Steel sheet type for new construction

Hello

First of all I introduce myself, my name is Miquel and I live in Stockholm, SWEDEN

I am planning to build a steel sailboat, I am a furniture carpenter with some experience in boatbuilding with wood and composites. But I want to build a steel hull. I have the help of 2 other people that are welders.

I already have the place to build it and majority of the tools necessary.

Im currently deciding on which design to go for if Bruce Roberts or Dudley Dix. Im asking for different quotes to get all the pieces cutted in CNC. The question is:

What type/grade of 4mm sheet steel should I use? We are talking about a 45-48ft sailboat.

Thank you very much for your help

best regards

 

Should you use carbon steel (I'm not sure I translate this definition correctly): E24/A , E32-AH32, E36-AH36
I have extensive experience in the design and construction of steel and aluminum boats. I would be glad to help you in all aspects related to both disciplines, if you think it is appropriate.
Ahhh¡¡¡¡, and welcome to the forum.

 

Hello Tansl

Thank you for your answer. I see you are from Spain? I am from Barcelona but I live in Sweden..

I am not very experienced in steel, my field is wood. I really appreciate your help and is more than welcome!

I am asking for quotes for the steel and the suppliers keep asking me (obviously) what exact grade I need.

Is E24/A , E32-AH32, E36-AH36 = Type A grade?

We have a Mig/Mag continuos thread welding machine of 300A I guess it+s suitable for this type no?


thank you very much, I will keep asking and create a thread of the build as soon as I start!!

 

You should follow the plans. Each steel alloy has different material properties and can't simply be swapped without modifying the design.

 

I havent arrived to that step yet as I am still deciding which design to go for. But I would like to know what is the most used mild steel alloy in order to ask for material quotes.

 

The alloys that I have indicated are those recommended by the ISO regulations that, without a doubt, you will have to apply at some stage of your project.

 

Ok thank you,

Are they similar between them?

 

Miquel, you mention 4 mm thick steel plating for a 45' - 48' boat - is this what Bruce Roberts and Dudley Dix specify?
I am thinking this would be ok for the deck and topsides, with suitable stiffening, but if I was building this boat I would want the bottom plating to be thicker.

 

Hello Bajan

I havent purchased the plans yet, but yes for the bottom plating I read people use 5mm even 6 right?

 

Ideally you want it to be as thick as possible for corrosion purposes - but steel is heavy stuff. And expensive (relatively).
So you have to reach a compromise (as always).
Buy a set of plans for the boat that most appeals to you - it will be you living on it, and sailing it.
I think that if I was making a choice between Bruce Roberts or Dudley Dix, I would probably go for a Dix design.
But don't be too hasty - do some googling, and see what other designers have come up with - there are many different designs out there.

 

Thank you Bajan

Dudley Dix are more appealing to me, My dream is to build Dix57 but might be too big, so I am looking at something slightly smaller.
Ive been also checking Van de stadt, Kasten, and a few others.

 

As Gonzo notes, you should follow the materials shown on the approved dwgs.
But one assumes, this would be standard Grade A steel:

This is the most common Grade and easily available anywhere.
It is also cheap, relatively too.

Since for a vessel like this, small amateur build, it would be extremely unusual to be selecting a higher tensile steel (HTS) like the following:

These Grades are not cheaper and often not so easy to find a supplier.
You would also need to be much more quality control orientated to ensure good quality welds too. Grade A is easy to weld...HTS, not so.

 

Don't sweat over the steel. The designer specifies the grade in the plans, and you buy the appropriate grade. The difference between "ship building steel" and "structural steel" is the quality control, shipbuilding steel has an additional step (ultrasonic) and is certified by a classification society. Grade A or S235JR is the same thing, just a different name.
When building with steel the more important questions are: do I use preprimed or can I sandblast after welding, and what paint system do I use.
Before you comit, make a price comparison between steel with your chosen paint system, and aluminium, bare and painted. The simple fact that you don't have to paint the inside of an Al boat can sometimes offset its greater initial cost.
As to the design, build what you like, you must live with it afterwards, there is no sense in making compromises here.

 

Wise words - I found out about this (re choosing between steel and aluminium) the hard way 20 years ago when I was involved in the design and build of two power cats (12 m. and 15 m.).
We first built the 15 m. cat in ally (this is the cat in my avatar) and she has been working well ever since.
The owner of the 12 m cat (she was a floating self propelled bar) was trying to save $$'s, and the Builders told him that they could build her in steel for much less, so he went for that.
A bad move - The subsequent cost of all the paint required was astonishing, and although the boat worked well for a few years, she is now abandoned and rusting away ashore.
OK, there was a lot more to the story than just that, but it would take too long to explain.
If I was going to build another boat like this, I would strongly urge the owner to go for aluminium - it would have been cheaper in the long run, and the boat would probably still be operating today.

 

Some comments on the topic of pre-primed steel plate, profiles etc
The primer that often comes with pre-primed sheet OFTEN does not meet the proper specifications for paint application without a sand blasting process.
With hot rolled steel, a mill scale is formed which must be removed prior to any type of paint process. BUT mill scale can be removed in an acid bath that does not leave the metal with
an appropriate angular surface 1 1/2 - 2 1/2 thousands of an inch.
Without actually digging up the specifications on sand blasting, most paint primer manufacturers will have a sand blasting specification to ensure that their primer will adhere to the steel.

Additionally, the primer must be applied to a certain thickness to ensure that the micro valleys are filled and the micro peaks are covered with an appropriate thickness.

Often primed steel with a "shop primed" designation will not meet good standards to expect to just paint over top of the pre primer and call it a day.
The "shop prime" primer is thin enough to permit welding through the primer or with minimal effort to remove a thin primer

Ad Hoc,
I am curious as to what condition, shop prime?, finish prime? your ship steel arrived in. Did you have to pre clean the weld area prior to welding,
I suspect so, to meet codes, or did you have to sand blast prior to painting?



I agree with Rumars, consider aluminum. While the up front cost will be higher (but maybe not too much higher), the ease of working with aluminum with wood working tools and the savings in applying paint and subsequent maintenance will likely be cheaper over several years.
The difficulty is that it takes a little more care in the welding process BUT you can learn in a day or two how to tack the pieces together and then have a certified welder come in to complete the welding at various
stages