Enlarging the shaft tube

Ya know ... since I'm already on the hard doing a major upkeep including many major modifications I may as well do one more.  After talking with my prop guy at Proper Pitch Marine Props  http://www.properpitch.com/home.asp  I've decided to go with a 3 blade prop and increase the shaft size from 1 inch to 1-1/8 inch.  This means I have to also increase the cutlass bearing  http://www.deepblueyachtsupply.com/  and the shaft tube.  I'll make the shaft tube myself.  Hmmmm .... let's see what do I have that's almost the same size as the new shaft that I can use for a template???

How about a fluorescent light tube???  It's just a few 1000ths too small.  I can sand out that much and custom fit the cutlass bearing.

,So, you wrap PVA on the light tube, roll on a couple layers of glass mat along with a layer of peel ply and lay it in the sun to cure.  Then you smash it in the dumpster and dissolve out the glass and PVA with water.   ...  Next step ...

Two layers of 17 oz biaxial and 2 layers of 2 oz mat then spin it in the lathe to make it true, vacuum bagging every lay up, and do it again ... and again ... and again until the tube is 1/2 inch thick.

Then you get really brave and bore a big hole in the back of the boat.  There's no turning back now ! ! ! !

I welded up a special boring bit so the hole would stay straight.

An hour or so later, I've cored through 8 inches of glass and the new tube fits perfectly.

After taking careful measurements, I only get one shot at this, I mix up thickened resin and slide the new shaft tube in place.  Now to sand off some barrier coat and fair it 

All faired out and painted with Micron 66 bottom paint.  The 3-blade prop will turn farther away from the hull as original design so it won't be a shielded by the hull.  Also, with a 3-blade vs a 2-blade there are always 2 blades un-shielded for propulsion ... especially in reverse.