Seized blocks?

[winch2]

Do modern plastic/SS blocks seize with age? Since launching in the spring its become inceasingly harder to raise our Gaffs peak and throat halyards to the point at the weekend where it felt like the whole kaboodle had seized solid. And if they do size what might be the best way to unsieze them? Thanks everyone.

 

[Daydream believer]

They certainly do. Neither is it unknown for the bush in the plastic to wear through & collapse into the pulley. You may find that the pulley had actually broken, as happened to me once, or just worn on one section .
The obvious answer is to get them apart, withdraw the spindle & have a look. Abrade the spindle slightly to remove corrosion. Then with some abrasive paper rolled in to a tube push that in to the pulley & clean the bore by rotating against the roll of the paper
Clean out any sanding dust from both parts with a drop of diesel or similar. Lightly grease & re assemble.
Temporary bodges are not really worth while as it will always need doing

 

[footsoldier]

Also depends very much on the maker and thus the quality of the blocks. Spindles that are aluminium rather than stainless coupled with certain types of plastic are almost guaranteed to seize in a salty environment. Try pouring some boiling water over them, then if that improves any light lubricant.

 

[dunedin]

Unlike DD, in my experience good quality blocks don’t seize up if given basic maintenance - including occasionally washing the salt out, particularly ones near deck level (eg those at the mast base).
I would throw into a tub of hot but not quite boiling water for a while, then repeat and finally spray with a Teflon type spray.
However, if the sheave is still stuck then may need to replace with a better quality one.
Ball bearing blocks run free-er but need more care to wash the salt out, and generally have slightly lower breaking strain than plain spindle sheaves.

 

[vyv_cox]

My lower mast sheaves seized on the spindles. On knocking the spindles out I found the sheaves to be aluminium with nylon bushes. Nylon swells considerably when wet (I lived in Wales at the time!). I reamed the nylon out a little and they have been fine ever since.
My deck organisers have aluminium sheaves in an aluminium housing on stainless steel spindles. They are riveted together, impossible to separate. They seize occasionally due to carbonate salts. Hydrochloric acid, used sparingly and washed thoroughly afterwards, removes the deposits without damaging the aluminium.

 

[Sandy]

Do modern plastic/SS blocks seize with age? Since launching in the spring its become inceasingly harder to raise our Gaffs peak and throat halyards to the point at the weekend where it felt like the whole kaboodle had seized solid. And if they do size what might be the best way to unsieze them? Thanks everyone.

Do you not rinse them down with fresh water from time to time?

 

[rogerthebodger]

The sheaves at the bottom and top of my mast were also aluminum on stainless steel spindles that corroded and sensed.

I replaced all sheaves with vesconite which is lubricated with water and works very well

 

[winch2]

Do you not rinse them down with fresh water from time to time?

They are attached to the band 3/4 of the way up the mast so to far really.. tho u would think all this rain we've had might have helped but it hasn't.

 

[dunedin]

They are attached to the band 3/4 of the way up the mast so to far really.. tho u would think all this rain we've had might have helped but it hasn't.

Lack of use can also gunk them up. Give a soak and clean and see if works. Worth doing at least annually if possible.

 

[dunedin]

The sheaves at the bottom and top of my mast were also aluminum on stainless steel spindles that corroded and sensed.

I replaced all sheaves with vesconite which is lubricated with water and works very well

Aluminium sheaves are a bit of a pain. Only really needed for those persevering against the odds with wire halyards.
But the OP specifically said plastic and s/s.

 

[Bristolfashion]

Apparently, according to the guy that made a widget for us, delrin also expands a little when wet.

 

[vyv_cox]

Apparently, according to the guy that made a widget for us, delrin also expands a little when wet.

Hardly. 0.2% maximum. Nylon 66 expands by 11%.

 

[Bristolfashion]

Hardly. 0.2% maximum. Nylon 66 expands by 11%.

Er, I think that counts as "a little"?

 

[vyv_cox]

Er, I think that counts as "a little"?

More like negligible.

 

[Bristolfashion]

More like negligible.

And, from my materials data sheets, whilst 0.2% is a reasonable maximum at ambient type water temperatures, that does increase linearly to around 1.4% at 80° with immersion - the guy in question wasn't specifically talking about parts on boats that are immersed in sea water, so may have been talking generally.

From the Dupont Delrin design information sheet,

"Effect of moisture
DELRIN® absorbs a small amount of water which affects the dimension of moulded parts"

So it probably depends upon the design tolerance and the environmental conditions.

 

[vyv_cox]

And, from my materials data sheets, whilst 0.2% is a reasonable maximum at ambient type water temperatures, that does increase linearly to around 1.4% at 80° with immersion - the guy in question wasn't specifically talking about parts on boats that are immersed in sea water, so may have been talking generally.

From the Dupont Delrin design information sheet,

"Effect of moisture
DELRIN® absorbs a small amount of water which affects the dimension of moulded parts"

So it probably depends upon the design tolerance and the environmental conditions.

Seawater is quite warm in Greece but has yet to reach 80°C. Even 1.4% is a very small increase in a sleeve bearing on most yacht applications.

 

[Bristolfashion]

Seawater is quite warm in Greece but has yet to reach 80°C. Even 1.4% is a very small increase in a sleeve bearing on most yacht applications.

Is "very small" ≈ "a little"?

Sorry, I'm just teasing

 

[Daydream believer]

Seawater is quite warm in Greece but has yet to reach 80°C. Even 1.4% is a very small increase in a sleeve bearing on most yacht applications.

That is still a lot when it is stuck