How possible is it to build a stainless steel sailing boat?

Hello everyone,

I have this ambitious plan to build my own sailing boat. I got inspired by my professor from high school who built his own wooden sailing boat. So ever since I kinda had it on my to do list.

I like building stuff and doing DIY projects (on land) but nothing compared to this crazy plan of mine. This will most likely be my ultimate construction project so im going to take things really really slow and try to learn as much as I can. Apart from having some designing skills, I have very minimum knowledge of ship building / hydrodynamics/ sailing etc.

Before I start seeking other information about boat building I would like to know if such idea is actually doable or not.

The sailing boat I have in my mind is about 12 meters long with two cabins. I am the kind of person who is obsessed with objects and materials that are maintenance free. So my initial thought is to build the boat frame with stainless steel (304 or 316) square tubes and use stainless steel sheets on the exterior to cover the frame. Materials that may be expensive, but are not hard to get.

The plan is to acquire stainless steel rectangular or square tubes for example 80x40mm 3mm thickness, bend each one at the appropriate radius and mig weld them to make the frame. Use 4-5mm stainless steel stripes / plates to cover the frame by welding them into it.

The first main questions are:

A) will such structure be possible to make with this method?
B) will stainless steel as a material for a sailing boat work at sea? Will it need to be painted? Every when? If polished to a mirror finish will it be better than painting it?

I know this is a crazy idea for someone with no marine background to build such thing. but if ancient civilizations could build boats some 3000-4000+ years ago, then I would feel ashamed if I cant build something that will float on water.

All information will be much appreciated!

Thank you!

 

Stainless is not an appropriate material for the hull. It will have crevice corrosion and other problems. You should buy a plan by a reputable designer. It will include the correct materials, building techniques, structural calculations, rig, and most importantly have technical support.

That is a really arrogant statement. Ancient civilizations built boats from trail and error methods that took generations to develop.

 

Hello and welcome to the forum.

Your desire to build a better boat is fine. But first you need to find out why experienced builders do as they do, including not building stainless boats.

Let's take a look at a few boat builder profiles.
Third world, poverty-stricken builders with few, low-quality raw materials.
Inexpensive recreational craft for lower and middle-class customers.
Fast offshore fishing boats for wealthy clients.
Commercial fishing boats with a 1-person crew working some quiet backwater.
Commercial fish processors with 50-person crews.
Small dinghies.
Sailing circumnavigators.
Billionaire's mega yachts.
Cruise ships.
Ice breakers.
Supertankers.

The designers and builders of these and other craft include some very intelligent, resourceful and clever people.
Asking here is a good start. Study boat design and materials to take advantage of the collected wisdom and experience. It's almost impossible for an amateur to re-invent the wheel. It is actually common for an amateur to focus on one or two aspects at the expense of the entire project.

You will find stainless steel is tricky, even treacherous sometimes. In spite of that for some jobs it is still a good choice.

 

While I am not aware of any yachts out of "stainless steel" there have been yachts made out of monel and CU-NI. And there are a significant number of large stainless features in the offshore world. But most marine grade stainless steels like flowing water. Marine grade stainless - Wikipedia https://en.wikipedia.org/wiki/Marine_grade_stainless
The first monel yacht, SEA CALL circa 1915 was a failure due to construction issues, https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1559-3584.1915.tb00591.x
The others out of CU-NI have been more successful. Copper-Nickel : Ship and Boat Hulls https://www.copper.org/applications/marine/cuni/applications/hulls/performance_corrosion.html#Solid

 

Is a stainless steel boat possible

I remembered a thread from ages ago and found it just through the internet but it does not appear to be reachable by the search engine on the forum

UPDATE Thanks to Milehog to sort the link issue out in the second next post

 

And when you get to Angliques post #94, click on each of her links and this will take you to 3 other threads that discuss stainless hulls

 

Link:
Is a stainless steel boat possible? | Boat Design Net

They seem to have unpleasant surprises aplenty.

 

Metal Boats For Blue Water - Kasten Marine Design http://www.kastenmarine.com/metalboats.htm
Kasten Marines discussion of various metal boat material

 

Designing and building a boat are two different things. Designing a good boat is difficult for the informed amateur and almost impossible for anyone else. Given how cheap boat plans are, unless the actual goal is to learn boat design, it's not worth the time. Building is all about a wide range of skills, from handling the hull materials to installing plumbing, electrics, engine, etc. If someone doesn't want to learn a specific skill, he can always hire outside help.
In short, designing is hard, building is easy.

Using stainless for a hull is possible and has been done. Read post #7 here - - 44 ft Sailing Yacht - - Completely Build of 316 L Stainless Steel - - ? ? ? ? - - https://www.boatdesign.net/threads/44-ft-sailing-yacht-completely-build-of-316-l-stainless-steel.57257/ and you will understand why it's not more popular.
If a metal hull is required, aluminium offers the same advantages in lighter and simpler to work with package.

Regarding your proposed structure, square tubing is not used to make frames since it's not weight efficient (the side against the hull does nothing) plus many other problems like corrosion. Frames and stringers are normally plate or bulb, L, and T sections. It's very rare to see an omega or top hat stiffener in a metal yacht.
Plating is made by welding sheet material, and the usual minimum hull thickness is 3mm. Sheets can be bent in one direction only, or have compound curves worked into them.

What does "maintenance free" mean to you? The primary maintenance efforts for a new yacht are dedicated to its systems, not the hull itself. The design lifetime before major refurbishing or replacement is invariably longer for the hull then the systems, regardless of what the hull is made of, and this includes traditional wooden boats. Anyway, each hull building material has its own problems, you can read all about that.
To make it simple, you have materials wich depend on paint and the best paints today last 20-30 years, and materials wich don't need paint but have other problems. You choose hull material either according to specific needs or desires, and live with the downsides.
Example: you want to visit ice or are already a good metalworker, so you choose a metal hull. Carbon steel needs paint, aluminium needs careful electrical management.

 

True but simplified
Sheets can be bent into conical or developable surfaces. For example: if you take sheet of paper and hold each of the corners at the same elevation but with the center hung down into a curve, that would be a bend in one direction.
But you are still able to lift one of the corners (or two) and the sheet will still be developable but appear to be a more compound shape.
This does not negate Rumar's comment as the axis for the bend in a single sheet can change throughout a single sheet. The bend axis can be at various angles wrt the long dimension ( or the short axis) creating a sheet that looks compound.
ie more than one bend axis within a single sheet.

The big question to Elefterios: Maintenance free boats? That is a dream for just about all boats. A low maintenance HULL, certainly a goal. Fibreglass is pretty much maintenance free without corrosion issues and last a lifetime.
Aluminum will over a time exhibit corrosion, not structurally threatening unless poorly designed, at penetrations under certain conditions.

• WIKKI Developable surfaces
• Cylinders and, more generally, the "generalized" cylinder; its cross-section may be any smooth curve
• Cones and, more generally, conical surfaces; away from the apex
• The oloid and the sphericon are members of a special family of solids that develop their entire surface when rolling down a flat plane.
• Planes (trivially); which may be viewed as a cylinder whose cross-section is a line
• Tangent developable surfaces; which are constructed by extending the tangent lines of a spatial curve.
• The torus has a metric under which it is developable, which can be embedded into three-dimensional space by the Nash embedding theorem[2] and has a simple representation in four dimensions as the Cartesian product of two circles: see Clifford torus.

 

Sheets can also be rolled on an english wheel and achieve true compound curves. This can also be done by ambitious amateurs, not only pro builders.
Compared to multichine or radius chine construction it is of course more complicated, it's an additional skill one needs to learn.

A completely maintenance free hull that is imprevious to seawater, UV, biological and galvanic corrosion without any form of coating can certainly be achieved, but as you said gelcoated fiberglass already lasts a lifetime, so why go there.

 

I read about a steel hulled boat years back where the new owner was trying to find out what kind of steel was used in the construction . The boat was built in South Africa and ended up being an odd ball stainless steel that was used in SA for boat hulls . You will have to dig a little to find the numbers , I remember it was not 305 , 316 , or 318 , but it was a low grade SS .

 

In the heyday years 2x fishing boats were made if copper nickel. About half a decade later copper prices had soared and the scrap hulls were now worth more than the price of building new boats out of steel. Turns out just because the hull is near maintence free doesn't mean the systems are.

One of my last boats was a 50 year old glass boat,it had outlived two mains two top ends, 3x sets of wiring and both previous owners. Unless your under 30 well kept steel, aluminum or glass will probably see you out the door.

 

Elefterios, what you intend to do, we here in Austria call
"inventing the wheel anew!"
(& yes, it HAS been done in stainless before!
"INOX", Marcel Bardiaux, the first singlehander to round Cape Horn east to west
& we met a French ~38' ketch in Grenada in 89 built out of stainless too. I recall the shiny bilge the owner showed us.
& I am sure there were/are more)

 

lets word this the other way around: it aint impossible.
you want it to float by itself or with passagers on board? if so, how many passengers? how thick you want your hull plating to be? you better get all this numbers ready cuz old Arquimedes will need them.

now: just because it aint impossible doesnt mean it makes sense, unless turning money into rust appeals to you, in which case i say do it! you only live once and you only need a parachute to go skydiving twice!