Why is my Hull not drying out?

[GregOddity]

I really think you are wrong. If you dry the atmosphere the hull is enclosed in the moisture will migrate from the hull. Otherwise how could you air dry timber, it would stay wet by your measure?

The trees, are a phenomenon moving water to incredible heights, for that they developed and adapted specific conduits, that use the properties of the water membrane forcing it ever up until gravity action, finally intervenes on the water Colum such created and prevents it from reaching any higher. It also has to do it evaporation in the leaves that creates a negative water vapor pressure that develops in the surrounding cells of the leaf. Once this happens, water is pulled into the leaf from the vascular tissue
Having said that, should you place a small length of wood with the grain in water, you will see the water move through, albeit slower then on a living tree, until it reaches the top end.
This will not happen in a hull as fiberglass hulls are affected by a different phenomenon of capillarity and pressure (weight of the hull on surrounding water) forcing water into ever smaller spaces until it is trapped. The other phenomenon you have inside the fiberglass is the development of chemical reactions inside the hull itself due to minuscule amounts of uncured resins reaction with salt water. If you air dry it and seal it you will be sealing the moisture inside.
This article can provide you with a simple but effective view on the issue and how to deal with it.
Dehumidifiers are just used to guarantee a hull as dry as possible environment to work with.

http://www.pbo.co.uk/expert-advice/osmosis-the-professional-treatment-26525

 

[Vertor]

The IR by itself, will not be able to heat any compound trapped in your hull to boiling point. It would need to reach boiling point to turn into steam and expand enough to escape the hull. As it goes the only good solution seems to be to lower the boiling point of the liquid by using a vacuum and heat it up to above that value to volatise any compound and having the vacuum “suck it “out. Air drying will not dry any of the compounds created inside the hull and any water trapped there will remain trapped as well. There may be a marginal improvement but only marginal. Your options would be to seek professional treatment for the drying with a vacuum heating system. Or doing it DIY by buying a small vacuum pump and a silicone heated mat.

Greg, thank you for this link and the info. I will take a look. Appreciated.
There is a channel on YouTube were a DiY’er is doing that to his boat, “sail Life” that is the option he ended up using and its much more cost effective. I believe £ 200 ish for the pump and £250 for silicone heated pad.
https://www.youtube.com/watch?v=OXrCBKSAlqM Description of the osmosis

DIY Osmosis VAC System
https://www.youtube.com/watch?v=SfLZEiBiDU4&index=40&list=UU5xDht2blPNWdVtl9PkDmgA

 

[GregOddity]

Had another meter reading done today using a Soverign meter, the reading was far lower than that on my Tramex.

you will probably get different readings with different meters, I'm afraid. Non-destructive methods are just as precise as they are. In wood industries they use 2 different methods, they use meters then they drill a sample and evaporate the sample inside a chamber to be able to measure more precisely the amount of water present.

 

[Vertor]

All the osmosis treatment cases I know of used dehumidifiers. In one case a boat went ashore and the side was destroyed. Set out a sheet of plastic under the boat. tape plastic to the hull above the waterline, and to the floor plastic. Put two or three dehumidifiers inside the tent, and tape up the 'full container' switch, put hoses on the outlets, to the outsode world. In the case of the damaged 32ft FV I think it took three months, then they moulded a new side and glassed it in. Boat still 100% thirty years on.

Thanks Fisherman. I think we have managed to get a lot of the "clean" moisture out of the Hull with heat and air, I suspect your method would have been faster than ours. I do suspect the remaining fluid is going to be much harder to budge.

 

[GregOddity]

No worries, Im going to be doing the same to mine

 

[fisherman]

The trees, are a phenomenon moving water to incredible heights, for that they developed and adapted specific conduits, that use the properties of the water membrane forcing it ever up until gravity action, finally intervenes on the water Colum such created and prevents it from reaching any higher. It also has to do it evaporation in the leaves that creates a negative water vapor pressure that develops in the surrounding cells of the leaf. Once this happens, water is pulled into the leaf from the vascular tissue
Having said that, should you place a small length of wood with the grain in water, you will see the water move through, albeit slower then on a living tree, until it reaches the top end.
This will not happen in a hull as fiberglass hulls are affected by a different phenomenon of capillarity and pressure (weight of the hull on surrounding water) forcing water into ever smaller spaces until it is trapped. The other phenomenon you have inside the fiberglass is the development of chemical reactions inside the hull itself due to minuscule amounts of uncured resins reaction with salt water. If you air dry it and seal it you will be sealing the moisture inside.
This article can provide you with a simple but effective view on the issue and how to deal with it.
Dehumidifiers are just used to guarantee a hull as dry as possible environment to work with.

http://www.pbo.co.uk/expert-advice/osmosis-the-professional-treatment-26525

Well I may have to think again, but one point: It isn't the weight of the hull on the water, it is the pressure of the water at the relevant depth. I saw the water coming from the hoses attached to the dehumidifiers in the case of the damaged hull.

 

[GregOddity]

Well I may have to think again, but one point: It isn't the weight of the hull on the water, it is the pressure of the water at the relevant depth. I saw the water coming from the hoses attached to the dehumidifiers in the case of the damaged hull.

I do not doubt you in any way, and dehumidifiers really have a place in the first stage of repairing osmosis in a hull, any small microscopic cracks on the surfaces holding water need to be heated and evaporated as you would not even get a proper reading on the hull otherwise, it’s just the deeper part of the problem inside the GRP that needs to be addressed with vacuum as by then no evaporation will be possible unless you would heat up the hull to dangerous temperatures. The vacuum is a workaround, by lowering the boiling point, its easier to volatise the compounds. i'e. if the boiling point is lowered to 50 degrees Celsius by using vacuum (lowering atmospheric pressure) then applying 100 degrees will guarantee steam phase and the vacuum can them suck out the smaller particles.

 

[Hoolie]

I think you're possibly missing two points

1 The blistering is caused by acids that have formed in the laminate. The acid has to be neutralised, not just dried out

2 Once the new outer waterproof covering has been put on the hull, it will continue to dry out from the interior. No need to get the hull drier than the level compatible with coating with epoxy/polyester.

 

[fisherman]

I think you're possibly missing two points

1 The blistering is caused by acids that have formed in the laminate. The acid has to be neutralised, not just dried out

2 Once the new outer waterproof covering has been put on the hull, it will continue to dry out from the interior. No need to get the hull drier than the level compatible with coating with epoxy/polyester.

Given Gregg's assertions, how can that happen?

 

[GregOddity]

I think you're possibly missing two points

1 The blistering is caused by acids that have formed in the laminate. The acid has to be neutralised, not just dried out

2 Once the new outer waterproof covering has been put on the hull, it will continue to dry out from the interior. No need to get the hull drier than the level compatible with coating with epoxy/polyester.

Yes, I missed these two points for various reasons. The acid was not being addressed and the treatment is correct. Any base wash will essentially neutralise it.
The second point is a bit more contentious. There are various view on the subject that I can side with to some extent.
Economics comes into play in a major role and therefore creating a level at which science bends to common sense.
Scientifically, nothing inside that hull will dry out ( it would have to evaporate and escape ) It can react and crystalize or assume any number of other possible forms and shapes but always within the confined space it finds itself trapped in. There would also be no promotor or catalyst for movement from the inside to the outside, (temperature? Pressure?) Laws of nature are inflexible on that I’m afraid. There needs to be a cause for the “wetness” inside layers of fiberglass and resins to “want or need” to escape.
The hull will be back on the water, causing lower temperature on the hull and therefore inhibiting even more any possibility of evaporation, then the inside of the hull will be painted. Most modern paints are more effective at being impermeable then the composite resins. Which would mean a total seal.
But the great take away from what you say is this
“ No need to get the hull drier than the level compatible with coating with epoxy/polyester” at a certain stage, economics comes into its own and time is money as well so if the level it’s low.. seal it up for another 30 years by all means.
On the other hand, I don’t think any boat has ever sunk from osmosis.

Our hull will be dried until the meter shows acceptable levels, as dry as possible but not looking for absolute, and for that I would have to drill the hull in hundreds of places an evaporate the moisture to be able to measure it somewhat more precisely. So at which point is good enough good? There is the question. Meter with low humidity readings? Good enough for me and Seal it up Scotty.

 

[Topcat47]

I have a 50 year old Nic 26. Without going too deeply into it, when I had the hull peeled and coated, the hull had areas that did not dry, even under the hot vac pads. It was due to water collecting in voids. when we drilled into the voids, gallons of water gushed out and the drying process was duly completed in short order. The voids had been filed with foam originally but not totally sealed and water found its way in. The "foam" dissolved into the mushy water that poured out when we drilled into the keel. 6mm holes were big enough to drain them.

 

[GregOddity]

I have a 50 year old Nic 26. Without going too deeply into it, when I had the hull peeled and coated, the hull had areas that did not dry, even under the hot vac pads. It was due to water collecting in voids. when we drilled into the voids, gallons of water gushed out and the drying process was duly completed in short order. The voids had been filed with foam originally but not totally sealed and water found its way in. The "foam" dissolved into the mushy water that poured out when we drilled into the keel. 6mm holes were big enough to drain them.

Wich is the reason I did not buy an Ettap that showed a BIG beep, needle on the red on the meter. I was afraid of all the water that could be inside the foam, Love the boats.. I'm a "coward" for any "mushy" foam jobs.

 

[Flynnbarr]

My inch thick Hull wasn’t dry after a year on the hard down south after being peeled,washed ,steamed. We lost count in the end!
I spoke to surveyors,yards,trawled the internet etc.Adrian Baker of Advanced Osmosis Technologies was helpful.
It had to have the hot vac treatment.

 

[Vertor]

I have a 50 year old Nic 26. Without going too deeply into it, when I had the hull peeled and coated, the hull had areas that did not dry, even under the hot vac pads. It was due to water collecting in voids. when we drilled into the voids, gallons of water gushed out and the drying process was duly completed in short order. The voids had been filed with foam originally but not totally sealed and water found its way in. The "foam" dissolved into the mushy water that poured out when we drilled into the keel. 6mm holes were big enough to drain them.

Thank you Topcat. Not heard of that before. I need to chaeck.

 

[Vertor]

My inch thick Hull wasn’t dry after a year on the hard down south after being peeled,washed ,steamed. We lost count in the end!
I spoke to surveyors,yards,trawled the internet etc.Adrian Baker of Advanced Osmosis Technologies was helpful.
It had to have the hot vac treatment.

Yes Adrian is very good he peeled our hull. The "experts" at our yard told me not to peel the hull, I think they had seen it done poorly in the past. They were though very impressed with Adrian's work.

 

[fisherman]

Attitudes have changed a lot over 25 years, during which my boat continued to have osmosis. This year the insurance company (Coleman) said they were not worried about the osmosis 'as described' and that more damage could be done with peeling and substandard recoating. My question would be, had I not just sold the boat (after a survey), what about spot treatment, the surveyor suggested an angle grinder would tend to polish the substrate, but use soda blasting. Could you then over paint the remaining gel with epoxy, I know people who have

 

[Fr J Hackett]

I can think of two reasons:

There may be a pocket s) of water inside the boat that needs to be drained.

Once you break the link between the water at the surface and water trapped inside the laminate a very different drying process occurs. In the former the water is continually wicked from inside as there is a pressure gradient, osmotic pressure. Once the outside is allowed to become completely dry then the water inside has to be forced out and the most reliable way of doing that is by vacuum.