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Mast Exit Sheave Box

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weluvlife
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166 Posts

Initially Posted - 02/16/2004 : 14:21:23

Hello,

I'm very interested to learn of your opinions regarding quality
sheave boxes for exiting the halyards from the mast. Where can they
be found for a value and also, where should they be placed on the mast?
I read in previous posts that some place them 4 to 6 feet up the mast. What is the advantage over having them placed 6" above the deck?

I have a tall rig with four narrow sheaves in the mast head and have wire/rope halyards. I'd like to go with all rope, possibly using the four sheaves with rope instead of the wire. The two in the front for the jib and the spinnaker, and the two sheaves in the rear for the main and topping lift.

Any suggestions would be great!

Thanks,

Mark Eichman
La Grange, CA
'86 c25 tr sk

Mark Eichman
Lake Don Pedro,CA
www.lakedonpedrosailingclub.org
'86 c25 TR, SK

Edited by - on

Champipple
Master Marine Consultant

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USA
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Response Posted - 02/16/2004 : 14:42:35

Mark,

First and foremost, there are many different types of “sheave boxes”, as you call them, available for use. You might try Defender.com. If I recall they had a number of them for clearance. Many people have just used mast exit plates which do not even have a sheave in them. In hindsight, I really don’t think it matters for a boat our size.

As for mast placement, you ideally want them to exit at about shoulder to eye level. (exactly where you noted 4 to 6 feet) this is so that you can always jump them at the mast and still have plenty of leverage. Jumping would take for any number of reasons, including a problem with the winch back at the cockpit, an unavailable winch due to racing, or any other reason.

The original setup at the mast uses 4 sheaves, essentially to roll the wire over the top of the mast and back down the other side. I would submit that using all four individually would create multiple problems.
1. Four separate lines (at least three of which being 5/16ths, plus all of the wires running down our mast is fairly crowded, especially crowded at the point where the halyards enter the mast. Remember there is a sheave separator up there. (although it can be done, you risk entanglement of items within the mast).
2. You spinnaker halyard needs to be out in front of your forestay. Primarily, for proper sail control and shape. Secondarily, running it directly out of the mast will case override problems with you spinnaker. There is an extra clevis pin on the forward portion of the masthead to put a spinnaker block.
3. 5/16ths line might not fit the sheaves? (don’t know for sure)

I would recommend getting the 2 conversion sheaves from Catalina Direct and installing the Topping lift and Spinaker lines separately.

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 02/16/2004 : 14:44:14

Mark,
If you look at a Mark IV Catalina 25 you will see exit blocks. Slots further up the mast have no blocks in them and slots are free. With slots you run the line down to a halyard plate with what ever block you want, it gives you a lot of versitility. I have gone to ropes this year and am still external at this point. If I decide to go internal later I will simply use my Dremel and cut out the slots.

edit
I went with 1/4" halyards which are far stronger than the wire and rope original halyards. It means that the stock sheeves are an ok size, I did upgrade to new better sheeves, Bellpat marine 1-631-286-8368 $10 ea.

Edited by - Frank Hopper on 02/16/2004 14:54:27

weluvlife
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Response Posted - 02/16/2004 : 15:04:13

Very good. I'm a bit clearer now, after your thoughtful suggestions. Duane, your thoughts on the spinnaker halyard make sense. I didn't think about it before I asked the question. I in fact have my spinnaker halyard block out in front of the headstay now.

So, all I need to do now is find a very low chafe exit plate.

Thanks a bunch,

Mark

Edited by - on

OJ
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Response Posted - 02/16/2004 : 15:10:43

Mark,

I've found Ronstan products to be of very good quality and more competitively priced than Harken.

Good luck

http://www.ronstan.com/catalogue/R042-045.pdf

Edited by - OJ on 02/16/2004 15:18:17

John Mason
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Response Posted - 02/16/2004 : 19:59:50

When I internalized my halyards and ran them back to the cockpit, I just cut slots (3/8" width=dia.of the line x 3 1/2" height)in the mast about 4 to 7 feet up from the base and smoothed the edges. Very inexpensive. If you use this method, just make sure you stagger them up and down the mast so as not to weaken it.

Edited by - on

weluvlife
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166 Posts

Response Posted - 02/16/2004 : 20:48:22

>>>>>I went with 1/4" halyards which are far stronger than the wire and rope original halyards. It means that the stock sheeves are an ok size, I did upgrade to new better sheeves, Bellpat marine 1-631-286-8368 $10 ea.
*************************
Frank, thanks for the tips. How are the Bellpat better? How do you get a good grip on 1/4" halyards? Do you have to wrap them around a winch to get the luff good and tight?

>>>>>I've found Ronstan products to be of very good quality and more competitively priced than Harken.
*********
I'll check them out. Thanks OK

>>>>When I internalized my halyards and ran them back to the cockpit, I just cut slots (3/8" width=dia.of the line x 3 1/2" height)in the mast about 4 to 7 feet up from the base and smoothed the edges. Very inexpensive. If you use this method, just make sure you stagger them up and down the mast so as not to weaken it.
****************
John, Do you receive any wear on your halyards because of the slot? Any drag? The stagger seems of obvious importance. Thanks.

Edited by - on

Leon Sisson
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Response Posted - 02/17/2004 : 02:12:23

<blockquote id="quote">quote:<hr height="1" noshade id="quote">originally posted by Mark Eichman:

Very good. I'm a bit clearer now, ...<hr height="1" noshade id="quote"></blockquote id="quote">Well see here now, we can't have that! If the opinionated lot of us can't obfuscate a simple topic like this in the middle of the winter doldrums, we're not really trying.

When I converted from 1979 stock external wire&rope halyards to internal all rope (3/8" Dacron double braid) halyards, I used a pair of the wide single groove Catalina Direct replacement masthead sheaves. I drilled two 3/4" holes down through the middle of the masthead casting to get the halyards inside. My spinnaker halyard and pole topping lift are run entirely external.

As for "I went with 1/4" halyards which are far stronger than the wire and rope original halyards." -- fhopper. I don't doubt the superior strength and weight savings of the latest high-tech ropes. My reasons for going with more traditional low-tech 3/8" Dacron double braid halyards had more to do with my cruising oriented priorities of: ease of handling, conventional splicing, and cost vs. anticipated life expectancy.

I also installed thinwall PVC conduit inside the mast for the wiring harness to keep it separated from the halyards. (In the way of the spreader attachment hardware, I exposed the wiring, and ran the halyards in PVC for a couple feet.)

As others have described, I used (Schaefer?) stainless steel exit plates in staggered slots well above the highly stressed gooseneck area. I think there's a formula for spacing large holes in spar walls, but I can't seem to find it now. The exits I cut in my std. mast are 12" to 18" apart from each other and the gooseneck. Further is better. Avoid creating openings with sharp corners when cutting the slots -- they concentrate stress and encourage failure like a loose thread in knit fabric.

I use a mast base plate and swivel bullet blocks to turn the control lines out toward the deck organizers.

To aid in jumping halyards, etc., I installed a large Harken camcleat on each side of the mast just above ankle height. These allow me to temporarily cleat control lines at the mast while I'm up there. When I return to the cockpit, a tug on the line pops it out of the mast camcleat, returning control to the rope clutches.

I hope that didn't contribute too much confusion to the original question.

-- Leon Sisson

Edited by - on

Frank Hopper
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Pitcairn Island
6776 Posts

Response Posted - 02/17/2004 : 07:38:09

Layline.com is having its cordage sale now.
1/4" is bigger than it sounds. I would not think of raising a sail without putting it on a winch. Between the winch and the clutch I don't expect the tail to be hard to handle. Is there anything in the world that broadcasts "clueless" more than a scalloped luff

I wear gloves 80% of the time. I have still not sailed with m new halyards so I may discover that I am unhappy with them but I will be really surprised if that happens. The worst case scenario in my mind is an extra wrap or two on the winch which will still leave me with a "soft tail" that is easy to handle.
The Bellpat sheaves have more material in the center of them and are just nicer than the new sheaves I got from my dealer.

Edited by - Frank Hopper on 02/17/2004 07:38:55

Champipple
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Response Posted - 02/17/2004 : 07:53:55

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Is there anything in the world that broadcasts "clueless" more than a scalloped luff

<hr height="1" noshade id="quote"></blockquote id="quote">

As long as its not blowing less than 8 with residual choppy seas.

dw

Edited by - on

lcharlot
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Antigua and Barbuda
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Response Posted - 02/17/2004 : 08:11:18

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by fhopper@mac.com
 Is there anything in the world that broadcasts "clueless" more than a scalloped luff

<hr height="1" noshade id="quote"></blockquote id="quote">

Yes - one thing - boats that cruise around all day with fenders deployed and dragging in the water. Wait, I just thought of an even worse one: Skippers who allow very small children up on deck without PFD's. This one is the nautical equivalent of parents who allow small children to stand up on the back seat of a moving automobile and peer out the back window. Sounds ridiculous, but I see this at least a few times a year.

Edited by - on

John Mason
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Response Posted - 02/17/2004 : 16:51:43

<blockquote id="quote">quote:<hr height="1" noshade id="quote">John, Do you receive any wear on your halyards because of the slot? Any drag? The stagger seems of obvious importance. Thanks.<hr height="1" noshade id="quote"></blockquote id="quote">

Mark,
None that I've noticed. Not even the discoloration that happens sometimes when things rub against aluminium. The sails go right up and come right down, so no appreciable increase in drag either. I did put a healthy bevel at the top and bottom of the slot as well as the smoothing of the edges.

Edited by - on

weluvlife
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Response Posted - 02/17/2004 : 20:46:44

Thanks to all. As usual you all are very enlightening and entertaining.:)

One quick question for you, Leon.

>>I also installed thinwall PVC conduit inside the mast for the wiring harness to keep it separated from the halyards. (In the way of the spreader attachment hardware, I exposed the wiring, and ran the halyards in PVC for a couple feet.)

Exactly where is the short piece of PVC you run the halyards through? How is it attached?

I have been having trouble with the archive search funtion, so I apologize if this topic has already been explained in depth.

Edited by - on

Leon Sisson
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Response Posted - 02/17/2004 : 21:34:53

<blockquote id="quote">quote:<hr height="1" noshade id="quote">originally posted by Mark Eichman:
Exactly where is the short piece of PVC you run the halyards through? How is it attached?<hr height="1" noshade id="quote"></blockquote id="quote">I ran the wiring in one of the aft "corners" of the mast, against the sail track, attaching the conduit to the mast with short pop-rivets. As you've no doubt figured out, there are good reasons to install the PVC wiring conduit in two pieces -- the mast is longer than production lengths of PVC, the wiring for steaming and spreader lights needs to exit the conduit somehow, and any PVC large enough for all the wiring won't fit past the aft side of the spreader base thru-bolt compression sleeves.

To prevent the halyards from chafing the exposed wiring (or being chafed by the hardware) near the spreaders, I wedged a piece of thinwall PVC pipe in front of the spreader bolt compression sleeves. This piece of PVC is thin enough, and just large enough to be a very tight fit. It's long enough to overlap the ends of the wiring conduit. I routed both halyards through the same PVC pipe, being careful not to get them wrapped around each other.

My internal halyard installation is surprisingly free running. The only signs of use I've noticed on the halyards is in the section from the clutch to a couple feet onto the tail past the winch position with each sail fully raised. Even that is not yet what I'd call significant wear, just the slightest wisp of fuzz and discoloration from being handled.

-- Leon Sisson

Edited by - on

weluvlife
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Response Posted - 02/18/2004 : 19:27:30

I follow what you've explained Leon. It all makes sense now. How long is the upper (halyard) pvc section? This is 1/2" pvc? Did you remove your masthead cap, in order to run the pvc section into the small space between the spreader compression sleave and the mast?

thanks,

Edited by - on

Leon Sisson
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Response Posted - 02/18/2004 : 20:47:44

<blockquote id="quote">quote:<hr height="1" noshade id="quote">originally posted by Mark Eichman:

I follow what you've explained Leon. It all makes sense now. How long is the upper (halyard) pvc section? This is 1/2" pvc? Did you remove your masthead cap, in order to run the pvc section into the small space between the spreader compression sleave and the mast?<hr height="1" noshade id="quote"></blockquote id="quote">Not so fast. I was only kidding about trying to confuse anybody.

Let's try this again...

There are two thin wall PVC electrical conduit sections, upper and lower, each maybe 3/4" or 1" I.D. The lower one runs from a few inches above where the wiring enters the mast near the base, to a few inches below either the spreader hardware, or the steaming/deck light, which ever is lower. The upper section of electrical conduit runs from just above either the steaming/deck light, or the spreader hardware, whichever is higher, to a few inches below the masthead fitting.

As mentioned previously, the wiring conduit is pop-riveted in an aft corner of the mast, up against the mainsail luff groove. There are two rivets about 2" to 4" apart 2" from each end of each of the two electrical conduit sections. More rivets are spaced out evenly about every 18" along those tubes. These pop-rivets are just barely long enough to go through the mast wall and into the PVC wall -- shorter than would normally be the case. The idea there is to expand the rivet in the PVC wall, not in the open interior of the piping where it might chafe into the wiring harness.

This whole PVC mast wiring conduit procedure is explained in painstaking detail by Don Casey in his book "This Old Boat", which I suggest would be a wise investment for anyone maintaining and/or upgrading an older fiberglass coastal cruiser in the 22' to 40' range.

As for the halyard guide tube, let's suppose for the sake of this discussion that the gap between the upper and lower sections of electrical conduit at the spreaders is 18". In that case, the single 1" to 1-1/2" thinwall PVC halyard guide tube would be around 24" to 30" long, and centered on that gap in the wiring protection at the spreader area. Both main and jib internal halyards run through that same short wide section of guide tube. The tube is held in place by being a very tight fit between the forward most spreader base compression sleeve and the front of the mast. The tube is slightly distorted when installed, and so stays put without additional fasteners.

And yes, just about all of this work assumes that the masthead fitting is removed. If yours is held on by three or four #10 SS self-tapping screws, I suggest you be prepared for two things:

1.) The screw heads may break off instead of the screws backing out nicely. If this seems likely, try soaking them with penetating oil for a few days before applying potentially destructive force. If they do break off, it's no big deal. Just grind down the stub and make a new hole near by.

2.) Regardless of the fate of the sheet metal screws, I strongly suggest going back together with 1/4"-20 SS machine screws in tapped holes with silicon sealant or other insulator on the threads. Another alternative might be four 1/4" aluminum pop-rivets.

I generally prefer to use threaded fasteners when it's practical to do so, in case the assembly has to be serviced "in the field" so to speak.

One of my favorite cartoons on this topic of low-tech servicability shows a sailor wading ashore on a third world tropical island while dragging the damaged mast from his high-tech trimaran anchored just off the beach. He's talking to a local native who is one step above wearing a loin cloth and using animal bones for jewelery. (Not that there's anything wrong with wearing loin clothes and bone jewelery, so those of you in thong bikinis and faux-ivory necklaces just calm down.

) The cruiser is asking, "You weldum aluminum?" The native is giving the universal mechanic's shrug most car owners are familiar with.

Got all that?

-- Leon Sisson

Edited by - Leon Sisson on 02/18/2004 20:51:59

Frank Hopper
Past Commodore

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Pitcairn Island
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Response Posted - 03/01/2004 : 11:37:31

this is how high the exit blocks on the stock Mark IV are, see why I think they are "trip lines"? That is why I think a halyard plate will help reduce the trip factor and therefore mast slots up the mast are preferable to the exit blocks.

Edited by - on

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