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Date: Tue, 06 Jun 2006 23:37:09 -0600
From: Jarrett & Heidi Johnson <hjjohnson@sasktel.net>
Subject: Re: [FlyRotary] OT: Concrete forms
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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Finn, I have designed concrete forms in my day 
job, however they were of a different variety 
compared to what your doing.
[Metal pre-cast forms for man holes, city sew 
systems and various "under Street" concrete 
structures]

It would seem to me that your major problem is 
going to be hydraulic pressure at the bottom of 
the form.
If concrete weigh's 150lb's per cubic foot 16" x 
16" x 104"=26624/1728=15.4 cubic feet or 2311 lb's 
of concrete.
Now if my numbers are right you should be dealing 
w/ 9.0 PSI pressure around the form at 1" 
elevation.
I don't think just plywood is going to cut it..
if you strapped the bottom circ. w/ 2 x 4  and 
then the following elevations
[ all measured from Datum= bottom of colum]

3"
6"
9"
12"
15"
18"
21"
25"
29"
33"
37"
42"
47"
52"
58"
64"
72"
82"
104"

All elevations should be strapped by a 2 x 4  [23" 
lng + 2x plywood thickness]around the circ. [2" 
high x 4" out from the form]

These numbers should keep all loads below 500lb's 
force on the 2x4 strapping at each elevation[at 
each side].  Hydaulic pressure isn't my strong
suite [ I'm a draftsman not an engineer] 
Hopefully someone will look this over and tell me 
I'm an idiot.. but.. If I was going to do it..
this is how I'd go about it....
Also worth noting, if you do taper tha colum, make 
sure you secure the bottom of it to the floor or 
it will float off.. and all your concrete
will come spilling out the bottom [ don't ask my 
how I know this!]
Actually regardless how you do it.. it would be 
worth adding a couple concrete nails at the bottom 
to make sure it doesn't float.. a non-tapered
colum form could float also..

Jarrett Johnson.. [wondering how desperate Finn is 
to use/ my numbers now... :-)  ]


---- Original Message ----- 
From: "Finn Lassen" <finn.lassen@verizon.net>
To: "Rotary motors in aircraft" 
<flyrotary@lancaironline.net>
Sent: Tuesday, June 06, 2006 9:40 PM
Subject: [FlyRotary] OT: Concrete forms


> This is only remotely related to rotaries (home 
> of my future
> rotary-powered RV-4) so please reply off-list.
>
> After having worked for three weekends putting 
> up block and only having
> done 1 1/2 corners out of 3 so far, I'm 
> seriously considering building
> forms and having the 9 16x16" columns poured 
> rather that building them
> up with 16x16" column blocks.
>
> If anybody here on the list are familiar with 
> making concrete forms, I
> sure could use some advice.
> Columns will be 8' 8" tall and will be 
> supporting 10' long 8x8" lintels
> with a row of lintel blocks on top.
>
> How thick does the plywood have to be to handle 
> a 8'8" tall 16x16"
> column of concrete?
>
> I'm considering using my future 2x4 or 2x6 frame 
> wall studs to form the
> outside corners of the forms - two along each 
> corner of the form screwed
> together (8 per form).
>
> Another issue is the option of tapering the 
> columns: 16x16 at bottom
> tapering to 8x16" at top. In my mind that would 
> not change the structual
> strength of the columns; would save concrete 
> (25%) and possibly require
> less hefty plywood.
>
> I sure could use some advice on both counts.
>
> Keywords here are "cheaper" and "easier".
>
> 16x16" column blocks are now $3.21 a piece - 13 
> per column.
> The extra concrete to replace one block is about 
> $2.60 (or  $1.95 if
> tapering the columns).
> So I'd mainly just be paying  for the plywood 
> for the forms - seems
> worthwhile compared to the work of "stacking" 
> the 117 column blocks.
> Ideally the forms would also be able to support 
> the lintels and lintel
> blocks so everything could be poured in one go.
>
> Finn
>


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