Epiphany on the hull structure

I woke up this morning with an epiphany on how to join the superstructure onto the hull.  I had always intended to use PVC piping for the hull, but thought that I would perhaps make up a fibre glass superstructure... or something.

Sometime ago, my son and I scrounged around the local Mitre 10 store looking for off cuts of PVC pipes.  We found a nice 173mm length of 90mm pipe, which they gave us.  We then went home and worked out that Volume = Pi * radius * length.  We tested this by measuring the test piece of piping.  In this case the volume is around 6.3 litres per metre of length.  This means that having a hull length of 1.5m x 2 (it will be a catamaran), gives a total length of 3m and a lifting capacity of approx. 3 x 6.3 = 18.9Kg.  A bit more in salt water.

I have since worked on the presumption of using 90mm twin hulls.  However, today, saw us back at the Mitre 10 store, looking at 90mm-50mm-90mm T-piece.  That way, I could build the superstrucure out of PVC tubing.  Yes, I know, pretty obvious when you think about it!  Low and behold, they didn't have any 90mm to 50mm T-pieces, only 100 and 150 to 50mm T-pieces.

I came home, and spent 20 minutes hunting for an Australian PVC manufacture that has a catalogue on-line.  Found this company had a nice catalogue of PVC drain pipes.  Luckerly they didn't have any 90mm fittings.  That got me thinking about moving to 100mm hulls.  3m of 100mm PVC should be able to lift around 23.5Kg.  Just for stamps, I did the sums for 3 m of 150mm pipe.  It should be able to lift around:  53Kg.

One thing I haven't done yet is to find out how much 3m of 90, 100 and 150mm pipe weighs.  So far I have guestimated that all the batteries, motors and computers might weigh in at around 20Kg, so based on that, I think the Mark I will have a 1.5m x 150mm twin hull.  I will have to get my act together, and weigh everything.  More on this later.

Tomorrow we will pop down and pick up some scrap pieces of 100mm and 150mm piping so we can weigh them.  We will also get the dimensions of the 150-50-150mm T-Piece, as my son would like to do a CAD drawing of the Hull and super structure.  I will post the 3D drawing when he's finished.