Shutter board - Question on removal of shuttering

[TheVictorianCobbleCo]

I'm doing some huge flower planters for a client (700 x 700 x 600mm square 50mm thick concrete walls) The planter has an internal plug made of shutterboard, outer mould is 2 piece GRP. The first planter had the plug in for a week ,and had to be distroyed, as it would not come out, in spite of being tapered. I seem to remember that shutterboard should be removed within 24 hours of the concrete being cast. Any advice appreciated. (I AM using a good release agent, btw)

[seanandruby]

i take it plug is for drainage? Why not use polystyrene? internal walls need a striking piece to make striking easier.

[TheVictorianCobbleCo]

No the plug forms the internal part of the pot - made from shutterboard, sanded and painted and sealed. I dont understand the "striking piece" can you explain?

[GB_Groundworks]

the plug turns it from a concrete block into a planter, likea bath tub. when i first read it i did think you meant a stopper for a drainage hole, have you put drainage holes in?

only thing i can think of would be some way of decreasing its size, like a rachet etc to give you that 2mm extra

[michaelthegardener]

how about cutting it in half then screw it back togeather ( bit of board on the inside sort of thing ) then it might come out easyer in 2 bits ? or how about the 2 end pieces being removeable ?

[seanandruby]

striking piece....when you erect a internal shutter, each side needs to be made so it comes apart easy. Make each side with two, or three rips of ply ( vertical ) the wailings will keep them from folding. I know you have to strike it all apart and re-erect but it saves you smashing it.

[lutonlagerlout]

i think its like when we build an arch with an arch former
you always have a folding wedge under each end otherwise you cannot get the former out!
can you not get something made out of plastic for the internal plug ?
LLL

[GB_Groundworks]

just googleing around on the subject found this

get a shock if you slumped!! into it haha



http://www.grayconcrete.co.uk/sofa/



Edited By GB_Groundworks on 1289341160

[TheVictorianCobbleCo]

Thanks for all the replies, appreciated. the advice is right, I remember my dad making 3 piece cores, one pulled out the middle and the two outers came in and were removed. That was for car piston inners tho. This core is 600 by 600 by 550 with a 5 degree taper. I've now made the core, painted with a filler primer, sanded smooth, and painted a sealer on top. It will then get a RAMWAX polish and then a coat of release agent. So hopefully this one will work. I cast the first planter right side up, at 380kgs its hard to move around, this second I'm going to cast upside down, if this cocks up will then split the core with a removable centre section.

[TheVictorianCobbleCo]

BTW the sofa is amazing!!