Forestay attachment

[Renewithboat]

Hello everyone,

This is probably a basic question. But what different type of bolts can you use to attach the forestay. Right now I am using a basic clevis pin. The pin is too long and I have noticed it moving, and working it's way out. I don't really trust the split that holds it from working it's way out.

What other types of bolts can you use that secures the forestay better, with the same or better bolt strength?

Thanks
/René

[psk125]

Get a clevis pin that is the correct length. Bolts are not designed for the loads that clevis pins bear. Then get a cotter pin that you can trust to hold the clevis in place. Then tape over it so sails and lines don't snag on it.

[SailingHarmonie]

Everything PSK said, and I'll add: If you can ever see a clevis pin moving it is more than likely much too small in diameter for the job. It should exactly match the diameter of the hole it fits in. Anything smaller is just wrong.

[Don C L]

I'd echo psk too, but do you mean you have a split ring in the hole of the clevis pin? If so, yes, get rid of that and put in a cotter pin!

[PerfectPirate]

While I appreciate Don's abundance of caution, for those of us who de-rig and re-rig on a regular basis the split ring is a preferred and viable option. For rigging elements which do not get regularly de-rigged use a cotter pin. In either case, having the clevis pin properly sized, in both diameter and length, is a key safety issue, as is taping the whole thing with self-amalgamating rigging tape. PSK125 is completely correct in saying that bolts are not sufficiently strong for the loads implied. Your chainplate is secured with 4, or 5, or 6 bolts and you are going to fasten something to that with a single bolt, and then trust that for strength? Nope.


I pull my mast and de-rig it every season and I have been using split rings for this purpose for 39 years with no failures. Protective taping is key!

[Jim Cate]

Ummm... a proper bolt, one with a non-threaded shank that spans from one side of the fitting to the other, made from 316 s/s (just like the clevis pin), is similarly strong in shear as the pin is. Same material, same diameter, same load pattern, how could it be much different?

And if one uses a new Nyloc nut, or a plain nut with loctite, it is at least as secure as a clevis with a split pin.

Jim

[PerfectPirate]

Jim, my understanding is that bolts are cold-formed from wire stock and then threaded. They may or may not be heat-treated afterwards to increase their hardness. Clevis pins are machined from a higher-grade, solid rod stock, which is why they are more expensive and have a somewhat higher shear strength rating.

However, this is not the main issue. As Brion Toss points out in "The Rigger's Apprentice", the primary problem with using bolts in the place of clevis pins lies around the issue of smooth shank length. While the shear strength of a 3/8-inch clevis may not be appreciably different from that of the smooth portion of the shank of a 3/8-inch bolt, getting a bolt with exactly the right length of smooth shank for your rigging application is problematic. You need to have a bolt where the length of the smooth portion is exactly matches the width of the stay's fork going over the tang, with just enough thread to hold the nut. The staff at Klacko Spars discussed this issue with me at great length.

This means that you either have to get custom-made bolts, which is what Klacko Spars does, or that you have to buy an over-length bolt and then cut down and file the threaded portion. Which is more work than most over-stressed owners are willing to do and, even if they do it, the smooth shank may still not be exactly the right length. So instead they use shorter bolts which place a portion of the threads inside the fork of the stay, and possibly within the tang itself. Now, a 3/8 bolt is essentially 10 mm in diameter on the smooth shank, but only about 8 mm in diameter at the core of the cut thread. This is appreciably weaker, plus the threads will deform under load, meaning that the bolt now starts to wiggle and "point load" the opening in the tang and/or the forks of the stay. This creates yet another weakness and potential problem in the rigging.

So, if the person doing the rigging does everything properly, then there may not be an appreciable difference in strength between bolts and clevis pins. However, doing things properly with bolts is far more complicated and time-consuming than doing it properly with clevis pins, leading to more shortcuts and possible weaknesses in the rigging. It is safer to develop the habit of simply using properly sized clevis pins.

[pcmm]

Originally Posted by Renewithboat

Hello everyone,

This is probably a basic question. But what different type of bolts can you use to attach the forestay. Right now I am using a basic clevis pin. The pin is too long and I have noticed it moving, and working it's way out. I don't really trust the split that holds it from working it's way out.

What other types of bolts can you use that secures the forestay better, with the same or better bolt strength?

Thanks
/René

Cotter pins are plenty string enough in sheer to keep the clevis pin in place. but is the clevis correctly sized (SAE in a metric hole or vice versa). If your clevis pin is "walking" then its likely too long for the purpose, but the bitter question is to ask what loads are cycling to cause it to walk? Missing some toggles somewhere to cause the uneven loading?

[Renewithboat]

Thank you for all the replies.

I derig every winter, but just bought this boat last year. So, this is the first time, I am re-rigging it.



When I bought the boat, it had a ring in the clevis pin, which I replaced with a cotter pin and taped together as you see in the picture. I believe the pin is the right diameter, but I think the legs of the furler makes it walk while under sail. This is why I taped the legs together to minimize movement. To be clear, I cannot see it moving, I can see that i has moved. Sorry, for that. I had to take of tension to move the pin, and even then it was a snug fit, so I believe it to be the right size.



It might just be me being overcautious. I know regular bolts are not strong enough. I had just hoped, there was a better solution. Something like a not-normal bolt with a slotted nut and pin.

[pcmm]

Originally Posted by Renewithboat

Thank you for all the replies.

I derig every winter, but just bought this boat last year. So, this is the first time, I am re-rigging it.



When I bought the boat, it had a ring in the clevis pin, which I replaced with a cotter pin and taped together as you see in the picture. I believe the pin is the right diameter, but I think the legs of the furler makes it walk while under sail. This is why I taped the legs together to minimize movement. To be clear, I cannot see it moving, I can see that i has moved. Sorry, for that. I had to take of tension to move the pin, and even then it was a snug fit, so I believe it to be the right size.


It might just be me being overcautious. I know regular bolts are not strong enough. I had just hoped, there was a better solution. Something like a not-normal bolt with a slotted nut and pin.

The holes in those link plates in the picture look much larger than the clevis pin. Is the last hole in the link plate ( the one the clevis pin goes through) the same size as the clevis? looks, based on the positioning that it might be larger than the clevis.

Clevis looks the corect size for the foretay chain plate though.

[Bowdrie]

Originally Posted by Renewithboat

I believe the pin is the right diameter, but I think the legs of the furler makes it walk
Something like a not-normal bolt with a slotted nut and pin.

Yeah, the side plates for the furler are just wider than the deck fitting.
The easy way is just to stack a couple/three washers on each side of the deck fitting to keep the fitting centered between the side plates.
Bolts such as you describe are available.
They are called "AN", (Aircraft National,) and are super strong, use a fine thread and have a hole for a cotter pin that that passes through a hole in the nut and the bolt, the nut being not as thick as a regular nut.
These types of bolts were extensively used by Hinckely back in the '60s>'70s, in rigging the stays/shrouds at the masthead.
With a drill press and a bit of care you can drill your own bolt and either drill the nut or use a castle nut.

[Cheechako]

Originally Posted by PerfectPirate

Jim, my understanding is that bolts are cold-formed from wire stock and then threaded. They may or may not be heat-treated afterwards to increase their hardness. Clevis pins are machined from a higher-grade, solid rod stock, which is why they are more expensive and have a somewhat higher shear strength rating.

However, this is not the main issue. As Brion Toss points out in "The Rigger's Apprentice", the primary problem with using bolts in the place of clevis pins lies around the issue of smooth shank length. While the shear strength of a 3/8-inch clevis may not be appreciably different from that of the smooth portion of the shank of a 3/8-inch bolt, getting a bolt with exactly the right length of smooth shank for your rigging application is problematic. You need to have a bolt where the length of the smooth portion is exactly matches the width of the stay's fork going over the tang, with just enough thread to hold the nut. The staff at Klacko Spars discussed this issue with me at great length.

This means that you either have to get custom-made bolts, which is what Klacko Spars does, or that you have to buy an over-length bolt and then cut down and file the threaded portion. Which is more work than most over-stressed owners are willing to do and, even if they do it, the smooth shank may still not be exactly the right length. So instead they use shorter bolts which place a portion of the threads inside the fork of the stay, and possibly within the tang itself. Now, a 3/8 bolt is essentially 10 mm in diameter on the smooth shank, but only about 8 mm in diameter at the core of the cut thread. This is appreciably weaker, plus the threads will deform under load, meaning that the bolt now starts to wiggle and "point load" the opening in the tang and/or the forks of the stay. This creates yet another weakness and potential problem in the rigging.

So, if the person doing the rigging does everything properly, then there may not be an appreciable difference in strength between bolts and clevis pins. However, doing things properly with bolts is far more complicated and time-consuming than doing it properly with clevis pins, leading to more shortcuts and possible weaknesses in the rigging. It is safer to develop the habit of simply using properly sized clevis pins.

300 series SS is not/cannot be heat treated. If cold formed and thus work hardened, it would be stronger than machined from bar stock. But really , either type ought to be more than adequate in shear strength unless the rig is designed for an undersize pin.
I have not seen hardened SS pins but they may be out there, Wichard makes 17-4PH (PH= precipitated hardened) shackles etc so maybe....

[Silverlark]

You could always try an appropriately sized shoulder bolt...

[Bowdrie]

I've several shackles and clevis pins made by Schaefer from "back in the day".
IIRC they were forged 17-4 PH?
Perhaps they have changed?
Still use several pins made by Merriman out of bronze, no discernable wear on them.