Wednesday, 20 January 2010

Beams -Foam fill and top fitting

I have opted to foam fill the beams with a 2 part expanding polyurethane faom. It will add a bit of weight to each beam unfortnately, but hopefully not too much. I think I have used about 6/7 kilos per beam

It is a bit of a messy and laborious business. If you keep the 2 components at the optimum temerature for maximum expansion (least weight), then you do not get very long ( 45 secs) to mix well. i.e you have to mix lots and lots of small batches. The foam produces exothermic heat on expanding so it expands well, but then has an annoying habit of shrinking back slightly, leaving gaps around where it is touching the inside of the beam sides and bottom. Fortunately the next liquid pour and gravity  helps to fill these in.

If you spend too long mxing,  this happens! To get the foam into all the nooks and cranies, it reallly needs to be poured in whilst it is still completely liquid.

Here, I am cleaning up. I have tried to keep the foam off the areas that will later be usd as glueing surfaces for the lid.

Ready for the lid. This has been prelaminated already on the inside face.

Lid fitted.

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