Core Questions

[Randy Capstick]

The Balsa core on the cabin roof of my CD28 is wet (in patches) from the companionway to just aft of the mast. The problem originated with a poorly installed dodger. This was reported by surveyor using a moisture meter last summer and confirmed last week by drilling a few test holes. I think trying to dry the balsa without removing the outer deck skin would take forever and may not get all the core dry.

Does anyone have any suggestions on the best way to cut/remove the outer skin? Also, does anyone know if the balsa core is continuous from the cabin top around the bend to the vertical side cabin walls, or are there areas of solid glass at the bend?



rbcapstickNOSPAM@sympatico.ca

[Ken Coit]

I am contemplating removing the outer skin and it seems to me that it would be less destructive to drill holes every few inches until you hit dry core material, gouge out the wet and then fill. Is there a reason not to do this?

Keep on sailing,

Ken
S/V Parfait
Raleigh, NC

The Balsa core on the cabin roof of my CD28 is wet (in patches) from the companionway to just aft of the mast. The problem originated with a poorly installed dodger. This was reported by surveyor using a moisture meter last summer and confirmed last week by drilling a few test holes. I think trying to dry the balsa without removing the outer deck skin would take forever and may not get all the core dry.

Does anyone have any suggestions on the best way to cut/remove the outer skin? Also, does anyone know if the balsa core is continuous from the cabin top around the bend to the vertical side cabin walls, or are there areas of solid glass at the bend?

parfaitNOSPAM@nc.rr.com

[Nathan Sanborn]

I tried the drill and fill technique on my side decks. I would not do it again. It is extremely difficult to really get the wet nasty balsa out of those little holes, and you can't reach very far under the skin through those holes, which necessitates MANY holes. Finally, it is very difficult to really get a good fill through the holes without any voids under the skin. Even heating the epoxy didn't work nearly as well as the descriptions I had read had lead me to believe.

Oh, and doubly finally, solid epoxy makes for heavy decks!

It will certainly work, especially if the area is VERY limited, but I would definitely lean toward just cutting open the deck next time.

Good luck.

I am contemplating removing the outer skin and it seems to me that it would be less destructive to drill holes every few inches until you hit dry core material, gouge out the wet and then fill. Is there a reason not to do this?

Keep on sailing,

Ken
S/V Parfait
Raleigh, NC

The Balsa core on the cabin roof of my CD28 is wet (in patches) from the companionway to just aft of the mast. The problem originated with a poorly installed dodger. This was reported by surveyor using a moisture meter last summer and confirmed last week by drilling a few test holes. I think trying to dry the balsa without removing the outer deck skin would take forever and may not get all the core dry.

Does anyone have any suggestions on the best way to cut/remove the outer skin? Also, does anyone know if the balsa core is continuous from the cabin top around the bend to the vertical side cabin walls, or are there areas of solid glass at the bend?

Dasein, Triton 668
nathan@dasein668.com

[John Doyle]

I tried the drill and fill technique on my side decks. I would not do it again. It is extremely difficult to really get the wet nasty balsa out of those little holes, and you can't reach very far under the skin through those holes, which necessitates MANY holes. Finally, it is very difficult to really get a good fill through the holes without any voids under the skin. Even heating the epoxy didn't work nearly as well as the descriptions I had read had lead me to believe.

Oh, and doubly finally, solid epoxy makes for heavy decks!

It will certainly work, especially if the area is VERY limited, but I would definitely lean toward just cutting open the deck next time.

Good luck.

I am contemplating removing the outer skin and it seems to me that it would be less destructive to drill holes every few inches until you hit dry core material, gouge out the wet and then fill. Is there a reason not to do this?

Keep on sailing,

Ken
S/V Parfait
Raleigh, NC

The Balsa core on the cabin roof of my CD28 is wet (in patches) from the companionway to just aft of the mast. The problem originated with a poorly installed dodger. This was reported by surveyor using a moisture meter last summer and confirmed last week by drilling a few test holes. I think trying to dry the balsa without removing the outer deck skin would take forever and may not get all the core dry.

Does anyone have any suggestions on the best way to cut/remove the outer skin? Also, does anyone know if the balsa core is continuous from the cabin top around the bend to the vertical side cabin walls, or are there areas of solid glass at the bend?

We just finished replacing balsa. We used a skill saw to cut the top layer of glass, dug out the balsa & replaced it with end grain cedar, filling in all the areas around the pieces with epoxy so if one ever gets wet it won't spread.
John CD31 #18 & CD25 #69



redzeplinNOSPAM@yahoo.com

[John Ring]

Randy,

I drilled & dried a few square feet of cabin top on my CD28. It took many months to dry, even with occasional use of a heat gun. This was wet core, not yet decomposing.

The drill & dry technique is fairly easy to apply, but you never really get a good look at all of the balsa, relying on your test holes & wood chips to guage moisture content instead. The repair looks great now, but there is always the "what if I missed some" bug in the back of my head. Only time will tell.

The link below will show you more of what I did.

Best,
John Ring
CD28 Tantalus</I>
Beverly, MA




Tantalus Core Project
[img]http://www.yachttantalus.com/TantalusIm ... rn%201.jpg[/img]

[Steve Laume]

Just curious, but it seems a good time to ask. How hard is it to remove the deck skin once it is cut? It seems like it would be easy in areas where the core is wet or rotted but if you cut back to solid material isn't it bonded to the skin? If you do have this job ahead of you one of the small cordless circular saws with a very thin blade seems like it would be perfect for cutting carefully and controlled in tight places. My hats off to anyone who tackles this problem, Steve.

[Joel]

I had to recore quite a bit of deck on my Ty. You're dead on about removal of the skin. Where it's delaminated or rotten, it separates easily. While peeling up the skin, I had to use a chisel to separate some of the balsa from the fiberglass. I used a Rotozip the the Zipmate attachment basically converting it into a small circular saw. I set the depth for about 3/8" and removed the skin from the entire aft deck. The entire area was mushy. I couldn't get closer than an inch to any of the teak, so there were spots where the rot extended beyond my cut, some where perhaps I cut too far. I used marine plywood as the new core. Since it had a slight curve, I cut it into two sections, filling any gaps with thickened epoxy. I did a lousy job attempting to fair the skin, so a friend with good auto body skills came and helped out with the final coats.

On my Pearson, I had two small sections that needed work. One I tried to fix from below so I wouldn't have the fairing issue. That was a nightmare. All I'll say is, fluids run downhill; epoxy is a fluid. The other was under a deck fitting for the spinnaker pole. For that one I used the drill and fill technique. It was only about a half square foot and was totally covered by the fitting when done. I drilled many holes from the top and one from underneath. I then poured acetone in thru the top and caught the run-off down below. The acetone and water combine, leaving behind in the core a fluid that will dry much faster than water alone.

I hope to bever have to do this kind of work again!

Good luck,

Joel
Pokey III
'78 Pearson 323
PO Pokey II
'73 Ty #549
Bayside, NY

[winthrop]

I had to recore quite a bit of deck on my Ty. You're dead on about removal of the skin. Where it's delaminated or rotten, it separates easily. While peeling up the skin, I had to use a chisel to separate some of the balsa from the fiberglass. I used a Rotozip the the Zipmate attachment basically converting it into a small circular saw. I set the depth for about 3/8" and removed the skin from the entire aft deck. The entire area was mushy. I couldn't get closer than an inch to any of the teak, so there were spots where the rot extended beyond my cut, some where perhaps I cut too far. I used marine plywood as the new core. Since it had a slight curve, I cut it into two sections, filling any gaps with thickened epoxy. I did a lousy job attempting to fair the skin, so a friend with good auto body skills came and helped out with the final coats.

On my Pearson, I had two small sections that needed work. One I tried to fix from below so I wouldn't have the fairing issue. That was a nightmare. All I'll say is, fluids run downhill; epoxy is a fluid. The other was under a deck fitting for the spinnaker pole. For that one I used the drill and fill technique. It was only about a half square foot and was totally covered by the fitting when done. I drilled many holes from the top and one from underneath. I then poured acetone in thru the top and caught the run-off down below. The acetone and water combine, leaving behind in the core a fluid that will dry much faster than water alone.

I hope to bever have to do this kind of work again!

Good luck,

Joel
Pokey III
'78 Pearson 323
PO Pokey II
'73 Ty #549
Bayside, NY

hi joel...i did it on my 75 ty on both sides near the chain plates, about two feet long and six inchs wide, the only thing i did different was to use west system and four layers of cloth and it is hard as steel.
i had to do the aft section as well back in the 88, but i cut it out and put an hatch in its place, it looks alot better {teak}.
sounds like everone has had fun with it. ha ha
have fun sailing.
winthrop

[Troy Scott]

Folks,

I know this is an old thread, but I think I need to add some to it in case anyone checking the archives needs a solution.

The idea of replacing the core with solid epoxy is not a good plan. Solid epoxy is way too heavy. There are additives which can make the epoxy very light weight and thixotropic. If I had an area of deck with wet core, I would drill holes to remove the offending wet core using the bent nail technique. After getting the area thoroughly dry I would mix up a slow batch of epoxy using first enough quartz microspheres (q-cell) to make it light and second add just enough cabosil to make it thixotropic (not runny but more like mayonnaise or peanut butter). I would put this mix into an empty caulk tube and inject it into all the same holes that were drilled to remove wet core and dry the area. Once that's done, just fair and paint.

There are so many additives available to make resin do whatever it needs to do. We should utilize this technology more.

[Bill Jarrell]

Hi All,
I was wondering couldn't you use GitRot injected into small holes? Back in the dark ages of my youth many of the boats on the Chesapeake were 3/4 GitRot.

Regards,

Bill

[Troy Scott]

I've never used "Git Rot". But I've read and heard about it off and on for years. It sounds like thin, penetrating epoxy resin. There are many thin, penetrating resins. I suspect it's just a marketing thing. More power to them.... I prefer to use well known resins and modify them for the specific purpose.

[Paul Grecay]

Randy,

Before you start this job, make sure that the core really is wet. Moisture meters are notorious for being unreliable. I once had a part of my hull surveyed....I watched the surveyor and he said that the hull was wet. The next day, his partner came to have a look (he didn't know the other guy had already been there) and he showed me that it was completely dry. Same meter, different opinions. I have seen this kind of thing often so be sure that you really need to do the job before you start.

[Wayne Grenier]

I would definetly not -believe a moisture meter-the "thump method" is better-and test holes are fool-proof-

[Troy Scott]

I believe the moisture meter quandary is complicated by varying techniques. If one guy uses the same moisture meter repeatedly on the same deck the information can be useful. If the meter says an area is wet, and he drills into the suspect area and finds water, that becomes a reference point. If later he drills into another area the meter says is dry and, after drilling the area is found to actually be dry, then he has another reference. The meter is then reliable in THIS situation. Of course these readings should be accompanied by "tapping" and feeling for "squishiness".

[s-dupuis]

I used a RotoZip tool to remove the outer skin on portions of my Typhoons side decks. The tool works like an end mill or a router. Setting the depth to 1/4" allows for careful removal of the outer skin. It's easy to control and you can make curved cuts and radiused corners.

I worked in 10" X 6" rectangular sections and easily peeled off the layer where the balsa was wet. In dry areas the bond was still very good. I left a 1" 'space' of original outer skin between each section to maintain a thickness level reference, but dug out all the wet balsa under the 1" spaces.

I noticed that in places adjacent to where I removed a section and stopped for that weekend, after 5 days exposed to the air, the balsa core was still wet within 1/4" of the edges of the fully exposed section.
Drilling test holes will tell you where the offending areas are but a pattern of holes will not get the moisture out. The refilled holes only act as little fiberglass 'pillars' when refilled, giving the false impression that the deck has integrity.