Invader 22
My main site home allsorts *** *** The Mast Head

The mast head - stripped of it's triangular plate holding the Tri /anchor light - vhf ariel and wind vane.
This is the original mast - the 'Thames Marine' logo is stamped just above the upper shroud mount. It is set up for two halyards, with two sheaves for each, running fore/aft separated by a thin plate. The other pins pick up the backstay and roller forestay plus two spare.
I was thinking of altering this to internal halyards - but I feel four would be too much for this section of mast - given that I have two 3 core 1.5mm sq cables plus vhf from the steaming light down to base. Also, the mast appears to be loose filled with polystyrene strips. I may just do two - utilising one fore, one aft, leaving the other pair as normal - then put the topping lift either on the spare pin, or on a dedicated block out of the way of the main halyard. It will entail putting the new cables into fixed conduit and emptying the mast of all the fill - ( if it is in fact filled all the way ).
Also, I would need to change the sheaves, - they would need to be better than these if the line were to run all the way to the cockpit - and would have to be a very similar diameter.
Essentially, finding sheaves to fit this set up, determines whether I run the Halyards back - external or internal. They are quite large, but narrow.
Thinking simple - though, while writing this:-
I could fit a double block to the lower of the two aft pins, to take main and topping lift - then keep the present set-up for a genoa and spinaker ( although my present furler utilises it's own wire halyard ).
The block would be a good roller bearing, so would solve the sheave problem. It would also allow me to maybe seal the mast at the top against water entry in a capsize.
Will update this as have now decided to make up lazyjacks - so won't need a topping lift - with a custom made ( dust off that treadle singer machine ) sail cover, to match the new cover I'm doing for the sprayhood - jet black with white edging !