It’s a Nacra 5.5, one or the forestay bridle anchors failed, cut just under the edge of the hull. I think it was corroded because the surface of the cut was dark.
Anyone has replaced these anchors? I haven’t found a replacement yet, do they sell them? I see some for Hobies but not for Nacra. Any experience, advise, pictures will be appreciated.
It happened on the shore, I was about to jump on the boat to start sailing. Curiously I had the bridle in my hand, I was pushing the boat from it. The mast came down rather slowly with no on close, fortunately. It was a bit hard to remove the mast afterwards, the forestay with the other bridle and bow foil ended up with tension against the opposite shroud. I had to remove the shackle on the mast tang. I’m glad I had pliers on the boat. Had to cut a rope too, glad I had my knife too. ( trying to see the positive side...)
I think I have the incident on the GoPro, will share it later

You are probably going to have to open up the forward deck to access the chainplate. This is going to be a strip of stainless steel, and even if you can't find a part from a salvaged hull it should be possible to re-create in a shop. I have not previously heard of that part failing by fracturing above the hull. It had to have taken some bending in the past.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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What about laminating a tang onto the boat instead of cutting it open?

tominpa

This is going to be a strip of stainless steel

How is It fixed to the hull? The shroud chainplates are bolted or riveted, I thought the bow ones would be shaped to distribute the load inside the hull, or bolted to something inside. Just a straight plate seems weak? I hope it’s not necessary to remove too much fiberglass around it to take it off



Edited by Andinista on Nov 23, 2020 - 07:03 AM.

ziper1221

What about laminating a tang onto the boat instead of cutting it open?

That sounds not strong nor clean enough?



Edited by Andinista on Nov 23, 2020 - 07:25 AM.

Yes, it was evident.. I never imagined it would be corroded inside.

And the video...
https://www.youtube.com/watch?v=IgGG0U3SEZo
I could have turned the boat around and reach the beach downwind, the mast would have stayed up and I could have taken it down in more control and with help. Of course I didn't think of that, there was no people close so I thought it was the best thing to let it fall right there.
I secure the daggerboards with that line and carabiner after I saw a daggerboard falling down on a capsize. I'll change the line with a bungee.



Edited by Andinista on Nov 23, 2020 - 08:22 AM.

Andinista

And the video...!

The lack of expletives is truly remarkable.

Another thing to keep in mind is that if one side let go, the other side is suspect and should probably also be replaced.

sm

Dogboy

Andinista

And the video...!

The lack of expletives is truly remarkable.

Another thing to keep in mind is that if one side let go, the other side is suspect and should probably also be replaced.

sm

Yes, I wouldn't rely on the other one, mainly because of the rust stains. The shroud plates on the other hand look good, I'll remove them for inspection but won't replace them if not corroded.

You will have to pop the front deck plate off to access the bridle anchor as Tom stated. I have never done it but
it seems easy enough. I wonder if this may be the part you need?

https://www.h2o-sensation…-vorm-2000000001951.html

--
Pete Knapp
Schodack landing,NY
Goodall Viper,AHPC Viper,Nacra I20
--

The first step is to pop the top deck, and see what you have inside. There are a number of photos and videos on the forum showing NACRA decks being removed and re-glued. I don't know how this is attached or even its shape, but all of that will be very quickly determined once you have a view. It would not surprise me if there is an internal block that is laminated to the hull, and the tang is attached and laminated to that. Hope you will let us know what you find, and double check the shroud chainplates inside the hull...you already have a port.

That was a nicely controlled demasting. Could have been a lot worse if you were out on the water, and luck of the draw, you were just launching.



Edited by tominpa on Nov 23, 2020 - 11:37 AM.

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Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
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Unfortunately this repair isn’t all that uncommon.

I can relate to that helpless feeling when it popped off in your hand. Some of the old-school guys I see it with are very leery about pushing or pulling a boat by the bridles at any point. I find the orientation of yours curious as it seems most of them are mounted vertically over flat.

--
Greenville SC

Offering sails and other go fast parts for A-class catamarans
--

You won’t be able to check the shroud chain plates, they are under the 2nd bit of decking.
It is not difficult to remove the front deck.
A small ball peen hammer & a stiff putty knife. Often the regular putty knife,(yellow/green handle), work, but if not stiff enough get one with the thicker metal. They don’t all come off the same, I saw one old 5.2 removed just jamming the putty knife by hand.
Work it underneath, then using the hammer tap & work your way around the deck perimeter. I have also seen a fellow who owns an aeronautical engineering firm remove the deck from a 5.2 using an air chisel, with a fine blade, that went REALLY quick.
The deck will not come off with smooth edges, but don’t sand them down. Once you grind out & attach the new anchor mix a bit of epoxy, thickened with microfibres. Paint that on, place the deck, then a layer of Saran Wrap, then some sand bags to ensure the deck is compressed everywhere onto the hull. There will be a couple of cross braces between the sides of the hull.
There is enough room to get an angle grinder inside once the deck is off. Best have the hull separated, gravity can be your friend when setting the new fitting.
Make sure you attach the fitting properly, once you epoxy that deck back on, it will NOT want to come off easily.
I’m surprised you didn’t bend the DS rod, something at the mast base usually gives if the mast is lowered without being turned 90*.
Here is what the fron looks like inside.
https://www.thebeachcats.…aedefdb468dae2a12d81e355



Edited by Edchris177 on Nov 23, 2020 - 02:42 PM.

--
Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
--

Edchris177

You won’t be able to check the shroud chain plates, they are under the 2nd bit of decking.
It is not difficult to remove the front deck.
A small ball peen hammer & a stiff putty knife. Often the regular putty knife,(yellow/green handle), work, but if not stiff enough get one with the thicker metal. They don’t all come off the same, I saw one old 5.2 removed just jamming the putty knife by hand.
Work it underneath, then using the hammer tap & work your way around the deck perimeter. I have also seen a fellow who owns an aeronautical engineering firm remove the deck from a 5.2 using an air chisel, with a fine blade, that went REALLY quick.
The deck will not come off with smooth edges, but don’t sand them down. Once you grind out & attach the new anchor mix a bit of epoxy, thickened with microfibres. Paint that on, place the deck, then a layer of Saran Wrap, then some sand bags to ensure the deck is compressed everywhere onto the hull. There will be a couple of cross braces between the sides of the hull.
There is enough room to get an angle grinder inside once the deck is off. Best have the hull separated, gravity can be your friend when setting the new fitting.
Make sure you attach the fitting properly, once you epoxy that deck back on, it will NOT want to come off easily.
I’m surprised you didn’t bend the DS rod, something at the mast base usually gives if the mast is lowered without being turned 90*.
Here is what the fron looks like inside.
https://www.thebeachcats.…aedefdb468dae2a12d81e355Edited by Edchris177 on Nov 23, 2020 - 02:42 PM.

Thank you! Very useful tips. I won't repair it myself but take it to a boat shop, but last time they couldn't remove the deck plates and I had to add an access port in front of the front beam. I'll try harder myself now, with the putty knife. If on a previous repair (previous owner) they were epoxied, I wonder if it will still be possible to take them off.
The mast landed rotated, fortunately, I think the rod is ok. Will re-inspect a couple things before sailing again though.

Quote

ind the orientation of yours curious as it seems most of them are mounted vertically over flat

It's 45° actually, similar to the bridles angle, that seems ok.

My thought on shroud chainplate inspection is based on the location of the deck ports which should provide inspection access.

The removal of deck plates becomes much more difficult if they have previously been removed and epoxied in place.

--
Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
--

Andinista

ziper1221

What about laminating a tang onto the boat instead of cutting it open?

That sounds not strong nor clean enough?Edited by Andinista on Nov 23, 2020 - 07:25 AM.

good enough for forestays
http://2.bp.blogspot.com/-cjQwXBylsDg/UTODT1RIymI/AAAAAAAAElk/2DYNgAUWNvQ/s640/025-LP.jpg

Thanks, I'll consider it among the options

The putty knife did work . Just tested on an area but it appears to be straightforward. Thanks!

Quote

I’m surprised you didn’t bend the DS rod, something at the mast base usually gives if the mast is lowered without being turned 90*.

The mast went down with tension on one shroud against the remainder of the forestay, I think that helped to make the mast base rotate against the rod.

Andinista

The putty knife did work . Just tested on an area but it appears to be straightforward. Thanks!

Now that's commitment! Good luck and be sure to keep a record of the repair for future unfortunate mast demasters.

--
Tom
NACRA 5.7 (1984 Sail 181)
Pennsylvania
--

I demasted once with a hobie 18 shroud pin popped out should have checked before I left at least have it taped up.In the middle of the Ottawa river which is 1 mile across at this point .Shroud let loose on the leeward side kept sailing till I literally hit shore and the mast just fell in the water no harm done bundled up my mast and lines and called my club for a tow .This was the lucky version ,yours not so much. Good luck with the repairs.

Andinista

Yes, it was evident.. I never imagined it would be corroded inside.

With bigger boats, I find corroded stainless chainplates a lot. It is not surprising that it is corroded inside. Stainless doesn't like sitting water. Why it's very important to have caulk around the top of all the tangs.

--
Scott

Prindle Fleet 2
TCDYC

Prindle 18-2 Mod "FrankenKitty"
Tornado Classic "Fast Furniture"
Prindle 19 "Mr. Wiggly"
Nacra 5.8 "De ja vu"
Nacra 5.0
Nacra 5.8
Tornadoes (Reg White)
--

i have had 2 chain plates fail
both identical to yours
the corrosion is just in the hull/epoxy - as scott said - common place for this
the lack of oxygen in that location is the cause and well documented
here are the images of my front tangs

https://www.thebeachcats.…nc=viewtopic&topic=16179

Thanks for sharing! Mine isn't open yet, the shop is busy and I don't have the skills.. I will document too

A good case for rails and back up bars. What you see is what you get.

--
Bill Townsend
G-Cat 5.0
Sarasota
--

shortyfox

A good case for rails and back up bars. What you see is what you get.

pros and cons to everything on a boat

having exposed hardware is good for inspections and replacement but not the fastest design

not too many manufactures care about 10,20,30, 40 years of vehicles service after the warranty expires

Hi everybody!
I repaired the bow tangs too. Unfortunately I have no pictures because I wasn't there during the process. Some details:
- The old tang wasn't removed, just the tip was cut from outside with a cutting disc. The rest of the tang was laminated inside the hull, it looked solid and didn't make sense to remove it as I though initially.
- The new piece was made with two metal strips soldered together, and laminated over the fiber covering the old one (quite thick, you coudn't tell where the old one was). The fibre surface was worked out first to fit the new metal piece.
- Before looking inside the hulls I was concerned about their strength to hold the mast load. But I saw that the fibreglass is very thick at that area, especially at the upper edge that will hold the horizontal part of the metal piece.
- It wasn't necessary to remove the hull covers completely, just about 60 cm or so, which could be bent up and tied from the tip to the front beam to keep them open.