Soggy aft deck (former email exchange)

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August 14, 2010 at 00:38 #4281
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Adrian Weston said:
Wet lazarette and sagging deck: I have spent considerable time (taking rests from caulking) hanging upside down in the lazarette locker prodding and poking at wet wood. I hoped to have cured leaking here also by repairing the leaky teak not being convinced that the locker hatch or the large aft window were responsible. I opened the auxiliary tiller port and was astonished to find no seal and fashioned one immediately from car inner tube and also found some adjacent caulking that needed attention. Within the port I found lots of soft soggy wood. Following heavy rain I inspected again to find a bit of a puddle around the base of the mizzen mast which my efforts appear to have prevented from slipping through the deck and down the tiller port. Further inspection revealed that the glass laminate just aft of the mast was sagging a bit and cracked. Puddling clearly shouldn’t occur here and the tiller port would normally be proud of the surface rather than in the sump of the shallow puddle, so perhaps there was never the need for a seal here but I should think it advisable for all to check. Maybe originally there was a ring seal.

Others have spoken before of delamination of the aft deck lay up and I should be grateful for any information about this issue since I suspect the tendency for our lazarettes to get so wet is the cause of the problem, with frost damage in the UK leading to lifting etc, and elsewhere just rot. I shall undoubtedly have to rebuild the aft deck for which I imagine those drawings we hope to obtain could be very useful, but if anyone has ‘been here before’ I would appreciate advice and the benefit of any experience.

In the meantime I shall sail with a well reefed mizzen!

Ollie Holden responded:
Re: aft deck issues – I think this is a slight design flaw in the mizzen mast setup – but given the age of the boats it’s clearly something we have to live with! There are some complex and large stresses & strains in this area.

Simplistically, the compression from the mizzen mast (from the tension in it’s shrouds + mizzen sheet when hauled in tight) is balanced by the tension from the backstay which attaches to the mizzen heel plate – however it doesn’t seem to work quite like that.

Underneath the mizzen mast there doesn’t appear to be any specific strengthening of the deck, or bracing in the lazarette compartment – on Nutmeg there is only 1/2″ ply in a glassfibre sandwich below the teak deck. On inspecting the emergency tiller port and looking fwd (need to lie down or use a mirror!) the ply was all wet and had delaminated, presumably from the mast compression bowing the glassfibre underside of the deck, and water getting in through the tiller port. I was concerned that this was actually pushing down on the rudder stock but I can’t find any evidence of this. The teak deck is sagging a little – as it does on every Nic I have seen! I haven’t done anything about this as it really needs the deck cutting out to remove the soggy ply – doing it from underneath would be a hard job. I have loosened off the mizzen shrouds so they are taut but no real tension, in order to minimise the compression – after all, you’re not trying to keep a headstay from sagging so I don’t think you need any real tension on the mizzen.

One other thing to look for – I found a small fracture in the mizzen heel plate between the tab which takes the backstay, and the base of the plate. This is caused by the compression of the mizzen foot vs the tension of the main backstay. You can only see this by looking out of the aft cabin window. I marked the crack and it hasn’t moved after 2 Transats – but next time I take the mizzen mast down I will take it for re-welding. I also found that the four through-deck bolts holding the T-bar for the main backstay had tiny washers and did not have a backing plate – so they were pulling up through the glassfibre under the deck. Again, a job to be done via the aft cabin window. Worth checking.

All good fun!

George Nauman responded:
About a year and half ago with help I started apron the task of removing the teak decks on Raga. She is a 38 foot CN ketch built in 1973 Hull 123. We had to deal with the sagging deck below the mizzen mast. Here are a few things we found as developed a plan to rebuild the deck supporting the mast. If you will remove the board above the sink in the aft cabin you will notice two vertical pieces of 1/2 inch plywood which support plywood directly below the mast. Between these supports the deck was made (filled) mostly with a horizontal 3/4 inch to one inch piece of plywood. Most of that horizontal plywood was rotted away. We had unbolted the mizzen mast and carefully pulled it off center. To replace the section of deck below where the mast once stood and around the (emergency tiller fitting) we glassed 3 X 3 inch beams to the underside skin of glass outside the vertical support plywood. Our new beams ran from the aft cabin coach top to the aft hatch giving us good support. We kept the bottom skin of fiberglass which was below the rotted horizontal plywood as a base. We replaced the 3/4 inch plywood rot with west system epoxy, fiberglass and some marine grade plywood. We raised the deck level maybe 3/8 inch to make sure the deck would drain properly. The vertical Plywood supports prevented water from seeping beyond them. So the rot was retained directly below the mast. We had many adventures as we removed the teak deck but, now she is dry below and that makes the my co-owner and wife very happy.

Andy Fletcher responded:
Harlequin had the same problem with rot in the deck under the mizzen mast. It was probably triggered by over-tightening of the shrouds which pushed the mizzen into the deck cracking the surface and letting water in. It had been like this for about 5 years before I got the boat a year ago. The solution in this case was to cut out the offending section of deck, add a new stainless supporting structure below it, dig out the rotten wood between the upper and lower skin and replace the whole lot with lots and lots of fibreglass. It is all completely solid now and is probably one of the strongest parts of the boat.

Richard Garlant responded:
This seems to be a common problem. La Torchee had a cracked deck under the mizzen ,the cure was the same as for Harlequin except we used iroco timber to beef up under the deck after renewing the fiberglass.

February 3, 2011 at 19:37 #8611

Rhapsode
Participant

I hope it’s not too late to join this thread (I’ve just found the forum).

Rhapsode is in Salvador, Brazil and is suffering from the sagging deck syndrome (tho’ in our case the under-deck timber was perfectly dry). The aft facing section of coach-roof dropped away quite suddenly on a particularly wavy day leaving a gap of about 20 mm in the centre (now full of Sikaflex).

I’m finding it difficult to get a decent repair yard in Salvador so I need to make the job spec. as simple as possible. Also, I’m told that they don’t have teak here so it may well be impossible to replace the decking if it has to be removed.

I am wondering which solution to the rebuild is likely to be the easiest – getting access through the aft cabin or through the deck itself.

If I can’t find a good repair yard then Plan B is to fit a temporary support as best I can and then take the boat up to the Caribbean (perhaps Trinidad) to get the job done properly.

Views very welcome!

Peter

February 17, 2011 at 09:51 #8671

Archivist
Participant

Dear Peter,
I hope this gets to. If you can tell me a bit more I hope to be able to advise you. Is there a gap of 20mm or is it a depression?. It sounds as though the stiffening under the mizzen and/or the bulkheads aft have failed.

Yours Jeremy.

February 17, 2011 at 18:04 #8681
Jean Clair
Jean Clair
Participant

Dear All
Jean Clair also suffered from this problem which was pointed out tous by our purchase survey. We had it repaired using a large piece
of stainless on the deck and lots of fibreglass between. As someone
said, the surveyor said that this was a common problem with Nic 38’s

Regards
Alan & Pat

February 18, 2011 at 13:33 #8691

Rhapsode
Participant

Dear Alan & Pat,

Do you have any photos of the work?

I’m looking to find either a very simple permanent repair or a temporary repair whilst I get the boat to somewhere where they have heard of boats and their little problems.

Happy sailing,

Peter

February 18, 2011 at 17:49 #8701
Jean Clair
Jean Clair
Participant

Hi Peter,
Unfortunately the repair was done in Dartmouth whilst we were at work in Yeovil, somerset. Will be down the boat tomorrow and will take
some photos of finished repair to give you some idea of what was done.

Regards Alan & Pat

March 25, 2011 at 22:11 #8851

Rhapsode
Participant

An update – I have found a boat yard in Salvador that can do basic work. They aren’t well equipped and have little experience of sailing boats, and we are on the cusp of the rainy season!!!

However, after two days the electrics have been disconnected and the mast has been removed. Work will start on cutting the offending deck out tomorrow. I am very thankful for the advice from the forum, especially Andy Fletcher and very especially from Jeremy Lines who has been emailing me daily in response to my pleas for help.

I hope to post an update or two as the work progresses.

Peter

April 1, 2011 at 15:39 #8881

Rhapsode
Participant

Almost finished now and I have to say that there is room for improvement. The yard’s plan changed daily, sometimes hourly, depending on the snags they found. Snag 1 was that after starting to chop out the deck they discovered that they couldn’t get hold of teak to replace it.

The essential repair is a U profile length of stainless steel inserted across the compartment under the mast bracket and under the two fore and aft stiffeners. A mahogany insert fills the gap between the top of the stainless and the underside of the mast.

The profile is supported at each end by substantial blocks of mahogany glued and screwed to the main fore and aft bulkheads.

Access was gained by removing the cabinet / mirror.

The repair will do for now but I feel I have to view it as a temporary measure until I can get to somewhere where teak is in good supply. The U-profile needs to be through bolted.

The main damage that we found was that the athwartships length of timber under the window had cracked which allowed the deck to sink down.

Happy sailing.

Peter

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