Correct name for this block please?

skyflyer said:
Thanks - unfortunately if you look closely at photo you can see the edge of the spray hood so if we bypassed the block the sheet would chafe against that so definitely needs to be replaced or serviced.
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Could you use one of the new(ish) high load fairleads forward to give a good lead into the winch? Work best with high tech lines.

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LadyInBed said:
You can see the pin through the block on the pic, so it shouldn't be too much hassle to remove the block, knock the pin out and service it. If the block has to be replaced then you are half way there having removed it ;)
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Before taking a hammer to the pin, look closely to see if the lower end has been rivetted over with a big hydraulic press (to make it wider than the hole). If so you'll need to drill that end off, and then you'll need to acquire or make a new pin.

I've done exactly this for Lewmar plain bearing footblocks in the past, to replace sheaves that had broken after many years of UV degradation.

As for the placing of the block, while yes it does look as though there might be better locations for it, it looks to me as though where it is now is where the designer and/or builder wanted it to go, so personally I'd leave it there. Doing without altogether might be an option, provided you get a good lead to the winch whatever the position of the genoa car, but in general footblocks/cheekblocks/turning blocks are there for a reason.
 
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It is a cheek block, in that a cheek block is any block designed to be mounted on a surface with the sheeve parallel to that surface, rather than hanging from a shackle or whatever.
Functionally, that is a genoa sheet turning block.
Its main function is to ensure the winch loads correctly, which requires the sheet arriving at the winch from not too far away.
Change this and get it wrong, and you will forever get riding turns etc etc.
Yes it is heavily loaded, a bit less than twice the sheet tension.
You may be able to strip it and sort it, there may be a bush in the sheave you can replace?

Many people use the term footblock to mean the blocks at the foot of the mast, they may be wrong, but there is a danger of ambiguity.
 
s for the placing of the block, while yes it does look as though there might be better locations for it, it looks to me as though where it is now is where the designer and/or builder wanted it to go, so personally I'd leave it there.
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I fully intend to! As you say the deck has been moulded with a flat area there to take the block and it is factory fit. I would suggest that one of the main functions is to ensure the sheet arrives at the winch at the correct VERTICAL angle - (horizontal angle is irrelevant as its a circular drum!) - so you don't get riding turns. It also keeps the sheet forward of the block close to the deck and thus avoids a trip hazard. If you took the sheet straight from the block on the genoa car to the winch (even if there was no spray hood in the way) it would be a terrible trip hazard!

I appreciate the input but am not looking to do anything other than service it if possible or replace with something as similar as possible with the minimum possible friction
 
sailorman said:
I could have chosen the words better :o
the job if the turning block is to reduce the effort & size of the winch. mounted on the toe tail forward of the winch will make sheeting req more effort on the handle
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Totally wrong
The power through the sheet coming onto the block is say 100Kg then the sheet coming off the turning block will be 100Kg- NOt less ( taking the extra friction out of the equation)
The load on the turning block is 100+100 =200Kg. the load on the winch is still 100Kg
If one puts a block forward of the winch, so it just deflects the sheet direction, the load on the block will be less. The load on the sheet still 100kg
the main purpose of the turning block ( apart from re-aligning the sheet direction) is to lead the sheet onto the winch to allow it to feed on at the correct height. Turning blocks thus fitted can often allow a sheet to go to either one of 2 winches which can be handy if changing to spinnaker sheets etc
If one fits a block forward of the winch you have to check the angle the sheet meets the winch as it could allow an overriding turn if coming on too high
This is still the best place to put a block though if it suits the boat layout
 
skyflyer said:
Thanks - unfortunately if you look closely at photo you can see the edge of the spray hood so if we bypassed the block the sheet would chafe against that so definitely needs to be replaced or serviced.

I am well aware of the load - which is why I am worried about replacement because if they aren't fixed on firmly the consequences of one detaching and launching itself cross the deck could be catastrophic!

However I assumed that after this length of service it would need more than a service, i.e. possible needle rollers worn out of round or the sheave itself worn around the bearing. Not helped by fact that this is a US built boat so its probably some unusual make and imperial measurements!
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Looks like a standard Lewmar cheek block to me. Plain bearing, replacement sheaves and bearings are available. Similar to these http://www.lewmar.com/products.asp?id=7657&lid=24147
 
Daydream believer said:
Totally wrong
The power through the sheet coming onto the block is say 100Kg then the sheet coming off the turning block will be 100Kg- NOt less ( taking the extra friction out of the equation)
The load on the turning block is 100+100 =200Kg. the load on the winch is still 100Kg
If one puts a block forward of the winch, so it just deflects the sheet direction, the load on the block will be less. The load on the sheet still 100kg
the main purpose of the turning block ( apart from re-aligning the sheet direction) is to lead the sheet onto the winch to allow it to feed on at the correct height. Turning blocks thus fitted can often allow a sheet to go to either one of 2 winches which can be handy if changing to spinnaker sheets etc
If one fits a block forward of the winch you have to check the angle the sheet meets the winch as it could allow an overriding turn if coming on too high
This is still the best place to put a block though if it suits the boat layout
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I have already stated i ****ed up ok.
As it happens i have a double Harken sprung loaded turning blocks to lead the genoa sheet & spi guy`s onto my Lewmar 52s.
 
sailorman said:
I have already stated i ****ed up ok.
As it happens i have a double Harken sprung loaded turning blocks to lead the genoa sheet & spi guy`s onto my Lewmar 52s.
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why do you need sprung loaded?
if they are ratchet blocks surely the loads on the sheet will be too much to actually enable one to hold by hand
Also friction on the release will be higher until the load is enough to allow the spring to release because the ratchet will not release
So is there some special reason for them
 
I agree looks very like standard lewmar fitting. I'd take the sheet out and check carefully that the delrin plastic looking sheave hasnt worn a groove on one side and isn't turning at all. It's almost certainly bolted on and shouldn't be difficult to remove and service. Any good plastics company can make a new delrin sheave for it if lewmar cant supply.
 
Malcolm3 said:
I agree looks very like standard lewmar fitting. I'd take the sheet out and check carefully that the delrin plastic looking sheave hasnt worn a groove on one side and isn't turning at all. It's almost certainly bolted on and shouldn't be difficult to remove and service. Any good plastics company can make a new delrin sheave for it if lewmar cant supply.
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They do have a plain s/s insert / bearing
 
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