-------------- Original message --------------
From: Jarrett & Heidi Johnson <hjjohnson@sasktel.net>

> 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"
> To: "Rotary motors in aircraft"
>
> 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 wo uld also be able to support
> > the lintels and lintel
> > blocks so everything could be poured in one go.
> >
> > Finn
> >
>
>
> --------------------------------------------------------------------------------
>
>
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