Acetone to Aid in drying wet plywood core

[cburger]

Cabin top on Moondance has wet plywood core and have been using vacuum pump in an attempt to extract as much water as possible also working on stopping water Ingress so I don't spend my wheels with l in the wood. I'm wondering if any of the members have had any experience with this methodology. Ultimately I am going to try to get core as dry as possible and then use vacuum pump to draw in penetrating epoxy

[Celestialsailor]

How large are the affected areas?

[SailingHarmonie]

Acetone is not magic. You need to put enough into the wood that you physically flush out the water. In other words, liquid acetone needs to go in and liquid needs to come out. Acetone is good at this because it is infinitely miscible with water, and has a very low viscosity. Its high vapor pressure and low heat of vaporization means that you can pull the residual acetone out with vacuum after you flush out the water. Acetone also is compatible with most epoxy formulations, so if you don't get absolutely all of it out, it (usually) isn't a disaster for the cure.

HOWEVER...

Be VERY aware that acetone is extremely flammable. If you use a shop vac or electric vacuum pump to pull acetone vapor out of your deck the chances for a fire or explosion are VERY high. Do not take this lightly. I know personally one sailor who damn near killed himself cleaning a tank with acetone. He still wears a beard to cover the scars.

This stuff is MUCH more flammable than gasoline. I would say its just not suitable for use by amateurs, because some people will jump all over me. But it is not.

[osprey877]

Practical Sailor has a good article on wet core repair that Google will find for you if you haven’t read it. It suggests Gorilla Glue may be superior to epoxy because of the difficulty in reducing the moisture content to a level that will work with epoxy. Anyways, worth reading if you haven’t already.

[stormalong]

I have seen denatured alcohol used to dry out a foam core. The theory is that alcohol, dilutes the water and takes it with it as it evaporates. Acetone and water don't mix so the acetone would evaporate and leave the water behind.

I'm no expert on this. Suggest that you consult an expert before you put any highly flammable solvent in any type of core.

[Bill O]

Acetone is extremely soluble in water.

[Spot]

Love the pump and trap setup CBurger! Wish I had that much Gast hp working on my keel dry-out.

Old school nail polish remover is acetone + water.

[stormalong]

My mistake, so acetone is soluble in water.

I still would not want to soak a core in highly flammable liquid.

[Lake-Effect]

I also have a little wet plywood core to deal with, fortunately not in a critical area, and I have no deck softness yet.

It's my plan to, at the end of the season, remove a bunch of hardware, maybe drill some drain holes under the deck, protect the deck from rain and snow, and let a long winter hopefully do most of the drying for me. I might initially encourage the drying with some alcohol poured/injected into deck holes.

If the core is still wet after a winter's worth of drying... I dunno. Something more drastic, I guess.


Edit - Practical Sailor links
https://www.practical-sailor.com/boa...ix-rotten-core
https://www.practical-sailor.com/boa...core-panel-fix
https://www.practical-sailor.com/boa...rom-underneath

[Chotu]

I’m not sure what type of vacuum pump you are using, I’m not sure how much vacuum you can actually draw.

But I know when I built my boat, you could use the vacuum pump to dry things that were damp very easily. It would pull down to the point where the water would boil off and come out as water vapor.

There is also enough heat on such a large surface in most cases that the water doesn’t freeze when you pull it out. Nor is the vacuum pump usually strong enough to make it freeze instead of get extracted as water vapor.

So just the vacuum itself goes a long way toward drying it.

The solvent idea is a little weird because the solvent will boil off before the water does. So I’m not sure what good it’s going to do under vacuum. You’re going to pull all of the solvent out before the water comes out if it’s under vacuum

[Adelie]

I would expose one side of the core and use heat lamps on the exposed with insulation on the back side or heating pads on the back side. Then wait a week or two.

If using heating pads make sure it doesn’t have an auto-off function.

[wyb2]

Hey neat, something I actually have some experience with. Not the acetone, that seems a little sketchy. But drying out core with vacuum.

Originally Posted by Chotu

...
But I know when I built my boat, you could use the vacuum pump to dry things that were damp very easily. It would pull down to the point where the water would boil off and come out as water vapor.
...

^this. The boiling point is key.

You don't have enough vacuum in that photo to accomplish much. You might suck out excess liquid water, but the water that is saturated into the grain of the wood isn't going anywhere. You need close to 28 inHg of vacuum in hot sunny weather, more in cooler weather. 28 brings the boiling point of water to about 90 deg F. If it's 85 outside with the sun beating down, you can make progress. 29 inHg brings the boiling point to about 75 F. From there it drops dramatically, at 29.75 the boiling point of water is the freezing point of water (32 F).

https://www.engineersedge.com/h2o_boil_pressure.htm

The oiled vacuum pumps from amazon or wherever can pull this vacuum, but can't overcome much leakage. And they do mist a little oil, so you don't really want to run them inside, and a little breeze is helpful when they are outside.

https://a.co/d/606EYi1

Sealing up the area to get sufficient vacuum can be tough. Depending on the construction of the deck, it might be near impossible. On the upside, if you can pull 28 inHg, that's probably a good indicator if there are deck leaks.

But it can work. I got a huge portion of the deck on my little 25 footer from pegging the moisture meter to reading 10%. (note, it wasn't this side, I think I'm at about 25 inHg in the picture, weather turned before I got to the bottom of that.)

[pbmaise]

I suggest using the sun. Carefully. If you first add black plastic directly atop the deck then a clear plastic above with an air gap, you would get the deck hot enough on a summers day to more than cook an egg.

[Capt Gill]

When the moisture is removed, is there not an issue with the salt that is left?

[Dalestr]

Acetone can dissolve, soften cured polyester resin so not for this use. Exaggerated Solar heating can do harm too as the expansion of GRP vs core is an issue, causing tearing of what bond exists to plywood core, even a dry core.