Hi multifast,thanks for your tips,all info gratefully received.A book called Frank Bethwaite High Performance Sailing which has reference ISBN 1 85310 757 3 .Try your local library first ,because it is not a cheap book to buy. Ok it is for the high performance 18ft. skiffs which can get up to 35knts,but there is a wealth of information regarding sail, hulls,sailtrimming for different weather and waves.It is a very easy to read book.We have used it to develope our flexy rigs,and in choppy water,do just as Bethwaite says,they flex in and out like mad,and I don't mean dump the wind.In calm weather they behave just like an ordinary sail.The only difference is they are all swing rig,and no rigging except on the top rig,which carries a set back diamond.the reason for this is that in order to increase the very small amount of camber I tighten the diamond up which pulls more bend into the top part of the mast but retains its stiffness to side bend.It is the rig on the videos.Kite shops do a good trade with their carbon fibre and fibreglass tube and rods,the fibreglass rod is only used for the very top of the mast.we find that 8mmc/f tube is ok for all weathers,the 6mm tube slides inside this.So by playing around with them you can find out how much 6mm tube you need to get any bend you need in the mast overall.The pintal for the rig to swivel on is opposite to the standard practice.
It is minimum length of 15cm long and is about 4mm thick piano wire it must fit inside the 8mm c/f tume mast.It must have at least 55mm available for the rig to swivel on,and then enough for the rig to miss fittings on deck.I found for the swivel mounting to the hull use a bit of alu.mast tube[1M class will do],drive some wood dowel down it,drill the centre for your swivel to fit in,this to stop the wood splitting from the strain.[Yes you've guessed right]I learnt from my mistake! If you want any more info just ask,as it is an on-going task at the moment.Regards Scotty