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Cement Canoe With A Contrarian Approach
Markgor writes: "There is an article in Wired News today about a group of students at the University of Alabama (Huntsville) who entered into the 2001 ASCE/MBT National Concrete Canoe Competition with a canoe that was built to achieve forward propulsion through matching natural resonance."
"Normally, if two objects share an exact natural resonance, the excited vibrations would usually lead the weaker object to fall apart, much like the Tacoma Narrows Bridge did when the equal frequencies of the wind and the structure of the bridge matched. However, since the canoe was designed with a special mix of concrete, it was flexible enough to withstand the vibrations and harnessed it into forward propulsion. They're now talking about its possible use in space, such as interplanetary probes using natural resonance to propel itself."
Step 1. Fill outer space with water.
Step 2. Propel through water using resonance.
Boats can be made out of anything that that doesn't dissolve quickly and has the strength to displace the requisite volume of water. Iron, steel, concrete, waterproofed paper-laminate, whatever - they need not float on their own; it's displacing a volume of water of greater mass then their own mass that is key.
Concrete boats are popular in a number of parts of the world. In Africa they're popular as small calm-water ferries for their low cost, durability, and ease of contruction. Often they're a simple mini-barge with a line crossing the river. To power them one either pulls the line directly or employs a simple mechanism, dragging oneself across the water.
As to the concrete being used in this application - it's made with exotic materials as it has exotic requirements. Light-weight, flexible, etc. aren't usually the priorities for a concrete; durable, high compression strength, low cost usually are. None of this is breakthrough as the materials used in the boat wouldn't likely stand up under a season or two of highway or other civil engineering use.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
you mean save money on taxes? No, I doubt that this will ever make it to the national highway system.
Plus, the distance that the road would need to avoid moving would probably make the cost of the matierals far more than the 70 pound canoe.
are posted here. They're both PDF files. The rules are quite complex, explaining the ratios of different types of cement and so forth. Interesting read.
Quidquid latine dictum sit, altum viditur.
I only post comments when someone on the internet is wrong.
If they aren't expelling mass, they will need to push against something. Perhaps he is suggesting a largish RC circuit that pushes against the earth's magnetic field. This could be interesting, because the power requirements to keep an oscillator going are rather small. But I don't quite understand how resonance would help in that case, since a magnetic field doesn't work the same way as a fluid such as water.
If tits were wings it'd be flying around.
...go back at least 14 years?
Try more like at least 25 years. The guys in the CE department were making concrete canoes and competing with other schools' CE students back in the early-mid '70s. Us EE students thought they were daft but, then, we were amusing ourselves trying to do useful things with weird things called ``microprocessors''. (One guy was doing speech recognition on the department's Altair. Hand assembly anyone?). The CEs thought we were nuts.
--
CUR ALLOC 20195.....5804M
If you're interested in more details, swing by the UAH concrete canoe team homepage. It even talks a little about their recent launch of the world's first concrete-reinforced rocket!
Up here we know what to do with concrete. It's a great use of concrete engineering too. More info on the UW concrete toboggan team here
DataSquid.net, a little about me.
The concrete doesn't ever need to be lighter than water.
just the mass of the canoe and riders must be less than the mass of the water displaced if the water were at the lip of the canoe.
use LaTeX? want an online reference manager that
-- john
TANSTAAFL. Sure, in a river I can conceive of harnessing the power of the waves/water by getting the boat to resonate with some frequency and then use that somehow to push the boat. (Having read the article, I'm still a little unclear on the concept.) But how do you use this in a (near) vacuum?
To get something 'operating' at its resonant frequency, someone has to be putting power into the system. I just don't understand what's supposed to be vibrating the space ship that's giving you the power.
Anyone understand this? Is it harnessing external sources, or just an attempt to make use of every last scrap of effort put into moving the boat?
I live about 4 miles from there (near I-90 and I-405). Where can you see the remnants of the old bridge?
More insteresting is the resonant part of it, but I would think that steel is better because it's elastic limit is higher and the modulus is lower to give more elastic deformation.
If they can bend concrete, they may have just saved the national highway system. One of the biggest problems is roads that self-destruct when the soil under them shifts. With enough wet/dry, expand/contract, up/down cycles, our highways are in constant need of repair. If even a small portion of this rework can be avoided with the "flexible concrete", the potential savings are enormous.
The real news here is that they're positioning this cement blend for use in space structures.
They should wait till this guy launches his cement mixer.
Sadly, there is also an embedded sound file. Perhaps this web faux pas offended the Wired team so greatly they were forced to exclude the link.
Well, that's where I'm putting MY quarter.....
Don't confused concrete and cement. Concrete is a simple name for composite construction. A concrete highway is often made up of a composite of steel rebar, cement, gravel, etc.
Cement, on the other hand, is a specific name for a substance, often alumina, silica, lime, iron oxide, and magnesium oxide. Cement is often used in the construction of concrete as part of the composite.
Composite structures != carbon fiber/kevlar/etc exclusively. Composites have been used for hundreds of years to make lightweight, strong things. This is merely the latest example of exactly that.
like the Tacoma Narrows Bridge did when the equal frequencies of the wind and the structure of the bridge matched
Just to do a little karma whoring...
Google has some nice links to video of the Tacoma Narrows bridge moving. This one from the Smithsonian is pretty good.
--
"200 Quatloos on the newcomer!" "300 Quatloos against!"
Yeah, and make the contestants paddle through I giant course filled with bolognaise : )
Mmmmm, giant course filled with bolognaise......
Poses the question... If they could do it then, why hasn't it been resurrected now that we've got better technology?
--Fesh
--Fesh
Kill -9 'em all, let root@localhost sort 'em out.
The link.
--Fesh
--Fesh
Kill -9 'em all, let root@localhost sort 'em out.
strangely, Wired didn't include the homepage for the UAH Concrete Canoe Team:
E /
http://www.uah.edu/student_life/organizations/ASC
There's a pretty good shot of the canoe on the first page.
_f
The Mulberry harbours used during the D-Day landings were concrete as well, I believe.
For a while, concrete boats were popular amongst the build-your-own-yacht community. Quite a few are still going, although few are made these days since GRP is so easy, cheap and convenient. The advent of GRP pretty much stopped concrete dead.
The advantages (when done properly) are durability and ease of repair - the hull is very strong, and if you do hole it then you can make a permanent repair using materials available anywhere they build houses or roads. By contrast, GRP and metal require specialist materials and/or equipment to make permanent repairs. The thicker hull is also better at insulating than other materials.
The downsides are that they're heavier than other boats (particularly GRP ones), they don't have the nice smooth finish of GRP and steel hulls, and the extra hull thickness reduces the living area somewhat. It shares with GRP the problem that minor dents can cause holes, where steel just dents. But the main problem is just that since it was so popular amongst build-your-own ppl, there's loads of poorly-made, badly-designed and generally horrible boats were produced in concrete, and that's damaged its reputation.
Grab.
Here's something to give people new to Seattle the willies! You know those bridges that connect Bellvue to Seattle and some of the other islands and pennisulas? Well, they're floating bridges and they're made of concrete! This freaked me the first time I heard that, then I worked out the whole buyoncy thing and said "Cool!" If I understand the design, the engineers basically made a bunch of concrete hulls, floated them and connected them together with cables and ran the road over the top. Several years ago, one of the bridges did indeed sink, but that was because an inspector at some point in the past had left an access hatch open, then one year there was some really rough water and the structure began taking on water. A couple of days later the whole thing sank. They put a new one in, but when I was last tehre you could still see the remnants of the old bridge right next to the new one.
Just be careful that the mechinism dosn't break making the canoe just go faster and faster.
KFG
You're right - I was curious about the composite ratio in the rules.. I've now found out - The official rules state that the mix must contain 75% portland cement, and the UAH pdf list their mix as containing 80% portland cement. In fact they are using the same mix as the team from the previous year. I must admit I am suprised that a composite with 80% Portland cement could be that flexible. br>
air and light and time and space
Oddly enough concrete boats are not as rare as they may sound - There are many many large boats made of concrete, and from what I've seen they get real ugly, but last and last. A concrete boat sounds kind of silly at first, but when you consider that a lot of boats are made out of Iron and other heavy metals, its not that strange..
air and light and time and space
..Yeah, and if we could engineer the roads to the right resonant frequency we could save on gas! boing ..boing ..boing .. Probably have to beef up the suspension on the cars that travel them tho' ---this ain't the Dukes of Hazzard..
air and light and time and space
The concrete is made up of a mix of Portland cement, glass micro-beads (microscopic hollow spheres), latex, acrylic fortifier and water.
Mix these in the right proportions, allow the mixture to dry for 12 hours and presto -- you have concrete so flexible that it will bend and snap right back with nary a crack.
Hmm.. Yeah its got Portland Cement in it, but it sounds like it is primarily rubber and plastic.. Are there no limitation in the rules about the composition of your 'concrete'?
air and light and time and space
Yes, concrete ships were made way back during WWI. There were three ships built in Oakland in 1917, but they were never used. One of them is sunk at Seacliff State Beach in Santa Cruz, Ca. You can read a little more about it here.
It's all about enclosing a volume -- it's not like a block of steel floats either, but nobody blinks at a steel ship.
This next song is very sad. Please clap along. -- Robin Zander
...if you'll ask me. My roommate is the incoming president of UAH's ASCE chapter, and he was highly involved with this year's competition.
-- Geof F. Morris
I'm off to register boatse.cx right away!
Sure going a few hundred mph is fun for a while. What do you do for kicks after you have a whale embedded in the tip of your vessel?
Seriously I hope they wore filtered breathing apparatus if they did any machining or drilling while working on the concrete in their canoe. It was reported by the BBC Newsnight program that concrete used for building block materials has been contaminated by admixture with incinerator fly ash containing toxic dioxin chemicals. Concrete dusts can be nasty.
Scroogle
When reading this, remember that water is 1,000 kg/m^3 (1.000 for the Euros); a bit more if it's sea-water:
p df
http://www.silicafume.net/PDF/C4-20-NORDHORDLAND.
I think the pontoons are hollow.
--Blair
P.S. 1,615 m is almost exactly one mile and three Smoots, give or take an ear.
The concrete doesn't ever need to be lighter than water. The boat plus passengers and gear needs to be lighter than water. Which means the maximum displacement of the boat (fully loaded volume including outside hull sectioned at a plane level with the waterline) needs to weigh less than the load plus the boat. The concrete itself can be far more dense than water.
Having concrete that is lighter than water means you can make a raft out of concrete. It means your boat won't sink if it floods. It also means your boat has less inertia.
It looks like a minor point, I know, but this is an engineering contest. It's all about minor points and the error bars on them. To put conflicting statements in the brochure is to sandbag the less-experienced contestants.
The real trick is that normal building concrete is much heavier than water (and somewhat absorbent, which reduces its effective displacement in contact with water). But this contest years ago ceased to be about floating a hunk of sidewalk.
--Blair
In this house we obey the laws of thermodynamics!
AC's cheerfully ignored
In space it would be wiser to utilize a rotating magetic matrix which due to Lenz' Law would configuire into a magnetic 'ion drill bit. Can't wait to try that. NASA wouldn't let me it would work a whole lot better than the crap they're working on now.
I think you are off topic. Strange though, as almost nobody here seems to be actually on topic, aside from the basic pondering of concrete rowboats and wondering if the propulsion mechanism has anything to do wih harnessing the energy of polarized repressed crutons and why talking about physics that one has only a very vague conception on an internet discussion forum shouldn't itself violate any major conservation laws. I personally think the that the theory that the flexible concrete resonance boat works by propelling itself forward against the magnetic field is the best hypothesis so far since it succinctly describes why this conversation tends to spin around in tiny little circles (vortices of magnetic flux) rather than moving forward. For extra credit, I will accept a full page explanation of why the Heisenberg uncertanty principle prevents one from citing an exact reference for anything.
-K