Remove Water in hull

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bridaus

Senior Member
Joined
Jun 10, 2017
Messages
240
Location
USA
Vessel Name
Morgan le Fay
Vessel Make
KK 42
Let's pretend I have a bunch of water in a cored hull (I don't know if I do, I want to assume the worst and work backwards from there). If it matters, this is not balsa, it's closed cell foam.

Hauling in the winter in the Northeast would be bad, right? Freezing water in hull = damage.

Options:

1. Leave in water, pull in spring. Risk further issues, but it's been this long in the water (years) what's another three months?
2. Haul out nearby (there are NO heated buildings yet in my search very close by (NYC) but there might be further away, but now risk of travel involved) and keep heat inside boat to keep it warm (yard does offer this).

My mission/goal is to rescue the boat, so I'm very keen to be proactive here and assume the worst in order to counteract it.


Which would you do?


Second question:

Let's say you choose to haul it, and assume it has the water. What is the best way to drain a waterlogged hull?

All input and thoughts appreciated.
 
bridaus said:
Let's pretend I have a bunch of water in a cored hull (I don't know if I do, I want to assume the worst and work backwards from there). If it matters, this is not balsa, it's closed cell foam.

Hauling in the winter in the Northeast would be bad, right? Freezing water in hull = damage.

Options:

1. Leave in water, pull in spring. Risk further issues, but it's been this long in the water (years) what's another three months?
2. Haul out nearby (there are NO heated buildings yet in my search very close by (NYC) but there might be further away, but now risk of travel involved) and keep heat inside boat to keep it warm (yard does offer this).

My mission/goal is to rescue the boat, so I'm very keen to be proactive here and assume the worst in order to counteract it.


Which would you do?


Second question:

Let's say you choose to haul it, and assume it has the water. What is the best way to drain a waterlogged hull?

All input and thoughts appreciated.
Click to expand...


"2. Haul out nearby (there are NO heated buildings yet in my search very close by (NYC) but there might be further away, but now risk of travel involved) and keep heat inside boat to keep it warm (yard does offer this)."

IMO - this is not a viable option unless you are willing to remain there until it is completed. At this time you do not know if there is any damage of the extent of the damage. Subjecting that area or areas (if any) to numerous cycles of freeze thaw would be problematic.

"Let's say you choose to haul it, and assume it has the water. What is the best way to drain a waterlogged hull?"
Opening the hull by removal of glass and/or drilling pilot holes through the glass around the affected area(s) until you get to clean coring - this is a time consuming effort which often becomes a much larger area(s) then originally presumed.
Thoroughly neutralizing, drying and prepping the area for repairs is also often underestimated as it often depends greatly on the weather at the boat at the time
 
bridaus

A friend with a KK42 had water in his hull. No worries about freezing as it was in Anacortes in a heated area.

It was traced to a bad install of a depth sounder a decade or more previous. With tapping and moisture meters they were able to determine the extent of the saturation - quite large - maybe 10 to 15 sq ft? The details I'm absent, but in general they drilled the perimeter of the area, back to good core. They let it drain for a month or so

Then with a few larger holes they applied a vacuum device and sucked out more water until no more appeared. It sat for a few more months. They opened up all suspect through hulls and properly rebedded. Then they pumped in epoxy until the area would take no more.

The only way he knew the hull had a saturated area was a constant drip during a haul out for bottom work.
 
I should add: I was thinking of pulling either the lowest or the most suspect thru hull as a way to drain water... Drilling holes reserved for only if problems are found.

I think it's impossible to know whether heating from the inside would be enough to keep the hull from freezing if it had water in it... therefore I'm leaning towards the leaving it in the water even though I'm motivated to get answers sooner, I can be patient.
 
I would go with option 1 and avoid damaging the hull from freezing, particularly where the core is a key part of the hull's structural strength. Sunchaser describes well the process that may be involved.


Here is a good discussion on wet core, mostly balsa. https://downeastboatforum.com/threads/wet-core.20508/


On that site there is also discussion of a process that dries and replaces core, i am not sure if just for balsa, but i cant find it easily. If i do i will post.
 
I’d leave it in the water and work on a long term plan. Winters almost over, we’ll maybe.

We had water in the core on our last boat. The Airex core was wet as result of a grounding plate the op installed. I got nervous about the rest of the hull and I went around and drilled 1/4” holes about every 2’ about 12” up from the keel. About 50% dripped water. I opened up the wet ones and applied a vacuum to those. It took about a week to stop any drips. I left them open for another 2 months and then repaired the holes and rebedded all the thru hulls. All hull penatrations after the repairs were sold glass and expoxy.

I know another KK42 that removed all the glass over the core. They had to do it in sections. The hull couldn’t support it selve if it was all stripped at once. I think it was done in Baltimore and the cost was around $30K with a warranty for any blistering.

I saw another KK42 that hired a company that used Hotvac The core was seriously wet through out. It’s a heat and vacuum process. It took about 2 months and the cost was ~$25K. That was just for the process

Hotvac Boat Hull Drying, Osmosis Treatment, Osmocure
 
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I would think you could check for water in the hull by doing a pilot hole in the inner hull either side of the engine for peace of mind.
The refitting would probable best done out of the water if you can find a suitable covered work site. That would let you work during wet weather and help dryout the boat.
TF has several KK members that I’m sure can try to help with questions during your refit.
 
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After talking with some really knowledgeable KK folks and reading here, I decided not to take it out of water during the winter. Too much risk.
 
bridaus said:
After talking with some really knowledgeable KK folks and reading here, I decided not to take it out of water during the winter. Too much risk.
Click to expand...

That's your best course of action in my opinion as well. I know of a couple early kk42's here in the PNW that had to be 'peeled', the most extreme and costly fix. A machine like a belt sander removes all the coring and solid frp is laid up in its place. Very expensive and time consuming. ...hope that isn't required here.
 
I have dried out a boat with wet core. The process was the result of several experiments on a test panel, and then the boat itself.

0) Find the source of water ingress, or the whole exercise is pointless.

1) Map out the area that is wet with a good moisture meter (after learning how to use it).

2) Tent the boat to the waterline on hard ground or preferably pavement. Run a dehumidifier inside to dry the air in the tent.

3) Drill 5/16 holes in the skin at the wettest point or in the middle of the wet area, screw in a push-to-connect 1/8 NPT fitting, run 1/4" poly hose to a Gast vacuum pump, apply vacuum. Drill additional holes around the first one, a few feet away. Dry air will enter those holes, pick up moisture, and exit through the pump saturated. For quite a while there will be no change on moisture readings (like a couple of weeks even), then rather suddenly the moisture will be gone and it will read dry.

4) Move the vacuum to different wet areas, drilling new vent holes as necessary. Plug most of them with 1/4 push-to-connect plugs. By selecting the vacuum point, and open holes, you can steer the air towards and through the wet areas. Eventually you will dry the whole area as read on the moisture meter. By listening to a vent hole with a short length of tube held up to it, you will be able to hear the air going in if things are working right. There may be dams of resin blocking certain areas from certain directions, a bit of detective work with the moisture meter will suss this out. If water got there, you know there is an air path there. It helps to take a allen key or similar bent object, and poke laterally through the foam in 4 directions, as the hole may have been drilled in a block of foam between kerfs. Keep moving around, drilling new holes as necessary, until the entire hull reads dry. Be patient, it is a slow process.

5) Get a custom router bit made, as large as will fit in the base hole (about 3"), with a 5/16" pilot, and flanks sloped at 12:1 (the proper scarf for fiberglass). Plunge into the holes to create a shallow 12:1 cone cut in the skin. Fill the hole with West Six10, then two disks of 20 oz biax cloth with epoxy covered with peel ply. This should pretty much fill the indent. Fill over and fair. You can patch maybe 100 holes in an hour or two this way, another couple of hours to fair. Barrier coat and paint.

If a large area, this may take several months, the boat I did took 5, running 24/7. However when done, the core will be dry, not just drained. While it may sound extreme to have 100 or 200 holes in the bottom, the result is without doubt better than deskinning large areas and relaminating. Any subsequent survey will reveal a dry hull. If you just let the water run out, it will still be wet and will indicate wet.

We tried other methods such as heat, and blowing (carefully regulated!) dry air through. The vacuum pump, drawing dry air in, was the best and least dangerous and destructive method. It could be done from the inside skin and that might seem attractive as no holes would be made in the outside skin, but it was practically impossible to get to all the areas, and patching them harder still.

I found the point of ingress by carefully (!) pressurizing the core. This revealed a through hull penetration that had been backfilled with thickened epoxy, however when the epoxy was mixed, air was entrained and the resulting fill just porous enough to allow water in. To pressurize the core, a precision regulator set to 8 psi was used, backed up by a back dump regulator set at 15 psi as a safety precaution. By chance, I heard the air exiting at the faulty locations. A soapy spray would have revealed them more surely.

It should be pointed out that while freezing is a theoretical concern, in practice the water is in very thin capillary slivers in the foam kerfs and seems to do little damage, unless there is already delamination filled with big pools of water (such as in a sailboat rudder). This is from observations on seriously wet cored boats in the Great Lakes areas, stored outside with numerous freeze thaw cycles each winter for decades.
 
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Man DDW, that is some incredibly specific and helpful information.
 
Thank you DDW.


Relatively small outlay for some tools, and then it's just patience.


Nice write up of a solution that won't break the bank.
 
DDW said:
I have dried out a boat with wet core. The process was the result of several experiments on a test panel, and then the boat itself.

0) Find the source of water ingress, or the whole exercise is pointless.

1) Map out the area that is wet with a good moisture meter (after learning how to use it).

2) Tent the boat to the waterline on hard ground or preferably pavement. Run a dehumidifier inside to dry the air in the tent.

3) Drill 5/16 holes in the skin at the wettest point or in the middle of the wet area, screw in a push-to-connect 1/8 NPT fitting, run 1/4" poly hose to a Gast vacuum pump, apply vacuum. Drill additional holes around the first one, a few feet away. Dry air will enter those holes, pick up moisture, and exit through the pump saturated. For quite a while there will be no change on moisture readings (like a couple of weeks even), then rather suddenly the moisture will be gone and it will read dry.

4) Move the vacuum to different wet areas, drilling new vent holes as necessary. Plug most of them with 1/4 push-to-connect plugs. By selecting the vacuum point, and open holes, you can steer the air towards and through the wet areas. Eventually you will dry the whole area as read on the moisture meter. By listening to a vent hole with a short length of tube held up to it, you will be able to hear the air going in if things are working right. There may be dams of resin blocking certain areas from certain directions, a bit of detective work with the moisture meter will suss this out. If water got there, you know there is an air path there. It helps to take a allen key or similar bent object, and poke laterally through the foam in 4 directions, as the hole may have been drilled in a block of foam between kerfs. Keep moving around, drilling new holes as necessary, until the entire hull reads dry. Be patient, it is a slow process.

5) Get a custom router bit made, as large as will fit in the base hole (about 3"), with a 5/16" pilot, and flanks sloped at 12:1 (the proper scarf for fiberglass). Plunge into the holes to create a shallow 12:1 cone cut in the skin. Fill the hole with West Six10, then two disks of 20 oz biax cloth with epoxy covered with peel ply. This should pretty much fill the indent. Fill over and fair. You can patch maybe 100 holes in an hour or two this way, another couple of hours to fair. Barrier coat and paint.

If a large area, this may take several months, the boat I did took 5, running 24/7. However when done, the core will be dry, not just drained. While it may sound extreme to have 100 or 200 holes in the bottom, the result is without doubt better than deskinning large areas and relaminating. Any subsequent survey will reveal a dry hull. If you just let the water run out, it will still be wet and will indicate wet.

We tried other methods such as heat, and blowing (carefully regulated!) dry air through. The vacuum pump, drawing dry air in, was the best and least dangerous and destructive method. It could be done from the inside skin and that might seem attractive as no holes would be made in the outside skin, but it was practically impossible to get to all the areas, and patching them harder still.

I found the point of ingress by carefully (!) pressurizing the core. This revealed a through hull penetration that had been backfilled with thickened epoxy, however when the epoxy was mixed, air was entrained and the resulting fill just porous enough to allow water in. To pressurize the core, a precision regulator set to 8 psi was used, backed up by a back dump regulator set at 15 psi as a safety precaution. By chance, I heard the air exiting at the faulty locations. A soapy spray would have revealed them more surely.

It should be pointed out that while freezing is a theoretical concern, in practice the water is in very thin capillary slivers in the foam kerfs and seems to do little damage, unless there is already delamination filled with big pools of water (such as in a sailboat rudder). This is from observations on seriously wet cored boats in the Great Lakes areas, stored outside with numerous freeze thaw cycles each winter for decades.
Click to expand...


"It should be pointed out that while freezing is a theoretical concern, in practice the water is in very thin capillary slivers in the foam kerfs and seems to do little damage"

If freezing does no further damage the hull and you do not re-laminate the affected areas what is the purpose of drying it out?
 
Happy to relay what I learned, hopefully it will help someone. Some background: I did extensive research on different methods (and some testing). There have been some interesting ones.

Heating: this supposes that raising the vapor pressure of water will evaporate it and force it out of the core. Relies on some means of venting, and the vapor pressure of water does not increase significantly until above 160 or 170 deg which is potentially damaging. Much below that and evaporation rates are not increased much.

Vacuum alone: this lowers the boiling point of water and in theory could boil the water away at room temperature. It requires a very high level of vacuum (like 28+ in mg.) which is practically impossible to achieve with normal equipment on a leaky hull.

Microwave: some DIYs have removed the door and safety devices from a microwave oven, held it to the hull to vaporize the water. There is even some commercially available equipment. Somewhat dangerous, and still requires a means to transport the moisture outside the hull, otherwise it recondenses immediately just a foot or two over.

Strip removal: a very large yacht in Europe was salvaged by removing narrow strips of outside skin several feet apart, and a scheme constructed to feed dry air into one strip and extract it from the next one along. This worked, but was structurally difficult and expensive.

Heat and vacuum pad: this is a commercially available method, some of them require holes every three inches, no doubt because there is little circulation.

Mix with other chemicals: water can be mixed with other things, lowering the boiling point and raising the vapor pressure of the mix. The only thing I found that would lower the boiling point into a useful range was ether, impractical to use for a variety of reasons.

Almost any scheme beyond physically removing the wet core, requires air circulation to transport the moisture out. Air may not absorb much moisture unless it starts dry, then it can absorb quite a lot. In my testing, I convinced myself that once you have air circulation with dry air, nothing else was needed, or even helped much. If water can run through the core, then surely air can too. We even proved that foam core is somewhat permeable to air (this particular core at least), as some could be forced through a test panel done with solid, not kerfed core.

My initial tests used carefully regulated dried compressed air. This was disappointing at first, a few days trying here and there and progress was extremely slow. Finally it was left running for a couple of weeks in one place and to my surprise it created a large dry spot. It isn't really a puddle, but there is a reservoir of water in the foam or the kerfs, as long as any is left the moisture meter will read wet. Then the last of it is removed and suddenly it reads dry. Patience is a key ingredient. In really wet core water may run from one area to another, but otherwise is it bound by capillary and surface tension, and tends to remain where it is unless forced somehow. On this boat, we dried a large section with compressed air but ran out of time at that location, the boat was patched, relaunched, cruised for a season, then hauled in a different place to restart the process with vacuum. The dried section had remained dry.

We ended up with a random distribution of holes (guided by the moisture meter) but perhaps averaging one every 2 feet in the affected area. Some closer, some further. Structurally this is completely a non issue, but we were careful in patching them, it only takes one faulty one to undo the drying work.

I've only done this on one boat, but believe it would work well in a lot of situations. You need only a handful of fittings, manifolds, tubing (<$100), a 50 - 80 pt dehumidifier ($150), a good moisture meter ($250 and a 1 hp or so vacuum pump (<$500 used). The biggest expense is probably the yard space for a few months to do it.
 
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smitty477 said:
If freezing does no further damage the hull and you do not re-laminate the affected areas what is the purpose of drying it out?
Click to expand...

In a foam cored boat, that is a very good question. Experience suggests that the wet core doesn't typically cause much problem. Now that I own a moisture meter I entertain myself by walking through the storage yard measuring boat hulls. Quite a large percentage of them are saturated. Composite rudders with metal posts (which builds in a water ingress point) are almost 100% saturated. Yet they do not seem to fall apart or sink, even in northern freezing climates. Some kinds of foam seem to lose some structural properties when saturated, but even these don't seem to fall apart or sink at any great rate. Perhaps the primary reason is resale value, surveyors will ding a boat for wet core.

Balsa or plywood core is a different matter, it will rot and turn to dust. If caught early, I think the method I describe would work on those as well, and could save them.
 
DDW said:
In a foam cored boat, that is a very good question. Experience suggests that the wet core doesn't typically cause much problem. Now that I own a moisture meter I entertain myself by walking through the storage yard measuring boat hulls. Quite a large percentage of them are saturated. Composite rudders with metal posts (which builds in a water ingress point) are almost 100% saturated. Yet they do not seem to fall apart or sink, even in northern freezing climates. Some kinds of foam seem to lose some structural properties when saturated, but even these don't seem to fall apart or sink at any great rate. Perhaps the primary reason is resale value, surveyors will ding a boat for wet core.

Balsa or plywood core is a different matter, it will rot and turn to dust. If caught early, I think the method I describe would work on those as well, and could save them.
Click to expand...


Interesting - I have had 3 boats I owned surveyed with the results showing water in the hull. In two cases test boring showed that there was no water at all, in the third the boat was sold to a second party who had it surveyed and it showed no water in that test.

FWIW - If I really had a larger area that was saturated below the waterline I would assuredly correct the problem by removing the surface off of the affected area and re-laminating.
In the case of my 34 Mainship which had delam. in the hull top only I did use the method as described by Sunchaser above.
 
You might take a look at Carribean Sealife's blog, where he redoes the bottom of a Krogen 42 that had a wet core: the full blog is in the second link below, and here is the excerpt about the bottom job, which should provide a link to photos:
"We paid to have the entire bottom replaced; Scott just couldn’t do that monumental job on his own. The bottom was “peeled,” or sanded down to the core. Several spots of bad core were replaced, and then five new coats of fiberglass were laid back onto it. Once that was done, we followed with many coats of barrier coat, and then bottom paint (stinky, toxic stuff)."
photos:
https://photos.google.com/share/AF1...?key=RnRTN29nVV9qMG9CMjJSTUFYcTZfZ25zMG1ONlZ3

Full refit blog:
https://caribbeansealife.com/about-our-boat/refit/
 
A problem with moisture meters is they are very easy to misinterpret. The industry is notorious for erroneously condemning hulls on survey for moisture. That is why I say you must learn how to read it. I played with the meter for a few hours using various thicknesses of fiberglass panel with different with different wet substrates on the far side to see how it worked. I decided it is accurate, but requires knowledge on how and what fools it.

With wet foam core that is still adhered, and not delaminated, drying is it preferable to removing and relaminating in my opinion and also that of a couple of high end custom builders that I know. If it is delaminated for some reason (moisture by itself should not do that on a properly built boat) then de-skinning and replacement are called for. On a wood core there are many more variables, but I'd lean more towards replacement.
 
DDW said:
A problem with moisture meters is they are very easy to misinterpret. The industry is notorious for erroneously condemning hulls on survey for moisture. That is why I say you must learn how to read it. I played with the meter for a few hours using various thicknesses of fiberglass panel with different with different wet substrates on the far side to see how it worked. I decided it is accurate, but requires knowledge on how and what fools it.

With wet foam core that is still adhered, and not delaminated, drying is it preferable to removing and relaminating in my opinion and also that of a couple of high end custom builders that I know. If it is delaminated for some reason (moisture by itself should not do that on a properly built boat) then de-skinning and replacement are called for. On a wood core there are many more variables, but I'd lean more towards replacement.
Click to expand...


Removing water is one issue, Ensuring the skin is still bonded to the core is another. Thermal imaging, pulling 3" core plug or finding a surveyor with years of experience and a little brass hammer are the only ways I can think of that would be effective for that.

I agree, sometimes moisture meters tell lies. I have some explanation of these meters (lots of photos) and a few examples of Thermal images on cored structure in ....
Moisture Meter Mythology.
 
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I'd suggest you contact a Marine Surveyor in your area. The entire hull should be checked and a grid (blue painters tape) installed on the exterior with readings recorded and noted for each area. This will give you a better idea what you are facing and the extent of the intrusion which you need to stop. Additionally see if you can find a local Surveyor with an Infrared Camera. I won't comment on the repairs as they are well addressed already.
 
So even though the pvc core wouldn't rot the problem was essentially the same as if it was balsa.

I have now changed my mind about any core. previously I thought synthetic would limit the intrusion to a small area because or resin in between the blocks and there would be no rot migration. Now I see that, in that boat at least, water covered a huge area.

Any report on the source of the water?
 
Foam core does not limit water migration, as the kerfs required to make it conform create water channels throughout the hull. Builders will tell you they fill the kerfs with resin, but this is provably false, which can be verified by cutting one apart. Even infused hulls have channels in many types of cores, as the resin is too viscous to fill the tight kerfs. Many foam cores are structurally unaffected by water though, so there is no damage. If the skin is delaminated from whatever cause, then stripping and relaminating is about the only cure. Water by itself does not dissolve this bond.

Very rarely, cored boats are built by vacuum forming large foam sheets into the mold. These sheets do not have kerfs, usually only an array of holes. In that case, water migration should be severely limited. I've only seen that construction in recently built, very high end sailboats. It could be done fairly easily in a hard chine powerboat - at least over large areas - but I've not seen that either.

I mostly agree with Boatpoker's article. A moisture meter gives you some information, but not definitive information, absent other measures confirming. Thermal imaging can be incredibly revealing, but is even much more difficult to do properly than a moisture meter. If you can get conditions just right, you can see each individual block of foam, the resin in the kerfs between them, etc. Getting those conditions to happen on command it nearly impossible.
 
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After viewing those photos It appears that there was delamination is that what caused the water ingress? if so... is this caused by poor manufacturing practice, bad resin or?
 
A friend of mine for years managed QA QC for a major boat builder. As well, he traveled overseas to monitor new builds for the buyer.

His stories on what could screw up the molds, resin, the layup process, core, etc were fascinating. One thing he mentioned was the guys working in the molds and doing the layup sweat a lot dependent upon humidity and temperature. Any dripping sweat, building roof leaks, bird poo, condensation from water bottles or spilled tea/coffee onto the work in process created ideal spots for blister formation and potential delamination.
 
Ka_sea_ta said:
After viewing those photos It appears that there was delamination is that what caused the water ingress? if so... is this caused by poor manufacturing practice, bad resin or?
Click to expand...

Generally from what I understand, it's water ingress that causes delamination in this context. I'm sure twisting/structural deformation can cause it as well, but that's not the subject of this thread.

I'm also curious what caused it though, how'd the water get in?

I suspect I know some of the possible suspects:

1. Thru hulls
2. Construction technique
3. Gashes/holes
4. Osmosis?
5. Thru hulls
 
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