U bolt "chain plates" for shrouds (mast side stays)

[Andrew]

Hi everyone,

I have had an idea in relation to this issue of bolts breaking.

Now we all know it is due to corrosion where the us bolts go through the deck, and that is where the corrode, and then crack and then break.

My thought is why not replace with Pad eyes.

I am even thinking because I run upper and lower shrouds / stays, that i would place 2 pad eyes each side one for each stay.

Now my reasoning here, is that the eye itself does not go through the boat it is welded to the pad / plate. And then in me purchasing 4 of the 90mm size pad eyes, I have pad eyes that are rated at 4000kg, and secured by 4 8,5mm bolts through the deck. The chance of more than 2 bolts corroding at a time per pad eye, is highly unlikely, so with 2 bolts remaining in the eye, the mast would still remain upright, with the sails lowered. But with me having 4 pad eyes, I would be very unfortunate to ever lose a mast out on the water.

Anyhow, I have asked Peter T, as to what he thinks, but whilst I await a response, it would be interesting to see what other members think of this idea.

Here is the link.

https://www.metalhardwaresupplies.com.a ... steel.html

I've got a gut bush engineering feeling that pad eyes are probably not a good idea.

That photo with a $3 pad eye, its definitely very weak, i can see press in joins to the thin pad. The cost is too low. It would fail quickly within seconds for sure if used as a chain plate. All pad eyes have the load going through a right angled dogleg, its not a strong configuration, could shear off.

I'm going to stick with U bolts as designed and check them periodically.
The loading on the U bolts is straight down the shank of the bolt, so must be strong, its all in tension (no shear). go up a size or two from standard Investigator U bolts and check them (by pulling them out) before a big offshore trip. like the U-bolt from Witchards in the US, they have solid shanks all the way through, and a top plate carefully welded to it.

Radically changing anything like the chain plate configuration would need a professional yacht designer/engineer or rigger to oversee it.

[Ozzie]

I’d say the u bolt has a long track record and that’s why it’s has not been superceded by alternatives.

Given I did break a shroud once though, when the boat was on the mooring unattended, (see older post) I have wondered about redundancy though in the form of a strop from the shroud to the toe rail. Never seen nor heard of such a thing, has anybody. It would just give you maybe enough time to depower before tearing the rail off

I have one on my back stay block just in case and an extra forestay to back up the 436 potential failure points in the furler.

Ahh, forget it and go sailing

[Ozzie]

In only enclosed waters with multiple well known shelter points I’ll probably pass on the additional shrouds . While a broken shroud under sail would be a PITA it will take the mast over the side. I mast coming down into the cockpit at anytime due to a broken forestay was my main concern, mainly for the safety of crew as much as my own . My theory on hoisting a spectra line up the halyard attached to the chain plates to share the load on the mooring is still at the back of my mind but untried. On a mooring a boat is subject to stresses in weather far worse than I’m likely to experience when sailing. But then again that’s what insurance is for.

Anyway good post on the fitting the additional shrouds. Some 563s apparently have a lighter mast , no backstay and swept back shrouds. Ian B talks about them in an older post.

[Geoff]

Hi Andrew,

Just saw your rigging pics on FB, thanks.

A couple of questions...

Just to confirm what I think I am seeing, your upper shrouds pick up the spreaders, and the lowers are attached to the mast at the bottom of the spreader fittings?

Also, in the pics you have the spinnaker halyard running. Do you use a spinnaker?

[Andrew]

The new u-bolts were off the shelf at Rosshaven marine - Ronstan M8 316 stainless, about $25 each. Replaced both sides with silicone sealant under top plate.

PB120036 Teria New Ronstan u-bolt.JPG

Hi Andrew,

Do you happen to know as to how long these bolts are? And are they of, about the right length,or did you need to shorten them.

Cheers David.

Sorry, just found your message. and found an old spare one. Theyre 90mm long from top of arch to ends.

[Andrew]

Heres my old surviving u bolt, noticed it also has a developing rusty crack on one side only, that goes about halfway through.

[Peter T]

Yes David, they look fantastic. Another addition to my " to get list "
Thanks for the post.
Cheers, Peter T

[Watto]

Fell victim today in botany. Luckily I noticed before we lost the mast and dropped the sails and motored home from off Brighton back to Sylvania on the 2hp... the day I took the little motor.

[Andrew]

G'day Luke,
That's exactly what happened to me on my first sail on Teria, one snapped one side off but the mast stayed up long enough to round up, anchor and derig.

Davids spot on there, witchards the best. The U bolts must be pulled out and checked (best replaced) after buying an I563 , the boats are 30 - 40 years old. some recommend to replace U bolts every 10 years, reckon my ones were originals on an early boat #9. Didn't know any of this until after the event.

I replaced with same as before, about 8 years ago. Sealed them in with silicone and havent seen any rust streaks on deck (like the originals had) a tell tale sign they should be pulled out.

[Peter T]

These are the best to use and what David used and what I will be using before I launch my boat.
Cheers