Sheaves for toe rail blocks for my sailboat

[mickri]

Just spent 5 days at the boat working on stuff. Back home for 10 days before going back to the boat. I would like to at least get started on this project before going back to the boat.

The sheave for a toe rail block that I got from a friend is cracked in half. Amazing what corrosion can do. I am pretty sure that the other sheave will break when I press out the center bronze and stainless steel bushings. Any thoughts on what I could soak this sheave in to loosen up the corrosion?

I believe I have 4 options of what to make the replacements out of. The current sheave is aluminum. Probably 6061. A replacement made out of aluminum would need to be anodized or have some type of noncorrosive protective coating. Don't know if this is possible in a home shop.

Second option would be bronze. No protective coating needed. The bronze is probably expensive.

Third would would be some type of plastic. These sheaves can come under significant load depending on how the line runs through the sheave. Any suggestions on what type of plastic might work in this situation? Lots of sheaves are made out of bronze and plastic.

Fourth would be casting a sheave out of polyester resin and fiberglass cloth. Sheaves used to be made this way and they have a name. I don't remember it off of the top of my head. I would need to make a mold for this.

Looking for suggestions on what material to use. Once I decide on the material we can explore how to make the sheaves.

 

[mattthemuppet2]

I would suggest 316 stainless, it's made for marine environments. Or lignum vitae, though that's probably more expensive than bronze

 

[mickri]

Surprisingly sheaves for blocks on sailboats aren't made out of stainless steel. I can't remember every seeing a stainless steel sheave. Plastic is the most common these days. What type I don't know. I will have to look into the type of plastic used. Bronze is pretty rare too these days.

 

[mattthemuppet2]

all I know about boats is that they're expensive and they float There are a whole bunch of plastics for harsh environments and heavy loads (glass fiber reinforced and the like) out there that would be worth looking into.

 

[RJSakowski]

Delrin (acetal) is pretty tough and easy to work. It has self lubricating properties making it a good candidate for sheaves.I have a good collection of bronze saved from old outboards, props, etc. With access to a melting furnace, they would be a good candidate for a blank. See SV Seeker for his experience casting bronze.

 

[mickri]

Been researching the type of material used to make sheaves. Aluminum sheaves are made out of 6061-t6 that is hard anodized. The plastic sheaves are made out of delrin/acetal with uv inhibiters. Still looking into the type of bronze.

Don't have any equipment to melt and cast anything. Cheaper to just buy whatever material I chose.

 

[C-Bag]

You don’t mention the diameter of the sheaves. I would also vote for Delrin. It’s amazing stuff. Beauty is it’s already bearing material and doesn’t corrode. UHMW is also tough but I’ve seen it get brittle from UV.

In that mother of all estate sales here over 5yrs ago where I scored my Atlas shaper the guy was a boat repairman. In his metal stock shed I scored 3 8’ long bronze shafts that I assume were prop shafts for $20. Wish I would have bought more now. There was also a bunch of SS in there too but I never use SS.

 

[mickri]

The sheaves are 2 3/8" in diameter by 2" long. Making them smaller in OD would not hurt the performance of the sheaves. Don't think that I would go smaller than 2" OD.

 

[matthewsx]

I may have some bronze for you. How small can you go?

John

 

[mickri]

I think that I am going to try delrin first. There was enough left over from my rudder bushing project to make the sheaves. Right diameter too. I'll have to ask my friend what he did with the left over delrin.