Colin, Julian et al.
The mast should be somewhere between 2 and 4 degrees aft. On the BR20 and BRe, the mast base should be roughly evenly touching the deck all round. The deck slopes up by a similar amount, giving a good indication of rake.
There is some room to move though, with our tabernacle boats (all those starting with Bay).
Generally if you end up block to Jib head then you have too little rake. If you end up with an uncomfortably low boom, you have too much. Too much will induce weather helm (tending to round the boat up into the wind). Too little and you might end up with a neutral or even lee helm.
It is worth bearing in mind the following points.
If the lashing at the shroud base is new, or has been disturbed, then it will stretch a bit as it beds in. So always over do the rake slightly as the first stiff breeze will induce a more upright mast.
Colin was asking about tension. The tension is only put in by how much you haul on the jib halyard, and by how hard you sail her. The lashings at the base of the mast are only for setting the shroud length, not for tensioning them. FYI the tension in the shrouds reaches about 600kg when sailing downwind in a blow, in a BR20, but initially when you rig the boat, you would struggle to put more than 200kg into it.
Remember when you do adjust it, to put the lashing back as you found it, with at least 4 full turns between shroud and chainplate. A tip when adjusting is only to do 1 or 2 turns and tie off loosely. In this way you can quickly check the rake and any athwartships drift, before finishing the turns and tying off.
So in summary, the mast rake is important, but probably not worth loosing sleep over. It can affect the feel of the helm and the look of your boat and between 2 and 4 degrees is ideal.
Hope that helps.
Matt
