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RE: [PSUBS-MAILIST] milestone
But we're talking about very small particals of sand that are basically in
solution. I don't think either one is going to have voids. The voids that
are a problem are caused by simply not getting the plaster all the way in
the nooks and crannys. It's hard to actually know where they are unless
they are exposed. When mixing the cement it's best to first throw the water
in, then throw in the cement and let in mix into a solution, then gradually
add the sand. Also make sure there is no organic material in the sand, and
clean water.
Thoughout the US many collages have the concrete canoe competition every
year. The concrete expert that I spoke of had been involve with that
program for the last 20 years. I actually got to see one of these concrete
canoes up close at Cal Poly San Luis Obispo a few months ago while up there
with my daughter. Very nice piece of work they are. Each year they require
a little different parameters for the students to follow.
http://concretecanoe.org/
Cheers,
Brian
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of F. Marc de
Piolenc
Sent: Friday, January 22, 2010 9:02 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] milestone
There is one school of thought that points out that odd-shaped particles
have a greater tendency to form voids where the cement paste doesn't
penetrate, and that graded spheres have better and more consistent
space-filling properties, besides being easier to move around during
application. I plan to try both in my test panels - I have access to
both crushed rock and alluvial and beach sand.
Good tip about the ribs - I've often wondered how best to handle them.
Best,
Marc
Brian Cox wrote:
> Marc,
> I don't think there is any debate (kind of like global warming)
about
> the sharp sand vs round, but if you don't have access to the sharp then
you
> would just have to go with what you have available.
>
> The ribs are 5/16" mild steel and you can see mine on my site. Also it's
> helpful to rap the rips with the layered mesh right at the begining
because
> they are hard to do later.
>
> http://www.ojaivalleybeefarm.com/Brian's%20Sub/My%20Sub/Submarine.htm
>
> Thanks for the interest !
>
> Brian
>
> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org]On Behalf Of F. Marc de
> Piolenc
> Sent: Friday, January 22, 2010 12:49 AM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] milestone
>
>
>
>
> Brian Cox wrote:
>> Well if you must know... I guess I can take time out of my busy day. You
>> know I don't like going on and on about my sub. ( just tell me to shut up
> if
>> you've had enough)
>
> No, no - loquacious is good in my book. I've been interested in FC and
> concrete boats since my early teens, but have yet to actually build
> anything. When I do build something, I want it to come out right, so I
> collect as much info as I can from people who've done it successfully.
>
>> 8 total layers of 22 gauge galvanized hex netting. The hex netting is
the
> 1
>> inch aviary netting. That is 4 layers on each side of the rebar or the
>> internal armature. I basically followed the same proceedure as how one
>> would build a ferro-cement sailboat. Since the shape that I built was
>> relitively small (21 ft long), and only 8 ft wide at the widest point I
>> probably could have gotten away with not using ribs inside but I figured
>> since there was going to be some unique stresses on this thing I went
> ahead
>> and built just like you would a sailboat. I even spaced the ribs closer
> for
>> additional strenght (18" OC).
>>
>> I have some pics of my early construction on my web site.
>
> I'll go look. I'm especially interested in how you formed the ribs.
>
>> Anyway, using the ribs is better anyway because it gives you a framework
> to
>> tie on the stringers. The stringers are 1/4 inch hard drawn wire - it
has
> a
>> spring to it so you can bend it to make a nice curve. Those go on at
about
>> 3" apart. They get tied on with wire ties. Then you have diagonals,
which
>> are 1/8" hard drawn wire which go on - you guessed it - diagonal to the
>> stringers, this is so that any irregularities in the shape tend to get
>> smoothed out, so you have clean lines. Once all that is all wired on
then
>> you're ready to put on the netting. - with millions of more wire ties -
> can
>> you say carple tunnel syndrome !
>>
>> Once everything is hunky dory and all the mesh is nice and tight you are
>> ready to plaster ! I used a mix of 1 part sulphate resistant cement
(most
>> all cement is) to 2 parts sand. You can't just use any old sand. You
> need
>> to look for jagged shaped sand, you don't want to use round river sand.
> The
>> reason is that you want it to key together really good. I talked to a
>> concrete expert and he clued me into this sand over in Soladad Canyon
> where
>> it is blasted out of a rock quarry and ground up into sand. The other
> thing
>> is you also want an gradation of sizes of sand particals, not just all
one
>> size. The specs that I got on the make up of the sand from Solidad
canyon
>> was practially a text book perfect sand that I needed. You want to try
> and
>> hold the thickness to around 1 inch.
>
> So you're on the "sharp sand" side of the argument. Others argue that
> washed and graded round sand gives equally good strength on cure and is
> much more workable when applied.
>
>> I hired some plasterers on the first round and let them do their thing, I
>> was very nervious because I was very concerned about the water content
and
>> getting the mix right. But I just let them go because there is the
> practcal
>> side of it also, ideally you want a low water content but it's very hard
> to
>> get the penitration into the mesh if the plaster is too hard to work
with.
>> So you may have to sacrifice a few thousand psi strenght factor but you
> are
>> getting better penetration and ultimately a better finished product. The
>> top part of the clamshell I did myself with some extra help and
everything
>> went well.
>
> There are additives that are intended to improve workability and allow a
> low slump mix to be used. Fine silica (pozzolan) seems to both improve
> the strength of the final product and make it more workable, but there
> are also a bunch of commercial products intended only to make a
> low-water mix workable. I think sodium stearate is one..? Anyway, you
> didn't use any of that, I take it.
>
> Thanks for taking the time to lay this out.
>
> Best,
> Marc
>
>
>
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