivet or bond the wheel house in alloy for light hamper weight.

No need to weld to the the above water alloy sections.

 

Parkland
The biggest issues with steel is the weight, corrosion and weldability of thin material
If you are building a slow boat, and that slow boat is going to sit in a marina ie not towed home, then weight is not an issue.
If you go through a rigorous process of sand/shot blasting, urethane primer, urethane painting, then corrosion will not be a problem.
When you try to reduce weight, you reduce thickness of the skin, and that invariably leads to distortion of the skin so then you add some more thickness then you get more weight

When you factor in the costs of corrosion protection for a steel hull and then look at the cost of aluminum hull, the costs get very close. If you are doing a one off hull, with steel you need either a plasma or acetylene torch or time consuming grinding for cutting.
With Aluminum, all you need is a skill saw with a carbide blade and almost all other woodworking tool will work on aluminum. Because of the light weight of aluminum you can use a thicker skin which, when welding properly will not distort as much as a much thinner steel skin thickness.
Certainly aluminum can have weld crack issues if either not properly welded OR the boat is not properly designed but is not really a problem.

 

On another forum, they are building a 50' steel s/d boat (20 tons).
The quote was £60 k for the hull in steel, and £120k in aluminium!!!
But, when you factor in the total cost of the whole boat, aluminium only increases the cost by 20%.

 

I had seen this post and wondered what the actual weight of the material component was compared to the price of both hulls as the doubling of the hull cost surprised me.
We have not built anything over 40 feet so I would not hazard a guess as to the material costs. But on the labor side, the aluminum manufacturing labor cost should be the same or slightly less.
It would be interesting to understand why they would choose steel for a s/d (which I assume to mean semidisplacement) hull as hull weight is a huge detriment for fuel costs at semidisplacement speeds. The lighter the better. A person might easily save the additional aluminum hull costs with savings on a smaller engine to achieve the same performance and most certainly in fuel savings.

 

A steel hull and an alloy or composite superstructure would knock at least 5 tons of the weight. A 20 ton S/d boat is a big big boat to push through the water, when a Gand banks 42 (45' loa) at 15kts/16tons does about 0.5 mpg.

 

Have money?... Use teflon, fibers Glass, carbon and Kevlar. This combination will give the same strength to steel, but are much lighter...

Has little money? ... Use plywood, fiberglass and Teflon ... The boat will not be as light nor too resistant, but is the choice of most people...

Not have money?... Buy a monkey ...

 

From the point of view of a boat repairer, the ongoing maintainence matters far more than the material the boat is built from. If the boat is maintained as it needs to be for the material involved, there will be far less issues than than if it were built from the less suitable material.
My personal preferencd is fiberglass , mainly due to the smaller things that happen. For example, aluminium boats generally corrode around any through hull fittings that aren't plastic, and wooden hulls will rot around these areas if any bare timber isn't sealed at installation . Steel hulls will rust more readily at the weld for through hulls, but even if salt water leaks through the through hull fitting, it usually doesnt create any great issue with fiberglass.
opinions can be like assh*les, everybody has one and we don't necessarily need to hear them.

 

What to do with the monkey ?

 

I tend to agree, except for the vulgarity.

 

Comb it...

 

Is it better use the monkey hair in the fillet or is it just better to filet the monkey?

 

To Comb Monkeys

Don’t be surprised if someone tells you: “Vá pentear macacos! (Go and comb monkeys!)”. There’s no need to go to the zoo. Just look for someone else to annoy or bother. The phrase means that you're annoying the person who told you to comb those cute animals. It is an adaptation of a Portuguese proverb. The original sentence was about combing donkeys. Combing or brushing those animals was not a noble task, but one of little importance. In Brazil, the donkey was replaced by apes. Other expressions with the same meaning are “Vá catar coquinhos! (Go and pick coconuts!)” and “Vá plantar batatas! (Go and plant potatoes!)".

 

Very efficient ... I could not be more objective.... Thanks... ..... Você é brasileiro?...

 

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