Put the motor, prop-shaft and rudder in before doing the sides. It is much easier to get the angles right. Here I use a solid 3mm shaft going through the shaft AND motor to be sure that alignment is perfect.
Once set up, the prop-shaft tube is epoxied in place.
I install a set of 'blind bolts' under the sub-deck to a standard size, so that I can easily swap motors and mounts. Note the metal spreading the load, and the pins epoxied into the screw heads to cut down the chances of rotation...
The underside skin is fairly standard - note that the pattern is provided a bit big so that trimming will be needed.
Once one is in, it is trimmed to make the other an easy fit...
These are cheap bendy pins off ebay - but satisfactory for this soft balsa. I need lots to sto it tearing...!
Here you can see:
1: the blind nut epoxied to the deck underside for the cannon
2: the rudder shaft with a supporting wedge of balsa behind it
3: two strips of 1/8" on the transom to locate the servo tray rear
4: a hole in the deck above to access the rudder nuts
5: two bits of spruce glued to the front of F4 to hold the servo tray
It all seems to work well...
Sand the point on the sub-deck where the chine changes angle so that it is a gentle curve to fit the underside skin.
And then the lower formers are added.
Once the rudder servo is mounted and tested, the sides can go on.
As usual the front curvature is handled by cutting a bit of balsa across the grain, so it bends easily.