I have been chasing a problem with son’s (peter) mossie – a heavy helm problem and wanting to round up……not as bad now that I have moved rudders further forward……well as far as I can get them. David Dunk.
Until the mid 90’s most Mosquitos were built with the centreboard cases a bit forward from the maximum aft position allowed by the rules. Since then they have almost all been built with the cases back at the limit of the measurements. On these later boats the rig can be raked aft and the boat will still balance, but on the older boats the mast needs to be almost vertical and any aft rake will probably cause weather helm (wanting to round up). If you have a lot of weather helm try easing the sidestays.
Heavy rudders may be because they are at the wrong angle to vertical. The tips of the rudders should be about 15mm to 20mm ahead of the pintle/gudgeon centreline?
If the two rudders are not parallel that can also cause more weather helm.
Another way to get a lighter feel to the tiller is to buy a new set of Boyer or McKenzie rudders. They are very small and very efficient. Sailing with these rudders feels more like steering a dinghy.