What to think about these exit slots?

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What to think about these exit slots?

Postby Anstigmat » Sat Nov 14, 2020 7:00 pm

I got my proctor mast and the guy who delivered it I think made these cuts for exit blocks. They are pretty low down, above the slot in the cuddy. So somewhere between the deck and the slot where the gooseneck goes.

I've ordered the Harken exit blocks for the holes, but just curious how worried I should be about the structural compromise he made. If I should be worried, how can I make it a bit more sound?
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Re: What to think about these exit slots?

Postby GreenLake » Sat Nov 14, 2020 7:31 pm

First question: how long did he sail with that?

If the boat's seen extensive use with these, that should increase your confidence.

I'm not really sure how I would rate any strength reduction. Not sure whether you can eyeball this, even. That's why, if it's been used that way for a long time, I would defer to that experience.

Also, not sure whether it is even possible to "strengthen" the mast in this configuration.
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Re: What to think about these exit slots?

Postby Anstigmat » Sat Nov 14, 2020 8:13 pm

The dealer was sort of a marine salvage guy. I don’t think he sailed with it at all. I think he knew I needed to rig it for the DS1 and made the cuts himself. Kind of a weird situation... I’m inclined to think it’ll be ok as I am not racing and they’re low in the structure, but still kind of unsettling.
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Re: What to think about these exit slots?

Postby GreenLake » Sat Nov 14, 2020 8:57 pm

Did you request internal halyards?

On the other hand, if he's somebody who constantly 'tweaks' boats like that as part of a sale, he may have done similar to many boats (presumably w/o most of them coming back w/ complaints of failure). Hard to know. I knew a guy who was in the business of reselling windsurfing gear and small boats and he had it down to a science wrt to doing those repairs that buyers were willing to reward. He also liked to sail a lot of his stock once or twice in a regatta before selling them on, and for that purpose, he'd do things like jury rig a spinnaker on a boat never intended for that. I would have tended to trust that guys modifications, for example.
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Re: What to think about these exit slots?

Postby jalmeida51 » Sat Nov 14, 2020 10:15 pm

To put your mind at ease call Seldon Masts up in S.C. 843-760-6278. They bought out Proctor Masts.

john
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Re: What to think about these exit slots?

Postby GreenLake » Sat Nov 14, 2020 10:30 pm

Excellent suggestion!
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Re: What to think about these exit slots?

Postby Anstigmat » Sun Nov 15, 2020 2:14 pm

I mounted the new mast today and it fits well. There was only a few minutes of dremeling to get a fit through the cuddy. Another issue is that these dang holes are mounted low. I've ordered the exit blocks I need but the process of raising and lowering the sails might be a little awkward.
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Re: What to think about these exit slots?

Postby GreenLake » Sun Nov 15, 2020 2:21 pm

I assume your plan is to mount turning blocks next to the mast so you can pull back on the halyard while raising the sails?
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Re: What to think about these exit slots?

Postby Anstigmat » Sun Nov 15, 2020 4:47 pm

If I find out that it’s structurally safe that’ll be the way I go yes.
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Re: What to think about these exit slots?

Postby GreenLake » Sun Nov 15, 2020 6:28 pm

I think you'll be fine.

Any mast bend will be in the fore/aft direction at that location and that means the sides of the mast aren't highly stressed. So, should be no impact on normal operation.

In the unlikely event that you lose a shroud, the mast would be less stiff to sideways bending and may take heavier damage. However, a shroud failure always has the risk of bending the mast beyond the point where it's no longer reversible, so I'd say nothing has changed materially for you: you should already be monitoring and maintaining your shrouds, and the fact that you are less likely to get away with it, should simply be an added inducement. I lost one shroud through inattention during rigging, @zeroready just lost one in a new-to-him boat from corrosion. This does happen, but rarely. It shouldn't keep you up at night - as long as your rigging is new and well cared for.

And even without the cut-outs if you did lose a shroud, you would have stood a good chance of needing a new mast, depending on conditions.
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Re: What to think about these exit slots?

Postby Anstigmat » Mon Nov 16, 2020 10:43 am

That makes sense, and I asked another local expert. He said much the same. So I'll stop being such a worry-wort! This is just the kind of stuff you do in the off season. Think about the boat without being able to use the boat. But I may speak to my rigging guy about having a stronger overall shroud.
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Re: What to think about these exit slots?

Postby GreenLake » Mon Nov 16, 2020 3:39 pm

DR Marine sells standing rigging for the DS. Always like to support their business as they are the only ones carrying some DS-specific parts.
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Re: What to think about these exit slots?

Postby tomodda » Mon Nov 16, 2020 7:13 pm

I agree with GreenLake (for once!), you definitely want to make sure your standing riggin is up to snuff. New stays ($200ish, if I recall) are worth the peace of mind.

In the meantime, may I suggest racelitehardware.com for fitting out the bottom of your mast? If it were me, I'd get a pair of their exit plates ($6 each), and then either stand-up footblocks ($10/each) or go with a deck strap ($3?) and medium block ($12) with a stainless steel compression spring (a few bucks on amazon) to make it stand up. Then cleat the halyards off on your existing horn cleats. Using a strap and block gives you the advantage of a better angles leading into the mast exit hole, up to you. Whatever you do, make sure to put a good backer plate under your strap or footblock, maybe a piece of stainless bar if you have it lying around, or even a properly sealed block of wood. Spread the load across the cabin top a bit...

For what it's worth, racelite does not put their mwl and mbl ratings on their website, but they're happy to talk about your application if you call them up - it's a husband and wife-owned and operated company. They sell to airplane builders a lot more than to us sailors, which is why they'd rather discuss usage and loads directly with the builder rather than list anything on their website. Anyway, calculate the forces on the halyard and then give them a call. No reason to go any more robust than the breaking strength of your halyard line (2400 lbs for Samson 1/4 XLS3, for instance), but you'll have to do math to figure out the minimum, Google is your friend here.

Best,

Tom
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Re: What to think about these exit slots?

Postby GreenLake » Mon Nov 16, 2020 11:07 pm

The maximal static loads on the rigging are given by the capsize limit. (Any more force than that in the sail, and you go over anyway).

For a halyard that would be something like the original tension in the sail, plus the entire sail force assumed to act on the halyard (we're trying to estimate limits, so we take the worst case). Your supersized 600# of skipper+crew can get their COG perhaps out 4 feet from the center line or 5 feet from the one part of the hull still immersed as you heel the boat; the center of the mast, as seen from the sail is about 15' up, so 5 x 600=15 x sailforce, which comes to about 200# at the limit. More than that, and you go over. WIth 50# of pre-tension in the rig, you are at 250#.

There's very little sailboat hardware that isn't rated at least that (unless you go for the tiniest sizes).

You will encounter dynamic loads that are less easy to calculate. So, make up a safety factor. But I would think that sheets are more likely to see shock loads, e.g. in a patent gybe.

Whatever your calculation, look up what diameter rope you need to get a mean working load (MWL) of 500#. Almost nobody goes that small, although I have another boat rigged with 3mm halyards. So sizing blocks by what loads your lines can handle would mean that you are grossly overdimensioning your rig.

For example, 7/64" or 2.5mm Amsteel Blue has a "minimum strength" of 1400 lbs -- if that is supposed to be the breaking strength then the MWL would be about 1/3 or 450lbs. However, you don't want to use blocks rated at 1400 lbs. (One reason you overdimension your running rigging, other than handling, is chafe - so that even before you can detect and correct any damage, the line will still hold what it needs to).

(I'm happy for anyone to check these assumptions and my math. If you want to know how the pros are doing it read "Principles of Yacht Design" by Larsson & Eliasson).
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Re: What to think about these exit slots?

Postby GreenLake » Mon Nov 16, 2020 11:10 pm

I have a great local store and they don't stock racelite. So, I tend to go with the other brands, and at some point you also go with what you have good experience with. So you'll find me making different recommendations that Tom, but that's all OK.
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