capillary action

[cyclop]

My initial thoughts were condensation but this would be fairly obvious as all insulation was removed and v.little or no condensation occured,either on the fibre roof or the steel subframe.The crack you refer to is just a slightly proud lay up of the fibres.Interestingly,on the adjacent front corner,a similar thing appears i.e.ingress onto the subframe,rust, then a faint red stain on the headlining.As Paulatic suggests,some sika 512 sounds like a reliable sealant.

[Paulatic]

Sikaflex or Soudal are good when joining two surfaces but if you’ve a crack showing in the fibre glass I’d use a two part epoxy resin.Chandlers or EBay are often a good source. I had to do that with a Fleurette that was cracked from some hinge mounts

[NATURAL ANKLING]

Hi,

My initial thoughts were condensation but this would be fairly obvious as all insulation was removed and v.little or no condensation occured,either on the fibre roof or the steel subframe.The crack you refer to is just a slightly proud lay up of the fibres.Interestingly,on the adjacent front corner,a similar thing appears i.e.ingress onto the subframe,rust, then a faint red stain on the headlining.As Paulatic suggests,some sika 512 sounds like a reliable sealant.

If you can see fibres or evidence that they are at the surface then that will need sorting, the fibres on their own are porous.

[cyclop]

I,m just referring to the rough underneath of the roof.The gel coat is unblemished.

[Vorpal]

Condensation will behave differently with and without insulation. You might think it would be worse without insulation, but without insulation, the temperatures may normalise more quickly.

Also condensation is rather more unlikely when the vehicle is not in use. I you aren't sleeping and cooking in it, there is little resons for the outside to be very different from the inside. If condensation is a problem, you are unlikely to discover it merely by taking out the (wet) insulation and observing what happens.

That said, I still think that capillary action is likely. You could potentially test it through experiementation...
1) once everything is dry, re-assemble it as before, drive it some reasonable distance in the rain and immediately check for water ingress
2) when everything is dry, use it (either without driving it, or only driving it in dry conditions), then, when it is rather colder outside than in, cooking and sleeping inside, or even boiling a few pots of water so it gets nice and warm and damp, then checking for damp in the insulation afterwards.

[NATURAL ANKLING]

Hi,
I suppose you have not determined when water gets in only that its damp in the lining?
Roof up down left standing on drive driven etc etc?
I was going to say use a hose pipe and keep the area saturated to simulate rain.
Better when its died completely build a sort of barrier on the roof area where there is damp on outside fill with water and replenish to keep level topped up (a day when you are at home) then inspect for water ingress?

[cyclop]

Not just damp,actually able to squeeze water out and ice forming between insulation and roof,always in the same corner.A caravan engineer highlighted the sodden canvas as probably needing proofing again so water beads and runs off.Far too much water has ingressed the van insulation for condensation to be the culprit,especially as there nowhere for water vapour to get into that area in the first place.Additionally,an adjacent but separate piece of insulation was mildly damp.I,ve done the barrier thing in two potential areas,both without leaks.I think I will reproof the canvas and seal the corner area,then test with a hose.

[NATURAL ANKLING]

Hi,
Canvas?
Did you previously mention the canvas?
Forgive me, I have to think how it all goes together, as I said never done work in that area of van which has already got to 30 years old same canvas etc, apart from trimming the pop up roof edge.
I will try and look at it as soon as I can.

The canvas fits to what part?
IIRC the canvas falls on the out side of the roof so any water will not come inside?
There must be some thing on the end of the canvas which allows the canvas to be fixed to the main roof?
Or does it sit trapped between the trim alu and the roof, there must be a stiffener in end of canvas?

Off shopping now.

From inside you can see minute holes in canvas, old age but never has water penetrated.
Probably because the canvas sits some distance back from the pop up roof edge with rubber seal, 4-6 inches?

[cyclop]

Indeed,the canvas has a rubber tube sewn in the bottom.This then gets trapped by the ally trim,which is a straight hook shape,long side inside the van,with the canvas in the bend of the hook trapped on top of the roof upstand along with the headlining.If this canvas gets sodden,this then could be the source of water ingress.Hope the picture clarifies