Bad News - Wet Balsa Core

[Terra Nova]

AJ--that is wet.

What Min is saying is to keep the repair in the nonskid area so only the nonskid has to be refinished.

[taylormobile]

Check out git rot by rotdoctor.

Q & A Boats - Wood preservation, rot repair, and restoration using epoxy resin on boats, homes and log homes.

I used it on my tartan 30 and was very pleased. Sold the boat before I finished the project but was convinced it was the way to go. I drilled the holes from on top, pulled vacuum with a shop vac, pvc pipe and tubing for a 2 days, injected the epoxy and the deck was solid!

Steve

[ramblinrod]

Originally Posted by smj

It takes over 20% moisture for fungi to grow in wood.

The moisture content you are referring to is that used in the building construction industry for wood exposed to air. The actual value is > 28% tonsupport rot. This is exactly what I mean, just damp is a non issue.

In that circumstance, the "percentage" is the weight of moisture as a percent of the weight of dry wood. To measure this accurately one needs a meter with probes to penetrate the wood.

Now if one takes 100% saturated wood that has no fungus and seals it, no rot.

[boatpoker]

Originally Posted by AJ_n_Audrey

Fyi, I'm getting moisture readings way over 20 all over the soul - like 35.

Those numbers are absolutely meaningless without knowing what kind of moisture meter, the history of accuracy of that particular meter and knowing how it is calibrated. See Moisture Meter Mythology

Wood does not rot it "decays". Although fungus is widely accepted as the cause of decay there has been no scientific study of wood in a sealed de-oxygenated environment such as sealed within an FRP laminate, however there are some studies that suggest aenerobic enzymes may develop in such environments and cause decay.

i.e.
Most studies
involving bacteria associated with wood biodeterioration
have been conducted aerobically. Even
studies on obligate anaerobes have traditionally not
been conducted under strict anaerobiosis. Strict
anaerobes were thought to invade wood only in
aqueous environments. Work by Nilsson and Daniel
(1983) and Rogers and Baecker (1988) resulted in
the theory that there are anaerobic microniches in
wood structure caused by respiratory depletion of
oxygen by indigenous aerobic microorganisms. The
redox potential is lowered appreciably within the
microniches, creating zones ideally suited for anaerobes.
Collectively, these findings shed new light on
the potential role of anaerobes in the biodeterioration
of wood, even in an aerobic environment.
Tunneling was also demonstrated by Baecker and
Rogers (1991) using immunolocalization with
colloidal gold and electron microscopy. Nilsson and
Daniel (1983) and Singh et al. (1987) described a
pattern of tunneling decay in which the S3 layer of
the wall was penetrated. Penetration of wood is
typically limited to the outer 1 cm, so that transport
and dispersal of the invading organism must rely on
motility, transport by an aqueous environment, or
synergistic effects of multiple enzymes upon wood
cell wall penetration (Greaves, 1971).
Decay patterns caused by erosion.

PS. Other than a few semantic quibbles I'm with Ramblin' Rod on this one. It's all a matter of degree of moisture i.e. Mil spec for new balsa is 13%

[ramblinrod]

Originally Posted by smj

Another thought Ramblinrod, considering your business is located close to Toronto aren't you worried about water in the core freezing and causing delamination?

Nope. Wet core doesn't pose a hazard like standing water does.

The proof is, almost every 20 year old balsa cored deck has some water in it, and yet delamination is rarely an issue unless there is rot (and a void).

Show me a late 70's or early 80s C&C, Whitby, Mirage, Tartan, J, or any balsa cored hull that doesn't have elevated moisture readings? They pretty much all do, and yet guys take them out on the race course every week and pound the daylights out of them. They hold up amazingly well until something finally lets go due to total neglect for many years. Many of these boats seem like it is raining inside whenever it is outside.

Is water in core good? Nope, never. Is it the end of the world if a little water gets in? Nope. Can it become an issue if more and more water is allowed to get in year after year? Possibly. Is it a major problem if you catch it quickly and seal it up? Not likely.

[jimbunyard]

Drill a few quarter inch holes in the underside of the sole, starting the furthest distance from the place you know is wet. Use a slow speed so that you can catch the shavings.

Their condition will tell you if it needs to come out.

If there's no delamination, likely not, unless the wood is wet.

If the wood is wet, best to do the whole thing at once.

Minaret's route is by far the simplest and strongest method of attack for this; to do it from the bottom is madness.

This may appear intimidating but it's not really very hard. Looks like you have an area about 3' x 7', materials should be around 600.00, even less if you shop around and use the right materials.

Good quality, iso polyester resin is the best choice here, with a layer of biaxial or mat on the inner skin as a bonding layer, and 2-4 layers (depending on weight) of biaxial as the new skin.

1/2" coosa board is good (or whatever thickness is there now), but the embedded reinforcement in it is not really necessary in this application; any 5-6 lb/cu.ft. or greater PVC foam will work, at a moderate price savings. You can also use honeycomb, though I never have, for even less cost, though the area is so small there isn't much difference in the three...

If you do this yourself, don't be tempted to try and put a whole piece of core in at once. Better to put it in in sections so you can get the best adhesion between the core and the inner skin, and fair the top later if necessary.

The way I approach it, though some may not agree, is to cut the core into uniform squares on a table saw, say 2 or 3 inches on a side, and lay them like tile into a bed of resin thickened to about the consistency of mayonnaise, pressing them firmly in place and skimming the excess off with a putty knife, guarantying no voids between the core and the skin.

With polyester resin, in good weather, depending on the technique you choose, should take about three days, start to finish. With epoxy, maybe 4 or 5.

[Three Sisters]

Originally Posted by AJ_n_Audrey

Thanks, good input. Because of the extremely tight conditions under the sole, it may or may not be possible to cut and remove the belowdecks portion. I'll just have to evaluate. An easier approach may be to cut with a dremel along the edge of the non-skid on the topside of the sole, replace balsa with other media, glass, replace, try to make it look pretty.

Sounds good. If the cuts can be made where a moulding or trim piece could be applied after everything is sealed up..maybe save you a headache.

[ramblinrod]

Originally Posted by jimbunyard

Drill a few quarter inch holes in the underside of the sole, starting the furthest distance from the place you know is wet. Use a slow speed so that you can catch the shavings.

Their condition will tell you if it needs to come out.

If there's no delamination, likely not, unless the wood is wet.

If the wood is wet, best to do the whole thing at once.

Minaret's route is by far the simplest and strongest method of attack for this; to do it from the bottom is madness.

This may appear intimidating but it's not really very hard. Looks like you have an area about 3' x 7', materials should be around 600.00, even less if you shop around and use the right materials.

Good quality, iso polyester resin is the best choice here, with a layer of biaxial or mat on the inner skin as a bonding layer, and 2-4 layers (depending on weight) of biaxial as the new skin.

1/2" coosa board is good (or whatever thickness is there now), but the embedded reinforcement in it is not really necessary in this application; any 5-6 lb/cu.ft. or greater PVC foam will work, at a moderate price savings. You can also use honeycomb, though I never have, for even less cost, though the area is so small there isn't much difference in the three...

If you do this yourself, don't be tempted to try and put a whole piece of core in at once. Better to put it in in sections so you can get the best adhesion between the core and the inner skin, and fair the top later if necessary.

The way I approach it, though some may not agree, is to cut the core into uniform squares on a table saw, say 2 or 3 inches on a side, and lay them like tile into a bed of resin thickened to about the consistency of mayonnaise, pressing them firmly in place and skimming the excess off with a putty knife, guarantying no voids between the core and the skin.

With polyester resin, in good weather, depending on the technique you choose, should take about three days, start to finish. With epoxy, maybe 4 or 5.

Similar methodology that I use for core replacement with the exception of:

1. Larger pieces where possible, (especially to follow compound curves, without sharp bends.)

2. Honeycomb, cut with a utility knife. (Faster and less mess).

3. Polyester. (Faster, less risk of fire, lower risk of allergic reaction / sensitization, greater gelcoat compatibility, lower cost.)

[ramblinrod]

Originally Posted by AJ_n_Audrey

Fyi, I'm getting moisture readings way over 20 all over the soul - like 35.

These readings are meaningless on their own. What does dry core and saturated core read with this same meter, under same conditions? If 15 and 45 repectively, the areas reading 35 or higher may be an issue. I recommend drilling some core samples (just to and not thru lower skin). Again, if the core is missing (problem), saturated, water squirts out when squeezed lightly (peel, dry, and cover, or replace), slightly damp when pressed hard against a paper towel (not likely an issue).

Just about every leaky chain plate cover (unless left for like 10 years or more)will read very high, and sound dull for about 2" around the hole. It will read elevated and sound solid for up to 24" around the hole. Only the dull sounding section of core needs to come out (and can usually be dug out from the hole without removing any skin).

One can replace all "elevated moisture" but "sound" core if they wish to, but it isn't necessary.

[smj]

So how do I know that:
The core is within the percentages where you know it won't rot.
There is no chance of the moisture traveling and affecting adjacent core, therefore compounding the problem.
There is no chance of the wet core going through freezing and thawing cycles that could cause delamination.
The wet core is just as structurally sound as it was when dry.
Is there a way to positively assure me these issues won't occur or am I relying on an educated guess possibly Hail Mary?

[Colin A]

Originally Posted by boatpoker

Those numbers are absolutely meaningless without knowing what kind of moisture meter, the history of accuracy of that particular meter and knowing how it is calibrated. See Moisture Meter Mythology

Wood does not rot it "decays". Although fungus is widely accepted as the cause of decay there has been no scientific study of wood in a sealed de-oxygenated environment such as sealed within an FRP laminate, however there are some studies that suggest aenerobic enzymes may develop in such environments and cause decay.

i.e.
Most studies
involving bacteria associated with wood biodeterioration
have been conducted aerobically. Even
studies on obligate anaerobes have traditionally not
been conducted under strict anaerobiosis. Strict
anaerobes were thought to invade wood only in
aqueous environments. Work by Nilsson and Daniel
(1983) and Rogers and Baecker (1988) resulted in
the theory that there are anaerobic microniches in
wood structure caused by respiratory depletion of
oxygen by indigenous aerobic microorganisms. The
redox potential is lowered appreciably within the
microniches, creating zones ideally suited for anaerobes.
Collectively, these findings shed new light on
the potential role of anaerobes in the biodeterioration
of wood, even in an aerobic environment.
Tunneling was also demonstrated by Baecker and
Rogers (1991) using immunolocalization with
colloidal gold and electron microscopy. Nilsson and
Daniel (1983) and Singh et al. (1987) described a
pattern of tunneling decay in which the S3 layer of
the wall was penetrated. Penetration of wood is
typically limited to the outer 1 cm, so that transport
and dispersal of the invading organism must rely on
motility, transport by an aqueous environment, or
synergistic effects of multiple enzymes upon wood
cell wall penetration (Greaves, 1971).
Decay patterns caused by erosion.

PS. Other than a few semantic quibbles I'm with Ramblin' Rod on this one. It's all a matter of degree of moisture i.e. Mil spec for new balsa is 13%

Have to agree moisture meters can be a bit trickier to use then one might think. Pro Boat has had a few articles on just that. I have seen a few with readings that weren't close to reality when we opened the boat up. If you know there is rot by the pedestal start there were you know your going to have to hack the boat up and sample a few inches away to get an idea how far it extends.

[ramblinrod]

Originally Posted by smj

So how do I know that:
The core is within the percentages where you know it won't rot.
There is no chance of the moisture traveling and affecting adjacent core, therefore compounding the problem.
There is no chance of the wet core going through freezing and thawing cycles that could cause delamination.
The wet core is just as structurally sound as it was when dry.
Is there a way to positively assure me these issues won't occur or am I relying on an educated guess possibly Hail Mary?

The reason one hires a pro with experience dealing with these issues is so that they don't have to worry about it or repair it themselves.

When I am requested to inspect or repair suspected wet core, I prepare good, better, best options and present them to the customer, advising risks and setting expectations.

There is no way on a forum to guarantee total success, based on the work of others, having unknown skills and experience.

My primary position is 100%, "Before initiating extensive / expensive repairs, determine how wet, how much damage, and if core replacement is even necessary."

If you cannot ascertain on your own with certainty, consider hiring an experienced pro (vs a schmo who takes money for work they are unqualified to perform) to assess for you. It may cost you a little but save you thousands in material and time. Also it may help you decide whether your skill level is or isn't sufficient to perform the work yourself.

[boatpoker]

Originally Posted by ramblinrod

The moisture content you are referring to is that used in the building construction industry for wood exposed to air. The actual value is > 28% tonsupport rot. This is exactly what I mean, just damp is a non issue.

In that circumstance, the "percentage" is the weight of moisture as a percent of the weight of dry wood. To measure this accurately one needs a meter with probes to penetrate the wood.

Now if one takes 100% saturated wood that has no fungus and seals it, no rot.

FYI. Mil spec for new plywood used in marine construction is 14% max.

[smj]

Originally Posted by ramblinrod

The reason one hires a pro with experience dealing with these issues is so that they don't have to worry about it or repair it themselves.



When I am requested to inspect or repair suspected wet core, I prepare good, better, best options and present them to the customer, advising risks and setting expectations.



There is no way on a forum to guarantee total success, based on the work of others, having unknown skills and experience.



My primary position is 100%, "Before initiating extensive / expensive repairs, determine how wet, how much damage, and if core replacement is even necessary."



If you cannot ascertain on your own with certainty, consider hiring an experienced pro (vs a schmo who takes money for work they are unqualified to perform) to assess for you. It may cost you a little but save you thousands in material and time. Also it may help you decide whether your skill level is or isn't sufficient to perform the work yourself.

You didn't answer my question, how do you determine how wet and how much damage? Is it an educated guess or is there no sure fire way other than cut into the skin and then determine the scope of the job? Is there a meter you can use that will give accurate measurements of the percentage of water in the core or are you taking an educated guess with the amount of moisture showing up on a napkin?

[Terra Nova]

Originally Posted by smj

...how do you determine how wet and how much damage?...

Drill core samples and squeeze them between your fingers. If your fingers are wet replace the core.