Adding Masthead sheaves

[Nunami]

Any suggestions on how I should add masthead sheaves for a screecher? I figured I would use some aluminum plate that I have and make a forward facing duplicate of what is on the aft part of the mast. The photo here is of the main halyard and topping lift tied to a pin.



A plate across the top with 3 "legs" coming down the front should do it right?

[psk125]

Duplicating the fitting you have looks like overkill. All you need is a tang sticking out forward - a crane - that you can hang a halyard block (swiveling?) from. Adding flanges would end up having the halyard chafe as the screecher (or spinnaker) moved around.

[Spot]

Does the mast already have a fractional forestay and jib?

[Nunami]

the mast has a fractional forestay used to fly the jib and a spinnaker opening above that. I want the new halyard to be internal so thats why I wanted to duplicate the existing fitting..so the sheaves would be half in/half out.

[Spot]

Originally Posted by Nunami

the mast has a fractional forestay used to fly the jib and a spinnaker opening above that. I want the new halyard to be internal so thats why I wanted to duplicate the existing fitting..so the sheaves would be half in/half out.

OK, I think I am following along better with these details, thanks. I can understand wanting a similar look/feel/function to the additions.

Does the spinnaker opening have 2 sheaves and a similar cap? Are you using those as well? Enough room in the mast for all the lines? Any other cabling in there like VHF, anchor light?

Do you work with aluminum, or will you have to send it out?

[Jammer]

Don't make it so hard. Aluminum plate riveted into what's already there using some 1/4" aluminum rivets (or use rivnuts and aluminum bolts if you want it to be removable), stainless steel u-bolt held in place with four locknuts (use tefgel), and a block.



If you want the halyard to be internal, make an exit for it two or three feet down from the top of the mast.

[Nunami]

Originally Posted by Spot

OK, I think I am following along better with these details, thanks. I can understand wanting a similar look/feel/function to the additions.

Does the spinnaker opening have 2 sheaves and a similar cap? Are you using those as well? Enough room in the mast for all the lines? Any other cabling in there like VHF, anchor light?

Do you work with aluminum, or will you have to send it out?

I can do all the cutting for the aluminum so I was going to build a jig and then have an experienced welder come assemble it all. Its a stepped mast so no trouble to work on it.



The reason I'm not just sticking a tang up there is because my understanding is that a screacher halyard needs a good bit of tension so I'm picturing it going straight up the inside of the mast an over the sheave and not chafing on anything.