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Still balsa cored?
- Thread starter Karl
- Start date
Someone else will have to answer your question directly, but what I can tell you is they are still going to be cored with something. They pretty much have to be in order to be light/stiff. Hence (in case this is why you are asking), there will still be a "sandwich" that one wants to keep water out of.
If you already know all this, pardon my butting in, but I just mention it because I have noticed that there is an idea that many people have which is that if something is foam cored you lose all your worries about water getting in. (You may not even be thinking along these lines, I realize). While foam is less prone to rotting, there are still many reasons to keep water out of the laminate (de-bonding, water running down channels between core sections, etc.)
Balsa has some properties that foam doesn't (i.e. it is better for some applications). Foam has some tendencies that balsa doesn't. Both rely on good construction practices to be effective, and (in my opinion) water should be kept out of a laminate laid up with either.
Back to your direct question: I know that in around 2006 or so, C-Dory went to foam for the transom core. Since then I don't know (but I'm sure others do). It's also not uncommon for there to be some variation in production boats (as opposed to custom or semi-custom boats, wherein everything is specified. So various materials may be substituted for each other when both will be adequate (varying brands of fiberglass cloth/resin/core materials, etc.).
As far as I know on the 22's (others may be similar) there is coring in the hull bottom, the transom, the decks, the "outside walls," the bulkheads, the v-berth top, and sometimes the roof. Oh, and the flat cockpit sole.
Will be interesting to see what you find out.
If you already know all this, pardon my butting in, but I just mention it because I have noticed that there is an idea that many people have which is that if something is foam cored you lose all your worries about water getting in. (You may not even be thinking along these lines, I realize). While foam is less prone to rotting, there are still many reasons to keep water out of the laminate (de-bonding, water running down channels between core sections, etc.)
Balsa has some properties that foam doesn't (i.e. it is better for some applications). Foam has some tendencies that balsa doesn't. Both rely on good construction practices to be effective, and (in my opinion) water should be kept out of a laminate laid up with either.
Back to your direct question: I know that in around 2006 or so, C-Dory went to foam for the transom core. Since then I don't know (but I'm sure others do). It's also not uncommon for there to be some variation in production boats (as opposed to custom or semi-custom boats, wherein everything is specified. So various materials may be substituted for each other when both will be adequate (varying brands of fiberglass cloth/resin/core materials, etc.).
As far as I know on the 22's (others may be similar) there is coring in the hull bottom, the transom, the decks, the "outside walls," the bulkheads, the v-berth top, and sometimes the roof. Oh, and the flat cockpit sole.
Will be interesting to see what you find out.
I ask because there is a long history of whichever factory made the C-Dory, they universally failed to properly seal penetrations, by under-cutting all holes and filling edges with epoxy, then re-drilling.
Soaked coring is very costly to repair, and the new owner should not have to remove all hardware and do the installation properly before this becomes an issue, whether deck, hull, transom or what. 4200/5200 bedding is not equivalent to epoxy-sealing the edges of a cored penetration...even if a proper install adds $500 to the cost of a new boat.
Soaked coring is very costly to repair, and the new owner should not have to remove all hardware and do the installation properly before this becomes an issue, whether deck, hull, transom or what. 4200/5200 bedding is not equivalent to epoxy-sealing the edges of a cored penetration...even if a proper install adds $500 to the cost of a new boat.
Just a couple of comments. As noted above whether foam or balsa cored, it is better if the penetrations are sealed by under cutting and coming back with epoxy. However, foam core won't rot like balsa can. The biggest area of concern is the transom due to both the weight of the engine(s) and the constantly changing forces. Most of the penetrations of the transom are done during install of the engines by the DEALER, so the buyer of a new boat should have the dealer do it they way they want it.
Most dealers and boat builders seal penetrations with either sikaflex or 3M 4200, both of which can last a very long time. If it only cost $500 to undercut and seal every penetration with epoxy, I'm sure that most builders would do it up front. However, the cost is far more than $500. When I've done this myself, each hold that I was undercutting and sealing with epoxy took a few minutes to undercut. It then took a few minutes to prepare the area for the application of epoxy (taping off, applying neat epoxy). Then it took 5-10 minutes to get the epoxy to the appropriate thickness and a minute or so to fill each hole. Then I'd have to wait (usually overnight) for the epoxy to cure, grind down any excess (a few minutes per hole) and re-drill. I couldn't do too many holes at once without remixing epoxy so to do multiple penetrations could require mixing multiple batches. I know if I was going to charge for what I did and I was going to do all the penetrations of core on the boat this way, I'd have to charge several $1000 for it to make sense. In addition, it would likely be a multi day process in the build and it would add to the timeline of completion. So in practice, the vast majority of builders and dealers use 4200 or silkaflex.
One can disassemble the penetrations on an occasional basis (say every 5 years and re-bed). I did this on my previous 22 for everything on the transom. I never found any rot when I did this. For the sole in the cabin, I removed all the screws holding down the cabinetry (these weren't sealed at all) and in one or two of these, I found rot about 1/4" from the hole. Since the balsa core is end grain (e.g. all of the grain is perpendicular to the floor), the water didn't wick very far. I over drilled and filled the holes and then used fiberglass tabbing to hold the cabinetry in place. That process took about 4 days of clock time and maybe 5-8 hours of labor.
There are a lot of "improperly" built boats in the water with balsa core penetrations that have been sealed with silkaflex or 4200 that have lasted a very long time.
Most dealers and boat builders seal penetrations with either sikaflex or 3M 4200, both of which can last a very long time. If it only cost $500 to undercut and seal every penetration with epoxy, I'm sure that most builders would do it up front. However, the cost is far more than $500. When I've done this myself, each hold that I was undercutting and sealing with epoxy took a few minutes to undercut. It then took a few minutes to prepare the area for the application of epoxy (taping off, applying neat epoxy). Then it took 5-10 minutes to get the epoxy to the appropriate thickness and a minute or so to fill each hole. Then I'd have to wait (usually overnight) for the epoxy to cure, grind down any excess (a few minutes per hole) and re-drill. I couldn't do too many holes at once without remixing epoxy so to do multiple penetrations could require mixing multiple batches. I know if I was going to charge for what I did and I was going to do all the penetrations of core on the boat this way, I'd have to charge several $1000 for it to make sense. In addition, it would likely be a multi day process in the build and it would add to the timeline of completion. So in practice, the vast majority of builders and dealers use 4200 or silkaflex.
One can disassemble the penetrations on an occasional basis (say every 5 years and re-bed). I did this on my previous 22 for everything on the transom. I never found any rot when I did this. For the sole in the cabin, I removed all the screws holding down the cabinetry (these weren't sealed at all) and in one or two of these, I found rot about 1/4" from the hole. Since the balsa core is end grain (e.g. all of the grain is perpendicular to the floor), the water didn't wick very far. I over drilled and filled the holes and then used fiberglass tabbing to hold the cabinetry in place. That process took about 4 days of clock time and maybe 5-8 hours of labor.
There are a lot of "improperly" built boats in the water with balsa core penetrations that have been sealed with silkaflex or 4200 that have lasted a very long time.
On our Marinaut, the entire boat is cored with closed cell foam. Les Lampman's team over drilled holes, filled them in with epoxy, and then re drilled. This reduces the chance for water penetration and crushing of the area around the holes. My 2006 C-Dory developed a crack in the cockpit due to a manufacturing defect which allowed water to penetrate into the end grain balsa core. The warranty was not as valuable as the paper it was printed on, and We had to fork over $1,000 for repairs. So my wife and I were adamant in not wanting to ever by another wood cored boat again, unless it could be bought on the cheap. That said, we realize that closed cell foam can experience all sorts of issues as well, such as de-lamination and crushing; we rather deal with those risks than to have the added worry of having a wood-cored boat. It is nice to see, however, that new C-Dory's are cored with closed cell foam.
Rich
Rich
Karl":3skm2cui said:I ask because there is a long history of whichever factory made the C-Dory, they universally failed to properly seal penetrations, by under-cutting all holes and filling edges with epoxy, then re-drilling.
That is true, but... it could also be said of just about every other production boat builder. I'm not saying that thrills me, but unless you go semi-custom that seems to be the way it is (maybe there are exceptions).
Karl":3skm2cui said:4200/5200 bedding is not equivalent to epoxy-sealing the edges of a cored penetration...even if a proper install adds $500 to the cost of a new boat.
I've done most of the core penetrations on my boat. Granted, it would be a lot faster and easier to do it from the start (for example, don't even put coring where trim tab planes will be mounted - just make that solid fiberglass) vs. re-doing everything (and yes, I have muttered a few choice words while suited up and making dust), but... I can't imagine it adding anywhere near to only $500. Materials, labor..... it would be thousands. I would pay it gladly, but apparently most people would just move on to a more "competitively priced" boat. Or at least that is my guess as to why production boats are still built the way they are.
I bought a second-hand boat, partly becuase yeah, taking a brand new one apart would be aggravating (and having had to re-core several boats, I can't relax until I do the overdrill/fill). That said, they don't rot instantly, so one could buy a new boat and then when the time came to re-bed the fittings (as it always will, even if they are properly closed out) do the "routine."
I passed up a few foam-cored boats that had serious de-bonding issues (i.e. the skins and core had separated) (not C-Dorys). In a Bruce Pfund workshop on composite techniques, he did a demo showing a method for "encouraging" the foam to bond better to the skins, so it seems to be a little bit more of a challenge in that way than balsa. I don't see foam as a magic bullet -- it has its good and bad points, as does balsa. Care and proper build techniques are key.
I'd love to hear what the current C-Dory builders have changed, and what they've kept the same. It's always interesting to know how boats are built, and how things evolve.
My 2011 22 is all foam core as per Scott when he was in charge of the build and anything I've cut, ie for windlass was foam inside. Undercutting and epoxying is not done in any factory built boats that I know of but is done in custom builds if you specify it with the appropriate extra price. It is a simple operation, but consumes time so hard for production builders to do.
Before the CD 26 Venture, I had two custom cored boats built.
One a HP twin "deep V" with end grain balsa core. The other
an Atlantic 42 cat cored with closed cell foam.
The main important feature used on both was "vacuum bagging".
This literally sucks excess uncured epoxy (vinyl ester is best) out
to give improved strength/weight ratio; less total weight.
Can't say about water intrusion into either as it didn't happen as
far as I can tell.
Aye.
One a HP twin "deep V" with end grain balsa core. The other
an Atlantic 42 cat cored with closed cell foam.
The main important feature used on both was "vacuum bagging".
This literally sucks excess uncured epoxy (vinyl ester is best) out
to give improved strength/weight ratio; less total weight.
Can't say about water intrusion into either as it didn't happen as
far as I can tell.
Aye.