Question about mounting a cheek block on a mast or boom - SailNet Community
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post #1 of 12 Old 05-11-2008 Thread Starter
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Question about mounting a cheek block on a mast or boom

When mounting a cheek block on the mast or boom, do you use heavy metal screws to hold the block in place, or is a nut/bolt combo required? I've been thinking about re-running my jib and main halyards so that I can raise them from the cockpit, but I don't know if the stresses on the blocks would be such that they'd need more support than from screws.

Thanks!
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post #2 of 12 Old 05-11-2008
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It depends... many spars, both booms and masts are too thin-walled to properly support a cheek block safely using screws and tapped holes. In cases like that, you may want to mount the cheek block to a mounting plate that is fastened to the boom.

For instance, on my friend's boat, we made up aluminum mounting bases for the line clutches, which were pop riveted to the mast. She then through bolted the line clutches to the mounting plates. The line clutches are removable for maintenance, but the bases create a solid and reliable connection between the line clutch and mast...and allow the line clutches to lead fair to the winches and exit slots.

For my halyards led aft project, I'm having three stainless steel plates made up that attach to the mast step base plate, and the turning blocks will mount to these three plates.

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Quote:
Originally Posted by jaschrumpf View Post
When mounting a cheek block on the mast or boom, do you use heavy metal screws to hold the block in place, or is a nut/bolt combo required? I've been thinking about re-running my jib and main halyards so that I can raise them from the cockpit, but I don't know if the stresses on the blocks would be such that they'd need more support than from screws.

Thanks!
What is your boat? Deck or keel stepped? How old? Do you have a furler? Are there winches on the mast? How about a photo.
In my experience, machine screws are usually adequate for mounting cheek blocks but it really depends on the loads and as SD said, the wall thickness of the mast.
You have to make sure the load is applied to the block properly also. Fasteners that will be alright for shear loads may fail if you are pulling the block away from the mast.
You may want to consider mounting stand-up blocks through-bolted to the deck if you are deck-stepped.
In truth though, there are too many unknowns to be able to advise you confidently.
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If you have a deck-stepped mast, getting a mast step with spaces for mounting turning blocks for leading lines aft is probably the best way to go.

My boat has a deck-stepped mast, but doesn't have a step available with slots for the turning blocks to mount through... so I am getting plates made up that will bolt to the existing mast step that will allow me to add turning blocks to the mast step. Another reason I decided on having plates that bolt to the mast step, rather than modifying the mast step directly, is that actually simplifies my unrigging and re-rigging the boat, since I have a mast that is easily lowered.

Here are a couple of photos of possible mast steps that allow turning blocks to be mounted:







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Last edited by sailingdog; 05-11-2008 at 03:56 PM.
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post #5 of 12 Old 05-11-2008
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What are you trying to do? You asked about cheek blocks and got answers about routing halyards aft. Kinda apples v. oranges at this point. Maybe if you provide some more details about what you need the blocks for we could get you more specific answers.

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T34C-

Might want to re-read the OP. He's actually asking about running halyards aft... started with a bit about cheek blocks, but that generally isn't the best way to do the job.

Quote:
Originally Posted by jaschrumpf View Post
When mounting a cheek block on the mast or boom, do you use heavy metal screws to hold the block in place, or is a nut/bolt combo required? I've been thinking about re-running my jib and main halyards so that I can raise them from the cockpit, but I don't know if the stresses on the blocks would be such that they'd need more support than from screws.

Thanks!
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Originally Posted by T34C View Post
What are you trying to do? You asked about cheek blocks and got answers about routing halyards aft. Kinda apples v. oranges at this point. Maybe if you provide some more details about what you need the blocks for we could get you more specific answers.

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—Cpt. Mal Reynolds, Serenity (edited)

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Thanks Dog- I'll try again.

Cheek blocks are not really the best way to go to route lines aft to the cockpit. It is easy to buy a mast base plate that goes under your mast step like the ones SD- has shown above. Try here:
Dwyer Aluminum Mast Company- Manufacturers of Quality Sailboat Masts, Booms, Hardware and Rigging Since 1963.

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Here's a photo I have that shows most of the mast and step. It is deck stepped.




The line on the left in the photo is the mainsheet, the one on the right is the boom vang line. There are two winches mounted on the mast for the main and jib halyards. Would I be able to wind the lines around the winches on the mast, but carry the line down through the cheek blocks and to another cleat on the cabin roof by the traveler? Or is there loss of power or torque due to the pull coming so far from the winch?
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You really don't want to have the lines wrapped around the winches on the mast, since they'll add friction, and there's always the possibility of creating an overriding turn or wrap on them, and fouling the halyard there.

What you should do is run the halyards down to a turning block either mounted on the cabin top, or on a mast step plate (which is the preferred way to do it) and then to a line organizer and then to a line clutch that leads the halyards fair to one of your cabin top winches.

A good article to read is this one from Sailnet's archives.

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post #10 of 12 Old 05-11-2008
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Ditto, what he said.

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