Deck Repair –Intermediate Damage

[Steve W10]

Re: Mañana, 1988, #625

I've checked everywhere for a similar situation and haven't found anything quite like what I've got on Mañana.

Situation;
•   The deck around three stanchions appears wet for up to about 12" away.
•   Moisture Meter readings are consistently at 7 or 8% on virtually all of the deck except in these three spots where it goes to 15%.
•   The deck below one stanchion is especially weak and has certainly de-laminated.
•   The deck surface is in really good condition otherwise, so I much prefer to effect repair from below.

With all the reading I've done and speaking with some clever people I've come up with this plan and request any further suggestions and opinions please.

The idea is to...
•   cut a "D" shape out of the inner liner (slightly elongated from the image) to allow a repair piece of plywood to be slipped over the lip of the inner liner
•   carve out all rotten plywood
•   make plywood repair piece with stainless steel backing plate routered and epoxied into bottom of plywood – needs to be routered in because if mounted proud it would interfere with the inner liner installation later
•   insert repair piece with fibreglass matting bridging the inner liner surfaces (between the plywood and inner liner)
•   reinforce vertical lip of liner with fibreglass matting and epoxy
•   refinish the scar on the inner liner

One guy I spoke with highly recommended vacuum bagging to ensure good penetration seeing as it will be a repair from below.

Any insight would be greatly appreciated.  Thanks.
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[Stu Jackson]

Steve, it's not clear from your description whether or not you have taken the "in question" stanchions off yet and actually seen what the damage is visually, rather than depending on the moisture meter.  I'd start by taking the most suspect one off, and seeing what you have.  The old trick is to bend a nail in a drill and have at it, but I'll bet a dental mirror and a pick will go a long way in telling you how deep the penetration of the damage may be.  You should be able to do this from above.

Maine Sail has a good explanation of moisture meters, in case you haven't seen it, on his website.  http://www.pbase.com/mainecruising/moisture_meter

He may also have some good advice on what you're looking for, poke around (PI!!!) and see.

[Ted Pounds]

Stu has got a good point.  If you can get at the rot from the hole (you may have to expand it; not to excede the footprint of the stanchion) you may be able to just inject thickened epoxy into the void.  If the rot is too extensive I think your plan is a good one.  Which stanchions are they?  The ones that vent the holding tank and starboard water tank are well known for leaking.  There's a lot of excellent experience on this board; so keep us updated on what you find and we'll all be happy to offer input.  Good luck.

[mainesail]

Not knowing what MM you are using it is tough to comment but generally speaking a 15% reading is quite dry. Even bone dry, new uncored fiberglass will read 6-8% on the Electrophysics GRP-33 or CT-33.

Remove the stanchion and do a core sample under it. If it comes out looking good I would leave it alone. Just refill the core sample with some thickened epoxy. Bevel/countersink the holes and re-bed. The flex in the deck may not have anything to do with moisture as 15% is quite low. You should also sound it out with a brass or phenolic hammer and look for differing tones or delam tone. If delam is noticed then a repair should be undertaken but it is doubtful at a 15% reading..

Personally I would never undertake a repair that close to the hull deck joint from below especially with Catalina's deck liner etc.. I have torn into to many "below deck" repairs and have seen the poor outcomes to even begin to consider it. Why risk it over aesthetics? Gravity is not your friend. If still sold on below deck PLEASE use vacuum bagging as it is a good way to do this as close to properly as you can and not get voids or problems.

This is a wet deck and why GASKETS are a horrible idea.....

http://www.youtube.com/watch?v=ga0eeZ6ZhIY

[Steve W10]

Terrific input guys, thanks a tonne.

I've not yet taken the stanchions off, but I will certainly take your advice and have a look before butchering the interior.  Fortunately if I do have to make this repair all of the work will be done outboard of the teak trim/handrail, still visible but not as bad as way out in the open.

The nail trick, pick and mirror are also good ideas; I was going to use the nail to do the rest of the deck fixtures so I might as well have a look at these first.

On one of the other threads here I saw the recommendation to read Mainesail's article which I agree is terrific.  And from that and other advice I decided that the CT33 was the only way to go.  As you guys have correctly stated, even the manual says that 15% is right on the line between dry and moist, it's not until 23% when they describe it as wet.  I did knock around with a hard plastic mallet and noticed a difference in tone, albeit in a smaller area than the CT33 identified as 15%.  I guess I was thinking worst case scenario because of the noise and the fact that the rest of the deck was consistently 7-8%.

The three stanchions in question are indeed the vented ones and the one forward of that on the starboard; clearly people have been giving that ever-so-helpful docking assistance in the past; that third one is quite loose.
Interesting thing though, and I suspect this may have been done by the PO, but although the other two stanchions themselves do have vent holes, the vent lines on my boat go to 90 deg hull vents just below the rub-rail.  I don't recall seeing that on any other 34s.

I had not seen that video about gaskets, possibly the most effect 17 second video ever.  I do plan on the standard fix for all other deck fittings (bent nail and epoxy, then re-drill the holes) again thanks to the excellent entries on this site.

Mainesail, I also take your advice to go from the top very seriously, I know it would be a better fix.  Truly though, I'm having a terrible time coming to grips with messing up what is still a very nice deck surface.  I'm hoping that the vacuum bagging will be the answer.... and I'll no-doubt be looking for advice on that in spring.

I'll be pulling those stanchions off next week (we just hauled out this past weekend, with just a touch of snow to let us know that it was pretty good timing).  Once I get them off and have a look I'll update this tread, hopefully it's better news than I fear.

Again you guys, thanks very much.  I did so much reading before submitting this and you still come up with more great insights

[Stu Jackson]

Interesting thing though, and I suspect this may have been done by the PO, but although the other two stanchions themselves do have vent holes, the vent lines on my boat go to 90 deg hull vents just below the rub-rail.  I don't recall seeing that on any other 34s.

Steve, I'd guess that the PO tried to get hoses OFF those vented stanchions.  The port side is the holding tank vent and a mushroom thru hull would be a good idea.  The starboard is the water tank vent, thru hull not really required.

I'd check underneath in the cabin side to follow those hoses to confirm, and also check how the stanchion base holes were sealed, or perhaps the stanchions were replaced with non-venting units.

[Ron Hill]

Steve : BTW, on all the 1988 and 1989 C34s (at least those years for sure) both vent connections on the thru portion of the stanchions are attached to a short piece (2") of 1/2" hose that attaches to a 90 degree elbow and then to the holding tank or starboard water tank.

If both of the vented stanchions have been leaking quite a bit and for a long time - it will definitely show up in the ash battoning that is attached to the liner just below those storage areas where the stanchions come thru.  Also look closely at the "deck" of those storage areas inside the sliding doors on each side - it's a dead give away on the plywood decking if the stanchion has been leaking (because that's where the water pools first).

From that inspection you may be able to determine the real degree of the water damage. 
A few thoughts   

[pablosgirl]

Steve,

I found these document from West System to be quite invaluable http://www.westsystem.com/ss/use-guides/, The one on vacuum bagging is particularly useful as well as the one on bonding fasteners.  There are some good videos on youtube, watch the West System on first and then the others if you have more questions. http://www.youtube.com/results?search_query=vacume+bagging&aq=f    Don Casey's Sailboat repair book has an excellent chapter on deck repair.

Also, I share you trepidation for grinding into a good looking deck.  Ted had a good idea about going in through the foot print of the stanchion base.  I have made repairs to a balsa cored deck this way, using balsa blocks cut to fit through the hole and then packed into place in the repair with epoxy thickened with a structural filler placed between the blocks and between the blocks and the deck skins.  The thickened epoxy between the blocks will act as "I" beam like supports between the upper and lower deck skins.  In addition the epoxy between the blocks will stop/slow the spread of mostier into the repair and the rest of the deck plywood.  I would not use balsa core in your repair, but a good grade marine plywood cut into blocks.  Be sure to use the West System "Bonding fasteners and hardware" technique when installing the stations. (IE. bent nail and epoxy, then re-drill the holes)  If you use a Dremel tool with a small cut off disk to cut out the area around the stanchion base, you will be able to pry up that piece of the deck skin and reinstall it on the new wood deck core.

If you go in from bellow deck, I would not try and rout the SS plate into the replacement plywood for the following reasons.  First this is over complicating the repair for not any great advantage.  Second, epoxy/polyester resign do not bond well to stainless steel (SS).  the bond will be mechanical and it will be very difficult to get the surface of the SS plate rough enough to get any kind of bond.  Once the SS plate separates from the epoxy the plate will be "floating" between the plywood and the bottom skin of the deck, thus reducing the strength of your repair.  Better to use the SS plate as a backing plate to sandwich the repaired deck between the stanchion base and the backing plate.

Also, if you do the repair form bellow you will definitely want to use vacuum bagging, its the only way to get a good repair working against gravity.

[Albreen]

Great advice as usual from everyone! If I can add a thought, after digging out saturated core down to wet but intact core material I've had good results flushing the cavity with acetone to drive out any remaining water and then drying over many hours with a heater from below. Be sure to ventilate well. You can also use a penetrating epoxy like CPES afterwards to penetrate the core before applying the new epoxy filler and/or wood. Good luck.

[mainesail]

If I can add a thought, after digging out saturated core down to wet but intact core material I've had good results flushing the cavity with acetone to drive out any remaining water and then drying over many hours with a heater from below. Be sure to ventilate well. You can also use a penetrating epoxy like CPES afterwards to penetrate the core before applying the new epoxy filler and/or wood. Good luck.

Please be very careful using acetone between deck skins. Acetone poured in between a deck only serves to melt and damage the bond between the balsa and deck skin. The big problem is that acetone  becomes non-fast evaporating between deck skins and actually can become resin eating & softening. Removing water takes either excavation or many, many, many holes drilled or months of drying. Do the acetone trick on some foam cores and your really in trouble.

Keep in mind that with decks that were hand laid, not infused or vacuum bagged, that there will almost always be channeling of the moisture meaning that the water is usually more wide spread than just near the fitting as it rides the kerfs in the contour cut balsa or foam. It also rides voids well. Acetone will also ride these kerfs or voids and cause channeling which can lead to damage to the bond between deck and balsa or plywood. and you may wind up with some delamination in an area where you did not expect it.

Epoxy, penetrating epoxy, CPES etc. do next to nothing to stick to wet balsa. If you have dry balsa they can create a good bond interface between the wood and thickened epoxy. CPES or other penetrating epoxies are really a feel good measure unless you can assure the deck is dry when you inject it.

I have taken apart decks "repaired" with penetrating epoxy and I can assure you that it does not "penetrate" like the manufacturer would have you believe. All we had was hundreds of little plugs drilled into the deck that looked like epoxy bungs most of them not even adhered to the balsa because it was slightly wet when injected. Where it was dry you could take a nail and poke the core to feel how far it penetrated and it was perhaps at best a mm... Penetrating epoxies work best on dry rot that is dry when injected.

[Stu Jackson]

Maine Sail,

Is Git-Rot any good for this?

[mainesail]

Maine Sail,

Is Git-Rot any good for this?

Not if it is wet and if it is dry then only really any good for wetting it out before filling with thickened epoxy. None of them will work when the core is wet.

[Steve W10]

Thanks again guys for the advice.

After disassembly of the stbd shelving / cabinetry and stanchion removal I've found that the damage is not as extensive as expected, however, still bad enough that I've got to cut the inner liner to repair two sections.  With a much better view now I can see behind the Inner Deck Lip to the fibreglass covered plywood decking.  I can see the wet wood around the stanchions and know that I've got to get it out.  The PO had attempted repair from above, but just by drilling a few holes and filling with epoxy (see image) which unfortunately did nothing for the delamination further inboard.

Stu, I do believe the PO replaced one vented stanchion and swapped the other one with a non-vented (further forward) to limit water ingress after re-routing the vents and plugging the deck holes.  I kinda like that idea, especially when this deck repair is complete and it's water-tight.  I would like to plug the vent in the stanchion he moved forward though.

Ron, you are absolutely correct, the evidence is certainly there and now that I've got the interior apart I should be able to effect repairs/replacement of the damaged pieces.  (also I have a detailed description and photos of how to remove the shelving / cabinetry; would it be worth submitting a Tech Note?)

Paul, nice links, and with respect to the SS backing, after your suggestion and seeing that the inter-deck plywood is actually quite thin, appears to be only ¼ inch or so I totally agree that routing the SS in would not be smart, especially with the bonding issue that you mentioned.  There were some small, although thick Fibreglass backing plates under the two damaged deck areas (see image) but I was surprised to see that they were so small, I would have made them as large as possible to spread out the load.  I suspect those were added by the PO.  Once the repair is done I will be installing SS backing plates.  The other benefit to not embedding the SS is that they can be removed if one needed to get another moisture reading, as clearly the SS will throw off any measurements in that area.

Three more questions then....

1. Ideas on how to plug the remaining vent hole in the actual stanchion?  Or is it not worth the effort?
2. And this may seem silly but .... Could one, after excavating the wet wood in the decking, just fill the entire cavity with epoxy (with structural filler but no plywood) to more effectively fill the entire void?  Or would that turn brittle in time or have some other ill effect? (Still vacuum bagging)
3. Slightly different issue... some of my Deck Drainage Holes seem to leak into the cabin and I was thinking I would like them a little larger anyway.  Would it be sensible to enlarge the Deck Drainage Holes and then treat them as one would repair a stanchion hole using the West System "Bonding fasteners and hardware" technique to ensure a good seal with a final touch-up of gelcoat?  I saw that Herb mentioned something similar in Nov 1990 Mainsheet although he suggested embedding a plastic pipe.  Thoughts?
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[Ted Pounds]

#1 Tape of the bottom and fill with a shot of spray foam (Great Stuff).

#2 I think filling the void with thickened epoxy is exactly what you want to do.  It'll be as solid or even more solid than the wood. 

#3  I had the same problem with a couple of my deck drains.  The problem is that Catalina didn't put any glass in that area, just resin.     So if the area gets bumped hard (eg during docking) the resin can crack and allow water to seep in.  What you need to do is get at the underside and add a layer of epoxy and glass cloth.  There's at least one thread on this subject from a couple of years ago buried on this board.

Good luck.

Ted

[Lance Jones]

<<<<3. Slightly different issue... some of my Deck Drainage Holes seem to leak into the cabin and I was thinking I would like them a little larger anyway.  Would it be sensible to enlarge the Deck Drainage Holes and then treat them as one would repair a stanchion hole using the West System "Bonding fasteners and hardware" technique to ensure a good seal with a final touch-up of gelcoat?  I saw that Herb mentioned something similar in Nov 1990 Mainsheet although he suggested embedding a plastic pipe.  Thoughts?>>>

I actually did that. I used a 3/4 inch hole saw bit. I first inserted a 1/2 inch dowel into the drain hole. Then, I marked TDC on the dowel and drilled there between the top of the dowel and the fiberglass. Upon removal of the new plug hole, I coated with 2 layers of epoxy, sanding between coats. Final action was to repair gelcoat around the new drain.