pin size mismatch in standing rigging

[Megunticook]

I had a rigger replace my standing rigging last year. Just noticed getting the mast ready last week that the clevis pin sizes on all the turnbuckles are 1/4" but my TySenior has 5/16" holes in all the chainplates. Also noticed the same mismatch at the forestay tang on the mast (the rigger correctly sized the backstay eye at 5/16", and all the shroud tangs are 1/4").

How big a deal is this? I can see where having a clevis pin smaller than the hole would cause extra wear and stress.

Should I ask my rigger to replace these at no charge? Seems like he should've checked carefully. It's possible the old rigging was mismatched and he used that as a guide, but I would think a thorough rigger would look at the chainplates and tangs before ordering parts.

[bottomscraper]

Should I ask my rigger to replace these at no charge?

Yes. (but see below)

I can see where having a clevis pin smaller than the hole would cause extra wear and stress.

It will cause the holes in the chain plates to become egg shaped, not a good thing and not easy to fix except by replacing the chain plates.

How big a deal is this?

Big enough so you should do something about it.


I assume the rigger had access to the whole boat, not just the old rigging. If all the rigger had was the old rigging and just made replacements then you really can't blame the rigger.

[Edit]
What size is the wire and what size is the thread on the turnbuckle? Typically the thread on the turnbuckle matches the pin size. So a 1/4"-28 thread on a turnbuckle will have a toggle with a 1/4" pin. Unfortunately that may mean more than just changing the threaded toggle jaw at the bottom. While you are at it you may want to check what was done at the upper end also!
[/EDIT]

[Megunticook]

Thanks. I showed him the boat, the mast, and the rig when I first contacted him. I asked him to look everything over carefully for anything that looked worn, damaged, or near the end of its service life for any reason.

[Megunticook]

Just curious--is it possible my boat came from the factory with 1/4" pinholes in the turnbuckle toggles? I've had a few conversations with riggers and at least one of them speculated that it may have been built originally that way. Does anyone else have this mismatch?

My rigger says the original standing rigging had 1/4" pinholes in everything but the marine eye at the top of the backstay. I have no way of knowing for sure but I'm guessing that was the original rigging that came with the boat.

The rigger suggested bushings as a possible solution--that would definitely work.

[bottomscraper]

I can't answer the question about what originally came with the boat.

The owners manual says the wire is 5/32". You can get turnbuckles, swage and sta-loc fittings for 5/32" wire in both 1/4" and 5/16".
It's possible that the mast tangs are 1/4" and the chainplates are 5/16". Either way a conscientious rigger should have recognized the problem, even if the boat originally came that way.

Bushings don't sound like a great idea. The bushing would have a wall thickness of only 0.03125" and would introduce a perfect place for corrosion to start. I'm not even sure you will find off the shelf stainless steel bushings that size.

[Megunticook]

Yeah, I checked online about bushings and you need an extra 1/16" all around to fit one.

I'm guessing my rigger is not going to be willing to replace all the wires he made up in '15, which looks increasingly like the only real solution here.

Here's a photo of some wear I found on the pinhole in my bow chainplate. Just what I'd like to avoid:

[grluecke]

You might be able to drill out the cable (clevis) side of the holes to 5/16" diameter for the right size pin.

The rule is to have 2 x the pin diameter from the center of the hole to the edge of the part in order to develop the full strength of the pin--Edge Distance, ED. However, I personally have "ok'd" 1-1/2 edge distance on both DC-9 and DC-10 commercial aircraft--uses up some of the Factor of Safety, but...

When you get much less than 1-1/2 ED, and certainly down around 1x ED, you run the risk of tearing out the material with the pin.

However, aside from the egg-shaped holes, the pin is loaded in shear, and that is proportional to the area of the pin. We can compute the ratio of the areas, which is proportional to the diameter squared:

A_1_4 = pi* (1/4)^2 / 4 = (1/16)
_____ = ______________ = _____ = 0.64

A_5_16 = pi* (5/16)^2 / 4 = (25/256)


This is a 36% reduction in the load bearing capability. We have to tar and feather any engineer who designed anything with a Factor of Safety of less than 2--twice as strong as it needs to be--but in sailboats and most other things the maximum-ever-load is vague at best and a wild guess at worst.

So my best advice is to verify that the clevis hole has enough "meat" to drill out that last 1/16th inch diameter and still have 5/16th inch (or more) of metal 'twixt the inside edge of the hole and the outside edge of the clevis. The distance from the center of the hole to the inside edge is 1/2 ED, and if you have one more ED (or more) of metal to the outer edge of the clevis, you are good. Probably. Almost certainly.

20160605_212221.jpg

I am not giving this advice in my capacity as a Professional Engineer in the State of Maine and the State of Iowa (you have not paid me and I have just a little concern about the egg-shape you already have developing...), if it was anything but a Ty, I would agonize over just getting new rigging. Even if you don't, you'll just worry whenever you sail in a blow...

Know any New Jersey mobsters you can have pay this rigger a visit?

[Sea Hunt Video]

However, aside from the egg-shaped holes, the pin is loaded in shear, and that is proportional to the area of the pin. We can compute the ratio of the areas, which is proportional to the diameter squared:

A_1_4 = pi* (1/4)^2 / 4 = (1/16)
_____ = ______________ = _____ = 0.64

A_5_16 = pi* (5/16)^2 / 4 = (25/256)


Know any New Jersey mobsters you can have pay this rigger a visit?

Holy crapola Greg, this is a family website

[grluecke]

Ooops, sorry.

Lots of times when I spout this BS, I also like to include calculations. Sometimes the graduate students look at it, and find that I have made a mistake. If the are **my** graduate students, they are more polite about pointing it out...

Children shouldn't be surfing the 'net unsupervised anyhow...

[bottomscraper]

So what is the situation on the top end? Are the mast tangs also 5/16" holes or 1/4"? If the top end is ok, you may be able to replace the bottom end only using Sta-Lok extra long studs with 5/16" thread and replace the turnbuckles with 5/16". It would hopefully cost a bit less than replacing everything.

Here is the Sta-Lok catatalog. I believe you would want 176-04 on page 5:
http://www.stalok.com/images/pdf/Imperi ... ochure.pdf

If you do decide to go that route you may want to give Rigging Only ("Rigging And Hardware" is the online store) a call. They typically have the lowest prices and in my experience good people to deal with. Here is a link to that part on their web site:

https://www.riggingandhardware.com/p-45 ... -hand.aspx

If enlarging the clevis side is an option you may want to consider having a real machinist do it on a milling machine. They should be able to enlarge the hole but keep as much "meat" left at the edge as you currently have. (The green circle in the picture below.)

TangHole.png

[gates_cliff]

My mast is currently unsteped and I found the same thing. It doesn't look like the holes are distorted but I did find the pins to be smaller.

[Megunticook]

mast tangs are 1/4" for shrouds, 5/16 for forestay. (5/16 pin for backstay).

Spoke to my rigger this morning--let's just say he's not exactly taking full responsibility for this. Would've been so easy to correct when he made up the rigging but he didn't carefully check the pinhole sizes, just went by the old rigging. I'm disappointed he didn't apologize and offer to make it right. It was not the only oversight he committed, either.

He did say he could get some thin bushings with 5/16 o.d. and 1/4" i.d. Hopefully that will work.

[Sea Hunt Video]

Spoke to my rigger this morning--let's just say he's not exactly taking full responsibility for this. Would've been so easy to correct when he made up the rigging but he didn't carefully check the pinhole sizes, just went by the old rigging. I'm disappointed he didn't apologize and offer to make it right. It was not the only oversight he committed, either.

He did say he could get some thin bushings with 5/16 o.d. and 1/4" i.d. Hopefully that will work.

At some point you may want to consider mentioning the rigger's name so he can be separated from "the good ones" and placed in the category of "the not so good ones", assuming that is that he does not find it within his heart to take some measure of responsibility for the mistake.

If it were me I would wait to identify him until you are sure he has done all he is going to do and there is no chance of further effort on his part.

Totally unrelated: Tropical storm Colin will be moving over most of Florida in the next 2 days. South Florida, as usual, will get the "dirty side" of Colin - a lot of rain and some wind gusts to 45-50 mph. It's not even one full week into "H" season and we already have had three (3) named storms. I have got to get out of "H" alley ASAP. It is cripplingly depressing.

[Astronomertoo]

Roberto and all,

I agree that if the rigger put in smaller pins it is not a good thing. I also agree if he did that work, and noted ANY of the pins were undersize he should have notified you and added them to the parts list and replaced them. They would be an obvious observation. If he does not admit he noticed them and did not call it out to you at the time, he should offer to change them out with the owner paying for the new pins, which is a minor cost and worth getting them right. I would want the correct pins, not shims. If he does not offer to fix them, then I would let others know the name for future reference, not to be forgotten.

Its a good day for our grass. We are getting the brunt of TS Colin over here on the west nature coast, with Tampa an hour and a half south of us already getting high tides and only gusting to about 45 mph so far. This storm is happily very poorly developed, not expected to go over 50 mph, with no real center structure, and the low pressure center will fly across north of Crystal River and out the east coast around Jacksonville tomorrow. (see http://www.ssd.noaa.gov/goes/east/gmex/wv-l.jpg) I doubt we will see any gusts over 50 from the S/SW, and south Florida might not even get much rain.
BTW, I lived in the midwest tornado belt for the last 15 years of my nuclear life before I retired back down in my home state of Florida. Tornado sirens used to scare the bejesus out of me, and heading to a "safe" room was too much. Regularly.
Best wishes

[Megunticook]

It's not as simple as just replacing the pins unfortunately.