Friday, 29 January 2010

Mast base

This (part) of the rotating  mast base is one of those maddening little pieces that is difficult to get right, because of all the shallow angles. If you get one bit correct and nicely fitting you then find another bit has gone slightly AWOL! Very frustrating.


It did not take too long to make the individual bits, but fitting it all together and working out 'how' to hold the parts in place for  welding (without loosing the pin alignment for the sheaves) has been quite tricky. The sheaves are running on a 1/2 inch stainless steel rod. I will drill sideways  holes either end of the rod and fit  clevis pins to keep everything in place, and allow for replacement of the sheaves if neccessary in the future


Sheaves fitted and now ready for welding.

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.