Deck core - The heated debate yet again

[chowdan]

I have replaced our side chainplates, still need to do the fore/aft ones and am planning to do the rigging as well, however, this(rigging) will happen when I'm hoping to haul beginning of next winter. That being said, I've read multiple articles and forum posts talking about deck rock/soft decks/squishy decks and how to deal with it. Most, if not all of them say we need to pull the top laminate, remove the rotted core and replace then lay down the laminate and fiber over again.

We are seeing rot where the chainplates go through the decks as it appears that Bristol actually had the core go all the way up to the chainplates without "encapsulating" it. My original thinking was to just replace the core as described above, building up a good "plug" of epoxy where the plates run through the deck so I and the future owners never have to worry about this again. Coming to realize that the cost of doing this(time in the yard plus my free time) is actually pretty limited, and not being able to do it this way made me start researching about other methods, specifically the drill and fill methods.

I came across a blog post that described this drill and fill method. Has anyone ever does this? Sure it may not be the "right way" of doing this, however, is it an effective method? If you have done it, do you have recommendations on lessons learned? Would you do it again?

Here's the post: Diana's blog: JC's secret system for filling deck-core rot

I'm looking for responses from both sides of the party, ones who have done a full core removal and replacement and ones who have just filled that ****er full of epoxy.

I don't necessarily want to use a product such as "git-rot" rather, I'd just use epoxy, however, I'd love to hear everyone's take on git-rot too(if you have used it).

[cruisersfarm]

Don't bother doing it the wrong way.

Think about what is happening inside if you don't open it up.

You have surfaces that popped apart, potentially with smooth, shiny surfaces. Epoxy doesn't stick to smooth things.

Just make the repair as you first mentioned and be happy it was done correctly.

[Stumble]

Get-rot (and all 'penetrating epoxy) is junk. Basically it's just good epoxy that was ruined by adding a bunch of thinners to it. For far less money you can ruin your own epoxy, just buy some West or Systems3 and add 1 part epoxy to 3 parts acetone. It will be just as bad as the more expensive stuff at far less money.

The drill and fill method.... Its a little difficult. Basically it depends on what you want to do with the boat. If you just want to fix it for now and p,an on junking the boat in a few years anyway then go for it. It will hold the boat together for a few years more, and make it safe to continue sailing for a while longer.

But if you want to return the boat to good condition then it has a few major failings.

1) it traps water in what remains of the core, guaranteeing that the remaining core will continue to rot. So over time you just have to keep expanding the area that has to be drilled and filled. Eventually there is nothing left of the core at all.

2) the epoxy pillars make hard spots in the deck, so those areas start to push thru and break off. Much like trying to support a house foundation on pillars, but with no cross bracing

3) it's far heavier than it should be. As you replace the light wood with heavy epoxy you just keep adding more and more weight to the boat.



So where would I drill and fill? Basically on a cheap boat with extensive core damage. Where the core problem would cost more to fix than the boat would ever be worth, and the owner fully expects to junk the hull in a few years.

If the only core rot you have now is located close to the chainplates then fix it right. You have a nice boat and you should fix it correctly.

[neilpride]

A waste of time and money, do it the right way or don't do it...

[chowdan]

Originally Posted by cruisersfarm

Don't bother doing it the wrong way.

Think about what is happening inside if you don't open it up.

You have surfaces that popped apart, potentially with smooth, shiny surfaces. Epoxy doesn't stick to smooth things.

Just make the repair as you first mentioned and be happy it was done correctly.

Have you gone through the post I linked? I would highly recommend it as it has been written by John Cherubini II, who's father designed the Hunter 25.

John Cherubini the second, has a respectable background within the building field, and that includes restorations of these plastic classics. I have a hard time hearing something from someone who has been in the boat building industry for 40+ years and finding a reason to not believe it.

[chowdan]

Originally Posted by Stumble

Get-rot (and all 'penetrating epoxy) is junk. Basically it's just good epoxy that was ruined by adding a bunch of thinners to it. For far less money you can ruin your own epoxy, just buy some West or Systems3 and add 1 part epoxy to 3 parts acetone. It will be just as bad as the more expensive stuff at far less money.

The drill and fill method.... Its a little difficult. Basically it depends on what you want to do with the boat. If you just want to fix it for now and p,an on junking the boat in a few years anyway then go for it. It will hold the boat together for a few years more, and make it safe to continue sailing for a while longer.

But if you want to return the boat to good condition then it has a few major failings.

1) it traps water in what remains of the core, guaranteeing that the remaining core will continue to rot. So over time you just have to keep expanding the area that has to be drilled and filled. Eventually there is nothing left of the core at all.

2) the epoxy pillars make hard spots in the deck, so those areas start to push thru and break off. Much like trying to support a house foundation on pillars, but with no cross bracing

3) it's far heavier than it should be. As you replace the light wood with heavy epoxy you just keep adding more and more weight to the boat.



So where would I drill and fill? Basically on a cheap boat with extensive core damage. Where the core problem would cost more to fix than the boat would ever be worth, and the owner fully expects to junk the hull in a few years.

If the only core rot you have now is located close to the chainplates then fix it right. You have a nice boat and you should fix it correctly.

Now this is a respectable post, unlike the other posts that contain "it doesn't work, do it the right way". I am looking for a constructive discussion, one that provides value to me and all other future viewers. So I thank you for taking time to respond with such a post.

On to the discussion - Based on J Cherubini(JC), he has said that you dont actually need to thin it down if your using a syringe. I'm not trying to defend the method, rather I'm trying to completely understand the consequences that can come about of doing this method. Similarly I am also curious to know about consequences that can come about when you have 40 year old fiberglass being bonded to brand new fiberglass. This is likely in need of a seperate thread, however since were on the subject, 40 year old fiberglass has long gone past the "window" in which new fiberglass can bond to it. With that, it means the new fiberglass that is being bonded to the old fiberglass is a purely mechanical bond, and at some point in the life of the bond, it will fail.

The way you explained the pillar problem is quite interesting. I haven't thought of that as an issue mainly because I am under the impression that the epoxy will be absorbed into the wood that is present, making the wood, or rotted crap that is present, a wood/epoxy mixture in which the top and bottom laminates are then stuck too.

Also wouldn't the pillar concept be an issue for all parts of the boat where the manufactuer/DIY repairer completely removes the core and replaces it with solid fiber/epoxy? Such places would be the windlass, winches, cleats, any sort of thru-hull's(if on a cored hull), chainplate entrances/bolt holes? If not, why is it different when repairing a rotted core?

[neilpride]

Actually it don't work, if the balsa is rot ,what you are doing drilling pilot holes in top of the chainplate slot is just filling those pilot holes with epoxy, then if the top skin is delaminated you can get a bond again with epoxy and those holes but I guess your problem is just core rot,, Ge rot is just BS, it don't make your deck seaworthy again or sound , now if you can get rid off that rot core portion without major surgery in the slots and replace with a mixture of epoxy and filler then fine, but how can you do that without removing the plates is another history, Cheers...

[boatpoker]

If your core is wet/decayed or even turned to dust the epoxy will harden but you just end up with a free floating lump of epoxy.

Take a look at Balsa Core = Compost

[chowdan]

Originally Posted by neilpride

Actually it don't work, if the balsa is rot ,what you are doing drilling pilot holes in top of the chainplate slot is just filling those pilot holes with epoxy, then if the top skin is delaminated you can get a bond again with epoxy and those holes but I guess your problem is just core rot,, Ge rot is just BS, it don't make your deck seaworthy again or sound , now if you can get rid off that rot core portion without major surgery in the slots and replace with a mixture of epoxy and filler then fine, but how can you do that without removing the plates is another history, Cheers...

I have no problems removing chainplates as it is not a major task.

Removing the top layer, chiseling out and replacing rotted core then re-glassing in the top layer is a major task. Working over 70 hours a week on average(at times over 90 hours) means I have very little time as I am starting my own business while working a full-time salary position.

I don't think I could make this surgery with a single 2 day weekend, and I even doubt that I could make the drill & fill method fix in a single 2 day weekend either. I haven't worked with fiberglass all that much so this will be a first for me(i have fixed dings and dents and such on surfboards growing up, but nothing of this scale or importance).

[Cheechako]

IF your chainplates are outboard near the edge of the deck, and IF your glass is thick out there, I see no problem with filling. There is not going to be much deck deflection etc out there from walking. I'd use a mix in the epoxy. BUT, you need to get the wet core out for a good fix. You could use a small (1"?) hole saw on the interior and then scrape core out with a blade or screwdriver etc.
Hard to visualize what's going on.
I replaced the core over the V berth on a boat once from the inside. Thus no painting or heavy glasswork. After I cut a big V shaped panel and pried it off, I removed the core, and also got 5-6" into the sandwich outside of where I cut the big V off and scraped it out. Filled with Airex/epoxy mix all over, including shoving it into the gap on sandwiched area, and reglassed from the inside.
It is hard getting epoxy out of your hair though! :>)

[Stumble]

Laying new fiberglass over old glass is perfectly fine. The mechanical bond strength of epoxy is so high that as long as the new glass is layed properly the substrate will shear before the mechanical bond fails. This is one of the reasons epoxy is prefered to other goo, it's mechanical properties are just far better. Of course 'keying' the old glass with sandpaper is a good idea since it increases the contact area and allows a better mechanical bond.

Lifetime issue with fiberglass load cycles are a little beyond my engineering back ground, but we know that 50 year old boats, if well made, are still doing fine. FG panel flexing is really only a problem on boats with poor core bonds (or rotten core), or where the glass wasn't thick enough in the first place.


Finally rotten core... It's a bit of a misnomer because inside the core it isn't an either/or issue.

1) There is typically a void that epoxy can fill, fair enough. Epoxy works best here
2) Then there is a lot of wood pulp and remains that looks like an old wood pile left in the woods, some of it is fine, other parts have voids, there's a lot of leaves and dirt... It's just a big mess and is typically a little moist. Add epoxy to this and you get a hard shell of epoxy around a soggy mess of wood remains. Of course in areas where it's really wet the epoxy won't cure, so it just adds to the muck.
3) Finally is the pucky wood. This is a little damaged, a little damp, but not in terrible shape. It's the leading edge of the core rot. Add epoxy behind it and you create a waterproof dam so the water has no where to go but forward, slowely rotting away the rest of the core.


As an expirament get a flower pot and add about an inch of potting soil to it. Then wet it to just damp with epoxy. This approximates what your core looks like. Then pour epoxy on top of this muck and wait for it to cure, and report back what happens. What it won't do is end up as a solid consolidated structurally sound block.

[boatpoker]

Originally Posted by chowdan

Here's the post: Diana's blog: JC's secret system for filling deck-core rot

My Dad designed propellers (big ones like 20' dia.) then later moved to designing jet turbine fans, not sure if that qualifies me to comment on their repair

[skipmac]

Perhaps I missed it but I cannot see any comment on how much rot, wet and damage and how far it goes into the core.

Generally with end grain, balsa core, unless it's left very wet for a long time or there are channels allowing water to penetrate (like the glass skin has separated from the core or there are unfilled voids in the core) the wet and rotted area will be limited to a smallish area around the leak.

If that is your situation then pull the chain plates, gouge out the rotted, the soft, the wet and even damp. Leave it open for as long as you can stand to let the rest dry completely. You can seal the bottom of the openings and flush the hole with acetone to speed the process and absorb more of the moisture (be careful it's flammable).

If you have large areas then you may need to start thinking about cutting away the skin. If you have access do it from the inside and you can leave the decks with a perfect finish.

[PeteHalstedc]

Working on a 40 year old fiberglass boat of my own now, I can tell you what I am doing, have done so far.

Its a 1975 35 foot Chris Craft Catalina (Motor Yatch) not sailer, but Fiberglass and core are fiberglass and core!

Had one soft spot on the port walk around area, that was pretty bad, since I could get to it from the inside I tried the recore from the bottom method, and although I got it done, you would have to put a gun to my head to make me try that method again. If you do buy a hazmat suit or plan on losing every bit of hair off your arms, etc. Very hard to get the cloth to stay up, has to be wetted just right and smooth application, if you end up with any humps etc. they let the wetted cloth sag from the weight.

There are some soft spots in the bow that had been repaired with a drill and fill method (I didn't do so don't know how or when they were done) but since they didn't bother to seal all the water issues first it didn't do much but make hard spots around other soft spots. I have do some drill and filling to "patch" up this area in a few soft spots since the area isn't as structural and I will be doing a major rework of the windlass area next year and will probably recore the area at that time.

Both Aft Corners were more or less gone, just fiberglass with the core the consistency of soup. I have done one corner so far (other still to go) and since these house the aft cleats, is where we board, etc. I wanted them rock solid, so I did the recore from the top. This was a much larger area, than the one I did from the bottom, but I was able to do it just as quickly because it was so much easier to work from the top. If you are well prepped, you should be able to do a decent size area from the top in a long weekend (perhaps excluding finsihing, gelcoating etc.).

We are going to go with one of the "vinyl teak" when we are all done, so we have the advantage of just need a "good finish" not a matching finish, so that probably saves me an extra day of finishing work on the areas I am repairing.

Not sure any of that info really help you, all I can say after working on this project and seeing state of previous repairs, is other than small out of the way soft spots or as others have mentioned "just need to get a few more years out of it" repairs I would not consider drill and fill, I would never consider replace from bottom again, so that only leaves fix from the top.

[OS2Dude]

When I had my 1984 O'Day 23, the areas immediately next to the chain plates and several stanchions had leaked and there was a little core rot.

In this situation I removed the pulpit and chain plates, cut the top deck to a little less than the area covered by the various bases and used various tools to remove the rotted portion of core. (Largest depth from the exposed edge was about 1.5 inches.) I then filled it with epoxy, drilled the correct sized holes/slots, counter-sank the new openings and rebedded everything. The issues completely went away and it was in great shape when we upgraded to our current boat.

I like this method as it seals the core from any additional water than may get by the bedding material, and it gives a 'compression collar' so you don't have to worry as much about damaging the core by tightening the bolts too much.

That said, the areas of damage were small and localized. If your deck is soft/squishy over a larger area, I would recommend removing either the top of the deck (easier but will leave a 'scar') or the ceiling underneath (harder, but does not damage the gelcoat of the deck) and replacing the core in its entirety. As stated before you don't want a rock solid deck, it needs to be able to flex a bit or it will crack and break.

Good Luck with your repairs.