Cenetrcase and waterline

[saltnz]

Hello nearing the end of replacing a swing keel with a daggerboard and I have a question regarding how far above the water line a centercase should be to prevent water coming in to the cabin.
The trailer yacht is 6.7m (22ft) and the draft is 255mm according to the specs from the class website.
So how far up should the paneling of the centercase/trunk that keeps the water out go?
If I go for the water line or just a teeny bit above that suits me fine because I want to weld some reinforcement just above that point

[Landlubber]

..well it seems that you have answered your own question saltnz, cos it doesn't really matter all that much, and as you need to weld, then so be it. The higher the better if possible for many reasons, but it seals well anyhow, particularly on small yachts like you have.

[saltnz]

Thanks Landlubber.
I would like to think so be it, but I have nasty habit over over analysing everything and worring too much about things I should not.
Would you care to elobarate of some of the many reasons. Here are some I have considered
Higher means less chance of water spilling out when heeling
Higher means more chance of staying bouyant if swamped

I was thinking of using a neoprene gasket at the bottom to aid is the sealing, would that be a good idea? Or would it make it too mushy (keel weight 190kg)?

What about making way with the daggerboard up and hence not sealed? This is a class boat and they all race with daggerboard at varying elevations depending on point of sail.

[Landlubber]

Yes, your points are correct, have a look at some other boats the same, they will probably seal top and bottom, the bottom seal seems to do all the real work, it stops large volumes spraying up.

I used to make the cases after making the board, you use the board as the mould, just wrap it in plastic first. Use virgin plastic and heat shrink it so there is a perfect surface, double it up and you have nice clearance space for the board after removal. The case will shrink a bit so make sure that you have enough plastic thickness to allow this. Use 2x .016 is good.