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Advice wanted on strengthening chainplates...Urgent.

Badgered Cat

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Hi everyone.

When Grady McNee delivered my sails I purchased from Mark Colecliffe,  just a few weeks ago. He advised me with the Mark 1 maricat, which I do have, to strengthen around the gunwhales, where the side chainplates attach. I have not done this as yet, as I wanted to sail over the xmas New year.

Now he made mention that the NSW guys are unbolting the alloy plates from top and below the gunwhale, and then laying up extra fiberglass on the external perimeters, and then placing some stainless steel strips on the top and bottom before putting the alloy plates back on with larger size saddles.

Well today I sailed in fantastic conditions with flat water and wind ranging from 0 knots to 20knots. And gee whiz at 20 knots of breeze fully powered up, and hanging over the back beam was exciting. Including passing a Nacra 36, like it was still in the water. Anyhow at the ned of the day, the boat was getting slower and slower, and when I got to shore the starboard hull was half full of water. Well I should have listened to Grady, as the chainplate had pulled the gunwhale upwards, and fractured the glass and gelcoat under the gunwhale in a big way. I am very lucky not to have ripped the side out of the boat.

So now comes the repair job. I guess I need to remove the chainplates, and the rubber molding. Try and separate the gunwhale join a fraction, maybe epoxy that join and clamp back together. Then open up the fracture under the gunwhales with a dremel tool, lay up some glass over this fracture and under the gunwhales, with polyster resin and chopstrand mat. Then fair it back to a smooth finish and a layer or 2 of flowcoat.  Then on the good hull lay up extra layers of glass under the gunwhales at the chainplates.

What are the guys using for the stainless,steel, and have I got the correct procedure in place for doing everything. I dont want to do the wrong thing here.

I am a skilled and qualified fibreglass worker, with many years in the past gone by, building Kenworth Truck bodies, and before that, building Fibreglass Bathroom fixtures.

So all help and advice appreciated here.


Many thanks David.

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Thanks for that. So the stainless plates are used as well as the alloy plates, with it being alloy plate, then stainless plate, then rubber molding,  fiberglass gunwhale, then similar order but  in reverse on underneath side.


And do you know if the plates are custom made, or a  plate off the chandlery shelf, as in punched strap, or maybe foot plates, or maybe chainplates.

And yes, it was a real hoot of a day, with absolute fantastic memories to go with it. Man can these boats move on a reach with these radial sails, might be a bit scary in a big swell that the boys get down in south Tassie. I had a ball, now I have to pay for it......oh well!!!


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Not sure if these links will turn up as pics but they are pics of my chainplates.

I'm not sure what is behind the black rubber rubbing strake but it doesn't look like there is any more 'padding'.  If it were mine I'd be taking the shroud anchors off then pulling out the rubbing strip (it should stretch, if not cut it and then glue it back after - I used sikaflex for a similar job once).

You mention alloy but I don't think that gets a look in here.  Closest place it is, is where the sail track is fastened to hold the tramp.

Definitely epoxy is the go.  Do a bit of googling because I think Araldite isn't what you want.  Sounds like do it yourself with resin and fillers is the way to go. Maybe squeeze a layer of mat in but a glue like consistency is likely to be what's needed.

Then, based on these pics it's just a couple of stainless strips.  I think Sweet 16 had two wider strips that were curved.  Given that you're a bit handy maybe a C section to slip onto the gunwale and then drill through like mine.  The longer it is the better it'g going to be to strengthen the area.



On a Careel 18 I had, the hull/deck join had a tendency to break down and then leak.  Apparently the gunk that they used to glue deck to hull was of varying quality.  The Careel also had pop-rivets which made the whole lot much stronger.

See what your Ronstan supplier has, may well be available as pre drilled and given that it's a standard saddle that may fit too.

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A photo of the damage would help, If you are not worried about appearance (I wouldn't) just grind of gelcoat for about 4" either side and below damage and glass up I can supply the stainless Mk2 fittings (Replaces the cast alloy) modified with 1/4" saddles an bolts (As fitted to current models). You can also spread the load with triangular stainless plates bolted to the hull and folded 90 degrees and bolted to the 4 bolts already through the gunnel, you can cut out part of the storage compartment to gain internal access. Give me a call if i've confused you. 02 43591729.


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HI again James, and Hi Darcy.


Many thanks for all of the advice.

I have had Pete from Hobart, send me some photos of his Maricat.  I also have hime tell me in a recent email that this happened to a mark one maricat that he once had. 

I am very experienced with fibreglass, and know that side of things, my main concern was what thickness and size stainless plates were to be used, and whether they replaced the alloy ones, or were used in additional to the original alloy ones. Preblem solved there. I will go to the local marine chandlery to see what I can get off the shelf. I will have a look at the ronstan fittings, and if not able to find ideally suitable, there is a marine fabrication business at the back of the chandlery, and I can get something custom made within 24 hours.

My main concern I want to do it right, and I would like to be racing next Saturday at my club. As this will be my first sail at the club, since acquiring the boat. But the repair and the modification has to be right first, otherwise I will put it off for another week, before racing.

Here is 2 photos, one of the starboard hull which shows it as a crack in the Gelcoat,  ut actually when under stress and rig tensioned it opens up, and the glass is fractured right through. I can repair it satisfactorily from the outside.  Without opening up the inside of the boat. I nuse to be a specialist fibreglass worker in the production of new  Kenworth Truck bodies. Only 3 of us in the factory had the specialised training and skills for high load, and nigh stress fibreglassing.  So fibreglass wise, the maricat will be overkill when I am finished with it, and will be hardly noticeable that the mod has been done.......all going well !!!! The other photo is of the port hull, and this has not fractured, b ujt will be modded at the same time as doing the starboard hull.


Many thanks, for all of the help, I really do appreciate it. You guys are so far away, but it is like you are right next door, to me, to be able to give great advice........very appreciative.

Cheers David.


Port Hull Chainplate 1.jpg

Starboard hull chainplate fracture 1..jpg

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I have been spending the night researching off the shelf chain plates from all manufacturers.

The Ronstan RF 488 is way too small in length for the purpose. It is even shorter in length than the stupid alloy ones that are presently on the Maricat, as per standard Maricat Mark One.

The Ronstan RF 47 is the best available. https://www.ronstan.com/marine/product.asp?prodno=RF47#applications  A little short in length to what I would have preferred as they are 203mm in length. I would have rathered 250mm to 300mm. But at least 203mm is longer than what I presently have. Just hoping that there will be 4 sitting on the shelf tomorrow. With it having 5 holes is a good thing and 6mm   1/4" holes  means that there will be a little more tension can be applied when bolting them together. The only thing I may need to do, is drill an extra hole in each one, for the larger size saddles. As presently the Maricat has RF 134 saddles with 32mm hole centres, and I know that I need to upgrade to RF 1055 saddles that have 45mm centres. And these saddles will accept 6mm   1/4" bolts.

So finally all worked out.  Just a trip to town, and get the west system epoxy for fixing the gunwhale joins. Being a fibreglasser, I already have polyester resins, and all of the different mats, and flow coat. So all is good from that angle. Just the marine fittings and I think I am fine. 

Hopefully back on the water on Saturday.

Thanks Guys.


Cheers David.

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Removed the Saddles and the Alloy plates today.........OH MY GOD!!!!!!  I am very lucky not to have had a mast drop. The alloy plates were corroded totally on the inside. They had eaten into the the ever so small metal threads. Not much holding it all together. It now makes me wonder about the alloy plates and saddles at the bows. They at least do have more substantial saddles, bu gee the same thing is probably happening. 

Are there stainless plates being used on the Maricats at the bows, to replace the annoying corroding alloy ones. I dont want to touch them, without knowing if I can buy stainless, as I know that I can't buy off the shelf for this one.  Just hoping Maricat have something. 

Anyhow, picked up everything today to repair the side chainplates.  I have nice heavy duty saddles. Picked up 4 Ronstan chain plates. Got the epoxies and cloth. And already have stage 1 of repair completed. Opened up the cracks, cut them back, cleaned them up. and filled them with epoxy. Next  job is to grind back the gelcoat in the region and lay up chop strand mat, and a layer of tape. Then fair it all back, and then flow coat the surface. Rub that back, and then cut and polish.  And the good news is, or bad news, depend as to how you look at it, the bottom keel line in the centre of the starboard hull, was all soft, and even pin holes in spots. So I cut this open at the same time, and have commenced the repair.  So a good thing, that I had to upturn my boat to repair chainplates, otherwise I would not have known.

So now, please can someone tell me if there is Stainless plates available to replace the alloy ones at the bows.

Darcy if you have these, I will purchase a pair from you. As I wont replace these for a couple of weeks or 3, or 4. .

Many thanks David. . 

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Does anyone know if I would be allowed to race at Nationals, with ones made from Carbon Fibre /  Kevlar composite. As it wont cost me much to make out of kevlar with carbon fibre. It will be stronger than cast alloy, wont corrode, and will weigh about the same as cast alloy. But cheaper for me to manufacture than to have 2 custom made for me in Stainless. I really do hate using cast alloy on boats. It is a joke, and should not be used. I thought that is why Maricat did away with the castings on the side chainplates. Why did they bother, if they decided to keep them on the bows???????? (Silly).


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I can't see anyone having an issue with that.

Building a whole new boat out of carbon, well yes but not small pieces.

Do it. Your first responsibility is to make the boat safe. If you make the new piece within a similar weight then I can't see anybody worrying.

I don't think the class has an official measurer any more either.

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I'm a bit of a newby so take what I say with a grain of salt. Below regarding modifications from the Maricat Constitution and Rules document:


Shall be of fibreglass reinforced polyester material including fibreglass reinforced polyester with foam

sandwich construction and shall be to registered design specifications. No modification to shape is allowed.

The "Maricat 4.3" emblem on the side of the hull is an integral part of the boat and is therefore not classified

as advertising. The emblem is not obligatory.


And under equipment specifications:

m) General

i. Quick connecting couplings maybe used where ever required

ii. Unless specifically mentioned within these rules no other modifications or

alterations from standard production and specifications are permitted without the

approval of the Maricat Association. Therefore consult the Class Measurer for a ruling

before making any other modifications or alterations. In case of a dispute on a ruling, an

application for final ruling must be made to the full Association committee, A minimum of 14

days notice is required for a ruling by the committee.


From Appendix 1:

There will not be any changes to:

a. Hull shape

b. Sail shape and area

c. mast length and section

d. boom length and section

e. style of rigging

f. rudder blade shape and size

g. halyard and lock arrangement

h. sail fabric and weight


So with all of the above, my interpretation is: You aren't altering the shape of the Hulls, or the style of rigging (just the material for the bow blocks) so I can't see why not. But, I'd seek approval from the Class Measurer for a final ruling before making the modifiacitons - pretty sure Darcy is the Class Measurer? or at least he's named on the Maricat Association website as such.


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2 hours ago, Pointed Reply said:

Photos of the bits on Pointed Reply10131B61-34CC-4D02-A8C0-71FBCEBA98E3.jpeEFADFA02-9B75-43F4-9CCB-7F87CAAD4665.jpe5A9FB449-CA63-4813-8D34-2BB2D6F213A4.jpe

Hi Rodney.  Thanks for the photos. Man your side plates are beefy and nice.  The Bow ones, are the crap cast alloy.  Trust me....they will be corroding underneath as they get old, and, they then cause electrolysis into the bolts.......unless you regularly change the bolts every few years fro fresh ones. Cast alloy and stainless bolts just do not mix........so would I be allowed to make carbon fibre /kevlar ones. I would purely be doing it for reliability and safety.  The weight would still mbe about the same as that of cast alloy. So it is not a performance issue. I would have ones manufactured in stainless steel , but that would cost me more money, as I can not do that myself, whereas I can manufacture in fibreglass and composites. As I am a retired skilled and highly trained fibreglass manufacturer. Having worked making components for Kenworth Trucks, as well as making components for HSV Commodore, and Tickford Ford Falcon. So if I was allowed, it would be of quality, and be of reliability. Cheers David.

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Those add on brackets on the side stays are interesting.  They appear to be rivetted to the hull.  Since you wouldn't be able to get to the inside because of the storage compartment it must be a blind rivet.

I would think that it's the length of the stainless strips that are distributing the load rather than the bracket but I'm not an engineer.

My front castings are in a sorry old state but with the 1/4 bolts I hope they'll work.

On my Careel 18 it used big U bolts upside down for the sidestays.  One side of mine let go near the end of one race - didn't realise it, just wondered what the bump noise was.  It had corroded through where it was not exposed to the open air (ie through the deck which was ply and glass).  Changed them a couple of times in the eight years I had the boat.

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I have owed 3 Maricats off and on since 1984, and I have not had a problem with the bow fittings.

Maybe the fittings on the Mk2 and later are of better quantity than the Mk1 or maybe yours was not washed out properly.

You need to remember that your boat and fittings are probably over 35 years old so a good condition 2nd hand or new cast piece with good bolts and proper anti corrosion goop will probably more than out last the boat.

People do all sorts of customising to their Maricat - mast spanners, spinnakers , barber-haulers, home made fittings — but unless you are vying for the national championship then no one is going to worry what you do ....  but I think it is best to keep the boats as original as possible.

So for your MK 1 I would get a good second hand set from Darcy and bolt them on ..... and go sailing for another 35 years.


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Yeah James, thats what I have been thinking. If someone was to try to protest and ru8le me out of an event just for me making something safer, reliable and stronger, then I would be carefully scrutinizing everyone elses  boats. I have heard on the grapevine, that there are boats that have done away with the conduit for the rear trampoline track, and replaced with carbon fibre rod.  Now that is what I call going to the extreme.  As plastic conduit wont corrode or rust, and even if it broke, it is not going to be a big safety issue. I mean to say....I sailed my boat back to its spot on the beach, a week ago, when the trampoline ripped, so it would be just the same if a conduit broke.  Anyhow, I also notice those nice angled brackets on Rodney's boat.  Anyhow I dont need anything like that. My gunwhales are now well and truely beefed up, and there is no way it will even flex the tiniest bit now. I reckon I would have the strongest maricat in Australia when it comes to the side chain plate mounting points. Just finished it all off a little while ago. Wait for it to cure overnight, a slight rub back in spots, a cut and polish, and then bolt the chain plates on, along with the monster saddles. Oh and sikaflex the rubber strip back into place. She aint ever going to let go now.........it will have to rip the whole side of the boat out to do so. I am very happy with myself. :)

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HI Rodney.   Why then did maricat owners place stainless steel  on the side chain plates instead of just staying with the alloy.  Maybe I should send you a photo of the corroded and eaten through stainless bolts......if I can find them in the rubbish.  I totally agree with you keeping the boats to original as possible. But who really does have an all original boat now.  The sails are different now to back then.  The boom vangs have been thrown away. Your boat even has additional angled brackets on your side chain plates, that other sailors do not have. As I mentioned in my previous post apparantly someone has even changed plastic conduit  that is being used at the rear of the trampoline for carbon fibre tube. And then there are the guys like myself, that has changed the downhaul system. I am not messing about with sails as in trying mylar or kevlar, I am not trying out spinnakers, or gennakers, I am only looking at reliability. If I need to replace my front ones with alloy castings, then that is okay, and I accept that. But I wont be buying second hand, i will be buying brand new. But I need to know from the asscociation what the ruling is. As I would like to be bringing my boat up to NSW in 12 months time to do the Nationals. And i am not going to be travelling all that distance and such huge expense to be told that I am disqualified before even commencing

Cheers David..

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   Most Mk1s would be 40/50 years old and some still turn up with useable cast alloy bits (depends on maintenance and a regular rinse)Stainless and Al are a long way apart on the galvanic scale, so electrolysis is a problem, that's why we reassemble our boats using dissimilar metal compound (usually Duralac) between stainless and Al and on all Al rivets.   You will be welcome at state or nat champs, but I would not turn up with carbon fibre parts and expect no reaction, specially on parts that the manufacturer still supplies. As the current measurer, and a thoroughly easy going bloke, I would offer you the loan of a set of castings to head of any action.                         


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Thanks Darcy.

I wont bother making the replacement parts.

I suppose I will just replace the bolts every 4 to 5 years just to be safe. It would not have mattered here as to how much or how little the boat was washed as the corrosion would still have happened. It blew my mind away when I saw how much of the bolts had disintegrated. And yes my boat would be at least 40 years old, but I also know that . the bolts had been replaced at sometime probably in last 10 to 15 years, just because of the type of bolts used. And there was anti sieze compound showing on some thread that I could see, it being a pale yellow in colour.Where I live the air itself is very salty. It can rain, and in the morning you can go out and see and feel salt crystals over your car. 

I will get back to you over winter when I disamantle the front ones.

Thanks once more, cheers David.

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11 hours ago, cdoch said:

Why do you think carbon  fibre will  completely stop this corrosion? Suggest you do a Google search for carbon fibre and metal corrosion....the results might surprise. 

It all comes down to how you manufacture the part. There is ways to isolate the carbon fibre from being in contact of the stainless steel. I am not going to try and explain here, as it would be too difficult to explain by  messaging. Trust me, I know, as I have been in the industry for many years.

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