I notice alot of posts about water intrusion in balsa core decks recently. I was wondering if CDs fare better or worse than other boats in this respect. Alot of manufactures mention endgrain balsa in their specs. Is this considered only stronger or more resistant to waterr migration? Out of curiousity I am trying to figure out why some boats can have alot of crazing and cracks (like mine) and have the deck remain firm....while others can have a single poorly bedded fitting allow a large area to get soft? I suppose some sort of west layer at the time of manufacture could have helped to seal the balsa..at least from above?
hg@myhost.com
Moist Balsa Core
Moderator: Jim Walsh
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Russell
The main problem is that Cape Dory did not seal where the de
If you look on your deck, you will see lots of places where it is drilled or cut to install hardware. Ideally, when builders make the deck, they do not put coring where hardware is installed. This is called "voiding the core." If the deck is cut where coring is, the correct practice is to seal the edges of the exposed balsa. For holes, this can be done by drilling over size to the bottom skin, filling with thickened epoxy, and then redrilling the correct sized hole. For larger cuts, cut back the balsa between the two skins, and fill. The principle is that the coring should nowhere be exposed.
The coring stops before the deck edges. This is very clearly visible if you look at the layup from below. The toe rails, stanchion bases, and cleats do not pierce the coring. On the other hand, on the larger CDs, the tiller access and binnacle go right through the cored cockpit sole. Cape Dory did NOT seal the coring where this was done, but instead followed the common practice of cutting the deck and installing the hardware, trusting the hardware bedding to keep water out of the coring. I have seen one CD 33 where this caused a soft cockpit sole. From reports here, there have been others. When I look at my tiller port from underneath, I can see balsa exposed all around. I hope to fix this in the future, but it causes me to worry about the binnacle installation, which I cannot inspect without removing, which then turns into a big job. Maybe I'll just hope it goes another twenty years. Sigh.
The problem spots depend on the specific model.
I don't think that Cape Dory was worse than most builders in this regard. This practice was common in many, many boats. I am disappointed that CD did not do better, given the higher standards they practiced generally. Construction standards have advanced. Most production builders today make a point to void the core where all standard and optional hardware occurs. This makes me curious: I wonder what Robinhood does with the new 36's?
The coring stops before the deck edges. This is very clearly visible if you look at the layup from below. The toe rails, stanchion bases, and cleats do not pierce the coring. On the other hand, on the larger CDs, the tiller access and binnacle go right through the cored cockpit sole. Cape Dory did NOT seal the coring where this was done, but instead followed the common practice of cutting the deck and installing the hardware, trusting the hardware bedding to keep water out of the coring. I have seen one CD 33 where this caused a soft cockpit sole. From reports here, there have been others. When I look at my tiller port from underneath, I can see balsa exposed all around. I hope to fix this in the future, but it causes me to worry about the binnacle installation, which I cannot inspect without removing, which then turns into a big job. Maybe I'll just hope it goes another twenty years. Sigh.
The problem spots depend on the specific model.
I don't think that Cape Dory was worse than most builders in this regard. This practice was common in many, many boats. I am disappointed that CD did not do better, given the higher standards they practiced generally. Construction standards have advanced. Most production builders today make a point to void the core where all standard and optional hardware occurs. This makes me curious: I wonder what Robinhood does with the new 36's?
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Larry DeMers
Re: Moist Balsa Core
CD's are probably average to above average in hull strength and integrity. WHere they screwed up big time seems to be in their over application of gel coat. THey have the thickest gel coat I have seen on boats yet..and that translates to a very stiff surface.more stiff than the underlying substrate of laminations in fact, which causes all the small gel coat crazing. These start as stress cracking from normal deck movements..where a proper amount of gel coat would still be pliable enough to take the slight flexing of the hull. These crazings accumulate as time goes on, withthe older ones occasionally getting deeper into the gel coat, until some of the crazings turn into cracks..which I define as when they extend down to the first layer of laminate. Now you have a problem, as water will wick into the laminate..usually end-core balsa, or plywood. Foam is also used in the coach roof..so we have three coring materials to be concerned with.
The freeze/thaw cycle reeks havoc on these crazings (is that a word? -sounds good?) , with the water in the craze freezing, expanding and going deeper upon the next thaw..
End Grain Balsa is really the only way to use balsa , as the strength in balsa is in it's end-on direction only. Baltec balsa for instance, partially cuts their balsa panels up into small cubes, so that it provides a smoothly transitioning surface at a point where the boats surface curves. The kerfing as it is called, will let the balsa form a radius over the surface. At this point, the end grain should be sealed with epoxy..before applying the first glass over it. This is time consuming and more expensive..will not show up ont he surface at all, and would be hard to charge for. Consequently, few manufacturers do this anymore. In fact, it may be that Baltec preseals their balsa before shipping it..it would be a natural progression of technology if that were true.
So the reason the deck remains firm while there are cracks (crazes actually) in the gel coat is that water has not penetrated yet. Poorly bedded parts mounted on deck leak through the mounting holes, into the roving directly, so that will have a much more severe effect right off.
The deck crazing can be sealed up iwth a product called Captain Tolly's Creeping Crack Cure. It's sold by West Marine and all the rest, is very viscous so that it will be taken into the crack through capillary action. It eventually cures into a pliable, clear seal. I have used up a whole bottle already, and have more to do. I have to admit that ti does nothing to hide the crack/crazes, but it should seal it well. The test will be if that area ends up with a wet core or not.
Lastly, take care of those crazes now..or later. It is cheaper to do it now from my experiences with having the cockpit floor removed, and the coring replaced, and new floor applied. $12~ compared to $3000.
Good Luck!
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
The freeze/thaw cycle reeks havoc on these crazings (is that a word? -sounds good?) , with the water in the craze freezing, expanding and going deeper upon the next thaw..
End Grain Balsa is really the only way to use balsa , as the strength in balsa is in it's end-on direction only. Baltec balsa for instance, partially cuts their balsa panels up into small cubes, so that it provides a smoothly transitioning surface at a point where the boats surface curves. The kerfing as it is called, will let the balsa form a radius over the surface. At this point, the end grain should be sealed with epoxy..before applying the first glass over it. This is time consuming and more expensive..will not show up ont he surface at all, and would be hard to charge for. Consequently, few manufacturers do this anymore. In fact, it may be that Baltec preseals their balsa before shipping it..it would be a natural progression of technology if that were true.
So the reason the deck remains firm while there are cracks (crazes actually) in the gel coat is that water has not penetrated yet. Poorly bedded parts mounted on deck leak through the mounting holes, into the roving directly, so that will have a much more severe effect right off.
The deck crazing can be sealed up iwth a product called Captain Tolly's Creeping Crack Cure. It's sold by West Marine and all the rest, is very viscous so that it will be taken into the crack through capillary action. It eventually cures into a pliable, clear seal. I have used up a whole bottle already, and have more to do. I have to admit that ti does nothing to hide the crack/crazes, but it should seal it well. The test will be if that area ends up with a wet core or not.
Lastly, take care of those crazes now..or later. It is cheaper to do it now from my experiences with having the cockpit floor removed, and the coring replaced, and new floor applied. $12~ compared to $3000.
Good Luck!
Larry DeMers
s/v DeLaMer
Cape Dory 30
Harris wrote: I notice alot of posts about water intrusion in balsa core decks recently. I was wondering if CDs fare better or worse than other boats in this respect. Alot of manufactures mention endgrain balsa in their specs. Is this considered only stronger or more resistant to waterr migration? Out of curiousity I am trying to figure out why some boats can have alot of crazing and cracks (like mine) and have the deck remain firm....while others can have a single poorly bedded fitting allow a large area to get soft? I suppose some sort of west layer at the time of manufacture could have helped to seal the balsa..at least from above?
demers@sgi.com
-
Larry DeMers
Re: The main problem is that Cape Dory did not seal where th
Russel,
You are absolutely right. I was one that had to replace the cockpit floor due to water intrusion making black goo of the balsa coring. They counted on the seal of the binnacle mount, which people are constantly trying to rip out of the boat when they get up etc. -to keep water out. Poor idea..cheap in fact.
We used plywood coring in the cockpit, and sealed it on all 6 sides before installing. So far, so good.
Larry DeMers
demers@sgi.com
You are absolutely right. I was one that had to replace the cockpit floor due to water intrusion making black goo of the balsa coring. They counted on the seal of the binnacle mount, which people are constantly trying to rip out of the boat when they get up etc. -to keep water out. Poor idea..cheap in fact.
We used plywood coring in the cockpit, and sealed it on all 6 sides before installing. So far, so good.
Larry DeMers
Russell wrote: If you look on your deck, you will see lots of places where it is drilled or cut to install hardware. Ideally, when builders make the deck, they do not put coring where hardware is installed. This is called "voiding the core." If the deck is cut where coring is, the correct practice is to seal the edges of the exposed balsa. For holes, this can be done by drilling over size to the bottom skin, filling with thickened epoxy, and then redrilling the correct sized hole. For larger cuts, cut back the balsa between the two skins, and fill. The principle is that the coring should nowhere be exposed.
The coring stops before the deck edges. This is very clearly visible if you look at the layup from below. The toe rails, stanchion bases, and cleats do not pierce the coring. On the other hand, on the larger CDs, the tiller access and binnacle go right through the cored cockpit sole. Cape Dory did NOT seal the coring where this was done, but instead followed the common practice of cutting the deck and installing the hardware, trusting the hardware bedding to keep water out of the coring. I have seen one CD 33 where this caused a soft cockpit sole. From reports here, there have been others. When I look at my tiller port from underneath, I can see balsa exposed all around. I hope to fix this in the future, but it causes me to worry about the binnacle installation, which I cannot inspect without removing, which then turns into a big job. Maybe I'll just hope it goes another twenty years. Sigh.
The problem spots depend on the specific model.
I don't think that Cape Dory was worse than most builders in this regard. This practice was common in many, many boats. I am disappointed that CD did not do better, given the higher standards they practiced generally. Construction standards have advanced. Most production builders today make a point to void the core where all standard and optional hardware occurs. This makes me curious: I wonder what Robinhood does with the new 36's?
demers@sgi.com
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Chris Cram
can you paint?
If you use the "Captian Tolly's Creeping Crack Cure" can you paint over it? The areas where is might go into the non-skid you would naturally want to paint over it.
Chris
"Hesperus"
CD 30 C
"The deck crazing can be sealed up iwth a product called Captain Tolly's Creeping Crack Cure. It's sold by West Marine and all the rest, is very viscous so that it will be taken into the crack through capillary action. It eventually cures into a pliable, clear seal. I have used up a whole bottle already, and have more to do. I have to admit that ti does nothing to hide the crack/crazes, but it should seal it well. The test will be if that area ends up with a wet core or not.
cccobx@prodigy.net
Chris
"Hesperus"
CD 30 C
"The deck crazing can be sealed up iwth a product called Captain Tolly's Creeping Crack Cure. It's sold by West Marine and all the rest, is very viscous so that it will be taken into the crack through capillary action. It eventually cures into a pliable, clear seal. I have used up a whole bottle already, and have more to do. I have to admit that ti does nothing to hide the crack/crazes, but it should seal it well. The test will be if that area ends up with a wet core or not.
Larry DeMers wrote: Lastly, take care of those crazes now..or later. It is cheaper to do it now from my experiences with having the cockpit floor removed, and the coring replaced, and new floor applied. $12~ compared to $3000.
cccobx@prodigy.net
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Larry DeMers
Re: can you paint?
Hi Chris,
Sointenly..heh, this stuff is more viscous than water, and there is no buildup over the crack. It all disappears into the crack or at the very perimeter. I wouldn't even worry about sanding it in particular..just go ahead and paint over it. In fact, now that you mention it..there may be cause to be concerned about the opposite condition..a concave surface over the crazing/crack. Slight as it is, it will probably show up in the final finish, when done. That would seem to argue in favor of filling the crack with a thinned down gel coat material, followed by painting.
Larry DeMers
demers@sgi.com
Sointenly..heh, this stuff is more viscous than water, and there is no buildup over the crack. It all disappears into the crack or at the very perimeter. I wouldn't even worry about sanding it in particular..just go ahead and paint over it. In fact, now that you mention it..there may be cause to be concerned about the opposite condition..a concave surface over the crazing/crack. Slight as it is, it will probably show up in the final finish, when done. That would seem to argue in favor of filling the crack with a thinned down gel coat material, followed by painting.
Larry DeMers
Chris Cram wrote: If you use the "Captian Tolly's Creeping Crack Cure" can you paint over it? The areas where is might go into the non-skid you would naturally want to paint over it.
Chris
"Hesperus"
CD 30 C
"The deck crazing can be sealed up iwth a product called Captain Tolly's Creeping Crack Cure. It's sold by West Marine and all the rest, is very viscous so that it will be taken into the crack through capillary action. It eventually cures into a pliable, clear seal. I have used up a whole bottle already, and have more to do. I have to admit that ti does nothing to hide the crack/crazes, but it should seal it well. The test will be if that area ends up with a wet core or not.
Larry DeMers wrote: Lastly, take care of those crazes now..or later. It is cheaper to do it now from my experiences with having the cockpit floor removed, and the coring replaced, and new floor applied. $12~ compared to $3000.
demers@sgi.com