Soggy deck foam :(

[prv]

Took down the headlining on the new boat today to fit the new halyard winches. The deck is cored with foam, the headlining is screwed on with self-tappers through the bottom skin. After taking out the screw, one of the holes released several drops of water.

There's no deck fitting immediately adjacent. About two feet away is a hatch, and when I took off the trim around it I found wetness around one corner, the corner nearest the dripping screw hole. So it looks like the hatch is leaking and the water running down inside the deck. The whole thing isn't saturated, as none of the two dozen or so other headlining holes produced any water.

Obviously I'm going to rebed the hatch, but any ideas what if anything I should do about the deck? Doesn't sound crunchy or delaminated when I bounce on it. Just live with it? Drill some drain holes at the lowest edge? At least it's not going to rot like balsa would have done. Could really do without another project at this point!

Pete

 

[yoda]

Cure the leak and leave a hole to drain and dry has to be a good start. Water travels a long way in sandwich decks around this type of area because of voids that exist from build lay up of the foam. I had a very similar problem but didn't realise what was happening and ended up squeezing loads of water out by injecting sealant in from the top! When I looked below decks with lots of light I could see the sealant travelling along the voids!

Yoda

 

[corinthmistral]

i had the exact same problem last year - lewmar 60cm for hatch secured through balsa cored deck. Water had entered the deck and saturated about 6 inches of balsa core in one area. I removed the hatch and dug out most of the damp balsa core with a chisel. Then I made a temporary hatch cover to keep it water tight but which allowed air to flow around it. I left it for 6 weeks and routinely put a heater under it. When dry I cut up a load of chopped strand mat and mixed with resin to make a resin mash. This was then "poggled" into the void in stages. The area was first roughed up with sand paper to ensure a strong bond to top/bottom grp faces. It seems to have done the trick as it hasn't leaked since and has strengthened the aarea considerably and made it impervious to water. Time consuming and not a job I enjoyed but it definitely paid to take my time and do it properly. Hope that helps.

 

[oldsaltoz]

Don't be too confident about the foam core not breaking down when wet as many of them are a 'closed cell' foam.

To locate the effected area you to drill a number of holes on a 50 mm grid pattern and observe the material as it comes out to see if it has any moisture, a moisture will help but not essential.

Do this from the underside to preserve the deck moulding.

When you have established an outer edge of dry holes you can join the dots and remove the inner layer.

It's best to replace the old foam with a closed cell foam that will allow water to penetrate and soften it.

Just get some off cuts and shape them as required, you can clue thin sheets together to make thicker sheets with an epoxy resin.

Just prior to installing the foam, drill some 6 mm holes on a grid pattern, wet the underside of the deck with fresh resin and add a layer of resin and Micro-fibres about 10mm thick, push the foam into position, and trapped air or excess mix will come through the holes leaving you with a stronger joint.

The section on the under-deck you cut away can the re reinstalled using the same method as above to eliminate air caps and excess material, just have some props handy to hold in place overnight.

Good luck and fair winds.

 

[Deleted member 36384]

There has been an article in PBO on how to fix this problem and there is the West System download advice which details how to fix this as well. It's certainly worth a look when you decide to fix it.

I you believe that it is very localised then a perhaps a period dehumidifying the boat every time you leave it would arrest any moisture creeping along the foam allowing you defer the repair to next year. Of course as you say, fix the hatch to stop the leak first.

I left some wet balsa core where an old flue had been removed for a couple of seasons. After I removed the flue and sealed up the hole I dried it out from below using just heat and air movement. Later when I cut back the damage was only about a centimetre, but balsa is not foam.

 

[Blueboatman]

Compressed air can be used to drive the moisture and 'blown' foam from one hole to an adjacent one..
I also like to inject acetone as it both keys and helps dry the cavities thru evaporating.

Me I would be drilling a series of holes from underneath to map the wet area, dry/ remove then inject epoxy and fillers in a runny mix. Where you intend to thrubolt winches and jammers you will want a stronger epoxy filler, colloidal silica in fact.