Moving the chain plates

[purplerobbie]

The chainplates on my boat go through the middle of side decks and they are a pain they leak constantly no matter what i try. Its the constant flexing of the chainplate when the boat is heeling and the fact that the boat has teak decks and i cant seal under it without lifting the deck are my main problems.

I'm thinking of moving them on to the hull. Like in the more classical boats piece of stainless steel bolted through the hull

If i move them straight out its less than 6 inches I’m moving them to the side of the boat.
How much trouble would it cause and would it cause any problems for the rig?

I’m assuming the hull would be strong enough to take it? Can anyone see why it wouldn’t?

Can anyone see any problems with doing any of this?

 

[Rossynant]

First problem - there was probably a reason for placing them there. For instance - sail angle. Guess you still want a boat sailing to windward?
I assume its fiberglass:
Leaks can be dealt with, just you're not telling why they leak, Assuming they are through hull and attached to a strongpoint below - like bulkhead or knee, of wood - wood may be rotten (from leaks) or worked loose. Investigate. Point of attachment must be stiff and strong. Maybe this can be repaired or stiffened. You will have to put them back then on a sealant applied from below, can be done, no problem.
If they are mounted to deck only (possible) then deck is flexing or backing is insufficient. Possible to laminate some epoxy underneath to stiffen and put proper backing, or big backing plate may be enough.

No telling if hull is strong enough. Often not stiff enough - and it should not flex under load there. May be necessary to strengthen, for example by putting couple layers of epoxy/glass to the area.
On some hull-deck joints it's possible to mount a chainplate (like U-bolt or such), this depends on construction. This joint is a stiff place. Where there are two thicknesses of laminate and bolts going through both hull and deck - this is good way, only remember solid backing should be placed under.

Not much more to say, depends on the boat. Hope this may help a bit.

 

[Seajet]

I can easily imagine mid-deck chainplates flexing and leaking, even if the structure is all fine; though that should be checked of course.

A wider sheeting angle won't do windward performance any favours, but 6" is not much and barber haulers could be used to bring in the sheet angle; the haulers would have to be mounted to reinforced strong points on the coachroof or similar.

The spreaders would almost certainly require lengthening / changing.

The new topsides mounted chainplates would have to be at a bulkhead position, does the simple move 6" outboard bear that in mind ?

Personally I'd want to reinforce the hull at that point, and use generous 'strap' style chainplates with good internal backing.

So it's a fair bit of hassle to move chainplates; have you tried the various flexible sealants, maybe even 'creeping crack cure' would run around the mounting ?

 

[knuterikt]

The chainplates on my boat go through the middle of side decks and they are a pain they leak constantly no matter what i try. Its the constant flexing of the chainplate when the boat is heeling and the fact that the boat has teak decks and i cant seal under it without lifting the deck are my main problems.

I'm thinking of moving them on to the hull. Like in the more classical boats piece of stainless steel bolted through the hull

If i move them straight out its less than 6 inches I’m moving them to the side of the boat.
How much trouble would it cause and would it cause any problems for the rig?

I’m assuming the hull would be strong enough to take it? Can anyone see why it wouldn’t?

Can anyone see any problems with doing any of this?

I agree with Rossynant, better to find the cause of the leak and fix.

If the chain plates are flexing - something is wrong..

If you can post some pictures both inside and outside it will be easier to give advice.

 

[stav]

I agree with Rossynant, better to find the cause of the leak and fix.

If the chain plates are flexing - something is wrong..

If you can post some pictures both inside and outside it will be easier to give advice.

+1, I took my through deck chain plates out just to check for any crevice corrosion on my last boat, (45yrs old). When I refitted them I enlarged the hole slightly so it was not a sung fit but such that there was room for a 3mm bed of sealant and then fitted oak blocks around them on deck. No crevice corrosion was found except one nut in the wet hanging locker that split in to three when pressure from the spanner was applied. Good luck with it.

 

[Seajet]

Mid-deck chainplates very often cause leaks; it's not that they or the structure is flexing, it's the vibration and loads from the rig working laterally.

The forestay on my boat has an arrangement like this and is the only weak point on the design, as leaks follow the chainplate through the deck corroding the rather silly mild steel bolt which secures it, and if unlucky rotting the glassed in wooden structure as well.

This is a well known issue which the whole class has been warned about and most people have taken steps to rectify.

Nothing to do with the structure the chainplate is attached to flexing !

If you imagine a sail thrashing about in a strong breeze, think of the vibration set up through the rig, coupled with tension going on and off shrouds tacking in a wind; I bet that's what the OP's problem is.

 

[ALPHORA]

I own a Tayana 37 which has a similar sounding chainplate set up as standard, and as standard they leak. There is a lot of information on the Tayana owners website with a selection of 'cures'. Some have tried moving the chainplates outboard which does work, but can cause problems with the routing of the genoa sheets either inside or outside of the shrouds depending on genoa size. A selection of sealants have been tried, some are apparently more elastic and cope with the movement of the plates better. I am in the process of replacing my chainplates. I intend to stiffen up the mounting areas, and replace the chainplates with some about twice the thickness as the standard, in attempt to reduce flexing. I will also be increasing the size of the hole in the deck and packing with rubber rings round the chainplate,with a top plate to compress the rings down into the chainplate/deck gap. Having watched the standard chainplates flexing in gusty conditions the lateral movement is such that I can not see even a very flexible sealant coping with the movement. A further point to consider is the rigging tension. Make sure everything is at the upper end of the tension range to minimize movement.

 

[Iain C]

I investigated my chainplates last winter.

Port...actually "cranked" by design so it flexed when loaded, and bolted with 6mm brass bolts onto a bulkhead with a piece of spacing timber behind that wasn't actually bonded to the bulkhead, which in turn was bonded to the deckhead but not the hull. After a lot of work now the chainplate has a web to eliminate flexing, is bolted to a bulkhead by large 10mm 316 s/s bolts, running through a bulkhead that is filleted and glassed to the hull, deck and a substantial oak reinforcing.

Stbd...chainplate bolted to a wooden "shelf" in the heads that was glassed in so badly/dryly that I removed the whole lot with bare hands and chisels. Oh, and there was a piece of s/s threaded bar running at 30 degrees to the load to, erm, transfer the forces to a small wooden bulkhead that wasn't glued to the hull...that obviously wouldn't work. It's now bolted to a heavy steel structure that spans the distance between two bulkheads, and is glassed into heavy reinforcement on the bulkheads (which are also now filleted and glassed into the hull) and also the deck. Epoxy throughout.

How the hell the rig didn't fall over the side at some point in the last 40 years I have no idea...it's the only horror story on an otherwise very well built boat. Nice of the surveyor to pick it up too.

So yeah, well worth checking those chainplates!

 

[purplerobbie]

At some point on my boat they have changed the rig and the spreaders are too wide. If I move the chain plates to the hull they will be about the right width.

The chain plates are onto knuckles glassed into the hull. They come down to the seat backs and the bolts go through the seat backs into the knuckles.

The boat has been twice around the world and it looks like there has always been a problem sealing them as the headlining is water damaged and the seat back is also water damaged.

I can repair all the damage and put it back to standard but it has leaked so far it will just eventually leak again and ruin all the work done so I thought it would be better to move them.
If I move them to the stainless straps on the hull I can seal them up and not have this problem again.

Thoughts?

 

[Modulation]

I investigated my chainplates last winter.

Port...actually "cranked" by design so it flexed when loaded, and bolted with 6mm brass bolts onto a bulkhead with a piece of spacing timber behind that wasn't actually bonded to the bulkhead, which in turn was bonded to the deckhead but not the hull. After a lot of work now the chainplate has a web to eliminate flexing, is bolted to a bulkhead by large 10mm 316 s/s bolts, running through a bulkhead that is filleted and glassed to the hull, deck and a substantial oak reinforcing.

Stbd...chainplate bolted to a wooden "shelf" in the heads that was glassed in so badly/dryly that I removed the whole lot with bare hands and chisels. Oh, and there was a piece of s/s threaded bar running at 30 degrees to the load to, erm, transfer the forces to a small wooden bulkhead that wasn't glued to the hull...that obviously wouldn't work. It's now bolted to a heavy steel structure that spans the distance between two bulkheads, and is glassed into heavy reinforcement on the bulkheads (which are also now filleted and glassed into the hull) and also the deck. Epoxy throughout.

How the hell the rig didn't fall over the side at some point in the last 40 years I have no idea...it's the only horror story on an otherwise very well built boat. Nice of the surveyor to pick it up too.

So yeah, well worth checking those chainplates!

I
Interesting..................makes you wonder how much actual proper engineering design is involved in boat design. AND how much tolerance is built in to allow for poor construction. Not a lot I fear when one looks at the number of failures of rig, keel etc we read about!!

 

[knuterikt]

At some point on my boat they have changed the rig and the spreaders are too wide. If I move the chain plates to the hull they will be about the right width.

The chain plates are onto knuckles glassed into the hull. They come down to the seat backs and the bolts go through the seat backs into the knuckles.

The boat has been twice around the world and it looks like there has always been a problem sealing them as the headlining is water damaged and the seat back is also water damaged.

I can repair all the damage and put it back to standard but it has leaked so far it will just eventually leak again and ruin all the work done so I thought it would be better to move them.
If I move them to the stainless straps on the hull I can seal them up and not have this problem again.

Thoughts?

If I understand this - the existing chain plates is not bolted onto a transverse bulkhead?
So if you add new chain plates on the outside it will not be supported by a bulkhead on the inside?
To me this sounds like you must reinforce the the hull to support chainplates on the outside.

If your spreaders is to long - the can be cut down in lenght.

My boat (Beneteau First 38, 1984) has chaine plates that go through the middle of side decks.
Sounds like it is a simmilar install as you have.
I will try to take some pictures of this tomorrow.

 

[Iain C]

The boat was built in the 70s where many builders offered "home fit out" options, so this kind of thing is quite common. TBH apart from corroded rudder tangs (also now fixed by me) which were a factory fit it's the only real "nasty" I've found.

There have been other things that don't cut it in this day and age...gas bottles in sealed cockpit lockers, bilge pump under the navigators seat so inaccessible from the helm, **** seacocks, no jackstays, no waterlocks on heads and engine, all now done, and part of the "fun" on an older boat is going through this stuff and knowing that it's now done properly. I also get a bit of smug satisfaction when people poke about and find new headlining, modern "decor", LED lighting, a nav station and instruments that would put many a bigger yacht to shame, and a nice pokey modern diesel...people don't expect that on a 40year old MAB.

 

[wotayottie]

I’m assuming the hull would be strong enough to take it? Can anyone see why it wouldn’t?

Can anyone see any problems with doing any of this?

How can anyone on here possibly comment - you dont even say what boat it is on your profile. Not being snotty in saying this - someone will reply no doubt but you shouldnt rely on what they say since they dont have enough info to give a remotely sensible answer. The danger is that you take comfort from worthless answers and end up in the proverbial.

Really you need a decent surveyor.

P.S. Either I'm a very slow typer or everyone was trying to post an answer as I typed. Or maybe I should have refreshed before typing. Anyway I see that people have already replied and I dont want to be rude to them. But what I said is still valid. Dont rely on comments. Get a pro and find the cause.

 

[Tranona]

Agree with the need for professional advice. The construction method sounds inadequate for the job even though it might have seemed a good idea at the time. First thing is to contact the designer or builder if either are still around. Other owners may already have a solution. Hull mounted chain plates require a structure to take the loads so just bolting them through would not be a good idea. If you dont feel confident of working out the weakness yourself then time to call in an expert.

 

[knuterikt]

Agree with the need for professional advice. The construction method sounds inadequate for the job even though it might have seemed a good idea at the time. First thing is to contact the designer or builder if either are still around. Other owners may already have a solution. Hull mounted chain plates require a structure to take the loads so just bolting them through would not be a good idea. If you dont feel confident of working out the weakness yourself then time to call in an expert.

Problem is that is difficult to find "professional advice", the more knowledge you have the better prepared you are to know what to ask and what you don't know or are unable to fix.
Also better qualify the "expert advice"

For me a project like this have several phases.
1) Information gathering (this is where the OP is now I think)
2) Planning/preparing (decide on solution, design and sizing)
3) Execute (make parts and install)

Checking if there are other sources for information would be smart
(The boat builder/designer, class association)

We don't know what kind of qualifications the OP have, asking for advice is no indication that he is incapable of doing stuff.

In step 2 and 3 one have to decide what is suited for DIY and not.

 

[Blueboatman]

Wot Mr Tranona ses

Much easier to sort out what is there rather than widen the base angle and associated engineering.

Fibreglass is incredibly easy stuff to beef up.

And the boat is a world girdler ( good, rig hasn't fallen down then)..but you might as well get a good hands on guy along who actually sails and builds( a rare breed but ask around).
You must diagnose what lies behind the 'apparent symptoms', and run thru the strengthening processes required before improving the actual seal.

 

[wotayottie]

Problem is that is difficult to find "professional advice", the more knowledge you have the better prepared you are to know what to ask and what you don't know or are unable to fix.
Also better qualify the "expert advice"

For me a project like this have several phases.
1) Information gathering (this is where the OP is now I think)
2) Planning/preparing (decide on solution, design and sizing)
3) Execute (make parts and install)

Checking if there are other sources for information would be smart
(The boat builder/designer, class association)

We don't know what kind of qualifications the OP have, asking for advice is no indication that he is incapable of doing stuff.

In step 2 and 3 one have to decide what is suited for DIY and not.

It's not a question of whether the OP is capable or incapable. What he is asking requires a/ knowledge of the boat and its construction and b/ knowledge of engineering as opposed to spanner wielding or " common sense". Ideally someone needs to be measuring laminate thickness and doing calculations. Eyeballing it isnt enough IMO.

 

[Rossynant]

It's not a question of whether the OP is capable or incapable. What he is asking requires a/ knowledge of the boat and its construction and b/ knowledge of engineering as opposed to spanner wielding or " common sense". Ideally someone needs to be measuring laminate thickness and doing calculations. Eyeballing it isnt enough IMO.

a big + 1 to this. Engineering a chainplate attachment involves calcullation of loads, unless there is a similar construction already proven. There were tables also for this, easy to use. Someone involved in boat design can decide on the matter, or for this boat type advice already exist.

I would, nevertheless, propose another approach that is possible - but seek prof's advice anyway! As the boat made it around it seems original construction was OK, strong enough. May be weakened after long work then. Restoring to original construction and state may be best idea. Somebody has designed it this way for a reason, had it calculated - and it worked.
Seals fail with time, an this is up to an owner to maintain...

At some point on my boat they have changed the rig and the spreaders are too wide. [...]

The chain plates are onto knuckles glassed into the hull. They come down to the seat backs and the bolts go through the seat backs into the knuckles.

The boat has been twice around the world and it looks like there has always been a problem sealing them as the headlining is water damaged and the seat back is also water damaged. [...]
Thoughts?

Thoughts:
- Chainplate made as metal strap, flat that is, undergoes fatigue damage as it's flexed. Not only it gets more flexible then, but weakened. After two circles around, and moreover seeing a problem, I would like to change for new, and even for more thickness if original is flexing... Simply saying a deck fitting should not flex at all, as this is damaging to metal! Same goes for fiberglass, btw.

- Assuming the 'knuckle' is kind of construction knee or 'partial bulkhead' (stiffening the angle betwen hull-deck) this is best point of attachment. But this may be made of wood/plywood and damaged from leaks. It's common problem on old boats, that's why I mentioned it before. Take a look. Sometime just putting bolts in new places is enough to make it stiff again.

- As for sealing the 'through deck' point, many ways are possible. One I saw worked is to make a kind of flat 'flange' (if that is the word) around the flat bar that the chainplate is, welded on so it rests againts the deck underside. Sealant then is put on it, pressed into place so everything is completely filled with it, but very little pressure initially while it cures - so when the fitting is attached finally it is compressed like rubber. As rig forces then pull chainplate upwards, the sealant stays compressed.
Best to use adhesive type sealant, that stays glued to everything. I know an american one that used to work for this (3M 5200) - Sikaflex I know has similar, but let somebody else say which is proper.
Not silicone rubber, nor anything people use as easier and not getting theboat dirty - as this will not stay attached to steel, so the leaks again...
It is possible also to compress sealant onto chainplate opening from above, but this is more bother, only for short term remedy without removing the fitting. Not for wood deck I presume.

And another thing - sort out the line of shroud to chainplate - should be exactly in line. May be not lined up properly now, after modifications you mentioned. Proper toggle is mandatory with flat chainplates. Best to have two, something people forget with those sleek looking threaded swages.
Personally I prefer normal shackles on turbuckle than those "toggle endings" (however you call them), but important thing is: wire is flexing and putting the load in various directions, this flexing must not be transferred to chainplate - or it will leak

 

[purplerobbie]

- As for sealing the 'through deck' point, many ways are possible. One I saw worked is to make a kind of flat 'flange' (if that is the word) around the flat bar that the chainplate is, welded on so it rests againts the deck underside. Sealant then is put on it, pressed into place so everything is completely filled with it, but very little pressure initially while it cures - so when the fitting is attached finally it is compressed like rubber. As rig forces then pull chainplate upwards, the sealant stays compressed.
Best to use adhesive type sealant, that stays glued to everything. I know an american one that used to work for this (5200) and not sure but this is probably polysulfide - Sikaflex I know has similar, but let somebody else say which is proper

That is what I have been thinking.
The chain plates have been replaced and I was thinking if I removed them and had a flange welded on the bottom and then refitted them with a smaller plate slotted over the top of the chain plate then bolted the lot together with a good dollop of sikaflex that should stop all the problems?
Assuming I can get the chain plate back in with the flange welded on?

 

[Rossynant]

I am not a boat designer or builder, so don't ask for definite answer
Have seen this on some boat, and was done for same reason. Americans have a lot of boats with such problems and moreover decks cored with balsa wood; which is getting this water in and the whole deck rotting away...
So for details look at some american forum, surely you will find examples, probably with a lot of pictures. It was not particularly wide flange, a 1 centymeter or maybe bit more. Just so there is a seal underdeck, against a surface, not only floating loosely in this small crevice. A surface to bear on is the answer.
IMHO there's no need to put anything from upper side, onto a deck, but of course ask somebody who is actually looking at it No way to tell otherwise.
But there will be enormous difference in area sealed with flange against the deck, then just a small crevice in deck around the strip itself, so this may be the cure.

Actually the practice of builders was to put a 'beauty plate' of steel on deck so chainplate goes through, sometimes screwed down, and this was also to compress and keep a seal in deck around chainplate. (no flange underneath) But this was for a sealant that was not adhesive kind (polysulfid or silicone) and so they packed a lot around the hole and then screwed the plate on it. This kept for a year or a few and failed, so you had to clean everything off (almost impossible) and replace, and keep it maintained every few years or so and such...
So nothing against putting a top plate and compressing down, but indeed, would be a beautiful idea to make a big flange, so big that a plate above can be bolted to it. Never seen such, though.

If you were to go for such a great modifications, then there is another way, which was used on wooden ships sometimes: under the decks there were strenghtening strips (going up on the ribs) finished with plate under the deck - on deck there was a O-bolt or U-bolt, that was bolted to this strip below. So no thin strip through deck, but round bolt, having it's own plate above, bolted on sealantthus compressed in the hole. Kept dry all right. This method was used in fiberglass boats too, steel webbing laminated into the hull side and going under deck, so U-bolt chainplate is attached to almost whole hull of boat. Saw that in german ones, and also in UK some good constructor used this method, but this was 50 years ago... A lot of clever and so to say "proper" ways there were long ago, but in boat production the cheapest - the best.
U-bolt chainplates are very good idea, btw, provided there is something to bolt them on.


Another thing - do not enlarge the hole in deck. There is limit of how much a crevice sealant can 'bridge' if it's constantly teared apart, before detaching from the edges. In this instance from steel, but if the hole has dirty sides - clean, degrease, sand or scrape a little bit. Adhesive has to adhere to something, otherwise you can use just a bathroom putty as well...
As I said about an adhesive type sealant, have to correct myself - polysulfide is not that much glueing, this 5200 is something other. Maybe polyurethane? Sorry, old age I guess.. Will correct this in post before.