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 Balsa Core Issues 
This is a good picture of the most extensive damage.  The dark holes on the port side indicate rotten wood where the seat box pop rivets leaked the most.  I have left the swarf from the drilled out rivet holes on the starboard helm seat.  You can see by the color of the swarf that the wood is good and gets better towards the bow.  The V berth support posts were also removed (both good, but need reinforcement because of my new permanent gas tank).
This is a good picture of the most extensive damage. The dark holes on the port side indicate rotten wood where the seat box pop rivets leaked the most. I have left the swarf from the drilled out rivet holes on the starboard helm seat. You can see by the color of the swarf that the wood is good and gets better towards the bow. The V berth support posts were also removed (both good, but need reinforcement because of my new permanent gas tank).
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Here are the homemade clean out tools.  Bent nails.  I start with the smallest bend in a drill that has a clutch and work my way up, if needed.  When I hit solid wood, the clutch slips or the nail bends.  I go on a little further to make sure that I have gotten all the rotten wood.  This does not mean that I have come to dry wood!
Here are the homemade clean out tools. Bent nails. I start with the smallest bend in a drill that has a clutch and work my way up, if needed. When I hit solid wood, the clutch slips or the nail bends. I go on a little further to make sure that I have gotten all the rotten wood. This does not mean that I have come to dry wood!
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Here is the major damage.  This is too big of an area to fix by just cleaning out the holes.  I can get an idea of the area based on the pattern of the
Here is the major damage. This is too big of an area to fix by just cleaning out the holes. I can get an idea of the area based on the pattern of the "black holes." The second hole from the left (against the chine) is also black, and there was another single bad one on the starboard side. One good thing, since I had the seat boxes and V berth posts out, I put in a permanent 23 gallon gas tank (visible under the berth). I'll start another album for that.
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Here is what removing the top laminate revealed after I cut it off with a little circular saw.  There is a rotten area right in the center caused by several leaking pop rivets right at the aft corner of the seat box.  What I had suspected is that the leak migrated towards the center of the boat.  You can see that balsa does not rot uniformly, meaning that some pieces in the parquet have rotted while others simply discolored.  The dark rectangle on the right side of the cutout was completely saturated and rotten while some of the surrounding wood was almost dry. To the left of the cutout is another dark hole that was bad.  I will have to expand the cutout to include that area.
Here is what removing the top laminate revealed after I cut it off with a little circular saw. There is a rotten area right in the center caused by several leaking pop rivets right at the aft corner of the seat box. What I had suspected is that the leak migrated towards the center of the boat. You can see that balsa does not rot uniformly, meaning that some pieces in the parquet have rotted while others simply discolored. The dark rectangle on the right side of the cutout was completely saturated and rotten while some of the surrounding wood was almost dry. To the left of the cutout is another dark hole that was bad. I will have to expand the cutout to include that area.
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Using the cut off tool shown in the prior picture, the rotten balsa was removed so that I could see where I should concentrate my next expansion of the opening. This also shows why the rotten core wasn't revealed when I surveyed the boat.  The upper area of this wood is good in many places.  The rot is patchy and does not reveal itself readily when using the
Using the cut off tool shown in the prior picture, the rotten balsa was removed so that I could see where I should concentrate my next expansion of the opening. This also shows why the rotten core wasn't revealed when I surveyed the boat. The upper area of this wood is good in many places. The rot is patchy and does not reveal itself readily when using the "bonk with a hammer" test. The resin is drawn up into the kerfs in the balsa by capillary action, forming a resin lattice that helps masks a rotten core. Much of this area was only wet/rotten on the bottom.
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Here is the scariest part.  This is looking towards the center of the boat once all of the balsa was cleaned out of the initial section.  Even though the wood is showing less damage overall, there is a spot of wet rotted wood that is basically forming a tunnel against the outer skin of the hull.  Water in this area can be pumped into other areas by the hull pounding.  I found the adhesion to be very good, so I'm hoping this doesn't go far.  But the cutout has to be expanded until I find the end of the damage.  I made quite a few cuts, expanding by about an inch at a time, which is the amount that my vibrating saw could easily remove.
Here is the scariest part. This is looking towards the center of the boat once all of the balsa was cleaned out of the initial section. Even though the wood is showing less damage overall, there is a spot of wet rotted wood that is basically forming a tunnel against the outer skin of the hull. Water in this area can be pumped into other areas by the hull pounding. I found the adhesion to be very good, so I'm hoping this doesn't go far. But the cutout has to be expanded until I find the end of the damage. I made quite a few cuts, expanding by about an inch at a time, which is the amount that my vibrating saw could easily remove.
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Here is the extent of the removed balsa.  You can see by the strips at the upper right how much I was expanding with each cut.  The moisture was mostly against the lower laminate and when I no longer found structurally compromised wood, I stopped.  Well, first I drilled some outlying holes to examine and, since they were okay, I stopped.  I decided not to remove the core to the black hole at the top of the picture because the wood in between it and my major area was okay even though wet.  The moisture reading in the wood was 37%, which is basically saturated but not dripping wet.
Here is the extent of the removed balsa. You can see by the strips at the upper right how much I was expanding with each cut. The moisture was mostly against the lower laminate and when I no longer found structurally compromised wood, I stopped. Well, first I drilled some outlying holes to examine and, since they were okay, I stopped. I decided not to remove the core to the black hole at the top of the picture because the wood in between it and my major area was okay even though wet. The moisture reading in the wood was 37%, which is basically saturated but not dripping wet.
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I put the seat box/cockpit panel back in temporarily so that I could work on other projects.  You can see that the pop rivets at the aft of the port seat box were the primary problem.  They are spaced closer together, so the moisture did more damage.  There are five or six other rivets where the balsa is bad, but those can be fixed without removing the fiberglass.  Actually, the reason I put the panel back in is to measure for the Tempress access hatch that will be covering my heater, if all goes well.
I put the seat box/cockpit panel back in temporarily so that I could work on other projects. You can see that the pop rivets at the aft of the port seat box were the primary problem. They are spaced closer together, so the moisture did more damage. There are five or six other rivets where the balsa is bad, but those can be fixed without removing the fiberglass. Actually, the reason I put the panel back in is to measure for the Tempress access hatch that will be covering my heater, if all goes well.
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Another picture of the removed balsa showing the scarf joint preparation for connecting the new epoxy/glass top laminate.  I knew that there was a reason I hated fiberglass boats.  Grinding down the glass was horrible.  Also shown is a 160 degree heating pad that is moved around over the cockpit sole to drive out moisture.  I also used heat lamps under the boat.  Be careful with those.  They can get very hot.
Another picture of the removed balsa showing the scarf joint preparation for connecting the new epoxy/glass top laminate. I knew that there was a reason I hated fiberglass boats. Grinding down the glass was horrible. Also shown is a 160 degree heating pad that is moved around over the cockpit sole to drive out moisture. I also used heat lamps under the boat. Be careful with those. They can get very hot.
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This shows how the balsa core can form little paths for water.  This piece is actually upside down from how it sat in the hull.  All of this is stained but still structurally sound.  The little hole is from being poked with my moisture meter, not termites!
This shows how the balsa core can form little paths for water. This piece is actually upside down from how it sat in the hull. All of this is stained but still structurally sound. The little hole is from being poked with my moisture meter, not termites!
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Here I have flexed the piece to show how the balsa is not solid and that in between the pieces water has passed through, stained, and maybe even mildewed.  Fortunately, there was no rot.
Here I have flexed the piece to show how the balsa is not solid and that in between the pieces water has passed through, stained, and maybe even mildewed. Fortunately, there was no rot.
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This is a piece that I coated with penetrating epoxy a week before.  Penetrating epoxy soaks in to rotten wood, but barely penetrates good wood.  This wood, although water saturated and stained, was good.  One problem with applying penetrating epoxy too soon is that it can hold moisture in.  The piece (showing the puncture wounds made by my moisture meter) was still at 26% when some of uncoated pieces that I had torn out were already down to 18%, so I have to be very patient and let this dry out.
This is a piece that I coated with penetrating epoxy a week before. Penetrating epoxy soaks in to rotten wood, but barely penetrates good wood. This wood, although water saturated and stained, was good. One problem with applying penetrating epoxy too soon is that it can hold moisture in. The piece (showing the puncture wounds made by my moisture meter) was still at 26% when some of uncoated pieces that I had torn out were already down to 18%, so I have to be very patient and let this dry out.
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When I drilled out the deck fill for the gas tank, the moisture level (in the deck) was at 37% because of leaking bow pulpit and cleats.  Five days later when I rechecked the moisture in the plug, it was down to 18%.  But I know this one.  It's only down to 18 on the surface (or as deep as my sensor pins penetrate.)
When I drilled out the deck fill for the gas tank, the moisture level (in the deck) was at 37% because of leaking bow pulpit and cleats. Five days later when I rechecked the moisture in the plug, it was down to 18%. But I know this one. It's only down to 18 on the surface (or as deep as my sensor pins penetrate.)
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So I tore off the laminate and tested the interior of the plug.  Higher than the exposed wood, but still way down from the original 37%. It is kind of amazing how fast balsa can dry out.  A stick of red alder, which I use for smoking salmon, would take several months to dry out like this.
So I tore off the laminate and tested the interior of the plug. Higher than the exposed wood, but still way down from the original 37%. It is kind of amazing how fast balsa can dry out. A stick of red alder, which I use for smoking salmon, would take several months to dry out like this.
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I am still a long way off from what my replacement balsa shows.  And I am forced to guess how the balsa is drying out between the laminates where I can't get a reading with this meter.
I am still a long way off from what my replacement balsa shows. And I am forced to guess how the balsa is drying out between the laminates where I can't get a reading with this meter.
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And the edge of the balsa still in the boat is only down 10% (in the first 2 mm).  A long way to go.  I'm thinking months in a heated garage while applying heating pads and heat lamps.  That's not practical for most boat owners.
And the edge of the balsa still in the boat is only down 10% (in the first 2 mm). A long way to go. I'm thinking months in a heated garage while applying heating pads and heat lamps. That's not practical for most boat owners.
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Psychrometer in the boat shows high humidity at first with the garage heat at 68.  It later fell to 64%.  Still, it is going to cost me $75 a month to heat the garage and dry out the boat.  (Update: two weeks later it was down to 54% in the garage.) (Another update: my heating bill was up by more than $100).
Psychrometer in the boat shows high humidity at first with the garage heat at 68. It later fell to 64%. Still, it is going to cost me $75 a month to heat the garage and dry out the boat. (Update: two weeks later it was down to 54% in the garage.) (Another update: my heating bill was up by more than $100).
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The next balsa core issue was the foredeck.  This is the worst of the bow pulpit mounts looking from inside, looking up from the V berth.  I could tell that there had been moisture on the through bolts, but I thought that it was from condensation on the inside.  That could be part of it, but there was also wet balsa surrounding these fastenings.  I bored them out from the inside to check for moisture, allowed the deck to dry out, and provided an epoxy core when refastening.
The next balsa core issue was the foredeck. This is the worst of the bow pulpit mounts looking from inside, looking up from the V berth. I could tell that there had been moisture on the through bolts, but I thought that it was from condensation on the inside. That could be part of it, but there was also wet balsa surrounding these fastenings. I bored them out from the inside to check for moisture, allowed the deck to dry out, and provided an epoxy core when refastening.
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The hole closest to the hull had to be drilled out from above.  This shows the mildew/rust that was likely caused by water in the balsa deck, not condensation on the interior.
The hole closest to the hull had to be drilled out from above. This shows the mildew/rust that was likely caused by water in the balsa deck, not condensation on the interior.
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Down the starboard side (which had the worst pulpit leak) the wire to the navigation light had been attached with stainless screws that pierced the balsa deck core.  I thought that the rusty look was from condensation.  Nope, it was water trying to get out of the balsa that had leaked into the core from the leaking pulpit mount.  The interior screw holes were all drilled oversize and I found no rot.  I will dry out, fill with epoxy, and then find an appropriate fastener system.
Down the starboard side (which had the worst pulpit leak) the wire to the navigation light had been attached with stainless screws that pierced the balsa deck core. I thought that the rusty look was from condensation. Nope, it was water trying to get out of the balsa that had leaked into the core from the leaking pulpit mount. The interior screw holes were all drilled oversize and I found no rot. I will dry out, fill with epoxy, and then find an appropriate fastener system.
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The deck hatch was removed to find saturated balsa core.  It is so wet that the wood has a waxy translucent look, kind of like rotten celery.  There was a bead of caulking around the inside and the outside of the hatch.  The outside caulking had failed (or the screws) and the inside caulking had kept the secret.
The deck hatch was removed to find saturated balsa core. It is so wet that the wood has a waxy translucent look, kind of like rotten celery. There was a bead of caulking around the inside and the outside of the hatch. The outside caulking had failed (or the screws) and the inside caulking had kept the secret.
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The wood appears to be okay, but I'm digging it out enough to replace with epoxy putty and protect the balsa core once it dries out in a few months.
The wood appears to be okay, but I'm digging it out enough to replace with epoxy putty and protect the balsa core once it dries out in a few months.
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A floor heating pad is placed on the deck with foam insulation above it.  The heater gets up to about 160-170F, which is hot enough to kill dry rot spores in the deck, but not hot enough to damage the fiberglass laminate.  It is moved every couple of hours to allow the heat cycling to drive moisture out and dry air in.
A floor heating pad is placed on the deck with foam insulation above it. The heater gets up to about 160-170F, which is hot enough to kill dry rot spores in the deck, but not hot enough to damage the fiberglass laminate. It is moved every couple of hours to allow the heat cycling to drive moisture out and dry air in.
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Moving on to other deck penetrations, these are the holes that hold the helm bulkhead in place.  They didn't appear to have leaked, but the pulpit mounts forward had leaked and the core was saturated.
Moving on to other deck penetrations, these are the holes that hold the helm bulkhead in place. They didn't appear to have leaked, but the pulpit mounts forward had leaked and the core was saturated.
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