Where can I cut exit hole for new halyard?

[BAD ORCA]

I have a couple of un-used sheaves at top of mast. I want to add a spare Dyneema halyard. It would be an internal halyard so needs to exit somewhere around exit of an existing halyard. How far away do you think i need to be from one of the existing halyard exits to be safe?

 

[Foswick]

I would not take any advice, here, about that. The answer really depends on a number of factors. The problem with cutting a hole in your mast is that the strenght of the mast largely depends on the integrity of mast walls. (This is called "monocoque" or "semi-monocoque" in aviation construction. Might be the same term when referring to masts.) Think of an aluminum beverage can. It is pretty strong so long as you don't compromise the walls. But, as soon as you put a small dent or hole in the side, the structure is significantly weakened.

I do not know enough about mast construction to know to what degree this is true across all masts. My assumption is that lighter-weight masts will have less tolerance for this and will be more dependent on monocoque strength. Fortunately, the bottom several feet of the mast do not rely much on resistance to lateral stress. It is mostly resistance to compression that matters, at that part of the mast (and arguably, most of the mast).

If I were to attempt this, without consulting a good rigger, I know what I would consider. It has less to do with the distance from existing holes and more to do with the absolute position of the new hole and also to do with the absolute amount of material removed.

In general, I don't like to tell people, "Don't do it. Hire a professional." But, this might be one of those times. At minimum, by consulting a rigger, you will get an answer as to whether this is advisable at all and, if so, what the considerations are. Just be upfront about your intentions (obviously) so they don't spend time/effort giving you free advice with no chance that you will hire them for the actual work, unless they know that's what they are doing.

 

[BAD ORCA]

I would not take any advice, here, about that. The answer really depends on a number of factors. The problem with cutting a hole in your mast is that the strenght of the mast largely depends on the integrity of mast walls. (This is called "monocoque" or "semi-monocoque" in aviation construction. Might be the same term when referring to masts.) Think of an aluminum beverage can. It is pretty strong so long as you don't compromise the walls. But, as soon as you put a small dent or hole in the side, the structure is significantly weakened.

I do not know enough about mast construction to know to what degree this is true across all masts. My assumption is that lighter-weight masts will have less tolerance for this and will be more dependent on monocoque strength. Fortunately, the bottom several feet of the mast do not rely much on resistance to lateral stress. It is mostly resistance to compression that matters, at that part of the mast (and arguably, most of the mast).

If I were to attempt this, without consulting a good rigger, I know what I would consider. It has less to do with the distance from existing holes and more to do with the absolute position of the new hole and also to do with the absolute amount of material removed.

In general, I don't like to tell people, "Don't do it. Hire a professional." But, this might be one of those times. At minimum, by consulting a rigger, you will get an answer as to whether this is advisable at all and, if so, what the considerations are. Just be upfront about your intentions (obviously) so they don't spend time/effort giving you free advice with no chance that you will hire them for the actual work, unless they know that's what they are doing.

Thanks, i appreciate your candid reply. Maybe i will take this one slow so i dont do anything rash. The wire halyard is working fine so no rush. I do have another empty sheave directly in front of this one at the front of the mast, so one in front and one in the rear of mast. I wonder if i can run halyard externally through both sheaves instead? run the halyard up the front of the mast and exit at rear down to topping lift. I'm not against having an external halyard sitting there so long as i could keep it out of the way and from falling off the sheave and jamming.

Like this...

 

[garymalmgren]

External halyard = noisy.

I agree that this is a professional's decision, but...
Could you post some photos to show how crowded the mast base and halyard outlet area is?

Gary

 

[Don S/V ILLusion]

I would not take any advice, here, about that. The answer really depends on a number of factors. The problem with cutting a hole in your mast is that the strengh of the mast largely depends on the integrity of mast walls.

my suggestion is you follow the advice captioned above

 

[PaulK]

A rigger has insurance to be able to make this sort of decision. (Or they should.) Having a rigger cut the hole would be a good way of sleeping better aboard.

 

[colemj]

It is common for masts of all types to have multiple halyard exit holes in them. We have four on one side of our thin-walled bendy mast. The holes will be elongated ovals to allow the halyard to run free, and these ovals must be perfectly cut so there are no stress risers. Often they will have an insert in them for chafe. To put them on the same side of the mast, they should be staggered 15-18" vertically, and not line up horizontally (where they would interfere with each other anyway).

It sounds like yours will be on the other side of the mast from your main halyard, so that is even less of an issue.

I agree that employing a rigger is a good thing here, but it isn't the worry or even engineering tangle some are implying. It is more of a "where to place it to get a true run" problem, where a rigger would be helpful.

Mark

 

[colemj]

It has less to do with the distance from existing holes and more to do with the absolute position of the new hole and also to do with the absolute amount of material removed.

Not quite. It has most to do with distances from existing holes and little to do with the absolute position. It is assumed the position will be on the sidewall and not fore/aft walls, and this area is forgiving of this. You don't want them lined up next or close to each other vertically or horizontally, as that is a zipper. The amount of material removed will be fixed by the need for the halyard to make the transition from inside to outside without cutting itself to ribbons.

Masts actively bend fore and aft, so those are areas to not put holes. Mast should not be bending side to side at all even without holes. The sides of the mast should be in compression, with the exception of the small amount of tension/compression needed to effect any prebend or active bend from a backstay. As long as there are no stress risers in added holes, and the holes are shaped and placed for the compression forces to move around them, there's little issue with putting (proper) holes in the sides of the mast.

Mark

 

[David in Sandusky]

One reason it's OK to put halyard exit holes near the bottom of the mast is that bending forces approach zero at the ends of the mast. Bending forces in the middle of the mast can be high, and can be focused to a momentary peak by the mast shape, and attachments or holes there.

The advice to avoid horizontal and vertical overlaps, and to avoid any corners or other stress points in the hole are good. And hiring a rigger to bring his expertise into the implementation also sounds good to me.

 

[BAD ORCA]

Hey thanks for all the advice. What about running it externally over two sheaves like pictured in #3 post?

 

[colemj]

Hey thanks for all the advice. What about running it externally over two sheaves like pictured in #3 post?

That might work, but the issue is the line is not going to lay flat over two sheaves separated by that distance. This might cause it to jump the sheaves. So it would depend on the particulars in that area - are the lines contained enough to have slop there without binding something or chafing on something?

Usually a topping lift that can be pressed into service as a main halyard is mounted on the adjacent sheave. Do you have a topping lift? The factory didn't use that sheave at all, so no hole cut for a halyard?

Mark

 

[BAD ORCA]

That might work, but the issue is the line is not going to lay flat over two sheaves separated by that distance. This might cause it to jump the sheaves. So it would depend on the particulars in that area - are the lines contained enough to have slop there without binding something or chafing on something?

Usually a topping lift that can be pressed into service as a main halyard is mounted on the adjacent sheave. Do you have a topping lift? The factory didn't use that sheave at all, so no hole cut for a halyard?

Mark

topping lift is welded bracket/wire cable so they left two sheaves un-used. the halyards are on the adjacent sheaves.

yeah that what im wondering as well. i wonder if it will jump a sheave. i dont know why they didnt put the topping lift on a halyard. they had the extra sheaves. instead they used up one of only two sheaves in yhe boom for the toping lift instead which would be better used for a reefing line.

i would like a third halyard though one way or another. there seems to be enough space around the unused sheaves to prevent chafe or binding. they are also decent size and can easily accept 1/2 line with room to spare. i would probably use 3/8 dyneema so would sit down low in bottom of sheaves radius. might have to just try it and see if it works. worse case i then consider cutting a hole in mast.

 

[BAD ORCA]

actually, i think i might be good to go running them externally. i just found some pictures i took recently when mast was down. didnt realize i took pics of mast top. it appears there is a seperator/wall between the sheaves so they cant actually jump off. will try and post pic.

pic of front halyard. rear halyard/back of mast top is identical.

 

[jssailem]

When I had my mast refitted, I put all the lines internal. I replaced the 2 wire halyards with polyester line. The advantage of managing the halyards at the mast, you can space the exit blocks vertically so as to minimize the stresses on the mast. Placing the exit block high creates the opportunity to jump the halyard making raising sails a simple manual operation.

 

[Claude L.-Auger]

FYI, my 34 has 4 internal halyards rigged similar to image on post # 3 but running front and back (See dwg). All 4 exiting at about 1 inch below the top of the mast and 1 inch above bottom of mast. The 2 in front of the mast for jib and genoa (or spinnaker topping lift). Spinnaker bail mounted externally on top of mast with spinnaker halyard running above sheaves for internal running halyards and of course above headstay. The 2 in back for main halyard and spare (or boom topping lift). All 4 exit at the bottom of the mast, 2 on port and two on starboard side. Hope this helps.