Oday 35 Main Halyard chaffing

[CodeGrue]

Over the last season, the part of the halyard that runs through the sheave at the top of the mast received quite a bit of chaffing. Inspection of the block revealed two potential causes:

- this line is the exact size of the sail track, so it may be getting caught and rubbing on the sides
- the exit from the sheave to the track is not tangentially lined up, so the line may be rubbing on the top of the mast

I find it odd that the sheave doesn't line up. It's recessed about a half inch from where I think it should be. I am not the original owner so I don't know if this is normal of if (possibly) the sheave was replaced with a smaller one from the original. Does anyone with a 34 or 35 have any insight?

I can't post a photo because it's in storage right now.

 

[dmax]

My previous boat was an '87 O'day 35, it had the Isomat NG1 masthead: NG1 Masthead Assembly
If you have the NG1, rige-rite can tell what sheave sizes to use.

It looked like this with the top cover removed - I replaced the sheaves but don't have the exact sizes but I believe they were 2" diameter, maybe an 1/8 more (they do use a 10mm shaft, not 3/8"). I'm pretty sure the middle sheaves were larger, closer to 3". I didn't have the alignment problems you are talking about. I used 5/8" halyards and had no chafing issues. If yours is the Isomat, make sure everything was put back together correctly - the shafts need to be pushed all the way down in their slots and the cap acts as a spacer to line everything up. Here's what mine looked like with the cap off, you can see the middle sheaves (fore-and-aft direction) are not lined up, the cap does that):

 

[CodeGrue]

Very helpful! Thank you do much for the photo. The schematics were not super clear.

 

[dlochner]

Does the sheave at the masthead rotate freely? Older boats often used aluminum sheaves on a SS bolt. The sheaves often corrode and do not spin freely this causes the halyard to drag across the sheave causing more friction and chafe. Another issue is a flat spot developing on the axle which impedes spinning again causing chafe and misalignment.

New ball bearing sheaves are a really nice improvement, sails go up and down easily and hard hats may be needed when dousing the main. Garhauer probably has a sheave that will fit at an affordable price.

 

[eherlihy]

Another Pic of an O'day 35 Mast Head with the cover removed;

• Red with white tracer halyard is the Genoa
• Blue with white tracer halyard is the Spinnaker (unused)
• White with green tracer halyard is the Main

Sheaves are all aluminum (which I do NOT recommend).

Here is the masthead with the cover on. You can see the sheave that changes the angle of the Genoa halyard, to prevent halyard wrap.

 

[CodeGrue]

I can't get access to my mast until the spring to see what I can do. I don't remember it being able to open like this, but maybe I just didn't inspect it close enough. Here's the only photo I have with the masthead in the shot.

Edit: the marina said I can get in and take photos of my mast. I will post soon once I get down there.

 

[CodeGrue]

Here is my masthead and a view of the main halyard coming out the rear where it would head down to the sail along the track. My concern is the sheave is "inside" and the line rubs on the aluminum edge of the mast. Is something off here?

Also, this masthead look different than what you have posted for references. Any idea what this one is? And moreso, how would I remove it... I see some kind of bonding glue but no screws.

 

[dmax]

I think it's the same masthead - the cover is the piece with the anchor light attached. There are two screws you need to remove (bottom of the first picture) and it looks like a PO addition of a small piece of metal holding down the other end. The cover should come right off with the screws removed. Not sure why the main halyard exit is so close to the mast, mine had enough room so it didn't chafe but it was close. Maybe you can add some kind of fairlead block to pull it away from the mast: Rigging Only - to 5/8" line 3000 lbs Schaefer Half-Moon Fixed Fairlead Block, 2 3/8" OD 32-06

 

[eherlihy]

O'day used two (or three) different masts on the 35. It is vital for every owner to KNOW which appendages their boat uses.

My O'day 35, for example, uses an Isomat NG-51 Mast with an NG1 Mashead assembly;

Detail of the Isomat NG1 masthead assembly;

Note that the sheaves can either be NG1-3 or NG1-4. The difference is the diameter of the sheave. Below is a picture that I took of the aluminum sheaves that I ordered from Rig-Rite in 2019, and you can see on the paper, the dimensions and the price that RigRite charged. I do NOT recommend aluminum sheaves.

an Isomat NB-32 Boom;

With Isomat BF-3 Spreaders;

It may be worth your time to spend some time researching the Rig-Rite website to see what, exactly, you have on your boat.

 

[CodeGrue]

Thank you for all the details. Agreed I need to know what I have. I just got the boat in the fall so I am going through everything over winter. I have the owners manual which is dated 1983 and looks like it was created off a physical typewriter. Unfortunately, it does not say what kind of mast or masthead it has. Assuming I have the one you posted, I think I might be missing this part highlighted. At least this helps when I go look at it for what to look for.

 

[jssailem]

I am going to suggest that the halyard diameter appears to be larger than the sheave on which it is set. The halyard is supposed to fit within the sheave.