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Old 26-07-2012, 22:39   #1
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Forestsay - Slightly smaller clevis pin ok?

I recently purchased a new roller furling for my Cal 28. Its the Harken MKIV unit 0. The roller furling is long enough for my forestay and I bought the 7/16" toggle assembly to go with it.

After a test fitting I realized that that forestay actually has a 1/2" clevis pin diameter. With my setup, If I were to install the roller furling, I would be putting a 7/16" clevis pin in a 1/2" hole.

Other useful information is that the backstay has a 7/16" clevis pin just the forestay is a size larger - not sure if this is normal?

So the question is - should i put the pin that is 1/16" too small in the hole? Just looking at the clevis pin compared to the forestay wire diameter (1/4") I find it hard to believe that the clevis is the weakest link.

Obviously I would like to avoid the cost of upgrading to the next larger size and paying shipping costs and time etc... But I also do not want to do something that is unsafe. What do you think?

~Matt
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Old 26-07-2012, 22:56   #2
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Re: Forestsay - Slightly smaller clevis pin ok?

Matt,

Sorry but you need the right size.

In this application it is rarely strength that is the problem, but a smaller than spec pin will have a much smaller contact area. This leads to all sorts of distortion of the pin over time, and can cause a lot of problems down the line.

See the first paragraph Maintaining standing rigging
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Old 26-07-2012, 23:21   #3
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Re: Forestsay - Slightly smaller clevis pin ok?

I have seen folks use a sleeve machined from s/s to match the pin to the hole size. Don't know if that is adequate, but I surely agree that you shouldn't just use the smaller pin in the bigger hole.

Another possible fix would be to drill a 7/16 inch hole in a nearby bit of the fitting.

Cheers,
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Old 27-07-2012, 00:26   #4
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Do the right thing. Get the correct part. Forestay far more load and duty that backstay. Also failure can kill cockpit occupants.
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Old 27-07-2012, 00:31   #5
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Re: Forestsay - Slightly smaller clevis pin ok?

It should be just fine to use a 7/16" pin in a 1/2" puka. Looks like someone switched out the original headstay and put an oversized terminal on it. It's best to use the right sized pin if possible but your fittings are so over strength it won't make much of a difference.

FWIW, my boat had 5/16" pins in 7/16" pukas for the lowers. Probably done by the PO when he rerigged the boat at least 10 years ago. I sailed the boat over from the mainland and didn't discover how small the pins were till last month when I pulled the stick.
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Old 27-07-2012, 00:41   #6
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Re: Forestsay - Slightly smaller clevis pin ok?

A 1/2 inch clevis pin is $8. A rig for a Pearson 35 is probably $40,000. No way am I risking that much to save a few pennies...

Best part is if the rig comes down, and your insurance company finds out you had an undersized pin... You won't be insured. It would be considered not having a seaworthy boat, and almost all policies disallow coverage for it.
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Old 27-07-2012, 01:04   #7
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Re: Forestsay - Slightly smaller clevis pin ok?

A 7/16" pin is quite acceptable for use with 1/4" wire but a 7/16" pin must not be used in a 1/2" hole. Small pins in big holes cause point loading which can cause all sorts of problems. As Jim Cate says, make up the difference with a bushing and all will be sweet.
Happy sailing
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Old 27-07-2012, 01:19   #8
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Re: Forestsay - Slightly smaller clevis pin ok?

The problem is he's got a 7/16" toggle with a 1/2" wire fitting. He's stuck with a 7/16" pin unless he changes the furler toggle. The wire is only 1/4" and that's probably oversized from what was originally on the boat. 3/8" turnbuckles can be used with 1/4" wire, Pearson originally eqipped my boat that way. A 7/16" pin is more than strong enough and about the worst that would happen is the pin would wear the hole slightly elongated. The shrouds on my boat didn't and they had many many thousand of miles on them even though the pins were two sizes smaller.

A mast for a Pearson 35 would be less than 1/2 what you estimate even with shipping to Hawaii. One thing I've noticed is that many people have 6 figure boats, the income to support them, and not much experience in other than sailing the boats but no problem giving out advice that is usually quite expensive to have someone do it. It's a 29' boat, the loads just aren't that great and the parts he's talking about are more than adequate to do the job. If Bowhaus is concerned about using the smaller diameter pin, change it out every few years and inspect it annually'
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Old 27-07-2012, 01:40   #9
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Re: Forestsay - Slightly smaller clevis pin ok?

Peter,

The mast on my Beneteau 381 was $42,500 when it was replaced 6 years ago (before I got it). So I used that as an estimate. The J-22 rig I broke cost me $5,000. An Olson 30 rig is around $15,000. Those are just the ones I have seen bidded prices on in the last year or so.

Before you spout off at the mouth just a brief work history... Currently selling titanium parts for boats. Before that, I was a maritime lawyer, before that a commercial rigger (had to pay for law school), before that a boat yard worker (paying for college). I have been commercially in the maritime industry since I turned 21 and got my 100tonn license, and almost all of it has been working on other peoples boats.

Sure I can be wrong, and am all the time. And I learn just as much here as I could ever teach. But when all the experts in a field say not to do something, it is irresponsible for you to be making suggestions that fly in the fact of that. Find me any source that says its ok from an engineering standpoint to use the wrong size clevis pin, and I'll admit you are right. But no reputable source will ever say that.

Sources I know that oppose using undersized pins...
Brion Toss
Sailing magazine
Offshore Sailing
Dixieland Surveyors

The list goes on and on...

Do I give the cheapest advice? No. But then I give the same advice I would take on my boat, or any of my clients boats. If a skipper decides to cheap out and try and get by with substandard equipment, just don't be surprised when something breaks and someone dies, or the cost to repair the damage is more than the boat is worth.
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Old 27-07-2012, 05:30   #10
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Re: Forestsay - Slightly smaller clevis pin ok?

Quote:
Originally Posted by david samuelson View Post
A 7/16" pin is quite acceptable for use with 1/4" wire but a 7/16" pin must not be used in a 1/2" hole. Small pins in big holes cause point loading (sic: & dynamic loading & elongation) which can cause all sorts of problems. As Jim Cate says, make up the difference with a bushing and all will be sweet.
Happy sailing
Indeed.
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Old 27-07-2012, 06:23   #11
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Re: Forestsay - Slightly smaller clevis pin ok?

I would use the 7/16" pin for now and get a 1/2" pin as soon as practical.
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Old 27-07-2012, 08:26   #12
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Re: Forestsay - Slightly smaller clevis pin ok?

At the very least get a bushing for it, go to a good hardware store and find a 7/16 in 1/2 out bronze bushing and cut/file it to the right lenght,
Then talk to Harken, they may have the right piece for you.
As I understand it your furler has 7/16 clevis fork and the bow fitting has a 1/2 hole,
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Old 27-07-2012, 16:41   #13
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Re: Forestsay - Slightly smaller clevis pin ok?

Quote:
Originally Posted by Juniper View Post
At the very least get a bushing for it, go to a good hardware store and find a 7/16 in 1/2 out bronze bushing and cut/file it to the right lenght,
Then talk to Harken, they may have the right piece for you.
As I understand it your furler has 7/16 clevis fork and the bow fitting has a 1/2 hole,
Can't agree with that, mate: bronze bushes are not hard enough for this application and will quickly distort. I again recommend one of stainless steel if that route is followed.

Cheers,

Jim
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Old 27-07-2012, 17:03   #14
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Re: Forestsay - Slightly smaller clevis pin ok?

No question about this ! If ya used the smaller pin ya need a bushing!! not bronze but stainless steel !! any local machine shop can fix ya up ! Im sure if ya LOOK around ya can find something at a Commercial Fishing equipment store !! they have bushing stock of many different sizes, and are almost always cheaper then West Mar or such !! ya might ck with Hop Car on here !! he probly hook ya up !! just my 2 cents
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Old 27-07-2012, 17:16   #15
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Re: Forestsay - Slightly smaller clevis pin ok?

Wow, thanks everyone for your comments. I think you all had some really good points. In the end I decided to upgrade the furling to the next larger size.

Here is the rationale for my decision:
Risk statement: An undersized clevis pin could cause locally high stresses in the tang hole and cause the forestay to collapse
Mitigation: $300 to upgrade the furling to the correct size

Impact: Rigging collapse, value = $20,000
Probability: Based on your comments, I would say ~ 10%

since risk value = impact x probability, Risk value = $2,000

Since I can reduce the risk to 0 with a $300 upgrade, that means im getting a 7x return on my investment.

So the decision was clear, spending the money to do the upgrade is worth the investment until you assume the probability of the failure is less than 1.5%.

I wouldn't mind if you guys argued if the probability of the failure was less than or more than 1.5% though, could change my mind
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