Backstay chainplate bolts anxieties .

[IanCC]

My Nic 31 has an external chainplate for the backstay. It is fastened by 4 3/8" stainless machine screws through to an aluminum backing plate. The boat is 1979, so are the machine screws. Internally they are physically inaccessible and totally glassed in. There is no sign of rust externally and the screws face out and down so would tend to run out.
I struggle to imagine 4 3/8" bolts shearing at once.

Anyone else? As always all thoughts appreciated and seasons greetings to all.

 

[Boathook]

My Nic 31 has an external chainplate for the backstay. It is fastened by 4 3/8" stainless machine screws through to an aluminum backing plate. The boat is 1979, so are the machine screws. Internally they are physically inaccessible and totally glassed in. There is no sign of rust externally and the screws face out and down so would tend to run out.
I struggle to imagine 4 3/8" bolts shearing at once.

Anyone else? As always all thoughts appreciated and seasons greetings to all.

Stainless and aluminium don't normally mix well together. Have you tried removing a machine screw to see what condition it is in ?

 

[vyv_cox]

I assume UK? Stress corrosion is less an issue than in Mediterranean climate but is a possibility. Well worth removing bolts one at a time to check and rebed using a sealant to exclude water.

Example here Westerly Oceanmaster 48 chainplates

 

[IanCC]

Stainless and aluminium don't normally mix well together. Have you tried removing a machine screw to see what condition it is in ?

How do you mean "they don't mix well". I tend to think of ss jamming solid in Alu. Isn't that what we want here?

Not sure how i would go about removing a screw. Nuts on inside glassed over. I can imagine using a lot of turning force externally making the nut turn inside the glass then it's a proper nightmare.

 

[IanCC]

I assume UK? Stress corrosion is less an issue than in Mediterranean climate but is a possibility. Well worth removing bolts one at a time to check and rebed using a sealant to exclude water.

Example here Westerly Oceanmaster 48 chainplates

Thanks for reply. Yes UK.

In the link they are a lot lot easier get at than mine. I seriously don't know how to take one out. See my previous reply to Boathook.

 

[Boathook]

How do you mean "they don't mix well". I tend to think of ss jamming solid in Alu. Isn't that what we want here?

Not sure how i would go about removing a screw. Nuts on inside glassed over. I can imagine using a lot of turning force externally making the nut turn inside the glass then it's a proper nightmare.

If salt water has got in, the corrosion forms between the 2 metals causing issues with the S/S. A decent size and fitting screwdriver should be able to remove the machine screw ok as normally the nut being glassed in will be held unless there is corrosion.

 

[KevinV]

Thanks for reply. Yes UK.

In the link they are a lot lot easier get at than mine. I seriously don't know how to take one out. See my previous reply to Boathook.

If, as the title suggests, you are anxious about them then you have two choices - work out how to get them out to check, or stop worrying.

@Rum_Pirate sadly knows that the latter can be an expensive mistake.

Soldering iron on the screw head to soften the sealant, then an impact driver will probably get the screws out without disturbing the nuts - if they do turn then it's dremel time, which will take all of 10 minutes to clear 4 nuts.

 

[IanCC]

If, as the title suggests, you are anxious about them then you have two choices - work out how to get them out to check, or stop worrying.

@Rum_Pirate sadly knows that the latter can be an expensive mistake.

Soldering iron on the screw head to soften the sealant, then an impact driver will probably get the screws out without disturbing the nuts - if they do turn then it's dremel time, which will take all of 10 minutes to clear 4 nuts.

The question in my mind is more "should i be anxious?".

Depends on the quality of the glassing in. Very difficult to find a driver big enough. Cross head screws 5/8" diameter or so.

The nuts are not accessible with a dremel.

 

[vyv_cox]

Another link about SCC in chainolate bolts. Sadler 34 lower and cap chainplates

 

[KevinV]

The question in my mind is more "should i be anxious?".

You obviously are

Now, instead of finding reasons why it's difficult, get on with finding the solutions. They went in - they'll come out.

 

[IanCC]

Another link about SCC in chainolate bolts. Sadler 34 lower and cap chainplates

Really interesting thank you.

Those are much more complicated than mine. Mine just go through the deck with a backing plate and a couple of nuts.

 

[IanCC]

You obviously are

Now, instead of finding reasons why it's difficult, get on with finding the solutions. They went in - they'll come out.

I would say anxiety is a scale. If i redid absolutely everything i had the very slightest anxiety about i would never go sailing. My anxiety on this issue in uk waters is minimal, but going further afield would increase it.

I am open to ideas about getting them out. . The interior is totally inaccessible.

I have a transom hung rudder. The tiller comes into the cockpit through a window in the transom. So above the window is effectively a box section on top of which is the main sheet track. The nuts for the backstay chainplate are on the inside of that box section. It's not something i want to weaken by chopping holes in it.

 

[KevinV]

The nuts for the backstay chainplate are on the inside of that box section.

Silly question perhaps, but if these nuts are inaccessible, are you certain they exist? Could the backplate be threaded, or the nuts welded to it? How did they assemble it if they're inaccessible?

As I said - it went in - figuring out how often helps in figuring out how to get it out. I'd still start by just trying to take a screw out - there's more than a 50% chance you're lucky.

 

[PeterWright]

A couple of photos with the original question, showing the screw heads, the access problems and the glassing in would have forestalled some of thr replies you have rejected. It feels like you are not looking for advice to resolve the question, just someone to put an arm around you and say "Don't worry."

Peter.

 

[IanCC]

Silly question perhaps, but if these nuts are inaccessible, are you certain they exist? Could the backplate be threaded, or the nuts welded to it? How did they assemble it if they're inaccessible?

As I said - it went in - figuring out how often helps in figuring out how to get it out. I'd still start by just trying to take a screw out - there's more than a 50% chance you're lucky.

Well they are there in the drawings. But fair point I hadn't thought of that.

I am fairly certain they must have been installed before the hull and deck were put together.

I will try and get one of those gadgets for taking pics of inaccessible places.

 

[KevinV]

I will try and get one of those gadgets for taking pics of inaccessible places.

Really handy to have on board

 

[IanCC]

A couple of photos with the original question, showing the screw heads, the access problems and the glassing in would have forestalled some of thr replies you have rejected. It feels like you are not looking for advice to resolve the question, just someone to put an arm around you and say "Don't worry."

Peter.

Thanks Peter. I thought about that, but then i didn't think it was too difficult to describe a chainplate with 4 screws in it. I obviously failed. I can't get pictures of the glassing in with my present technology.

Yes, maybe you have nailed it, but vyv_cox pics have put that one to bed.

 

[Wansworth]

The trouble once you become fixated by the idea it nags ….is there not an owners association.Nicholson area good make so Iwouldcertainlyputit far down the instó worry about

 

[IanCC]

The trouble once you become fixated by the idea it nags ….is there not an owners association.Nicholson area good make so Iwouldcertainlyputit far down the instó worry about

I don't know of anyone who has done this.

 

[doug748]

I would say anxiety is a scale. If i redid absolutely everything i had the very slightest anxiety about i would never go sailing. My anxiety on this issue in uk waters is minimal, but going further afield would increase it.

I am open to ideas about getting them out. . The interior is totally inaccessible.

I have a transom hung rudder. The tiller comes into the cockpit through a window in the transom. So above the window is effectively a box section on top of which is the main sheet track. The nuts for the backstay chainplate are on the inside of that box section. It's not something i want to weaken by chopping holes in it.

See what you mean:




As you say, a camera shot inside would help quell your fears, otherwise it is a difficult re-engineering job. I think the chances of getting the four screws in and out cleanly are about zero, unless you drill access holes under that builder's plate.

.

.