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  #31  
Old 06-24-2008
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Repairing the core

Just a few years ago there was a sailing magazine article concerning a deck core problem. The boat owner addressed the repair from underneath the deck in the forward berth: carefully scoring the edge of the entire skin under the deck, removing same in one piece, scraping out the offending sludge and replacing it with some sort of honey-combed synthetic core with glue or fiber-glass. The skin which was removed was then glued-up and replaced. It was then temporarily pressed in place with a labrynth of wood and plywood supports to secure the sheet to the core and upper deck. Only the cut edges where the removed sheet met the fixed part of the forward berth ceiling needed refinishing. The result was complete satifaction: providing a large solid deck with no evidence of drilled-hole repairs on top.. The drilling and filling method is OK for attaching hardware and such where you need a solid bolt through surface but unless you can see the damage underneath you'll never know where the trouble ends.
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Old 06-24-2008
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Yes, but you'd need to grind and glass over the edges anyways.

Having solid fiberglass, instead of cored laminate, beneath the mast step is probably a very good idea. Also a good idea to have solid fiberglass at any high load hardware mounting points—winches, cleats, line jammers, windlasses, etc.
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Originally Posted by fredmole View Post
I am going to be soon joining the recore group and it is always interesting to see how others deal with this problem. For my 2 cents worth, unless you are very good with resin and fibreglass, I would recommend going in from the top. Gravity works with you not against you, you have a fraction of the fumes (even if you do have a double cartridge organic vapor mask). Even from the top i would recommend vacuum bagging as it inevitably makes for a better cure and helps eliminate any trapped air or voids. Drilling, nope, not going to work, it needs to be DRY in there. I would take a zip disc and cut around the rotten area to expose the rot and remove the surface laminate. my question is ---- if one can get the surface laminate off in one or more pieces (obviously there would be a size limit), and if it is not compromised, can you resin it back on to the new core and then only be left with a seam to fill?? And under the mast step would I be best to use just laminations and no core? Will that give it more strength in that area or will it compromise the flex (I think that it would work) Also I would think that an iso formula of resin might be stronger and/or better than the general purpose or layup resins. The general purpose of course would also have to be sanded before each layer of glass to remove the curing wax.
Glenn/fredmole
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  #33  
Old 06-24-2008
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Spongy Deck

Oh God, I am so confused on this subject, I don't know what to do! Have read Don Casey's book, and would rather go from the top side to cut out the bad spot on the foredeck. However, we have some sort of old rubber coated non-skid, that can't be removed or painted, so I just ripped out the headliner underneath, planning on seeing what's what under there.
I was thinking of cutting it out and using thin layers of marine plywood to coating each with epoxy, but now I really don't know what is best. The guys in the marina are all telling me to just inject epoxy, but how do I do that from the bottom up anyway. We have a 1978 Mariner 28 and I have been putting this repair off for quite a while, but it is getting a bit crackly under there, so I thought it was time. Help!

I am in the process of reading all of the old posts on this subject, so maybe I'll get some more ideas from there as well. Thanks.
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Old 06-24-2008
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I did mine from the bottom up, as the interior needed to come out anyway. To say it's a big chore is an understatement. Since I had no idea what I was doing, I didn't save the original interior skin. You can't imagine how much fun it is trying to lay up a 50x60 inch piece of resin soaked biaxial cloth. Going from the inside isn't a bad deal if you already have to pull the interior out, or have a very good compelling reason not to cut the outer skin off. Either way, save the skin. Much easier to reattach the skin than make a new one.

As far as coring material goes, it really depends on what the loads are in that area of the boat. My boat came from the factory with balsa, foam and plywood. Since I'm not an engineer or a naval archtect, I stuck with what the factory put in there. Of the 2 materials I had to work with (the foam was good) the balsa was much easier to work with.

FWIW, I saw a chart somewhere a couple years ago comparing the strength of different coring materials. Plywood wasn't on the list, but most of the structural foams and honeycombs were there as well as balsa. Balsa was the strongest by far. Go figure.
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Old 06-24-2008
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Here's a post I made on another forum - you may find it helpful:
__________________________________________________ ___

I know this topic has been covered a bit, but I spent last weekend in my anchor locker and I'll be spending much of this weekend in the same place. So, I thought I'd hit this horse one more time and reiterate the importance of properly sealing hardware.

I knew about these spots when I bought the boat last year, but I've waited until now to repair them. A good section of the foredeck forward of the bulkhead needed to be replaced, as did a smaller section near the anchor locker. The foredeck was inundated with water from a deck plate and the waste pumpout fitting. The area around the anchor locker was damaged by the hinge screws.

Here's the cross section of deck with the deck plate removed:



I did this from below so as not to ruin the deck finish. Here's the first cut:


Here's the exposed core with the lower skin removed. Note the two pieces of wood right in the middle of the deck. This came from the factory as there was no indication of a previous repair in this area. An old foredeck cleat had two fasteners through the wood (see the epoxy plugs), but the other two were through regular balsa. It's strange and I'd love to why these two pieces are here. Did TPI run out of balsa?


I don't have any photos showing the new core exposed as I laid up the new core and replaced the lower skin in the same operation. I wasn't about to touch my camera. So, the two photos below show the lower skins replaced. In the anchor locker photo, I put that brace back for the picture. There were three braces in place while the epoxy cured.





Since these photos, I've water washed the repair to remove amine blush, sanded the area, and solvent washed it.

This weekend, I'm going to grind the seam back several inches on each side and reinforce with two layers of tape. Eventually, I'll repaint both lockers with Bilgekote, but that will be done later.

This work could have easily been avoided if the core was isolated from these fittings with thickened epoxy. Before the new hardware is installed, all fasteners or through-deck hardware will pass through the epoxy, not the new balsa. I omitted a lot of the core in the area where the deck plate passes through and I'll ream out the area around the waste pump out fitting. Fasteners will be installed in the standard way - potting the overdrilled holes with thickened epoxy and drilling and tapping the holes for the fastener.

The first time I did a recore from the inside I made a few mistakes. The largest mistake was not sufficiently preparing the braces for shoring up the new core. This time around, all of the braces were cut and set near by, so that went much, much easier.

Another difference is that I was able to reuse the bottom skin. On the Triton, the skin was not salvageable so I just laminated a new lower skin. I had some issues with trying to install pieces (particularly the biax) that were too large and therefore were a real challenge to keep from falling back off the overhead surface. It went a lot easier when I started using smaller bits of glass.

This time, the old skin was replaced. However, I'm not convinced that's really the best way. You still have to clean and prep the old skin, it has to go back in precisely the same location (meaning your going to hold in place until the epoxy kicks and you can add the braces), and you'll still have to grind and glass the cut seam. It seems that with that much effort, it may be easier just to lay up new glass.

The only minor downside this time was gluing myself to the drop cloth. Last time I stuck the back of my head into fresh glass, so things are improving with practice. No haircuts needed (yet).
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Old 06-24-2008
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The project above is finished (except for paint, which I'm putting off as these repairs are in lockers). Here's a photo of the isolated deck core. It doesn't do any good to recore, unless you solve the source of the water ingress. If balsa stays dry, it will stay good indefinitely. I've seen 45 year old core that is bright and dry.

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I have worked on my Able 20 for 4+ years. The previous owner glassedn 1/2" marine plywood under the foredeck and other areas with 1/4" plywood. I also cot it out from the top and laid glass and marine plywood in the deck. At other places I drilled 1/4" holes in the top and it looked like a pegboard. I dried it with time, fans and acetone and injected epoxy w/ a large syringe. I spent eons fairing it w/ fair
results.
This is the most tedious project I've ever undertaken
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  #38  
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NOLASailing-

It was a fairly common practice to replace the balsa core with marine plywood in areas of high load, like where cleats would be mounted. Not a great practice, but fairly common. That's probably why there was those two pieces of plywood there. However, they look like they were put in the wrong place...
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  #39  
Old 06-28-2008
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Hi Dennis,

I have used Smiths CPES Epoxy system, which I purchased from Jamestown Distributors in RI.

". . . there is a product called smiths cpes epoxy which is supposed to soak into the rotted epoxy and restore its strength. you can find it at rotdoctor.com"

There's a number of articles around on how to do it, but in my search, the ONLY epoxy (I did call West Systems Applications) which claims to work in damp (not wet) environments.

In my case, I had mushy balsa core near my mast step, but I think under the mast step I had plywood core. No matter. First off, I began the project in the fall in central Massachusetts after I had it fully covered.

I used a moisture meter to determine the worst spots. In a 1 foot pattern around the mast step I drilled 1/4 inch holes (using a drill stop) 1/2 inch deep. Sucked out as much moisture as I could with a baster.

I tried the suction with a vacuum cleaner with very limited success. I think next time I'll investigate the "vaccum bagging" technique for this purpose.

I left an oil filled type heater on inside the boat under the mast step area, and left for a 2 months vacation. We came back 5 months later, giving the whole thing 5 months of non-freezing drying out.

I used the Smiths CPES (two parts, I recall). One part is very thin, gets soaked up by the rotted and consolidates the wood into something hard that will mechanically hold the fibers and epoxy. I did that. After curing was done, I sealed the whole area with epoxy, smoothed it down and repainted the area with skid proof paint.

CPES is sold by "Temperature Range" of use, so be sure to get the one thermally designed for your temperature zone.


The traditional method, and perhaps the best method, is to strip the fiberglass back, cut out the offending core, and replace the same with either more end cut balsa or man made 'honeycomb' material.

(Also see West System materials for "How To .." ) Also see "GitRot" for similar material. But neither claimed any fame to working on 'damp' wood. Only dry material.

The CPES system is similar to what "Old House" restorers use to repair well rotted timbers and deco pieces. I had used the home restoration stuff by Minwax to repair one of my older single hung window sash, so I had some knowledge of what kind of repair might work.

If you ask me, now is two years later, how well is the repair holding up, I would be at a loss to say how well, unless I ran outside and drilled a couple of holes to investigate (which I am not).

My coach roof system appears to have plywood core under all major fittings (grab rails, mast step, hatch slides) and balsa core under the rest.

I also have a double, or what appears to be a double core system. Perhaps what I have is the "coach roof" of two fiberglass molds with the core in between them. Then a void between the inner salon coach ceiling and the coach roof. Hmmph that makes sense.

btw I have a 1978 Hunter 27

Bob

Here's a couple of web pages I found along the way: Unforunately, this system won;t let me post them until after I submit 10 posts! Desolee'

Just search on the following terms. ( For every rule there is an equal and opposite workaround. Hah!) OK, these searches both work
"Smiths Warm CPES Epoxy"

"Restoration of Rotted Wood with Penetrating Resin"

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Old 07-02-2008
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Here's my experience with the balsa core repair from the top. In case anyone wants to read or see pics of the process.
Replace "XX" with "tt" (can't hyperlink, friggin forum nazi's.)


hxxp://mangomadnessj30.blogspot.com/2008_04_01_archive.html
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