Steel Planking

[TimothyB]

I spoke to Phil Bolger some time ago and during that talk he told me about a boat he had designed for arctic conditions that had a wooden frame and steel hull sides. In this case, it was welded steel hull sides.

How crazy is it to suggest the idea that you could use steel planking for a larger boat? That is to say, using steel strips, fastened to the frames and splined/sealed somehow to provide watertightness..

Besides the obvious problems of the wood/steel interface, is there a glaring reason why this should not be done?

I was just thinking about it over a cup o' joe. Gotta watch that ;)

--T

[Scott Rosen]

I don't understand why a steel hull would need framing at all. Did the design have steel held in tension over the frames? Doesn't make sense. Once you weld the seams and install bulkheads, it would be be a pretty solid, stiff structure.

Trust me. When it comes to steel hulls, I'm the voice of complete inexperience. ;)

[Mike Vogdes]

Finally a use for 5200 as corking.

[Scott Rosen]

Come to think of it, how would you weld the seams without the frames catching on fire?

[TimothyB]

Re: Welding seams.. I really don't know scott. I am assuming that the hull was molded with a steel mold, then wooden frames were added later.

The frames allow for heavier construction as well. And something to attach stuff to smile.gif

I honestly don't recall teh whole discussion, though I'm sure Mr. Bolger would write you about it if you sent him a fax or letter. He is pretty good that way.

5200 as corking? Woot! Hey that could actually work! ;)

The reason I was thinking about this was that planking wood is usually the best in the boat, considering the job it is doing. If you could replace it with steel wouldn't that save $$? And even if it cost the same or a bit more, the strength you could build into a structure like that could be pretty massive, no?

You could just back the steel loosely with thin planking and secure the steel planks both to the frames and to the backing planks. Perhaps something as simple as flexible gasket material could be used as a compression fitting under the steel.

Just food for thought.. any reasons this is crazy? ;)

--T

[JeffH]

'Tain't crazy at all.... That's how it used to be done, at least for those who wanted a steel boat with a flush hull in the days of rivets. Essentially, what you had was steel plating butt-welded into long strips, riveted to the frames (steel frames, though), then the edges riveted to a long, narrow backing plate on the inside of the seam. This was in the days before they really understood welding, and attempts to entirely weld a whole ship wound up with either a bulging, twisted mess or something that broke in half and sank with the first decent storm (an early Bath Iron Works welded ship had the bow canted off a couple degrees to starboard.. Oops).

Bolger's design sounds like a typical Bolger concept of combining advantages of different types to come up with something for a specific purpose. MacMillan, with his schooner Bowdoin (still sailing, incidentally) chose a wood hull because he wanted something that would take the abuse of being frozen in solid up in Greenland without becoming permanently deformed or crushed. The boat, however, needed a ironwood belt to keep the pack ice from abrading the hull. Bolger's design, it would appear (at least, the only reason I could think of that makes any sense), had a wood frame to be flexible, with steel plating for abrasion resistance. Interesting idea, but not something I would want to do, since I can't see any particular advantages for day-to-day applications... Steel plating for a sizable boat is not exactly workable with hand tools, and needs to be machine bent to shape and/or furnaced over a mold, and so long as you're going throuhg all that trouble, and since the technology now exists, you might as well weld the whole lot with steel frame and call it a steel boat.

Steel hulls of size, by the way, do need a fair bit of framing, since the hull plating is comparatively thin and light. You might notice old steel boats that have this hungry-dog look, with the plating beaten in between the frames.

Jeff

[TimothyB]

Originally posted by JeffH:
<snip>and so long as you're going throuhg all that trouble, and since the technology now exists, you might as well weld the whole lot with steel frame and call it a steel boat.
Heya JeffH smile.gif Thanks for the comments on rivetted construction!

Well, actually there is a great advantage to that wood framing besides flexibility and etc.. wood doesn't conduct heat too well does it? ;)

After experience, it takes far less oil to heat that boat than a regular steel boat, even with insulation blown in. Apparently it is really good at keeping the heat in.

And of course, since it was a wooden frame it didn't need insulation blown in. They used square batts and an air gap between the ceilings, the insulation batts and the hull. Neat idea no? ;)



Steel hulls of size, by the way, do need a fair bit of framing, since the hull plating is comparatively thin and light. You might notice old steel boats that have this hungry-dog look, with the plating beaten in between the frames.

JeffOh right.. the 'Starved Dog' thing!

Hmm. Well, you can get steel plate these days pretty cheap, and if you laid them up like planks the boat could be designed to take basically flat sheets of modest width.

Bolted to the frames, backed with softwood and corked with 5200 or equivalent and you could have something which would be great for northern latitudes cruising, be worm resistant and be hella strong.

--T

[imported_Conrad]

Just because you can do something doesn't mean you should! ;)

[Scott Rosen]

Tim, it sounds as if you're talking about a double-planked hull, with the inner planking of wood and the outer planking of steel. Is that right?

[TimothyB]

Right Scott. Perhaps '1/2 planked', i.e. many many 'stringers' instead of planks, all placed such that the butts of the steel plates would meet on their centerlines.

But.. perhaps a better approach would be to plank the hull with something like plywood and then 'sheath' with steel. So if a hull needed 2" of ply to cover, you do 1" + whatever steel thickness was needed. perhaps 1/4" ? Or would that be too much weight do you think?

Crazy idea #2, what about sheathing old iron/steel fastened carvel boats with steel by removing 1/2 their planks...? You could even do bronze fastened ones if you used irish felt. Ha! Now that's NUTS ;)

--T

PS: Hey folks, this is just a brainstorm. Im not going to actually do this anytime soon !

PPS: Hey.. the Brits did it with copper.. why not steel? ;)

[ 06-22-2003, 11:51 AM: Message edited by: TimothyB ]

[Paul Denison]

As with fiberglass covered wooden boats I would think it would turn into a big mess of rotted wood, especially with the way steel sweats.

[ishmael]

I don't know much about steel as a material, yet I've thought about structure quite a bit in my life, and I have to say the original proposition, steel over wood, makes absolutely no sense to me. Why?

In making a welded steel monocoque you don't want flexibility, as someone suggested. And steel web framing is going to be stronger than wood. I don't get it.

But if Bolger said something to this effect he must have had something in mind I'm not seeing. What?

In order to make a livable boat out of steel one has to insulate it, but wood? My understanding is that foam is used, with a thin wood ceiling to give the aesthetics.

I'm tempted to say that Tim has mistaken the first day of summer for April first. ;)

[ 06-22-2003, 09:02 PM: Message edited by: ishmael ]

[TimothyB]

Well, no.. As I said that boat is doing very well in the Arctic. It is warm, tight and dry and is even doing better than anyone had hoped.

Here is why: Yes, perhaps if you encased a wooden hull in steel that would cause problems with sweating and et al. I was really just thinking out loud on that one ;) But Bolger's design is welded steel with wood frames and bulkheads.

Now, it has wooden frames, so you install wooden ceilings of plywood, and on the side facing the steel hull you put a few inches of square batting, leaving a few inches of an air gap between the steel hull and the rest of the boat. The ceilings are made in sections so they can all be removed and inspected from time to time. The entire inside of the hull should be accessible. Small holes are cut here and there in the ceilings.

That gives both an insulating barrier and a good deal of ventilation to the steel/wood interface.

Before he described the design to me, he talked about waking up one morning and looking up in Resolution to behold a steel bolt with an icicle hanging from it. He decided that he would try the wood framing idea after that smile.gif

Now, as far as sheathing wood with steel, why would it necessarily lead to rot if you tarred and felted under it?

--T

[ishmael]

As I said that boat is doing very well in the Arctic What's the boat?

[ishmael]

Not to push or question in an untoward way; I would like to know what boat you are talking about.

There are many times I think I know and end up foolish. But I want to know what this boat is: that is framed with wood and sheathed with steel. Hrumph. smile.gif

If I have a design to examine, then we can agree or disagree. At this point it's all fluff.

What's the boat Tim?

[PugetSound]

When it comes to building a steel hull, you do not want a monocoque design (way too heavy). In a steel hull, the longitudinals are the primary support for the steel plate and the frames are there to support the longitudinals. The plate wouldn't be very thick (mabey an 1/8 inch thick)in say a 36 foot boat. Home building a steel hull boat is actually well within the average boatbuilder's capabilities (take a welding class) and finances. Working steel really isn't that much of a mystery, you just have to have the right equipment.

As to the wooden frame/steel hull business, frankly it sounds like way too much work!!! If you want a steel hull boat then build a steel hull boat and install a wood ceiling. Less work and more conventional. You could probably contract out the hull construction . . .

[ 06-23-2003, 01:29 AM: Message edited by: PugetSound ]

[ishmael]

When it comes to building a steel hull, you do not want a monocoque design (way too heavy). Honestly confused. What the hell is wrong with a monocoque design? My understanding of 'monocoque' is that it uses the minimum of material for the maximum strength. Welded steel, or whatever in what amounts, in an engineering sense, to an exotic box beam, the more curves the better.

Help! Really, tell me. I'm still a babe in the woods.

[TimothyB]

I'll admit, I don't recall the name of the boat that Phil was telling me about. I think I'll fax him and ask. Perhaps he can give some enlightenment to the question as well.

If you are interested, I have looked at steel construction.. a truly monocoque steel boat would be something like Brent Swain's Origami Boats. There is a group here:

http://groups.yahoo.com/group/origamiboats/?yguid=2717934

Some of these boats have done really tough passages in vary harsh conditions.

--T

[ 06-23-2003, 02:04 PM: Message edited by: TimothyB ]

[Ken Hall]

Every time I see a grimy, tough ol' Inland Seas soldiering along, I think a steel boat might have something going for it....

[swingking]

This was written on the Bolger list:

http://groups.yahoo.com/group/bolger/message/27216

Bolger's scheme to attach external steel plate ballast to the Jochems schooner is to finish the bottom "as you would without the steel, covering the wood in glass and epoxy...." The plate is cut into 15 sections, all 3/8" thick, most less than 48" in the longest dimension to keep expansion below the 1 mm range, the heaviest section is 122
lbs. To attach the plates, Bolger says five countersunk holes in each steel plate (4 in several of the smaller pieces) for flathead 3/8"
bolts, with nut and big washer inside over the oversized holes in the 1" thick plywood with 5200 filling the gap around each bolt, as well as a
single bead of 5200 along the perimeter of each plate and as "grout" in the 1/4" gap between the plates. His big worry is expansion of the plates as the original Jochems was to trailer from below freezing temps to the 130 degree western deserts in less than one day.

[TimothyB]

Right swingking. smile.gif I knew about that, as well as his ideas for using copper plate as ballast on future designs!

No, this is an entirely different boat than his regular sharpie designs. It was designed to deal with ice and really cold conditions.

Still awaiting his reply smile.gif

--T

[Steve Redmond]

Saw this interesting topic and wanted to mention a couple of things.

I've designed both steel and wooden boats. I think you'll find that almost every steel boat ever built contains some wood elements. Whether framing or ceiling or cleats to attach other elements to, or wood decking, etc. Generally the transitions require careful bedding of some sort.

Smaller steel sailboats, (under 35 feet) generally benefit for stability purposes from a plywood deck. Also generally, steel boats in this size range are not made any thinner than say 11 guage, or an eight of an inch (3mm). This is mainly due to the need to weld easily and minimize weld distortion, and to provide at least some extra material for longevity where corrosion starts in a breach of coating. Helpful anti-corrosive coatings include flame-sprayed zinc, and epoxy/tar emulsion compounds.

From the standpoint of strength, the plating on smaller boats (under 35') is much thicker (at 1/8") than necessary for the loads.

It is possible to design a small monocoque hull in steel provided the necessary form stiffness is provided to support the plating. That means generally rounded or corrugated shapes. Flat panels usually require stiffening in the form of frames.

Condensation in cold climates is a problem in boats of any material -- I've lived aboard a wooden houseboat in Vermont and can attest to this.

Where cold temps are a concern, or more correctly, where temperature differentials between parts of a boat and high humidity are a concern (even in the tropics), insulation has some value.

However, it's not a simple cure. Insulation, by its nature restricts air movement. This can trap extremes of humidity in boat sections leading to rot or corrosion. A ventilated space is not an insulated space.

If an insulated space does not include a vapor barrier (making it basically gas tight) heat and humidity will move across the insulation, often causing the very problems we are trying to eliminate.

An air space between plating and the insulation will definitely be a problem if warmer humid air is allowed to penetrate into it.

In a steel boat, fiberglass bats may encourage this more than an appropriate and properly prepared and applied sprayed-on foam application, which presumably creates no air gap.

For a fg batt-insulated boat, a vapor barier over the insulation on the inside of the boat will help when temperatures are colder outside than inside. Unfortunately, the reverse will occur when outside temps are higher than inside temps.

In addition, the waterline is particularly difficult to insulate for, since the temperature differential is great across a small space and can also can vary a lot.

Decks also tend to fluctuate in temperature, and I would bet that a majority of northern climate wooden boats will at some time in their life suffer deck rot problems as a result of condensation in this area. Other than direct deck leaks, I would guess that this is the major killer of wooden boats, in general.

In an imperfect world, of course, none of the methods of insulation is fool proof. It takes some thought and experimentation, specific to a climate to get the hoped for benefit.

Clearly the boat in question was designed for a specific job and climate, and the ability to inspect the plating was important to this type of installation.

--Steve

Steve Redmond
www.sredmond.com (http://www.sredmond.com)

[Aramas]

You might notice old steel boats that have this hungry-dog look, with the plating beaten in between the frames Actually you'll see this even more on new designs, particularly for military applications. It's called 'plastic design' and treats the steel plates as deformable membranes suspended on frames like the skin on a drum rather than as a rigid plate. This allows much lighter and cheaper construction but won't win any beauty contests.

[ 03-18-2004, 01:56 AM: Message edited by: Aramas ]

[MarkC]

Aramas - I thought you didnt like to discuss steel??? :D

[Aramas]

It's just the years I spent at uni. Steel ships, steel ships, and occasionally for a bit of a change, aluminium ships.

I'll probably get over it eventually smile.gif

The plastic design component of Advanced Ship Structures was actually quite interesting :rolleyes:

[mattb]

After years of running steel hulled tugs offshore believe me... You want the stringers and frames in a metal boat.