uncertain of structural matrials in new project

[donjames]

I have aquired tons of research on a new project and am reseach overloaded
with having to make a decision on the type of structural materials to use.
Brief decription... I have aquired study plans for a 38'' cabin cruiser from
overseas and am very satisfied with the design,look, and overall appearance
of the boat. Although, there are three choices as to structure. i.e.steel,
aluminum, round bilge fiberglass-plywood core.
I will be using the boat in the greatlakes area specifically for pleasure
cruising and island hopping Lake Erie. River runs and short term vacation
trips throughout the other northern lakes. Can anyone out there help me
make a decision as to which one,given my description. And are the mood
swings in price between the three moderate or extreme?

I would appreciate all opinions and advice don

[gonzo]

I think it depends on your skills. Plywood/fiberglass is the easiest. Welding is more difficult, particularly aluminum. Steel is the cheapest and heavier. Also, it ends up with rust streaks.

[Eric Sponberg]

Don James,

Based upon on-going studies I have made over the last few years, I have tried to trace the cost of boat construction and gauge sailing performance based on different factors. For boat construction, I have found that the most reliable indicators are cost vs. length, and cost vs. weight. These studies are focused on sailing yachts, but they should apply to motoryachts in many cases, since the two types of boats consume similar amounts and kinds of material in their construction (save for engines vs. rigs). The shortest boat was 30', the longest 159'. The lightest boat was 7,000 lbs. displacement, the largest 842,000 lbs. Here is what I have found:

Cost per foot for different materials of construction:

Wood construction: US$16,400 per foot

Aluminum construction: US$15,200 per foot

Composite construction: US$14,500 per foot

Steel construction: US$11,800 per foot.


Based on displacement, the materials rank this way:

Composite construction: US$21.59 per pound of displacement.

Wood construction: US$21.56 per pound

Aluminum construction: US$20.78 per pound

Steel construction: US$17,89 per pound


You'll see that Wood, Composite, and aluminum all rank very closely, and steel ranks the lowest. I should qualify this data in that it derives from published reports in yachting magazines. Remember these are sailing yachts and so have a significant costs in rigs and lead. By comparison, motoryachts and power cruisers don't have rigs or much ballast, but they do have expensive engines, so maybe the costs are a wash and valid for both.

Also, these costs are based on prices up to and including some in 2003. Since then, the prices of metals have skyrocketed thanks to the increased worldwide consumption of commodities, primarily by mainland China. Also, the price of crude oil has gone way up, and this affects the prices of boatbuilding resins which are petrochemicals derived from crude oil. Therefore, the absolute value of these figures may not be correct, but perhaps the relative standing of the different materials may still be valid.

As always, too, there are intangible factors that have to be considered. How do you really want this boat to look? Would you be happy with steel vs. aluminum vs. composite vs. wood? There will always be a beauty factor here, and execution of construction is important. (Cardinal rule of boat design: all boats are beautiful, but some boats are more beautiful than others.) Are you going to build the boat yourself or are you going to hire a professional boatbuilder to do it? If you build it, what materials are you familiar with? The same applies to a professional builder--there are good ones and bad ones, and the best are expert in the materials they specialize in. A good boat built in an expensive material will last longer and provide more enjopyment, properly maintained, than a bad boat built in a cheap material. Obviously, you would like a good boat built at reasonable cost.

Remember also that the cost of the hull and deck is only a small portion of the total cost of the boat, perhaps 20-30% or so. The rest is the interior construction (which consumes A LOT of labor) and equipment which makes up the other 70-80%, and is common to each boat, no matter what material.

So do not judge the project based solely on material of construction. Too many other factors, tangible and intangible play a part.

Good luck!

By the way, if you want to consider a good professional boat builder for wood construction on Lake Erie where you intend to cruise, I know a very good one in Lorain, Ohio, who could build it for you, and you could launch it right there.

[brian eiland]

Thanks Eric, that's some interesting info. Have you ever had the occassion to consider the copper-nickle material??

Here's a portion of a note I wrote a potential client on the subject:

> Well, honestly, my family and I want to be able to take this vessel to the
warm and cold climates. I am personally still a little concerned about the
overall safety of a composite vessel in icy waters. Any thoughts? We really
want a catamaran - personally I am convinced of their viability as a voyage
making hull form. However, I seem to see far more steel monohull vessels in
the higher latitudes. The holy grail of boats for us would have the safety of
a large steel vessel, the comfort in the seaway of a large cat, the
spaciousness of a cat, the great advantages of a motorsailor (not underpowered
when not under sail), the range and economy of a sailing vessel, the speed of
a big cat, and the whole thing should be manageable by a reasonably healthy
couple in most conditions. If I can't outrun thee weather, I want to be able
to safely turn into it and feel that, properly equipped and handled, I can
ride it out. I do like the reassurance that a steel hull offers if a mistake
is made and we meet a jagged reef, rocky beach, or underestimated ice chunk.
Again, I am truly open to thoughts. The 65 foot motorsailor on your site is
almost there for me. Ridiculous as it sounds, I wish I could build it as very
nearly as designed in steel.
________________________________________________________________
Brian responded:

Composite boats have been around for quite some time now. And when I speak of
composites as related to multihulls I mean sandwich composite construction
where the sandwich core acts as the web of an I-beam and the inner & outer
skins act as the flanges of this I-beam to take the 'bending loads'. Numerous
materials have been utilized in these sandwich constructions with various
degrees of success. Even kevlar with its association as a 'bullet proof'
material has been touted as useful for one of the skin materials (although
this is not exactly so).

What it really boils down to is a question of 'toughness' of the sandwich
structure. This toughness quality is what we seek out when we want the hull
structure to be able to absorb an impact and recover. Least understood, but
most important to this toughness capability is the bond between the core
material and the fiberglass skins. There are any numbers of different methods
and materials utilized to obtain this bond, and many of these will bond the
skin to the core. BUT, many of these methods and materials produce a 'brittle'
bond. The bond interface can fracture upon impact thus rendering the I-beam
structure severely diminished. And/or a number of the core materials will fail
in shear (primarily because of their brittle nature), resulting in the same
diminished structure.

A look thru the history of the applications of these materials is one of the
best endorsements of any particular choice. And there is a lot of
documentation that can be sourced. Suffice it to say there is some
documentation that can be shown to prove the survivability of these sandwich
structure boats even over a metal one thrown upon the rocks.

For a lightweight metal boat, aluminum is probably the most apparent choice.
And alum has a ductile nature that allows it to deform substantially before it
fractures. There is tons of documentation to recommend alum construction. One
aspect I don't care for is its lack of insulating qualities, either sound or
heat. They can be cold, noisy, sweaty hulls. And they can be a bit of a
challenge to keep a fair paint job on.

A third material that I would suggest looking at would be copper-nickel metal.
Years ago there were a couple of commercial shrimpers built of this metal, and
they faired very well I believe. I think they may even still be in service (40
years now). I just did a quick look under Goggle and found
http://marine.copper.org/ . You might also look under Copper Mariner. I am
not suggesting an entire hull of this metal That would be as heavy as a steel
vessel. I'm talking a hybrid here....copper/nickel to just above the waterline
in a knuckle style hull (refer attachment), and then composite above that. Now
I wouldn't have suggested such a possibility until fairly recently as there
were not really good methods available to join these two dissimilar materials.
But the advent of these super adhesives, Methacrylates, that are being
utilized in ever increasing manners to bond deck/hull joints, stringers, etc,
are very likely just the ticket to make this work. Now you'd have your "metal
bottom" and on top of that you'd not have to ever bottom paint it....what a
world cruiser. This idea deserves some exploration.

[brian eiland]

Eric, what do you think of this generalized chart of building cost??

I tried to add the image of the chart in here, but I did not know how. So I believe it will end up as an attachment??

[IMG]boatbuilding cost chart[/IMG]

[Eric Sponberg]

Brian and Don,

First of all, as to costs, Brian, I think you gave me a similar chart when we met in my office back in Newport. At this point, it is too generalized, I think, to comment further. I do not have enough data in my database to suggest any split between the different material categories and labor. All the quotes I have seen in the last few years have been based on detailed construction specifications and equipment lists, but since I am not the decision-maker on costs, I don't get to keep and study the quotes.

As for copper-nickle alloy, I recall some fishing boats built in England some years back (20+ years ago??) that were all copper-nickel alloy. They survived very well. 90-10 copper nickel, as I recall, has more strength than aluminum, and about 50% more stiffness. The copper content (90%) is a natural anti-fouling, so you don't need to paint the hulls below the waterline. I had occasion to specify copper-nickel bolts for a keel repair some years ago, on the advice of the person doing the repair, and the job came out beautifully. It is a ductile material that welds really well. So if you can afford copper-nickel alloy, it is a worthwhile material in which to build a boat. I do not know the relative costs of plates and shapes of copper-nickel, so I can't hazard a guess on the cost of construction. I do know structural shapes are readily available, but I don't know about plate. One other thing, I have never been a fan of metal composite construction, wherein a composite part of the hull is mechanically joined to the metal part. It just does not make any sense, and only creates a joint that is asking to fail at some point in the future. (And Murphy's Law says that it will fail.)

As for catamarans as transoceanic voyaging boats, particularly for a couple, I would recommend against it. Read C.A. Marchaj's (pronounced MAR-ki, long sound on the "i") "Seaworthiness, The Forgotten Factor", and you'll see why catamarans do not make sense for voyaging in waves. My friend and superstar multihull designer Nigel Irens, who has designed some of the best racing trimarans in the world, once told me that he would never go voyaging in a multihull. He would take a heavy monohull any day to cross an ocean either single-handed or short-handed.

As for materials for a voyaging boat, I crossed the Atlantic, the Caribbean, and cruised the Pacific Coast of Central America in a fiberglass sailboat. I expect that the next boat I buy will be a fiberglass sailboat in which I will sail the rest of the way around the world. If you want to go into ice (I don't) I would recommend aluminum or steel for their ductility. Composite boats, however, would behave against ice as they would against rocks and coral--they'll get bashed up, but properly built they should survive afloat, depending of course on the degree of damage. Both steel and aluminum can be insulated sufficiently against cold and wet, so that is not a problem.

Depending on how prudent and prepared you are, all materials stand up very well to the rigors of cruising. Boats do get bashed, and a good fiberglass boat will survive a grounding well. The trouble with fiberglass is that if you have to repair the vessel, it should be done in a relatively controlled environment (which basically means dry and under cover--a tent will do). Wood builders are everywhere, but wood-epoxy builders are a bit rarer, like composite builders. Aluminum and steel can be repaired just about anywhere. So what I am saying is, if you think you are going to need a major repair someplace, you can pick your materials accordingly. But don't base your choice on that alone. As a said earlier, there are many intangibles that govern your choice of building material.

We had a major repair to our boat on the deck beneath the mast (the deck split open), in Majorca, which we thought was a pretty remote place being in the middle of the Mediterranean. But we found a fiberglass boat builder right away, and he repaired the deck for $175, which lasted through two more surveys and another 20 years.

Thems my thoughts, and I hope they help.

Eric

[brian eiland]

Originally Posted by brian eiland

Have you ever had the occassion to consider the copper-nickle material??
....A third material that I would suggest looking at would be copper-nickel metal. Years ago there were a couple of commercial shrimpers built of this metal, and they faired very well I believe. I think they may even still be in service (40years now). I just did a quick look under Goggle and found
http://marine.copper.org/ . You might also look under Copper Mariner. .

That was an older website I referenced above. For a newer site have a look at:
http://64.90.169.191/applications/marine/

and more specifically at: Copper Nickle boat Hulls
http://64.90.169.191/applications/cuni/txt_hulls.html

[brian eiland]

Originally Posted by Eric Sponberg

As for catamarans as transoceanic voyaging boats, particularly for a couple, I would recommend against it. Read C.A. Marchaj's (pronounced MAR-ki, long sound on the "i") "Seaworthiness, The Forgotten Factor", and you'll see why catamarans do not make sense for voyaging in waves. My friend and superstar multihull designer Nigel Irens, who has designed some of the best racing trimarans in the world, once told me that he would never go voyaging in a multihull. He would take a heavy monohull any day to cross an ocean either single-handed or short-handed.

Now Eric, how about these multihulled vessels from Nigel's own work:
http://www.nigelirens.demon.co.uk/nid_power.htm
http://www.nigelirens.demon.co.uk/nid_power2.htm This one was particularly successful
http://www.nigelirens.demon.co.uk/nid_power3.htm

I do know that Nigel is also much interested in traditional craft.....I think he has designed one scheduled for building in Nova Scota soon (I have a friend who recently bought property there who let me know). Then a visit to:
http://www.nigelirens.demon.co.uk/nid_sail2.htm certainly confirms that interest as well.....quite a diversity of capability as well as interest.

How about the Navy's interest in multihull craft:
http://www.naval-technology.com/projects/trimaran/
http://www.nationaldefensemagazine.o...le.cfm?Id=1504

Don't write those multihull craft off so easily.

And finally a little quote from my website, "Heavy boats carry their momentum into each trough and crest in a battle with the sea, while relatively lt-weight boats with slender hulls slice through with less battering. 'YOU CAN OUT-THINK THE OCEAN, BUT YOU CAN'T OUT-SLUG THE OCEAN', quoting a sign posted at the U.S. Naval Academy."

[Eric Sponberg]

I had in mind, in my comment, more traditional, wide-beam sailing multihulls crewed by a minimal (2-4) amateur crew. All the ones you refer are very narrow designs, more outrigger-type designs than true multihulls, except for the surface piercing Navy ship which is a wave-piercer design, and crewed by professionals. When with a very experienced crew, then a multihull can be considered safe. Examples of more yacht-like vessels are the Jules Verne Trophy multihulls which race around the planet, but again with a professional crew who can watch and sail the boat safely (or relatively safely, all things considered.) I would own and cruise a multihull if my sailing were restricted between here (Florida), the Bahamas, and the Caribbean. I would not attempt a transoceanic crossing unless I were 1) younger and stronger as in my older days, and 2) I have experienced crew on boat who could keep watch all the time.

But that's just me.

Eric

Since then, the prices of metals have skyrocketed thanks to the increased worldwide consumption of commodities, primarily by mainland China. Also, the price of crude oil has gone way up, and this affects the prices of boatbuilding resins which are petrochemicals derived from crude oil.

I stumbled on your comment (above) whilst looking for construction and technical info on my small speedboat. It is an interesting notion to me as a uk resident that an american would be aware of commodity consumption, as a nation that has had such a large share of the global pie for so long. I recently read that 'you guys' deposit more oil in the ocean each year from small boat useage than was spilled in the the exon valdez slick. Also, if the US of A had the same spec cars as UK residents, you'd cut oil use to one tenth of it's current rate, (giving us a 1000pc increase in the time that is oil we use to build our boats will last, as it is a finite resource) along with corresponding greenhouse gasses etc. my small (by your standards) and very ordinary 2 litre car engine takes me easily to 130 miles an hour where appropriate, and cruising around at 60 to 70 is the norm. And your speed limit is only 55 or 60!!! so why the big engines? As an obviously inteligent and influential man, i though you'd be a good person to make aware of the international perspective on your nations percieved environmental unscrupulousness. and with your conection to the ocean through boats, perhaps you may care more than the average citizen? no offence intended by this message, just hoping to help start change in some small way from one man to another, bypassing the usual (and usually ineffective) goverment channels. I hope your (mis-ellected) president is replaced by a more caring and environmentaly friendly fellow in the coming months. best wishes, UK.