Strange thing with damp?

[chrisbitz]

My seat cushion often feels slightly damp to the touch, not surprisingly because the boat has been a little damp inside due to a leak...

Just as an experiment, I stood the cushion up on the seat and got this strange damp mark at the top the next day. Ahh, I thought - there's a drip above that's causing this. So I dried the seat out for a day in front of the heater, and stood it up on the floor that night, and this is what I came back to in the morning...

So it's not a leak in the roof dripping down. Is the foam or material absorbing water out of the air, or is there another phenomenon at work here?

Maybe the foam wasn't completely dry when I stood it up? If that was the case, I'd have imagined it would have collected at the bottom, not the top?

 

[MoodySabre]

If it is closed cell foam then the damp won't travel through the foam. Just the outside layer that is soaking into the cover. I'd take the cover off and dry the foam and the cover separately at home. Wash the cover too in case there is salt in it which is attracting the damp.

 

[chrisbitz]

It's a 1978 boat, so I doubt it's any sort of foam, other than very old, very cheap foam

And the zip has long since metamorphosed into a somewhat metallic blob. So the cover's not coming off any time soon

 

[lw395]

Could just be water held in the thick seam at the front edge.

 

[Spirit of Glenans]

In 36 years it's highly likely that many people have sat down on it in wet oilies - salt is your problem. Cut the zip, if necessary, remove the cover and wash it in a cool wash. Put it back onto the cushion before it's completely dry, so as to retain its shape and prevent any shrinkage. Buy a new zip (plastic) from a haberdashery or online, then take it to your local alterations shop to have it sown in.
IMHO fabric covers don't work on boats and are best replaced with a waterproof material.

 

[VicS]

I,d agree . Been soaked in sea water along that edge at somtime.

The hygroscopic salts in seawater attract dampness.

Youll need to wash the foam as well as the cover to totally cure the problem.

.