Adding a Halyard with mast up

I have an Isomat Mast, the size is their #50 or 60 I think, about 8" fore/aft. I would like to add an additional main halyard, on an unused second aft facing sheave. Can anyone tell me how I can do this going aloft without removing the Isomat masthead cap casting (lots of stuff connected to it).

[Brion Toss]

Hello,
We used to use a length of bicycle chain on a long messenger, but found it too easy to get a foul in it. So now we use a series of peanut-size lead fishing weights, the kind that clamp onto a string. Try about 10 of these, spaced an inch or less apart. Wrap tape between the first few, so they form a slightly stiff section, easier to push over the sheave.
Lean the boat over to the side the exit is on first. Tighten all other internal halyards. Fish the messenger out with a bent piece of TIG rod or the like.
Fair leads,
Brion Toss

[tpg]

I may attempt another method, unless Brion or someone else, talks me out of it.
A know-it-all friend of mine sez to send an electricians "snake" up the mast from the
halyard's exit box at the base of the mast. He asserts that it will be easier to see and grab the snake at the sheave - with me at the top of the mast. Then pull the snake's end out, attach the new halyard, pull it back down. Whadda' you think?

[Brion Toss]

Hi again,
There are many paths to the mountain top ó or the masthead ó but this is a bad one; that snake might be able to support its own weight all the way up there, but it will almost certainly wind around other halyards en route. And when/if it does get to the top, it will be far from easy to "grab it". Let gravity do the work for you.
Fair leads,
Brion Toss

[Sailalibi]

I like the top down approach but am having a devil of a time getting thru a blockage about head high on the mast. It seems there must be some foam sound deadener that is blocking my messenger. Any thoughts on how to get around it??

[Brian Duff]

If there are exits near enough you may be able to use a piece of 1 by 19 cable , 3/8" or 1/2" try different sizes, to knock some holes in the foam from below and drop a much heavier weight through that hole, or try a snake from the top and jam it through , either way get some sort of passage through the blockage, and tie something bigger to the messenger, and pull that through your mast to grab and jam the foam to one end or the other of the spar where you may pick/tear it out and then drop a proper messenger on weights to get a fair lead, and your done.
Might find the rig has to be pulled to get the obstrution out.