Water dripping from deckhead, wet core?

[steve yates]

Screwed a batten up to the roof couple of weeks ago, noticed some dark gunge on cushion below it yesterday. Today there was a steady drip of liquid from end of batten. Took screw out and sure enough, liquid dripping out of the screw hole. This is from where the deck curves down just above the window.
I am assuming water in the balsa core, probably from elsewhere , and finding an outlet via the screwhole.
Two questions,
1) How to desl with it? Im thinking cut off the end of the batten that got damp, and drill a bigger hole right through to the deck to try and see the state of the balsa, but then what?
2) Its scorching, had no rain for 3 weeks, why has it suddenly appeared in the last couple of days?
the pics show the batten, the drip and the amount dripoed in 10 mins this morning.

 

[RunAgroundHard]

You have drilled a hole and it has taken time for the moisture to work its way through. Perhaps the scorching weather has increased pressure in the coach roof space which is relieved through the hole you drilled. If it was me, I would use a suitable moisture meter to find the damp bits before drilling any hole. Well bonded, dry core, should be easily differentiated from wet core. Alternatively, use a hole cutter to remove the GRP to the core at some distance away, say 1 foot, up hill, if core is good, move halfway and drill again, repeat until you find the damp spot or stop if not obvious and do moisture meter.

How to fix the matter, will depend on the problem, West System have an excellent manual of various repair methods, which can be downloaded for free. You dont need to use West products, other products can be used: -

Fiberglass Boat Maintenance | WEST SYSTEM Epoxy

Good luck with the repair.

The likely reason why the leak is now happening, from a quick google search: -

Effect of temperature on capillary action

Now, as the temperature of water increases, the surface tension of the water diminishes. This makes it easier for attractive forces between water molecules and other surfaces in the vicinity to pull water into capillary crevices and pores in those surfaces and wet them out. This is why hot water does a better job rinsing dirt out of your clothes than cold water does: it reduces the contact angle between the water and the solid surfaces, enhancing the wettability of those surfaces.

 

[steve yates]

Interestingly, the drip had slowed then stopped by about an hour or so later, and not much more in the jug.
I suspect there may be more in the morning but it dries up again as the heat rises?

 

[Concerto]

It sounds like you have a failed sealant on a deck fitting. As water is dripping out of the balsa core, I suspect a fitting or cable was added by a previous owner as he did this through a balsa core and failed to seal the balsa core. As it has stopped dripping, I would check any suspect access point. To do this, I would build a small wall around it using Plastacine. Fill with water and leave to possibly soak in for several days. If checking several places, use different coloured food colouring to identify which fitting is leaking.

 

[geem]

Interestingly, the drip had slowed then stopped by about an hour or so later, and not much more in the jug.
I suspect there may be more in the morning but it dries up again as the heat rises?

When the balsa is installed, it's normally in squares glued to a scrim. This allows it to go around corners but as a result you can get voids in the core. They can channell water some distance from where the water is getting in. It may be that the problem is some distance from the location you have found water. Check deck fittings everywhere for the source of water ingress. If deck fittings haven't been rebed for a number of years, there is no harm in rebedding everything for peace of mind.

 

[jwilson]

When you do find how extensive the water in the balsa core is, the best way to fix it is to cut one skin away completely. Professionals usually cut away the top skin, as the world's worst job is laminating new core and GRP when working above your head if you cut away the underside. I did it once from the underside: never ever again. I'd drill quite a few more holes from the underside to let most of the water out, seal them up and if there really was a lot of water think about another boat before the balsa gets any mushier. Or do the good fix from the top, but that takes some skill.

There's a special place in hell reserved for those who don't do a proper job of adding fittings to balsa-cored decks or hulls. Judging by how often it happens though it must be a bit crowded down there as well as extremely hot.

 

[steve yates]

Well I’ve already drilled out and filled 25 old badly patched holes in the coachroof, and just found another half dozen when on closer inspection I pulled out this

Its like they were plugged with wads of cardboard or similar!
The boat was surveyed in last couple of years and no moisture indicators flagged. And no soft/mushy areas of deck apparent. Its been ashore for 4 years.
I’ve already drawn the screws for the grabrailsbthat arent glassed over, countersunk the holes and replaced old sealant with butyl . Its on my list to remove and rebed all deckfittings and refill all old /redundant holes.
These look suspect to me, cos of the rust. They are for the strongpoint a leecloth hooks into.

 

[steve yates]

Came back to this today. Walked up and down the coachroof, did that area feel a bit softer after all? Or am i getting paranoid. The rusty bolts on deck are on opposite side, so walked up and down that side. Right at end, by hard doghouse, the deck definitely flexed! Now that one area feels different from the rest. Drilled a hole through and dug out some core, it was definitely damp, and i squeezed out a drop of water gouging out some core.
It looked this this.

Is that what rotten balsa looks like?

I also noticed the doghouse is screwed straight into the deck with self tappers and a washer, the screws would definitel reach the core and there is no sealing in evidence. If I remove the doghouse to repair the deckhatch, is it worth bedding it down in butyl?
And if I’m doing that would the same apply to the hatch garage?

 

[Tranona]

Normally factory fastenings do not go through the core as the layup will either be solid or ply/aluminium where fastenings are planned. It is the subsequent add ons like your doghouse that cause most of the problems. They might be hidden for a while through the use of sealant but when the sealant breaks down water gets into the core and as suggested earlier travels down the gaps between the block or into the balsa itself.. I would think the hatch garage is original and could be solid in that area.

 

[ridgy]

Truly rotten balsa is black and wet. That looks positively dry. Really wet balsa stays wet till it finds an outlet. I feel your pain I have similar issues to attend to this winter. I have no spongy decks because the top layer of glass is strong but I know what lurks beneath. It's like osmosis, the boat won't sink just do a bit each year. I was going to replace the balsa in sections with lightweight marine ply. Bit heavier maybe.

 

[steveeasy]

Just wondered if a moisture meter might help here comparing different readings within the coachroof. If you get a high reading in the area that flexes more, then you can focus on that area specifically in time. Im sure most boats with foam cores have areas like this.

Steveeasy

 

[geem]

Just wondered if a moisture meter might help here comparing different readings within the coachroof. If you get a high reading in the area that flexes more, then you can focus on that area specifically in time. Im sure most boats with foam cores have areas like this.

Steveeasy

Our deck and hull are foam core. Deck has no soft patches. It's a much better product that balsa if done to a proffessional standard. It's a plastic foam and doesn't rot like balsa.
A few friends have repaired soggy balsa core by replacing with a foam core product such as Airex in the failed areas of balsa