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Date: Thu, 08 Jun 2006 14:14:38 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: OT: Concrete forms
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Finn Lassen wrote:

> Thanks Bill (and to all others that reponded)!
>
> I've had my eyes on these. Haven't found a place to rent them yet. But 
> I doubt it'll be cost effective. Looks like I'd need at least 6 per 
> column: 36. Let's say they rent as cheap as $6/set, that would be 
> $200. >From all the data I've gotten on and off the list so far, the 
> cheapest way seems to be using the 16x16" concrete column blocks. 
> Either pick up speed in doing it myself (which may well happen by the 
> time I'm done with my third corner and ready to start the columns - I 
> *will* learn how to do it) or hire some "illegals" to do it for me.
>
> The only problem is that when I placed the rebar in the 
> slab/foundation I was leaning towards poured columns and placed the 
> rebar as close to corners as possible. Some of them won't quite fit in 
> the column blocks so I'd have to cut the inside of some of the blocks 
> sitting on the slab (of course I could mix and pour the first 8 inches 
> of those columns). Ah, choices...
>
> Remember, I intend to have a concrete truck and guy with a concrete 
> pump come out to pump the corner blocks and the columns, and 
> preferably also the lintels and lintel blocks all in one go.
>
> Did anybody check Jarrett's numbers? Would I really have to brace the 
> forms every 3 inches (near bottom) with 2x4's? Any way of reducing 
> that to, say, every 2 to 3 feet by pouring the columns and corners in 
> a round-robin fashion, so that the concrete would start to set and not 
> exert such big pressure on the forms? How would one calculate and 
> control this? My knowledge of concrete viscosity, plywood and 2x4" 
> strength is woefully inadequate.
>
> As you can see, I haven't completely given up on forms and still have 
> a couple of weeks to decide. I was hoping to find someone with real 
> world experience - how thick plywood, bracing distance, etc. Jarrett 
> seems to come close, but his experience is not really with columns.
>
> Finn


I won't pretend to be an authority, but I suspect that the problem with 
plywood forms is the same as rectangular mufflers on a rotary: the flat 
sides. Have you considered using the paper tubes that are made for 
pouring columns? Slide 'em over the rebar, brace to prevent movement, & 
pour. Then you just peel 'em off after the concrete sets. Adapting to 
the round cross section (framing lumber & a powder-charge anchor gun) 
should be a piece of cake compared to all the work on forming a square 
column. If you pour in the round, don't forget the circles of rebar to 
tie the vertical runs together (remember that no-longer-elevated highway 
in CA?).

Charlie