|Topic Review (Newest First)|
|05-18-2009 11:14 AM|
Yup, it looks like that's the only way to do it to be sure I got it all. From what I have read, the rot can keep on rotting if I don't get every last bit
I ordered the moisture meter, and I want to see where else I can expect the same issue before I start cutting open the deck. I'm worried I'll find it around all the fittings. I don't think I'm up for a recore of the entire deck, but we'll see how much there is.
|05-18-2009 07:32 AM|
|sailingdog||Also, opening it up and seeing the situation for what it is, first hand, will give you a lot more assurance about the repair being done properly. Fewer nagging doubts about what is going on inside the deck.|
|05-18-2009 07:09 AM|
If the rot is that extensive, I have to agree with 'dog -- open it up for a recore. An inch or two is one thing, but now that you're approaching half a foot, well, that's a whole different kettle of fish.
The non-invasive fix I suggested earlier would still work, but at a substantial epoxy cost, and a weight penalty, and it would also cause a hard spot in the deck. Plus, the longer the trip to the "good" core, the more the chances that the "pour-in-place" method will leave significant voids.
For rot this extensive, a recore will be the best solution.
|05-17-2009 08:17 PM|
When I probe with the coat hanger, I can find small spaces that run further than the 3 or 4 inches of the void. I thought (possibly wrongly) that there were spaces between the pieces of core so that the core could curve. Wouldn't the liquid run down those?
If not I probably have more rot. Either way, it does not seem like the void inside is liquid tight, although I can't know without looking, and I am sure not going to pour any water in there to see if it leaks
|05-17-2009 10:20 AM|
|05-17-2009 08:20 AM|
Nothing against 'dog's idea of replacing the core, if you want is an end-product which is identical to the original -- and as vulnerable to rot as it was the day it left the factory, with a somewhat cosmetically-flawed top skin. Personally, I like my repairs to be at least a little better than the original work, if at all reasonable.
However, regarding "re-coring the area properly", my considered opinion is that there is no such thing as a "proper" balsa core, ever. Coring is a weight-saving and economy-minded stiffening technique. Balsa coring, with its inherent rot risks -- from even a minuscule leak -- is a cheap way to stiffen the laminate. Foam coring is a different story, of course, since foam doesn't rot like balsa. An epoxy-filled repair, even if it has a couple of bubbles trapped in it, will be much stronger than balsa could ever be. Properly done, it will exceed the life of the rest of the boat, even if the tang develops a leak in the future.
As for the damming technique I mentioned, I'm sorry if I wasn't too clear about how it's done. It's not done inside the core area, but rather on top of the deck. Might look kind of like a "volcano" or "funnel" of vinyl tape. Think of it as a "filler pipe" for the liquid. In fact, the initial epoxy repair can stand proud of the gelcoat, and then be sanded down flush before re-cutting the hole for the tang. End result is a solid plastic laminate, molecularly bonded to the internal balsa, and physically bonded to both the inner and outer skins. Very strong, and exceptionally waterproof. The nice thing about extending the form a little above the deck is that it provides a reservoir for the liquid epoxy. This allows gravity a little more room to float any bubbles up, and it also provides a reservoir so you don't have to refill the epoxy liquid as often during the time when it is soaking into the existing core.
I've prepared a lot of deck penetrations -- both new openings, and rot repairs -- with this technique, and they are all still in service. Some are decades old. I find this approach to be economical, easy, fast, effective, cosmetically invisible, and considerably better than the original construction.
If the finished surface isn't going to be covered, you can even add pigment to the epoxy, though it does tend to darken with UV exposure. The technique has a lot going for it.
I wouldn't repair an entire rotted-core deck this way. The cost would be too high, evacuating bubbles would be difficult at best, and it would be a lot heavier than the original. In that case, I would use foam coring, bedded in thickened epoxy. But for fixing rotted deck penetrations, I know of nothing that beats this method.
|05-16-2009 10:43 AM|
I only have a small opening, 2 in by 1/2 in, to work with, although I could open it up a bit and use a larger chain plate cover int he end.
How do I use tape to build a dam inside the core?
|05-16-2009 10:30 AM|
Originally Posted by sailingdog View Post
EDIT: But you raise a very good point about it making a future repair difficult.
|05-16-2009 07:39 AM|
If it were my problem to fix, I would proceed as follows:
1. Confirm you have removed all the rot. A moisture meter will help, but the fact that color of the core is good at this point indicates you are there.
2. Dry with heat lamp until bone dry. May take a few days or a week. The moisture has to leave via the slot where the tang used to go, so it will take time.
3. Close off the lower side with vinyl rigging or electrical tape. Seal it well, to contain the epoxy during the fix.
4. Flood the cavity to soak the existing core with Smith's clear penetrating epoxy. CPES is watery-thin, extremely slow-setting, and will penetrate the existing core. It can also mix with minimal amounts of moisture. It will disappear into the balsa over the course of a day. You may have to re-fill the cavity a few times as it soaks in. The cavity will look almost empty after the CPES soaks into the core.
5. After a day, inject a good epoxy, such as West, thickened a bit with colloidal silica. Thin enough to inject, but thick enough to increase strength. It will crosslink to the CPES (which will not blush). Use a slow hardener to avoid exotherm heating, mix with as few bubbles as possible, and allow bubbles to rise in the mixing cup. Draw the epoxy (from the bottom, where there shouldn't be many bubbles) into an epoxy syringe, and slowly flood the cavity, allowing air to exit. If there is significant camber or angle to the area, you can apply vinyl tape to the lower edge to contain the fluid, or you can actually form a "cup" or "tube" (that is higher than the deck) with the tape. You may need to refill the void a few times as the epoxy soaks into the core and bubbles exit.
6. Result may have some minor bubbles, nothing structural, and it will be waterproof and solid. Probably harder than the surrounding balsa-cored area, and definitely stronger. Remove the vinyl tape.
7. Re-cut the opening for the tang, reinstall the tang, and bed the top to keep water at bay.
8. Finished fix will maintain the original skin (inside and out) and should outlast the rest of the boat.
|05-16-2009 06:03 AM|
The problem with filling the existing void with thickened epoxy, without opening up the deck's skin—either from above or below—is that you can't be sure you filled it completely. Also, adding thickened epoxy to it isn't going to return the deck to the same level of strength that re-coring it would do, and will make any proper future repair much more difficult to do.
Why not just re-core the area properly??? It isn't that difficult a task to do.
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