Eventually, a giant bulldozer with a hefty winch was procured
September 1, 2014 10:10 PM   Subscribe


 
For once, the comments didn't diminish my faith in humanity.
posted by Harald74 at 11:12 PM on September 1, 2014 [4 favorites]


Talking about concrete in shipbuilding always brings to mind the ice cream barges, made from concrete and deployed to the Pacific during WWII to keep the US Army supplied with ice cream.
posted by Harald74 at 11:17 PM on September 1, 2014 [2 favorites]


When he opened with About forty-three years ago, when I was a mere 55-year-old lad, I thought it was going to be a pisstake. And then it was just beautiful. Thank you.
posted by Ahab at 11:20 PM on September 1, 2014 [4 favorites]


When 98 years I reach write as well I should hope.
posted by Spatch at 11:26 PM on September 1, 2014 [2 favorites]


The real zinger was how, when they had finale launched her he mentions that he'd never sailed before.
posted by From Bklyn at 11:47 PM on September 1, 2014 [6 favorites]


I remember a concrete boat being built in Everett Washington about forty years ago when my dad had a house on 1611 Rucker a block from Grand park. One time a very old man, when I was coasting my sorry go-kart stopped me and offered me an aspirin, an ex-lax, and a butterscotch.

My sisters and I used to slide down the bluff to the harbor and fish, catching bullheads which are a fish that has spikes and are mostly a head with a tail attached and only useful for getting the kids to leave you alone.

My dad explained how a concrete boat could float by putting a heavy bowl in the sink.
posted by vapidave at 11:48 PM on September 1, 2014 [2 favorites]


I remember, about twenty years ago when I was going to Sonoma State, I was visiting a winery, or a friend's house (or both, I was kind of drunk and depressed that year), and there in the woods on a hillside, surrounded by redwoods, was a concrete sailboat hull. It was bizarre. It had a small hole, and some chips out of it, but it was probably repairable. But instead, it was slowly gong back to the land.

Some archaeologist a couple thousand years from now is going tobe mighty puzzled as to why this shipwreck was a hundred miles inland.
posted by happyroach at 11:57 PM on September 1, 2014


fun elementary physics question:

a barge is sailing across a reservoir when it capsizes, and its cargo sinks to the bottom. does the water level in the reservoir rise, fall or stay the same?

you can catch party guests off-guard and win money in bars with this.
posted by bruce at 12:01 AM on September 2, 2014


Assuming the barge isn't packed at 100 percent efficiency, the water level might even fall.
posted by pwnguin at 12:05 AM on September 2, 2014 [1 favorite]


Talking about concrete in shipbuilding always brings to mind the ice cream barges, made from concrete and deployed to the Pacific during WWII to keep the US Army supplied with ice cream.

Yep: Million-Dollar Ice Cream Barge Serves Sailors.
posted by pracowity at 12:22 AM on September 2, 2014 [1 favorite]


"might even?" lol. you don't sound too sure of that. i'd like to get you in a round of bar bets.

the water level absolutely does fall. when the cargo is on board the barge, it displaces an amount of water equal to its weight. when it's on the bottom, it displaces an amount of water equal to its volume. the equivalent weight of water would have to be greater than the equivalent volume, OR ELSE IT WOULDN'T HAVE SANK, NOW, WOULD IT?

conversely, if the cargo had been styrofoam that floated, the water level would have stayed the same.
posted by bruce at 12:26 AM on September 2, 2014 [3 favorites]


bruce: "conversely, if the cargo had been styrofoam that floated, the water level would have stayed the same."
Can you sink a boat by filling it with things that can float?
posted by brokkr at 12:40 AM on September 2, 2014


Also, this is a great snark from the comments:
you could replicate all the joys of sailing by deliberately giving yourself food poisoning, and then standing under a cold shower and ripping up wads of 100 pound notes.
posted by brokkr at 12:59 AM on September 2, 2014 [11 favorites]


brokkr, your question is the same as "can you sink an iceberg by snowing on it?" if you stack the styrofoam high enough, you can sink it below the waterline, but you can't sink it to the bottom unless water gets below deck into its previously watertight compartments.
posted by bruce at 12:59 AM on September 2, 2014


Via Wikipedia: Learn the basic steps of building a cement boat. It's easier than you think.
"Pool your spare change and weekends with a few friends and you can build the hull of a 36-foot fishing boat in 700 man-hours for a materials cost of less than a grand! Or bring in a 50-foot work boat hull—with deck and bulkheads—for less than 2,000 man-hours and about $4,000"
posted by effbot at 1:02 AM on September 2, 2014


Depends on how floaty the floaty things are, but the boat must be made of something heavier than water.

Suppose the boat displaces a total volume V when underwater, and has mass M when empty. If the available cargo volume in the boat is Vc, and you fill it with some material with density dc, you get a total mass of M+dc*Vc, and the boat will sink if (M+dc*Vc)/V > dw, i .e. dc> (dw*V-M)/Vc.

For the cargo itself to float, you need dc < dw, so the magic dc must be (dw*V-M)/Vc < dc < dw.

For this to have any solution, your boat must be such that (dw*V-M)/Vc < dw <> dw*V-M < dw*Vc <> dw*(V-Vc) < M <> M/(V-Vc) > dw, i.e the boat must be made of something that cannot float.

Now if we are allowed to pile the floaty stuff on the deck (and presumably strap it down so it doesn't float away), we can also keep a floaty boat entirely underwater, though it won't sink to the bottom.
posted by Dr Dracator at 1:03 AM on September 2, 2014 [1 favorite]


bruce: "but you can't sink it to the bottom unless water gets below deck into its previously watertight compartments."
At that point (assuming sufficient water depth) we can surely just pile on more cargo that floats to keep the boat from sinking completely?

Edit: or what Dr Dracator said. Thanks!
posted by brokkr at 1:07 AM on September 2, 2014


Can we assume the boat is a perfect sphere?
posted by logicpunk at 1:08 AM on September 2, 2014 [5 favorites]


"a barge is sailing across a reservoir when it capsizes, and its cargo sinks to the bottom. does the water level in the reservoir rise, fall or stay the same?"

It stays the same as long as the barge sinks and both the barge and the cargo have the same density as the water. [A barge barely floating full of water] in effect.

If the density of the material in the barge is greater than the water it is displacing, the water level will rise.
posted by vapidave at 1:08 AM on September 2, 2014


logicpunk: "Can we assume the boat is a perfect sphere?"
Yes, and it can also sail without friction.
posted by brokkr at 1:12 AM on September 2, 2014 [1 favorite]


Imagine a barge but it is upside down and full of air. It's not rise or fall but equlibrium. If you took the air out of the upside down barge the water level would rise.
posted by vapidave at 1:23 AM on September 2, 2014


If the density of the material in the barge is greater than the water it is displacing the water level will rise.

A barge uniformly filled to the brim with dense material?

It wouldn't get to that point. In the case you're considering, the barge would sink in port while you're adding the cargo to it. An example would be: I float an uncapped 1 liter plastic bottle in my bathtub. I hold it and fill it with mercury. I release it. It sinks.

(As compared to the 1 liter bottle filled with water.)

I don't think you can construct a scenario where a free-floating bottle capsizes and the water level rises.
posted by sebastienbailard at 1:24 AM on September 2, 2014


the ice cream barges, made from concrete and deployed to the Pacific during WWII to keep the US Army supplied with ice cream

Keeping the world safe for democracy, one cone at a time.
posted by Ice Cream Socialist at 2:12 AM on September 2, 2014


There is a ferro-cement vessel in our local harbour, the Hardiesse, used as a training vessel for kids. Its quite a decent size and looks pretty impressive under sail - it would likely never occur to you that it was anything but wooden built even up close. It was out for the Tall Ships event this weekend and went right past us.
posted by biffa at 2:34 AM on September 2, 2014


Keeping the world safe for democracy, one cone at a time.

My Dad was stationed on a supply ship servicing the Pacific fleet at the end of WW II. He was a gunnery officer but was also in charge of morale. During a mid-ocean resupply he scored an ice cream freezer in a swap for cigarettes and made ice cream using powdered milk. Apparently this was a massive hit with his shipmates.

I'm guessing those barges bypassed the Enoree.
posted by kinnakeet at 2:58 AM on September 2, 2014


"It wouldn't get to that point. In the case you're considering, the barge would sink in port while you're adding the cargo to it.

A barge uniformly filled to the brim with dense material?

It wouldn't get to that point. In the case you're considering, the barge would sink in port while you're adding the cargo to it. An example would be: I float an uncapped 1 liter plastic bottle in my bathtub. I hold it and fill it with mercury. I release it. It sinks."

But the mercury in your example isn't afloat. The barge is also full of air which is less dense than water and that is what provides displacement.

I will bet you one beer.
posted by vapidave at 3:02 AM on September 2, 2014


"Can we assume the boat is a perfect sphere?"

Can we assume it is a perfect sphere sitting on a treadmill that will exactly match its forward speed in the opposite direction?
posted by flug at 3:14 AM on September 2, 2014 [1 favorite]


The barge took off dammit.
posted by vapidave at 3:19 AM on September 2, 2014 [1 favorite]


I don't think you can construct a scenario where a free-floating bottle capsizes and the water level rises.

Suppose your cargo is a bunch of helium balloons tied to the rigging. Something like this.

Even there you're going to have to do some tricky work to get the water level to rise. I'll leave you to work out the details at home as an exercise for the reader, but the long and the short of it is that you'll need the upward force of the balloons to be almost enough to lift the boat out of the water but not quite enough to actually lift the boat out of the water. You'll want some displacement of water by the balloon+boat combination, but you'll need less water displaced by the boat in that configuration than the volume of the sunken boat.
posted by flug at 3:26 AM on September 2, 2014


What is the air-speed velocity of an unladen swallow?
posted by freakazoid at 3:42 AM on September 2, 2014


Isn't there some concrete canoe competition for engineering students? At any rate, there's a concrete canoe in, er, O'Brien Hall at Berkeley, together with an exhibit on the history of/original plans for BART, assuming they haven't gotten rid of it.
posted by hoyland at 4:52 AM on September 2, 2014


The art of building small craft from concrete has certainly not been lost, but rather perfected over the past 40+ years.
posted by drlith at 5:14 AM on September 2, 2014 [1 favorite]


What if the boat is filled with super-dense unobtanium, and kept floating using some sort of anti-gravity device? Also, it's a full-moon and the boat is less than a planck-length long.
posted by blue_beetle at 5:26 AM on September 2, 2014


In Halifax there is a marine construction company that still uses an old concrete WWII barge that was used, I believe, to maintain the submarine netting at the harbour entrance. It's quite something to see what appears to be a giant block of rock floating on the ocean.
posted by beau jackson at 5:55 AM on September 2, 2014


That was great -- thanks, Sebmojo! One of the things I think he had going for him was his age when he started -- after a (very, very long) while do-it-yourselfers learn when to bring in the experts, as he did for the plastering and the mast. Great that someone in the comments found the boat and sent him a picture.
posted by Killick at 6:01 AM on September 2, 2014


With 3D concrete extruding printers, making a fully-formed boat, complete with internal cabin, pleats, tables, etc. might soon become cheaply available.
posted by stbalbach at 6:10 AM on September 2, 2014 [1 favorite]


Read the comments, quite interesting commentary.

Cement is a perfectly fine material for boats and not particularly heavy for larger (50ft+) vessels. The problem of that period was that many backyard builders were not skilled at laying the actual concrete. This guy hired an expert for that step. In the comments there was a photo of the boat currently in Samoa. Looked great.
posted by sammyo at 6:11 AM on September 2, 2014 [1 favorite]


The real zinger was how, when they had finale launched her he mentions that he'd never sailed before

My impression is that the comparative simplicity of ferrocement means that it attracts amateur backyard builders who are not skilled sailors. I've been tempted myself, but so far my better sense has prevailed.
posted by Dip Flash at 6:19 AM on September 2, 2014


The problem of that period was that many backyard builders were not skilled at laying the actual concrete.

Yeah. The critical thing is getting the cement fully packed into the mesh with no voids. It's trivially easy if you do the normal ChickenWire-Rod Grid-Chicken Wire layup to just lay the cement on the chicken wire and leave a big void where the rods are.

Those rods are what provides much of the strength. The problem is they flex, so they don't offer much except in tension. Once you pack them in cement (which is very good in compression and lousy in tension) then they don't move and become stronger in compression, remain strong in tension, and don't bend, which means the hull flexes less and they stay strong.

As a bonus failure mode, if seawater gets into that void, it rusts out the rods, and your boat falls apart. It will almost always do this under stress, which means it will do that at the worst possible time. So, the plastering work is absolutely critical in this sort of construction.

The biggest problem with ferrocement is that it's not very good at flexing (unlike FRP, wood, or steel) so you need the hull to be very rigid. This is why it's useless for tiny boats and bad for small ones. On a larger hull, it works very well indeed -- when you can get a couple of inches of thickness. You can make a small boat with thick walls, but then most of the buoyancy is going to keep the hull floating. I recall that it's about 25-35' of length where a ferrocement and wood hull end up weighing the same. Theoretically, you could make an aircraft carrier or a large ore boat with ferrocement, but the cost would be huge and the walls would have to be a couple of feet thick, so at a certain point, steel takes over.

For most people, though, wanting a small sailing craft, FRP is the right answer. If you have the space to build and keep a large cruising sailboat*, however, ferrocement is a perfectly cromulent way to build them.



* A boat is a hole in the water you fill with money. An airplane is a hole in the sky you fill with money. A racing car is a hole on the land you fill with money and occasionally scrape off a wall.

Hobbies can be expensive.
posted by eriko at 6:53 AM on September 2, 2014 [6 favorites]


A boat is a hole in the water you fill with money.

It does not have to be that way. There are a lot of boaters doing just fine on a reasonable budget, probably less expensive than a good model train set. I think my first sailboat cost less than some model train engines. You do need to skip the shiny marinas that have pools and require a jacket for dinner. Anchoring is free. Sails can be found for insane racing budget (one Americas Cup sail is certainly more than I'll spend on boating my entire life) but a dinghy sail can be made from Tyvek and I've heard Tyvek can be found unprinted white.

Just a derail for any boater wanna be's, find something small and get out there, it's great!
posted by sammyo at 7:30 AM on September 2, 2014 [3 favorites]


sammyo, I have a small Jester dinghy that had a Tyvek sail for years, it worked great, despite being free advertising for house wrap.
posted by Mei's lost sandal at 10:38 AM on September 2, 2014 [1 favorite]


I was going to say, the cheapest tyvek has "TyVek House Wrap" printed on it and bright red seams.
posted by eriko at 5:00 PM on September 2, 2014


Model train engines are expensive. Model plane engines are worse. Model jet engines are amazing.
posted by eriko at 5:02 PM on September 2, 2014


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