Usually cement boats are made by trowling mortar into a mesh form.

For a quick and cheap alternative, mix your cement and soak burlap in it.
Lay the soaked buralp over a form which could be made of wood, paper mache
covered in plastic, wet sand, or whatever. Cover the whole thing with
plastic for a few days until the cement cures. Then lift your boat hull
off the form.

Cheap durable house walls have been made in Africa by draping burlap soaked in
cement over wires stretched between poles. You might find something about
it on the Internet.

) writes:
I have to build a cement boat that will hold as much weight as
possible. It must be made completely out of cement, no styrofoam, wood,
or anything that would provide buoyancy. It can be 1 cubic foot
maximum. How would I go about doing this??



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I am more concerned with the design of the hull. This is a project for
my High School Engineering class, and our teacher wants us to use only
cement to get our craft to float.

we can use some sort of mesh or something to get the cement to hold a
shape, but it cannot be wood, or something else that would provide
buoyancy that way.

On Wed, 04 May 2005 05:40:12 -0700, iceman390 wrote:

we can use some sort of mesh or something to get the cement to hold a
shape, but it cannot be wood, or something else that would provide
buoyancy that way.

Use chicken wire, then.

Make the boat a simple sqare box maybe half an inch thick.

You'll have to work out how big each side is based on your cu. ft. limit.

Since it is a school project, I won't say much more than that. Come to
think of it, I'd probably lead you in the wrong direction anyway since
I've never had any training as a marine architect.

Good luck!

--Mac

wrote:

we can use some sort of mesh or something to get the cement to hold a
shape, but it cannot be wood, or something else that would provide
buoyancy that way.


Dig a hole in the ground, line it with plastic, drive in some pins
to position rebar or position chainlink fencing for reinforcement,
plaster or even spray on concrete. Make it into a basement for a
floating house with several compartments, wait for spring floods to
launch.

Or did you want a speed boat?

Terry K

Terry Spragg ) writes:
wrote:

we can use some sort of mesh or something to get the cement to hold a
shape, but it cannot be wood, or something else that would provide
buoyancy that way.


Dig a hole in the ground, line it with plastic, drive in some pins
to position rebar or position chainlink fencing for reinforcement,
plaster or even spray on concrete. Make it into a basement for a
floating house with several compartments, wait for spring floods to
launch.

It's also been done upside down. Pile up some wet sand and sculpt the boat
you want, cover that with burlap or something (I forget the details,
plaster over smoothly with wet cement mixed with beach sand (mortar),
cover with plastic sheeting (you want to keep the water in while the
cement cures), and when it cures turn turn it over and drag it down to the
water. I read aqbout this being done by someone who could not transport a
boat to a waterside vacation spot. The cement boat was left behind after
the vacation for the use of local residents. Claimed it was a success.
Note that cement has to remain moist to cure. If it dries out before it
cures it will crumble into pieces.

Piling up the sand might be better than digging down in wet locations
where a hole would fill with water. Just a thought.

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A highly regarded book on this topic is:

Ferro-cement

by Bingham.

HTH,

Courtney


On Fri, 26 Aug 2005 10:19:55 -0300, Terry Spragg wrote:

wrote:

we can use some sort of mesh or something to get the cement to hold a
shape, but it cannot be wood, or something else that would provide
buoyancy that way.


Dig a hole in the ground, line it with plastic, drive in some pins
to position rebar or position chainlink fencing for reinforcement,
plaster or even spray on concrete. Make it into a basement for a
floating house with several compartments, wait for spring floods to
launch.

Or did you want a speed boat?

Terry K

wrote:
I am more concerned with the design of the hull. This is a project for
my High School Engineering class, and our teacher wants us to use only
cement to get our craft to float.

I think I would model it after river barges. very flat bottom, straight
sides and rounded up at both ends. Rectangle shape. It is used to haul
tons of coal around here every day. It is also a very simple shape to
produce. Also agree with everyone else that you need a mesh inside to
keep it all together.

There certainly are lots of cement barges plying the costal rivers of China.
Staight sides and flat botton, but probably for ease of construction and
load handling.

Might want to play with the math a little to get a fix on the shape that
encloses the greatest volume with the least surface area. Hmmm. Sounds a lot
like half a sphere. Could cast it inside a basketball...

surfnturf


"No Spam" wrote in message
news:UTeee.7459$Rl6.7151@trndny08...

I think I would model it after river barges. very flat bottom, straight
sides and rounded up at both ends. Rectangle shape. It is used to haul
tons of coal around here every day. It is also a very simple shape to
produce. Also agree with everyone else that you need a mesh inside to
keep it all together.

How is the teacher testing the resulting shape? Is he/she using lead shot,
pea gravel, water. Is the teacher really looking for a boat/barge or the
theoretical practical solution? Lead shot in the bottom of a hemisphere
would be stable enough for a test and give you the least amount of surface
area.
Clark
"surfnturf" wrote in message
news:MIfee.1223692$6l.94600@pd7tw2no...
There certainly are lots of cement barges plying the costal rivers of
China.
Staight sides and flat botton, but probably for ease of construction and
load handling.

Might want to play with the math a little to get a fix on the shape that
encloses the greatest volume with the least surface area. Hmmm. Sounds a
lot
like half a sphere. Could cast it inside a basketball...

surfnturf


"No Spam" wrote in message
news:UTeee.7459$Rl6.7151@trndny08...

I think I would model it after river barges. very flat bottom, straight
sides and rounded up at both ends. Rectangle shape. It is used to haul
tons of coal around here every day. It is also a very simple shape to
produce. Also agree with everyone else that you need a mesh inside to
keep it all together.