When does Steel Make Sense?

I agree that something would be left after the fire, but the question is - would it still be usable? We are talking about residual mechanical and corrosion resistance after the fire, which is a foggy area of our knowledge because it is very dependant on structural loading, time-temperature curve during the fire event, and even on materials which happened to be close or in contact with the steel structure. A series of heat treatments occur to a steel during the fire, when temperatures can reach 1000 °C (orange heat) and more. They can be any combination of annealing, tempering and quenching (due to firefighting water jets), carburizing etc.
In few words, before the fire breakout you have a structure made of a well-known and certified steel. After the fire, only lab technicians might tell what other kind of steel did it become and is it still usable as a marine structure.
But it is also true that high-strength alloy steels are much more likely to change their residual material properies than a mild carbon steel under these conditions - fortunately so, because the latter ones are commonly used for boatbuilding.
Cheers!

 

Daiquiri, I think you will find that a steel that changed composition due to heat would not be used in a boat because the welding of the plates would also change it. You would be looking at a low carbon steel that can't be heat treated.

 

Historically there have been any number of vessels which have been completely burned out and were rebuilt. Many remained in service for decades thereafter, which tends to indicate that the damage to the steel is not necessarily fatal.

 

Poida & Cthippo,
I never said otherwise, on both your points. It suffices to take the historical example of many steel warships damaged in battle and then rebuilt. But I was considering the size too. On a big ship a fire can leave extensive damage, but the remaining intact part of the structure can still be so big to justify a repair.
In the case of a small fishing trawler the fire can easily involve the whole structure, imho, making very incertain the possibility and convenience of rebuilding, at least until a thorough damage assessment is performed by surveyors.

There's one way we can establish the truth - moore a steel fishing boat with it's load of nets and fuel right next to a FRP luxury yacht of a local mafia boss, burn the FRP boat and see what happens to the steel trawler.

 

An interesting experiment Daiquiri, but our bay at present is unsuitable. It is unbelievable how many officials make excursions to the crime site. After the local wizzards, police, fire brigade, harbor masters and insurance people, now is the time for delegations from the mainland.

I forgot to mention that there also was a small frp rowing boat next to speedboat: the only damage there was the scorched hood of the outboard.

The event happened between 18.30 when I was outside to say goodbye to our dinner guests and approx 23.00 hours when I closed the entrance gate of our property and noticed that two boats were missing. I assumed the fishing boat was on an -illegal- fishing trip. There was a faint red light near the opposite shore of the bay, but no smoke or smell, so nothing alarmed me.

 

CDK, I am tempted to hijack this thread and to ask you if you can advice a good red wine from your zone, I think they have the renown Plavac Mali grapes down there... Of course I will not hijack this thread, but if you have something to say on that regard, please feel free to do so.

Back on track... From Diesel Duck 41 on (in terms of size) steel hulls with aluminum superstructure can be made with competitive weights and structural resistance with respect to wood or frp. We are talking about displacement motorsailers where some added weight will not make too much damage in tems of speed and fuel economy. You will loose maybe around 1/4 of a knot for each additional ton of weight, for the same power.

Steel does require a good craftsmanship during both design and assembly phase, as M. Pierziga has mentioned in the post #5, including some additional precautions when designing and installing the electrical system.

Cheers

 

Thanks all. Thanks daiquiri. That's pretty much what I was wondering. It seems like it doesn't make sense for a smaller boat, but these larger displacement boats are designed around an awful lot of weight. Anyone taken a look at the Buehler designs. His layouts are clearly by and for people without kids (at least at home), but I really like the look of the ducks.

 

I'm afraid I have to disappoint you Daiquiri.
The spot where our house was built, once belonged to an 80 ha vineyard abandoned several decades ago when the Italians imported deer and the local farmers didn't immediately fence off their properties.
Since then, the "maquis" shrubs have taken over the valleys and there has been sheep farming. A few years ago the government started an olive program by subsidizing cleaning the shrubs, free olive saplings and 10 year tax exemption if the plantations are successful.
By the time the olives are old enough for a good yield, there will be an enormous over-capacity....

Plavac is still a popular wine, but the origin can be Istria, Dalmatia or some inland chemical plant. My personal favorite is "Tga za Jug" from Macedonia.

 

If I had been thinking I would have built my boat from steel instead of glas-on-ply but not for reasons of fire. Most boats sink if the fire is fought effectively but for durability alone. From beaching to dock abrasion to log strikes to rotting wood to delamination to...

-Tom

 

Comments such as "Steel boats are heavy" need qualification.

It's more sensible to consider the displacement length ratio before deciding on or judging a hull construction material. Small steel boats are usually heavy because it's one of the sensible materials to build small heavy boats from.

Once a boat gets over around 40 feet and medium heavy displacement steel makes as much sense as any other material and arguably has some considerable benefits at times over other materials. I'd include ease of Construction, Durability Repairability and material cost. Why would you ever build a medium-heavy or heavy displacement comfortable cruiser out of expensive light weight materials ?

Put money into a good initial paint coat and then maintain that coating and a well designed steel boat will last hundreds of years. Part of that maintenance means removing the internal linings and checking the interior paint job from time to time too. That's where seamless glued in fit-outs should be avoided in favor of more easily removed ceiling.

Trad timber vessels can have have charm and quality, but in reality the commercial world moved to steel, alloy and composite designs for very good reasons. And also consider that wood in composite form produces a stronger more watertight and stiffer vessel than trad planking can.

 

make mine steel! as a professional welder there is no dificulties in fabrication. I have also fabed small diving tenders in aluminum as well as doing maintenace, repairs and mods to fishing boats. I am retiring soon and I am also looking at the duck series and a few other designs.

Living and working in the pacific north west in industry at the waterfront you can see the direct benifit of steel in fishing vessels, steel long liners and draggers. Steel tugs, even small sidewinders or boom boats under 20 feet! Plus local small friegters. All these vessels navigate tricky coastal waters with + 5 knot currents, 12 to 25 foot tides, rocky shores and bottoms with a ton of dead head logs in the neiborhood of 2 to 5 feet in diameter and up to 60 feet in length. To me in these conditions steel makes sence. Typaclly a 200 amp AC/dc welder , Either portable or 220v /575v shop. Grinders and a cutting outfit plus all the riggin for lifting.
.

Aluminum is nice but a higher skill level ,greater cost in material and a greater outlay in equipment would only benifit you if you were to make several boats at a time. Skill range from plasma cutting , TIG and MIG welding. Fabrication problems include distortion control and oh hot shortness durring welding. A breeze in the shop or outside blowing your shielding gas makes for a few minutes of swearing and grinding too! Any boat in aluminum will require a real MIG welder not a 1000 dollar toy. A miller 30 amp spool gun even used with an AC control box will run you 1500 bucks and then you need a 60 to 100 % duty cycle welding machine that will give you at least 250 amps. If you go TIG as well for the small parts you will need a flow meter hose , tig torch set , around 300 bucks then a AC welding machine with High freqency and a foot controller as well. Better think of a 300 plus amp machine because of the surface aluminum oxide layer you need a lot of jam to start the weld puddle and then back off the amps to continue and finish the weld. So skill level is a wee bit more than steel. Aluminum is about 3 to 5 times the cost of steel depending on the latest pricing. Bottom line leave the aluminum to the professionals. Typically I used a deisel 300 amp DC welder with a Miller 30 amp spool gun, Ac controller for dock work . Running .035 or .045 5356 wire. A 500 amp miller arcrafter AC/DC shop welder with High Frequency and a food controller , A 80 amp plaz, circular saw, A9 cutting fluid and jigsaws. plus all the riggin for lifting.

As far as looks, I have gone onboard several steel draggers and longliners that were exceptionally well kept and built. One such dragger was built and hailed out of Victoria and I asked him you want me to weld what? The boat was so faired and rounded I swear I was on a plastic boat. It was amazing. He must have had stock in a fairing compound company or owned his own rolls but everthing was rounded! Again amazing!

In my humble opinion and I kow I'm a newbie to this forum, If you really want o use your boat day after day running in all weather with tides, currents and debris in the water. Tie up to a log boom for lunch, Tie up to a typical logging company dock for over night or weather out a storm I would use steel. If you want to spend your time at the dock and a quick evening cruise with cocktails around the bay, a plastic boat with a nice shiny white gleam, smoked glass and coutesy cockpit lights might be better. Oh by the way dried salmon/halibut blood is a real chore to clean on texturized white plastic. My current plastic boat has spider cracks that I need to constantly tend to. Mainly around high stress and radical changes in direction in lighter roof sections where the radar arch bolts on . Uggg Black rubber tire marks from the gov. docks! Bird droppings when the blackberries are in season!! Scuffs, dings, gel coat repairs , waxing and polishing.So plastic boats have maintenance issues too.

 

One other thing to consider is the area of operation. In fresh water, the plating can be a bit thinner and corrosion is less of a concern.