Lignum vitae: fact or fiction?

[Phil Thien]

I've read numerous times that, due to the natural oil in the wood, that lignum vitae is used for submarines and ships (apparently as a bushing for the prop shafts?).

Is that still the case? Or is that only for older vessels, where new ships are using synthetic materials?

[Jamie Buxton]

Have you priced lignum vitae recently? It can't be used for that any more.

[Joe Hardesty]

Here ya go;

http://en.wikipedia.org/wiki/Lignum_vitae

[Wes Grass]

Have you priced lignum vitae recently? It can't be used for that any more.

Have you priced a submarine lately? I think it can ;-)

[Phil Thien]

Thanks Joe! Why didn't I think of looking on Wikipedia.org?

[Don Abele]

Phil, it is still used, but not as much as it used to be. My previous command, USS CONSTITUTION, used a lot of it. We made all of our belaying pins out of it. And having turned a few of them myself, I can tell you it's some nasty stuff to work with - hard as rock. But it weathers well and the oils keep it self-lubricating.

As for the price, when we purchased it (via a government contract), it was by the pound. Don't remember what it was, but one belaying pin was about $250 (which is why we tied them down when we didn't have an active line on it).

Be well,

Doc

[george wilson]

Lignum vitae also was used for tackle blocks in sailing days. In the Science museum in London I saw machinery made in the very early 19th.C. (Maudsley? Can't recall). They were for carving those blocks,and saved a lot of labor. I couldn't help but wondering how well they held up,since by any later standards they weren't very heavy,and used carbon steel cutters. They must have needed constant maintenance by skilled workmen.

[Chip Lindley]

I do not believe the U.S. Navy wants any wood on its nuclear submarines! Salt peter takes care of that.

[Wes Grass]

I don't know if I have the 'real stuff' or not, but I made some tuner bushings for a mandolin out of it and it machined absolutely beautifully on my metal lathe. Has a waxy feel to it, and it sure smells nice too.

First time I ever used any wet wood (no Chip, no) and I was shocked by how much it shrank. Bear in mind these are 1/2" diameter, and after roughing them out and letting them sit for a couple weeks they'd shrunk about .030 ... and way out of round as well. You could easily tell the grain direction by measuring. I didn't have any problems with them cracking as I'd drilled the holes through them already.

[Roger Bolen]

Yes it is true. I served aboard Submarines for 20 years and that was one of the qualification questions.

Roger

[Gary Curtis]

The heavy woodworking mallet I bought on the UK eBay site has a head made of LV. It has to be 50 years old and has some slight checkering.

So I keep it in a plastic bag when not in use. I don't need the hardness so much as the density. Man, that thing is a clunker.

Gary Curtis

[David Keller NC]

"Is that still the case? Or is that only for older vessels, where new ships are using synthetic materials?"

It's my understanding that it is still used. One of the advantages of lignum is that in contact with water it will swell, so using it as the seal on a prop makes it self-fitting. It's difficult to get a synthetic material that will do that but is also hard and very long wearing.

[Mike Cutler]

Yes it is true. I served aboard Submarines for 20 years and that was one of the qualification questions.

Roger

Roger

I remember that oolie question as "Where can you find enough wood and sand underway to make a sandbox?" ;)

[Pete Hay]

It's not used as a seal, but rather as the outboard shaft bearing in the skeg. It's machined so that end grain is in contact with the shaft, meaning that several segments have to be machined to then fit together in a concentric circle. Down in Beaumont TX, the Bethlehem shipyard had dozens of LV logs underwater in a slip, all chained together. Said they'e received a shipment during WW II. I brought a slab home, but it split badly as it dried. Made a lamp base out of it - very stable!

[Mike Henderson]

Roger

I remember that oolie question as "Where can you find enough wood and sand underway to make a sandbox?" ;)
Okay, where do you find the sand?

And is the answer supposed to be that you remove the lignum vita from the shaft, or do subs carry spare parts of lignum vita. Seems that if you removed it from the shaft you'd get a leak which might be a problem.

Mike

[Mike Cutler]

Okay, where do you find the sand?

And is the answer supposed to be that you remove the lignum vita from the shaft, or do subs carry spare parts of lignum vita. Seems that if you removed it from the shaft you'd get a leak which might be a problem.

Mike

Mike

The answer, for an Ethan Allen class Submarine and a Lafayette Class Submarine, is that there was enough wood under the OOD's feet (Officer of the Deck), the place where the periscope is viewed from, in the form of cribbing and plywood substrate to build the box. The "sand" is in the main shaft. The actual shaft is hollow, and the sand is there for balance and additional rotational mass to relieve the stress on the main engine gears. Additionally the nose cones for a Posiedon C3 Missle were made of seven layers of laminated Sitka Spruce shaped in a cone.
What was really un-nerving one patrol was the shaft developed a pinhole leak interior to the boat and a few grains of sand would come out periodically during it's rotation. The sand wasn't actually sand, like play sand, but a mil spec's silica material, and while sand itself is actually mostly silica, this stuff was all silica.
The lignum Vitae was not the actual seal for the shaft itself, but was an integral component of the shaft gland seal assembly, and the "Stuffing Box".The shaft seal itself is actually designed to leak, and there was always some form of leakage in shaft alley. However, the deeper the boat went the less leakage as the hull contracted around the shaft. It used to be unnerving for new folks to watch the stainless steel "ladder", or stairs, to the control room buckle while diving deep, and thenn pop back into shape when ascending.
The shaft seal itself was a multi stage seal assembly, not a single stage donut as some may be envisioning. Repairing the shaft seals underway wasn't really an option. It took a few weeks in Dry Dock to replace an actual shaft.

I was a "Bubblehead", Submariner, in my past life on the USS John Marshall, SSBN 611, and the USS Andrew Jackson, SSBN 619.

[Phil Thien]

Mike

The answer, for an Ethan Allen class Submarine and a Lafayette Class Submarine, is that there was enough wood under the OOD's feet (Officer of the Deck), the place where the periscope is viewed from, in the form of cribbing and plywood substrate to build the box. The sand is in the main shaft.

I have to admit that I got that completely wrong. I thought the sand was at the bottom of the ocean, and the wood was the young men thinking of time off with their girldfriends. :D

[Mike Henderson]

Thanks, Mike. I appreciate you explaining that. I don't know a lot about boats (or ships). I was a "ground pounder" (army).

Mike

[harry strasil]

On Missouri river push boats and excursion boats, the bearing at the props is rubbber incased in brass with grooves in it, to let the sand out of the bearing and the shafts are undercut and have a layer of SS welded on for a wear surface. The Belle of Brownville, an excursion boat, had these, the shafts were small 3 inch diameter and the Brass Propellors were only 3 ft in diameter. I used to build up the shafts after a summers use and also build the screws back as the sand does a good job of wear on them. Shafts have a long taper for the screw and a short taper for the motor coupling. I also worked in a boat yard after I got out of the Navy for a short time, reconditioning barges and building new tow (push) boats.

[John Thompson]

A gentleman from around Ontario if I remember correctly that builds replacement prop shaft bearing for boats on Great Lakes boats sent me some about 6 years ago in exchange for a splitter mechanism similar to Lee Styrone's Shark Guard I built him. So... at least at that time it was still be using.

[Mike Cutler]

I have to admit that I got that completely wrong. I thought the sand was at the bottom of the ocean, and the wood was the young men thinking of time off with their girldfriends. :D

For those guys we had 38 tons of lead to remove, and put back, one brick at a time, through, a 24" diameter hole in the hull when we had to replace the blower on the diesel.:p

I threw enough lead off the end of that drydock during that little escapade to keep a skeet club going for decades.;)

[Phil Thien]

I threw enough lead off the end of that drydock during that little escapade to keep a skeet club going for decades.;)

What a PITA. I'd be very reluctant to purchase a submarine knowing that. At the very least, I'd take the extended warranty.

[Mike Cutler]

What a PITA. I'd be very reluctant to purchase a submarine knowing that. At the very least, I'd take the extended warranty.

That particular repair happened after 30 years of service.

Now to be serious, and all sea stories aside,( of which you've been a good sport about;)) the seal assembly package is a multi stage system in which the actual shaft and the seals are an integrated package that has been machined to incredibly tight tolerances. (We did a shaft in Guam and had to wait for the midwatch do to the expansion/contraction of the metals in the ambient temp enviorment).
The primary seal was a bronze/ stellite(sp.) interface between the shaft itself and the seal/bushing housing. The secondary seal, which also acted as an emergency seal was Lignum Vitae. This seal was pre-torqued, but could be further torqued. The Tertiary seal was a flex packing seal design that compressed under pressure. ( Pressure at test depth for the boats I was on would have been slightly greater than 550 psi) The final stage was the gland seal stuffing area.
From the outside the secondary seal appeared as a steel housing. The interesting concept for a shaft is the amount of longitudinal forces exerted on it. so not only do the seal have to resist pressure in the form of sea water pressure at depth, the seals also had to accomodate the twist and gain in the shaft.

I'm doing this all from memory, as it has been over 25 years since I saw my last submarine shaft replacement in Holy Loch Scotland, and the classes of submarine I was on have been decommissioned and recycled to scrap, so I may be a little off on some points.
As for whether the technology for a newer class sub is the same, I honestly don't know. I haven't seen the inside of a submarine since I took my mom on a tour of the Nautilus in the early 90's,and I was a civilian then and not allowed back aft.
I'm sure Glen Cabo could provide a factual answer.

[Don Abele]

Mike, I started chuckling when you mentioned ooile questions...and now I'm just impressed. All that from your memory!!! You must have studied hard to remember all that after 25 years (I can't remember what I had for breakfast :p).

As for Glenn chiming in...I'd suspect he's being quiet, just as I am, because that system on modern submarines is classified. Almost everything on modern boats is classified. Go figure.

I will tell you that I went through a shaft replacement when serving aboard the JACKSONVILLE (aka CrashVILLE) after our at-sea collision (3rd in her career). I got very intimate with the seals and was impressed by the system. But I don't think (even if I could) post it in such detail as your recollection. I guess because I didn't actually work on it, it didn't stick.

Me, I was a boat Doc (hence the nick name) aboard JACKSONVILLE, FLORIDA (GOLD), FLORIDA (BLUE), and the SSGN FLORIDA.

Man I miss boats!

Be well,

Doc

[george wilson]

I had a private tour of an attack sub,which I THINK was the Jacksonville,back in the early 80's.