I made the attached clamps to hold the centreboard case in position whilst screwing and gluing. Hope this helps answer the question from Sinfronteras. They are made from a metre of threaded steel rod (8 or 10 mm) which conveniently comes in 1m, lengths from hardware stores and can be cut down to 2 x 500mm pieces. The ends are scrap timber with appropriate sized holes, some nuts and washers.
I also have a related question. I am about to glue the centreboard case in position and am wondering if I also need to screw it to the sole to provide extra strength - it's what Francois Vivier suggests, but turning or raising the boat to gain access to insert screws will be hard for me as I'm single handed until Covid restrictions are lifted and I can have helpers!
Frame 3? - Cutting? It is supplied as one-piece port-to-starboard, probably to ensure correct hull shape. I guess you'd be hard pressed to fit the case without cutting it.
IIRC we took a little off at a time till it was right.
Graham's comment "take it easy" is especially significant when shaping the underside of the "logs" to fit the actual line of the sole. Take off a little at a time, and keep checking, eg with paper/card as a feeler gauge. Don't stand in the boat when doing this, because distortion of the sole gives a false reading.
Screwing - YES - Screw it.
Working alone? Can you get someone to slip bricks under your cradle while you lift one end at a time?
Clamping - Peter's threaded rods are a great idea. Graham seems to have used long clamps. IIRC we used car batteries. And I think we used odd lengths of wood, jammed between the case and the buoyancy/lockers, to ensure the case remained vertical.
FWIW - We subsequently in-filled the space, between the logs, each end of the case, to prevent water and debris loitering. See Here. Not annotated, but evident.
Further pics available via the "Proteus" link in the table of Known UK Morbics.
To gain access under the boat I took PaulW's advice and lifted the bow with a pulley and rope arrangement tied to a beam in the garage and through the hatch hole in the front bulkhead. After that it was lying on the floor to drill upwards into the sole - a bit like under the car maintenance if you remember when we used to do that! See attached photo.
I too used a paper gauge to level the logs - though I think total accuracy is not essential as long as the position is stable when the screws are tightened - the thickened epoxy should fill the gaps. All boat building books I have read call for lots of thickened epoxy here. Peter.
I'm impressed with the clamping idea - obvious when you think about it. I made the centreboard case assembly while waiting for the laminated stem to be finished, so once it's made up, offer it up to the sole before fitting that, and then you can drill and countersink the screw holes in the right place.
Then, when it comes to fitting the case inside the completed hull, the predrilled holes will help with alignment when crawling underneath to put the screws in. But on the other hand, clamps is a smart idea!
Re : cutting the bulkhead, yes you have to do that, and that will help aligning the case athwartships too