maths....more maths & drilling holes and gearboxes

So I read all the posts I could find about drilling the holes.  It didn't look (& isn't) that complicated.  Figuring out where and how to drill the holes is just another process.

First had to figure out where the rudder was going.  I have settled on a RH prop and so that coupled with the helm being on the right side called for the rudder to be offset to the left.  Couple of quick measurements showed that I need to put a block beside the keel to give a nice landing point for the rudder port.  So I made an glued that block in.

Having now decided where the rudder was going to be, I can position the end of the prop shaft and you essentially work forward from there, prop nut, prop, strut.  You have to leave enough gap between the end of the prop shaft and the rudder to allow the prop to be removed without dropping the rudder.

Then I set about doing the maths on where the hole for the prop shaft needed to be.  This is calculated using a bit of simple trigonometry and Pythagoras theory.  I found a nice description of the process written by Dave Lott.  Followed his process more or less and came up with the entry point for the drill.  Once the entry point is found I made a block to start the drilling process on.  Because of the low angle (14 degrees) you need something to land the drill tip on otherwise it will just skip off.  I'll post a photo to make that description make more sense.

The drilling is guided by using the strut.  Where the strut needs to sit had to be flattened, to do this I made a template with plywood and then used the pattern attachment to my router and flatten it.  Was pretty easy, just took a bit of time prepping.

All that done I discovered my drill bit is too short by about 250mm, so it gone to a machine shop to have 300mm added to it, overall length will then be about 1100mm.

Tonight I drilled the rudder port hole.  Did it with a standard hole saw.  This is OK, except yo have to stop every 10mm or so and use a chisel to break the centre out.  the whole (hole ?) process took about 10 minutes.  Seems wrong to drill big holes in the bottom of your boat.

Last weekend I also got some bolts for the gear box and bolted it up to the engine.  Even though its the wrong gearbox it appears to be the same dimensions as the same as the correct gear box.