Titanium in Yacht construction?

Good subject Codger.

I'm not overly familiar with titanium's properties, but a couple of things come to mind. The first and most obvious is... cost. A Google search turns up plenty of reading on the subject. Here's one link...

http://www.janes.com/aerospace/military/news/jdi/jdi060228_1_n.shtml

Given it's anti-corrosion properties, it could be ideal for marine applications, but I wonder what it is like to work with... i.e., forming, bending & welding. How pliable is it? Does it mate well to other alloys? And if you weld it, does it loose some of its properties.

I didn't read much further into the subject, but maybe some of our members have first-hand experience?

Hi Codger, here is an extract from a link I posted earlier, refering specificaly to titanium and yachts.


"Titanium
With very high strength, extreme nobility on the galvanic scale, virtual immunity to corrosion in sea water and in the atmosphere, and about half the weight of steel, there is no reason Titanium should not be considered the "perfect" hull material.

Among the higher strength Titanium alloys there is little spread between the yield point and the failure point. This reveals a limited plastic range. However, elongation before failure is fairly high compared to, say steel.

Another characteristic is "stiffness" expressed through the modulus of elasticity. For steel, it is 29 million psi. For aluminum, it is 10 million psi. For Titanium, it is 15 million psi. This indicates behavior that is somewhat closer to aluminum in terms of material rigidity. In other words, before Ti is made to yield (the point at which a material is deformed to the point where it will not return to its original shape), it will flex about twice as much as steel, but about 50% less than aluminum. Interestingly, Ti has about the same stiffness as Silicon Bronze, but Ti has less stiffness than copper nickel, which has an elastic modulus of 22 million pounds.

Yet another consideration is the ease of welding, which has to do with several properties.

Titanium melting point is above that of steel (3,042 deg F, vs 2,500 deg F) and about a third that of aluminum (1,135 deg F). Titanium forms a very tough oxide on exposure to the air, so welding must be done only after thorough cleaning of the weld zone, and must assure a complete inert gas shroud of the weld zone as the weld is being made, both on the side being welded and on the opposite side. The weld must be shielded until the metal cools below 800 degrees. These characteristics are surmountable by thorough attention to detail, good technique, and aggressive measures to assure post weld shielding. These characteristics would however dramatically increase fabrication costs over those associated with, say, aluminum.

Among the other material properties that contribute to ease of fabrication of any metal are the heat conductivity, and the thermal expansion rate of a material. Aluminum expands twice as much as steel, per degree of temperature change, and is three times as conductive thermally. The thermal conductivity of aluminum is a big help, but the expansion makes trouble. As a benefit however, an equivalent aluminum structure will have greater thickness and locally greater yield strength, so the score is more or less even between steel and aluminum, with aluminum having a slightly greater tendency toward distortion while welding.

With Titanium, this latter consideration will be the overriding factor in determining the minimum practical thickness for plating. Thermal conductivity is given as 4.5 BTU / Sq Ft / Hr/ Deg F / Ft for Titanium. For steel, it is 31, for aluminum it is 90. Thermal expansion is given as .0000039 in / in / deg F for Titanium, about 50% the expansion of steel and about 30% that of aluminum. These figures seem to indicate that the material would be fairly stable while welding, but that welds would take a much longer time to cool. In other words, the heat would remain concentrated.

Based on these factors, as a very rough guess, a thickness of around 3/32" may possibly be the smallest practical titanium hull thickness for a welded structure. As a comparison, the least thickness for other materials (mainly due to welding ease and distortion issues) is 10 gauge mild steel (.1345") and 3/16" aluminum.

An interesting Titanium alloy is the experimental alloy 5111 (5% Al; 1% SN; 1% Zr; 1% V; 0.8% MO), described as "a near alpha alloy having excellent weldability, seawater stress corrosion cracking resistance and high dynamic toughness." It has a high elongation before failure, a "medium" overall strength of about twice that of mild steel, and has a slightly greater spread between its yield point and failure point than the "high" strength Titanium alloys.

Although I believe Titanium would be an outstanding hull material, it would require extreme care during construction. Titanium is possibly the "ultimate" in terms of heirloom boat hull materials...! "


The site also discusses other metal types and can be found here....

http://www.kastenmarine.com/metalboats.htm#Which Metal

No problem Codger.

That Monel does look interesting, unfortunatly I don't think anyone has used it for a hull before.
I was thinking it would go really well with the SPS system you posted a few months back.

http://www.yachtforums.com/forums/technical-discussion/3964-hull-material-pros-cons-please.html

Wallypower lists their 55m yacht proposal as having "High tensile steel", I'd be interested to find out what exactly that means.

Wallypower gas turbine exhaust pipes were built in titanium.
They look pretty nice, they're light (quite easy to handle in that packed ER) and did not get affected by the hi gas temperature. They obviously do not show any sign of corrosion due to marin enviroment.

I'd rather go for zinced iron pipes. Maybe you'll have to change them every one or two years but the cheap price will allow you to do it.

SimonB

Titanium milling or lathe process can produce burning chips flying away, scarry for the operator machining, some people keep scares on face from burned chips landing on their faces....

If you let it be machined inside your vessel you should be aware of that and take necessary precautions...

I am manufacturing golf caddys in titanium and the material is very fine to work with it, just need proper tools,correct speeds...

We have a CNC department and some machines have Thinner Inflammable liquids nearby, so when we will work Titanium we just make sure this is not around

The bending of tubes is great and easy, the welding can be easy handled by some experienced stainless steel welder with Tungsten Inert Gas (TIG )

Very interested to hear about some Titanium hull as well....

Imagine an 80-120 foot open styled boat made of titanium. No paint, no fairing, just show off the the welds and beautiful color of the titanium.

nas

I believe the largest hulls built of Ti would be the Russian Ballistic Missle Submarines. I forget the class name now but the pressure hull was titanium.
You may be able to get a good deal on some scrap Ti from that fleet these days!

Dave

Just make sure you have a GEIGER detector, as they can be a bit radioactive...

Sailronin,

I believe the russian subs class name is Typhoon.

titanium

I repaired several part from a half tonner.the hull is carbon kevlar and all the hardware is titanium.I just got some rods and though I´d give it a try with my TIG.I mainly weld aluminium and found it quite easy to get used to.I asked a technician what would be the correct process and it´s true you need to clean the parts with acid (which I did not do,just brushed it with stainless steel brush).(not that I recommend this).Ti is a beautifull material,but it´s true that the excess material removed on a lathe for example is highly flamable.Anyone interested should buy small surplus parts on the web and try on small projects.I found once a website with the pictures and description of a russian runabout prototype made of titanium,powered by a small diesel engine and equipped with foils.It was said to speed to 40knts+.I´ll try and find the link if anyone is interested.

gja

A titanium bicycle left out in the rain looks good over time and one would imagine that a Ti hull would do well, esp. as evidenced by posters noting the (previously) Evil Empire's subs.
Interestingly, our new F22 will contain ~34% by weight Ti, the highest ever for a warplane.

Sadly, there's no free lunch, just expensive hammers.

The price of hot rolled plate steel is roughly $650 for a metric ton and about thirteen times that for Ti sponge... and this with Ti prices having been on the decline after 9/11.