I have a 79 P-30 #1143. My current line to wire halyard is quite frayed where they join together and needs replacing. Can this be done with all line since the stretch factor is no longer an issue ?. I know there is a groove in the masthead sheave. Does this preclude using all line, if not what's the largest diameter rope that will fit ?
Also I would love to run the halyard back to the cockpit. Has anyone done this?
Could I relocate the winch on the mast to the cabin top. How would I make it secure enough ? What other hardware would I need to add ?
I'm not sure what you are asking in the bolded sentence. But, if your sheave is U-shaped with a smaller groove for the wire, it's okay to go with all line. The wire sheaves that are V-shaped will cause chafe on the line.
I would think that you can go with whatever size line that you have now with the wire/rope halyard. Probably 7/16".
If you are going to go with high-tech line. You can get away with a smaller diameter, but you should really change out your sheave if you are going to decrease diameter much.
Think long and hard before deciding to run the halyard back to the cockpit. You are adding friction every time you turn the line and you will find it more difficult to raise the sail. Not really an issue if you plan to use the winch a lot. I can raise the main on my boat completely without ever using the winch at all. I couldn't do that if it were run back to the cockipit.
I'm not sure about the construction of your cabin top, but you will certainly want to use a substantial backing plate and be sure that you get no water intrusion in the bolt holes. Otherwise you will likely cause serious damage to the core of the deck/cabin top.
Headliners can also complicate mounting stuff on the cabin.
If you do run it back and move the winch, (which I wouldn't do unless it's a self tailer), you will probably want to add a rope clutch in order to free up the winch. If the mast winch isn't a self tailer, you would be better off just leaving it on the mast and purchasing a new winch for the cabin top.