How much Core to remove?

[BigSmile]

Originally Posted by Cheechako

I have to agree. I foresee a lot of damp left in there. even if done for weeks. Your gonna need a drier.

Is bone dry, has had lots of time and the right environment to dry, so no worry there presently. Just hope I can keep her that way, as "It does not matter" yard is sticking to position, and need to move. Best way is by water.

[finefurn]

If it's wet you need to dry it out, doesn't matter how long it takes, it has to be dry. Or whatever your trying to adhere to it won't stick. If the wood fibers themselves are soft they got to go, there only compost at this point. If the wood veneers are only delaminated but still intact, saturated the plywood with a penetrating epoxy. After saturation but not yet fully cured epoxy in the fresh plywood with epoxy with a thickening agent added.

[ramblinrod]

Answers embedded in bold red.

Originally Posted by Elie

Brandon from Sheen marine, thank you very much.
So much destruction occurs when one tries to replace wet balsa core that your proposed approch is almost magical. Yet very logic and seemingly working, without major glass work.

I presume tha the bleed holes on perimeter are small (1/8. 1/4?. Yes, just a clearance hole for whatever size self tapping screws you use. (Ensure the screws are short enough they don't penetrate through the opposite skin.)

Is a 2x8 ft area is too big for this solution?. Can it be done is steps, smaller area at a time?.

Areas larger than 1 foot diameter with core that has been rotting for some time, often suffer from skin deformation (sagging), so this method may not work well. In some cases, the bottom skin can be supported to hold its proper position while the top is done. (The bottom will have to be done separately. It is possible to do 1 foot diameter sections at a time.

What about the idea of using a refrigeration vacuum pump to glue back the skins after drying?.

Vacuum bagging will work, but takes a little more equipment and skill than the average DIY has.

Have you tried your method of drying core?

Yes, I do it all the time. A wet core is undesirable, but not a terrible thing, almost all cored boats have some. A rotted or delaminated core needs to be addressed.

Does it works all the time?...

The possible solution(s) depends on the boat.

I hate peeling off perfectly good skin, especially hard to match non-skid, and avoid it unless it is just not salvageable.

For smaller areas (about 1 foot diameter) the method I posted works fine.

In some cases, larger areas can be done this way.

Forced air drying time depends on core material, thickness, and saturation.

(If one lays a piece of soggy 1/4" balsa core in bright sunshine on a dry hot day, in 24 hours it's drier than a popcorn fart. If you blow warmed forced air over the surface, it takes about the same time.)

When the core is rotted over large areas, and skins are thin, the skin is often damaged and requires replacement anyway. In those cases, I peel back the skin, remove the rotted core, and use plastic honeycomb core material.

When I prepare deck repair estimates, I offer good, better, best solutions:

Good - dry core, repair delamination.
Better - Remove skin and rotted core, dry remaining wet core and repair delamination beyond that.
Best - Remove skin and replace all rotted and wet core.

The owner can then choose the method that meets their life expectancy and budget expectations.

Racers of older boats on a limited budget often go for "Good". Life owners of newer boats with deep pockets often go for "Best". Everyone else lands somewhere depending on their sensibilities and budgets.

Thanks again.

[foufou]

Vacuum bagging might dry it out fastest. If the vacuum bag can be sealed such as to get a very good vacuum the moisture will be drawn out more quickly. And do not forget the acetone trick. Acetone and water mix but somehow evaporate faster than water. I have seen repairs done on wet fiberglass composites within 1/2 hour of soaking wet. Granted not soaked balsa. Good luck, F

[minaret]

Originally Posted by foufou

Vacuum bagging might dry it out fastest. If the vacuum bag can be sealed such as to get a very good vacuum the moisture will be drawn out more quickly. And do not forget the acetone trick. Acetone and water mix but somehow evaporate faster than water. I have seen repairs done on wet fiberglass composites within 1/2 hour of soaking wet. Granted not soaked balsa. Good luck, F

http://www.cruisersforum.com/forums/...ac-102611.html

[ramblinrod]

Originally Posted by foufou

Vacuum bagging might dry it out fastest. If the vacuum bag can be sealed such as to get a very good vacuum the moisture will be drawn out more quickly. And do not forget the acetone trick. Acetone and water mix but somehow evaporate faster than water. I have seen repairs done on wet fiberglass composites within 1/2 hour of soaking wet. Granted not soaked balsa. Good luck, F

The issue with vacuum is it tends to collapse cavities, whereas forced air opens them up, to help blow warm dry air across, and pick up the moisture.

(Vacuum bagging works great for resin infusion, but not so much for moisture extraction with skin in place.)

One can tell instantly if forced air is working because one can see the moisture come flying out of the vent holes.

I was going to post about the Methyl Hydrate (more effective than acetone) flush, before the drying stage, but was afraid people would start lighting their boats on fire.

After more thought, since I'm working on freshwater boats and most here are saltwater, this is likely an essential step to get the core to dry quickly (or even at all).

The alcohol also helps kill mold and rot.

So the process is, after one has shimmed up the centre hole...

a) Blow the initial water out.
b) With a fire extinguisher at the ready in case some idiot flicks a lit cigarette your way, pour in some Methyl Hydrate and let it sit for a few hours.
c) With the perimeter screws all out, blow it out with the shop vac.
The Methyl Hydrate helps to draw the H2O out of the wood into itself.
d) Leave the shop vac going for 48 hours to continue drying.
e) Drill some core sample holes to verify dry. If not repeat steps b, c, and d.

[ramblinrod]

Originally Posted by ramblinrod

The issue with vacuum is it tends to collapse cavities, whereas forced air opens them up, to help blow warm dry air across, and pick up the moisture.

(Vacuum bagging works great for resin infusion, but not so much for moisture extraction with skin in place.)

One can tell instantly if forced air is working because one can see the moisture come flying out of the vent holes.

I was going to post about the Methyl Hydrate (more effective than acetone) flush, before the drying stage, but was afraid people would start lighting their boats on fire.

After more thought, since I'm working on freshwater boats and most here are saltwater, this is likely an essential step to get the core to dry quickly (or even at all).

The alcohol also helps kill mold and rot.

So the process is, after one has shimmed up the centre hole...

a) Blow the initial water out.
b) With a fire extinguisher at the ready in case some idiot flicks a lit cigarette your way, pour in some Methyl Hydrate and let it sit for a few hours.
c) With the perimeter screws all out, blow it out with the shop vac.
The Methyl Hydrate helps to draw the H2O out of the wood into itself.
d) Leave the shop vac going for 48 hours to continue drying.
e) Drill some core sample holes to verify dry. If not repeat steps b, c, and d.

BTW, as always, use at your own risk, offered solely as friendly advice, no charge. Everyone is responsible themselves for ensuring they don't set their boat on fire, if you aren't skilled, hire a pro, etc.

[smacsdesign]

I lived this scenario three years ago on my Tartan 37, although little or no delam of plywood, a lot of wet plywood. Three weeks of heat lamps and a heat gun after drilling approx 300 3/16 holes to just short of lower glass. I recommend West System. The technicians at Gougeon Brothers proved to be extremely helpful with advice and technique. Go to www.westsystem.com. Attached are a few shots of my process. I was on the phone with Gougeon during work on site many times. They`re there for you if you need expert advice. The most helpful knowledge was that, after drying, when the wood fibers are heated up, they actually suck up the neat epoxy laterally into the core. The epoxy just disappeared into the holes. Hope this helps in some way.