Masthead Halyard Sheave for 3/8"

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Masthead Halyard Sheave for 3/8"

Postby Brianl289 » Tue May 17, 2022 12:07 pm

Howdy,

I am doing some tune ups on my DS1 now that I have got it on the water a few times. With my instructor recently we addressed some rigging issues and got the traveler and other items set up. However, as soon as one thing is fixed another breaks it seems! Last time out the cheek block on the lower part of the mast that routes the main sail line to the cam cleat broke off as well as the main sail line (it was time). So my instructor insisted on upgrading that line to 3/8". I purchased a new cheek block for 3/8" but see that the masthead sheaves are a little small. What should I do to accommodate the 3/8" line in the mast head? I am having a hard time finding a 1 1/6"x7/16x1/4ID sheave that will accommodate a 3/8" line (obviously the width would have to change)
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Re: Masthead Halyard Sheave for 3/8"

Postby GreenLake » Tue May 17, 2022 12:36 pm

I hear you on stuff breaking. Not unusual as you start setting up a boat that "one thing comes after another" but at some point that should settle down.

The "mainsail line" you mention would be the "main halyard".

Going to 3/8" is seriously oversized for a DS! And totally unnecessary for a halyard.

Depending on the type of rope you use, different sizes are appropriate. Not so much for strength, but because some ropes are too stretchy.

If you can upgrade to a rope that is Dyneema or has a Dyneema core, then you don't need more than about 1/8" for your halyard. (Example w/o cover would be Samson Ropes AmSteel, and with cover it would be FSE Robline Dinghy Control -- or equivalents from other rope makers)

If you only have standard double-braid, then 3/16" to 5/16" is a good size range. If you get anything classed as "low stretch" you can go down in diameter.

Forget about upgrading your mast to an incorrect choice of rope, just get the correct rope for your halyard and done.
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Re: Masthead Halyard Sheave for 3/8"

Postby Brianl289 » Tue May 17, 2022 12:56 pm

Ok thanks for the info! Yes 3/8 did seem a bit large considering the hardware in place. In this case, how many feet should I be ordering for the main halyard?

Also I did replace the original cheek block with a 3/8 cheek block. Can I still use this larger block with a 3/16 line or do I need to downsize it as well?
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Re: Masthead Halyard Sheave for 3/8"

Postby GreenLake » Tue May 17, 2022 2:35 pm

Having a slightly oversized block is usually not a problem. For cleats, some sizes may have a minimum diameter that they can grip.

Total mast length (keel to top) is 25'.

You need the distance from about the gooseneck to the top, down to cheek block, over to the cleat and then about 1' extra so you can grip something. Better get a foot or two extra and cut down to size than to order a foot too short.

That said, if you take the distance keel-cheek block, double it and subtract that from 2x25' = 50 and then add the distance cheek block-cleat that should get you in the ballpark (assuming the cheek block sits lower on the mast than the gooseneck).

(Also, some allowance for making a splice or knot to attach your sail)
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Re: Masthead Halyard Sheave for 3/8"

Postby Brianl289 » Wed May 18, 2022 1:47 pm

Ok excellent, based on my current budget I went ahead and ordered 60ft of 1/4" double braid. Thanks!
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Re: Masthead Halyard Sheave for 3/8"

Postby tomodda » Wed May 18, 2022 5:27 pm

Look at using a "halyard hitch" at the head of the main (Google it). Saves you an inch or so compared to a bowline hitch. Every extra inch you can hoist your mainsail up the mast is precious, IMHO. Including giving you more space for your vang setup at the bottom. As you've proly seen by now, space between the deck/tabernacle and the gooseneck is in short supply, take ever inch you can get! Anyway, halyard hitch, I believe GL clued me in on that one, thank you.

Tom
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Re: Masthead Halyard Sheave for 3/8"

Postby GreenLake » Thu May 19, 2022 12:22 am

Tom, I agree with saving every bit of hoist (especially as sailmakers for the DS tend to cut these sails large.

The halyard hitch is a fine hitch, and not that hard to learn. However, there's an alternative. You ca splice something into the end of the halyard. A short round bit of metal called a dogbone might be the most standard. With that in in place, you can just tie a "luggage tag hith" (aka cow hitch).

That's super easy, but uses a trick. There's an extra step in this list:

  1. push a bight through the grommet
  2. loop the end with the dog bone over and through the bight sticking through the hole
  3. leave a generous amount of slack in the end of the halyard, because:
  4. you now pull the bight back out, and the free end now forms a bight on the other side
  5. you now pull that bight above the headboard and finally,
  6. you feed the dogbone through that.

You now have a nice hitch, like you would use for a luggage tag, with your sail being the tag and two parts or your halyard going up. One is the main part, the one going over the top of the mast and which you use to raise the sail. The other is a short free end, ending in a dogbone, that prevents the free end from slipping through the hitch.

You will want to work the hitch tight so the dogbone rests against the hitch, so nothing can "give" later. That's all.

Now, why do I like this? Because instead of a dogbone, I have an eye splice with metal eye (the one for rope, not wire, with the rounded edge at the narrow part). Like a dogbone it cannot slip through the hitch, but when I'm re-using the halyard to hold up the boom, it attaches to a shackle, which a dogbone wouldn't.

However, if you are not planning on doing that, or if you are happy to tie a knot for that use as well, the a halyard hitch is definitely a good way to go.
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