Yes, as I said the keel box is strong arrangement - it should be, for this very reason - but then what happens if hull is not (daggerboard of Vendee boat): https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-snc6/250640_10152511660250338_1645993348_n.jpg
As raced in lift keelers and centreboarders would like to comment: much depends on design idea. And on mixing terms centreboard with Lift keel (for me centreboard, even ballasted, is centreboard).
On this I will say as Seajet:
Vertically lifted 'finkeel' boat may be lighter and more stable, simply because she may be given more draft then fixed keel - will lift the keel if needed. But i this idea is not for sailing shoal waters - keel must be kept down.
If such boat is designed to sail on shoal waters, then she needs stability with keel raised, hence ballast in the hull.
Those are two different design approaches.
When the board is not acting as ballast, then it's not a "keel", but centreboard, for me at least. And I can attest personally centreboarders may be fast
So when made as proper offshore boats, with good stability, then may be heavier, but not necessarily so if their draft "board up" is substantial, like 3-4 feet. Many successful racers were made this way in US, under CCA rulings.
For OP question - draft of 4 feet, say 120-130 cm is very convenient in Europe, also in Carribean - I'm not familiar with UK waters. This draft can be had in boats over 30 feet long. But 140 cm is more common.
My boat has 140 cm draft, in fact bit more and I would like to sail french canals, but have some doubts
For drying out - she has legs.
Wishing You health and hope you will get better. I am coming back to sailing, after some two years spent mostly in horizontal position... so please, have hope.
P.S.
As for steel - not only better paints, but also better steel can be used today, quite resistant to rust. Even in old days more resistant, such as Cor-Ten was in use; this only is difficult to bend, but for simpler shapes, easy to plate on, was used with good result.
Now in Poland boat may be ordered also in stainless or aluminium, and this is even cheaper than normal steel (or fiberglass). Much less is spent on protective coatings which are costly and labor intensive. But such boats are mostly custom built.
then we would run aground. The keel is very heavy (2 tons for the lifting part on our S49). This would slow us down and we would realize we had lost the channel. We then take stock and plan our new route, press the keel button and move back into the channel. This is a GREAT feature of any of the boats that can raise the keel, and that don't have any damage from grounding. We regularly sneak into places even shallow Cats wouldn't venture because they get stuck if they run aground. And cats are rare in many of the European destinations you are looking at since the dockage is expensive and more difficult to accommodate.
