Does concrete float?

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Jun 19, 2006 | 08:52 AM

#31

fabmandelux

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From: Paradise Found!

Quote:

Originally Posted by Beemer Nut

A 3' draft, whats it got a swing keel? Kind of like my friends Engilman (sp) ketch I believe at 38' with full running gear. Under sail you feel like your sailing the BOUNTY.

sierraben; what's this Yerba Buena stuff, you get a "Willie Brown sneaky housing deal" for low income with that million dollar view in the center of the bay?
.....=o&o>.....

It has NO keel, the mass of concrete in the bottom won't allow it to roll very far over.......don't ask how I know..............

FABMANDELUX.

Jun 19, 2006 | 01:47 PM

#32

sierraben

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From: San Francisco, Ca.

Try this.

Get a sewing needle/pin and carefully place in on top of some water.

It floats.

Jun 19, 2006 | 06:09 PM

#33

KSUwildcat

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Having been on a concrete conoe team myself at Kansas State University, I can tell you that cement itself has a specific gravity more than water (something in the neighborhood of 3.15). But it's the lightweight aggregates and reinforcing that contribute to the floating nature of the concrete canoe.

Using silica beads (very, very fine) as the aggregate and layers of fiberglass and/or carbon fiber reinforcement, the concrete canoe is able to "float" even when submerged with water. No magic, just the canoe being lighter than the amount of water she displaces. We also used air entraining admixtures to get the final air void content to be about 7% of the total volume of the canoe.

In fact, I was paddling one year and had a rougly 12"x12" hole develop directly under where I was sitting. We finished the race still sitting in the canoe, and it was about 1' under the surface of the lake.

As far as strength, I never got into the mix design and testing, but I seem to remember the compressve strength being comparable to normal concrete. The flexural strength, however, was significantly less than the normal.

Jun 19, 2006 | 06:44 PM

#34

sierraben

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From: San Francisco, Ca.

Quote:

Originally Posted by KSUwildcat

In fact, I was paddling one year and had a rougly 12"x12" hole develop directly under where I was sitting. We finished the race still sitting in the canoe, and it was about 1' under the surface of the lake.

I can see it now. You and your crew, partially submerged, and a guy on the horn, sitting at the stern of the canoe, yelling "Dive dive dive."

Jun 19, 2006 | 09:15 PM

#35

pchristman

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From: KCMO

One of the rules of the concrete canoe competition is that the boat must still float, even when completely full of water (just the same as any other boat that's sold in the US).

During WWII, hundreds (maybe thousands) of concrete ships were produced to help keep pace with the tremendous logistic demands of a war across an ocean. They were called "liberty ships" and I understand that many are still in service today, registered under the flags of many nations.

Jun 19, 2006 | 09:24 PM

#36

Ford_Six

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From: The Big, Oregon

Huh?
There were 36 ships built for the government between WWI and WWII, none are still sailing. A few are still floating as a breakwater in OR, and one is a hotel off Cuba.
Liberty ships were steel, built to go from the US to England to deliver supplies.

Jun 20, 2006 | 12:42 AM

#37

"Beemer Nut"

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From: "Islander"

The Jeremiah O'Brien one of two complete and original Liberty Ships, she is docked in San Francisco. Back in 89 the wife and I took a all day cruise on her. Standing on top of that triple expansion steam engine under way as well listening to the head with broom stick to ear, OMG the clanking, clunking of the bearings and chuffing of steam with all that heat, what a thrill. They almost had me as a volunteer but the Hornet's in Alameda, also a 100' tug / fireboat from WW 2 is docked with needed volunteer help.

Check into http://www.pbase.com/chris67/ss_jeremiah_obrien

.....=o&o>.....

Last edited by "Beemer Nut"; Jun 20, 2006 at 12:52 AM.