Moisture around windows question

firstbase · Dec 26, 2016

Grand Banks 42 shows high moisture around two cabin windows and trim. Nothing soft, a little cracking paint on the trim. Some interior staining from a leak but not too bad. Again, interior teak veneer plywood isn't soft or punky just stained. In one place the veneer has curled and lifted. Fixing that is another thread though. My question is about the moisture in the core. Can stop the problem, stop the leaks, but what is the appropriate thing to do to dry out the core? Can you dry it out? Is stopping the leak enough and it will dry out naturally or would I be better off "helping" it somehow? Thanks advance for any comments..

JDCAVE · Dec 27, 2016

Hi FB: A leaking window(s) does not necessarily mean you have water intrusion of the core. Clearly the windows involved need to be removed and rebedded, but it's something that can be achieved with some sweat equity. I did mine and it doesn't require special skills.

Cigatoo · Dec 27, 2016

There is enough info on GB windows and repairing them to keep you busy for most of the new year. Grand Banks Owner's Resources

Good luck.

firstbase · Dec 27, 2016

Thanks. I see all the threads on window rebuilding, rebedding, etc. I guess I should back out of the particular window situation and ask the question in a more general sense. If water does get into a core is there a particular method or need to let it dry out to prevent rot? Is simply stopping the leak enough? The water is in there and my impression is that the rot damage is due to long term exposure or intrusion of moisture. Does it dry out naturally even though it is somewhat airtight? Thanks!

jungpeter · Dec 27, 2016

Firstbase-a somewhat open-ended question, which likely requires the removal of the windows, and an inspection and opinion from a professional shipright to answer definitively. Issues like the moisture level, the extent of moisture intrusion, what core material, how deep are your pockets, what's your standard of repair, etc. all influence going forward.

In VERY general terms, moisture plus organic material (wood in cores, for instance) equals rot. Simply "plugging the leaks" won't mitigate the moisture issue already in the core. In time, the core will fail. Again, in general terms, drying of the core prior to sealing the leaks is best. There are some treatments that claim miracle cures for displacing and sealing wet wood. Depending on all the findings in para no. 1, they might be appropriate. The only sure cure for an abnormal level of moisture in cores is to expose it, dry it, reef out and repair any damage, and go from there.

"Helping" the core dry out is a tough issue, depending on where the boat's located. Water molecules travel from wet to dry (no surprise there!), so enclosing the affected area in a relatively dryer environment to promote that transport is paramount. Heat helps also. Vacuum bagging might help too. Simply rebedding the windows without mitigating the moisture is, IMHO, a waste of time and $$$. Ditto application of goo like Smith's Epoxy or Git-Rot.

I'm sure that last statement will unleash a volley of objection from the proponents of fast-fixes by application of a variety of snake oils to core materials in order to mitigate water absorption! Do what works best for you in your circumstance. All the best in your endeavor.

Regards,

Pete

koliver · Dec 27, 2016

FB
Is your GB a woodie? If so, a whole different approach to dealing with wet wood from that for a GRP boat.

I don't have a GB, but I think the house on a GRP G is molded GRP. Thus the wood "core" is not structural.

When you remove the window to expose the edge of the plywood, you will see whether the surface veneer is part of a 3/4" plywood wall or is a thinner, finishing piece, placed on top of whatever forms the structure. Then you can decide how easy or difficult a task you have ahead of you.

If the window opening was properly designed, there would be no way for water to enter the edge of any piece of plywood. Well, as we all know, these and most other trawlers are not properly designed and they almost all leak water into the plywood below the metal track. Now you get to design a repair that will not fail in the same way.

Some GB 42s have a drain from the track to the outside. Your re-design will need to ensure that drainage path is clear, and the highest point is below the lowest point on the track.

When you have it apart, take and post some pictures. Then we can all re-visit this repair.

Good luck

bnoft · Dec 28, 2016

While you may have a serious issue, what Koliver said above would be my 1st point of inspection. GBs do have a drain under the windows that needs be kept clear. The window tracks will collect water and if this drain is clogged, airborne dirt and pollen will do it, the water backs up in the channel and overflows into the interior. usually there is evidence of staining inside below the windows. If this is the case, it is very easy to correct, clearing the drain will stop the overflow but if excessive (any?) moisture is in the plywood core it should be dried and cleaned out. This may require the removal of the offending window. As already noted, the GB Owners website has a ton of info on this.

firstbase · Dec 29, 2016

jungpeter said:
Firstbase-a somewhat open-ended question, which likely requires the removal of the windows, and an inspection and opinion from a professional shipright to answer definitively. Issues like the moisture level, the extent of moisture intrusion, what core material, how deep are your pockets, what's your standard of repair, etc. all influence going forward.

In VERY general terms, moisture plus organic material (wood in cores, for instance) equals rot. Simply "plugging the leaks" won't mitigate the moisture issue already in the core. In time, the core will fail. Again, in general terms, drying of the core prior to sealing the leaks is best. There are some treatments that claim miracle cures for displacing and sealing wet wood. Depending on all the findings in para no. 1, they might be appropriate. The only sure cure for an abnormal level of moisture in cores is to expose it, dry it, reef out and repair any damage, and go from there.

"Helping" the core dry out is a tough issue, depending on where the boat's located. Water molecules travel from wet to dry (no surprise there!), so enclosing the affected area in a relatively dryer environment to promote that transport is paramount. Heat helps also. Vacuum bagging might help too. Simply rebedding the windows without mitigating the moisture is, IMHO, a waste of time and $$$. Ditto application of goo like Smith's Epoxy or Git-Rot.

I'm sure that last statement will unleash a volley of objection from the proponents of fast-fixes by application of a variety of snake oils to core materials in order to mitigate water absorption! Do what works best for you in your circumstance. All the best in your endeavor.

Regards,

Pete

Thanks Pete. Answers my question. I thought since there doesn't APPEAR to be significant damage that it may be as simple as stop the leak, let the moisture wick away and dry. Appearances are deceiving on a boat, at least that has been my experience. The only way to find out is to open it up. Maybe you get lucky. And then maybe....!

firstbase · Dec 29, 2016

koliver said:
FB
Is your GB a woodie? If so, a whole different approach to dealing with wet wood from that for a GRP boat.

I don't have a GB, but I think the house on a GRP G is molded GRP. Thus the wood "core" is not structural.

When you remove the window to expose the edge of the plywood, you will see whether the surface veneer is part of a 3/4" plywood wall or is a thinner, finishing piece, placed on top of whatever forms the structure. Then you can decide how easy or difficult a task you have ahead of you.

If the window opening was properly designed, there would be no way for water to enter the edge of any piece of plywood. Well, as we all know, these and most other trawlers are not properly designed and they almost all leak water into the plywood below the metal track. Now you get to design a repair that will not fail in the same way.

Some GB 42s have a drain from the track to the outside. Your re-design will need to ensure that drainage path is clear, and the highest point is below the lowest point on the track.

When you have it apart, take and post some pictures. Then we can all re-visit this repair.

Good luck

No, it is a GRP boat. Seems everyone agrees that you don't know until you disassemble and give it a look. Always a scary thing on a boat!

tadhana · Dec 29, 2016

I cannot say for sure how your GB is built. Most builders core the horizontal (deck and cabin top) surfaces but do not core the verticals. But if the wood inside is stained, it is important to find and stop the leaks or it will get much worse and that can happen quickly. This can be a big issue if/when you sell the boat.

Moisture around windows question

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