Need Help On Lead Ballast for Type VII

[ir3aus]

Still trying to get some help on lead ballast and foam for the Type VII, this is my fourth attemps. I think I understand the process of adding the lead ballast. I assume I am to get the boat to the waterline (Ballast Tank Empty) level in both the pitch axis and the roll axis. What I do not understand is how to apply the foam in order to get the boat to the right trim, i.e. just so the top of the sail breaks the surface. The version of the sub that I built is the one with the short sail.

Please, a tutorial, a set of instructions, a pointer to a place in the forum where this process is described, anything!!!!!

I am sure that someone on this forum has the answers.

Thanks in advance,

Iran