Hi Chf,

I am thinking that you would be better with a beam around 80cm for a 1.2mt cat...but I have not built a RC cat myself so am no expert.

I did spend a fair amount of time investigating building a 1.2mt cat though.

I would have thought mast height between 1.6-1.8 mt would work for you..(at 54cm beam).

Rudders and fins ...hmmmnnn..well you could probably use rudders from a IOM mono ( if you are running twin rudders) otherwise if you are using a centre mount rudder and centreboard (and I have seen this work very well on a few 1.2mt cats) then you probably need rudder around 250cm deep and centreboard 350mm deep. Both would need to be around 6cm wide. As for the thickness , that is anyones guess??..but probably between 5-8mm thick at widest point.

Sorry I cannot give you better info..there are much more experienced cat builders out there who could give you wiser advise I am sure..good luck.

Gary