H37c Porthole Rot Fix (Updated)

[Mathurin]

We've started repairing the cabin sides core last year. I had started this thread back then:
http://forums.hunter.sailboatowners.com/showthread.php?t=136363

Here is a picture update of the job (from the beginning):

 

[Ed Schenck]

I see it but I don't want to believe it. There is not a Cherubini out there that isn't like your original pictures. Unless they have done what you have done of course. Not even going to give it another thought.

 

[Jim Legere]

That's the trouble with you engineers, Phillipe - you are all so THOROUGH!

I have routed out core around my windows and filled the gap with epoxy putty because the moisture meter didn't shown any problems in the cabin side...I'm keeping my fingers crossed!

 

[DianaOfBurlington]

Looks like WAY more work than I would have done. I have made these repairs many times before (though not on as wide a scale at one time) and have never opened such damage into such a gaping wound. Usually I sound the core, be it of whatever material, and determine where I can drill into it and fill it with epoxy. In most areas, smaller than this, this proves more than adequate-- it's a permanent fix to that area.

Of course sometimes several affected areas seem to combine into one big one; but I wonder if each of these under-portlight areas, treated in isolation, would not have proved easier to fix. My foredeck is not much different in area than the cabinside in this example; and I filled it with epoxy and it's rock-solid now.

 

[DianaOfBurlington]

BTW-- did you really leave no meat of (well-saturated) wood (or, better, solid 'glass) around the window openings to which to bolt the new portlights? Bolting them through foam will leave the foam available to further water intrusion when the sealants fail in the not-so-distant future.

And will you then redo all this work for the sake of the then-rotten foam core?

 

[carina]

Now don't you wish you hadn't wasted your money on those cheap-a** Har**Fre*** clamps? I did but returned them after the first attempted use.
Cheers, Hugh

 

[Mathurin]

So many things to write down, so little time. First let's say that the cabin sides where still very ''solid'' even if the core was fully saturated and fully delaminated and in an advance state of rot. This is because there are two thick layers of fb on both sides of the core. Was is still strong enough to keep everythig where it had to be to use the boat in light air every now an then? Yes (it did well in 12 foot seas). Could we have done it differently ? Probably. Would I ever considerdrilling and filling with epoxy ? No (the explanation that follows won't come from hours of reflexion, but from someone who spent 14 hours on the road today).

I'm sorry DianaOfBurlington but I do not feel that this is too much work, and do not consider drilling and filling with epoxy to be a proper way to fix such a problem. Just take a look at the video I linked in the post above. I think that it's better to do this job once, and to do it right. In this case, drilling and filling with epoxy would have been as effective as injecting epoxy in oatmeal (the core is about as mushy and watery anyway). For sure it's going to be better than what you've started with, but as far as I'm concerned, you end up with mushy stuff stuck in a somewhat hard matrix. It may feel rocksolid underfoot, but that doesn't mean it's going to handle a sharp impact as it should. It takes little energy to cause a fracture to migrate in such an heterogeneous matrix. You also have to remember that things rarely break when it's dead calm out at sea... Furthermore, the original construction technique, with marine plywood, was far from ideal. Water migrates very far from the point of entry. The cabin sides where basically fully delaminated, we could peel every layers of the plywood by hand, even dead center between two portholes. Nothing sound could be found when sounding with a hammer, and the moisture meter was showing sky high readings. I do not think that filling with epoxy at such a large scale would have made a big difference timewise. Remember that we've done the whole deck two years ago, so the learning curve is behind us. This is a fairly quick job to do, the last pictures displayed are about 40 hours in the repair process. Also, the whole process will cost less than 500$ in material.

As for the comment about solid meat around the portholes to avoid further water intrusion, the pictures are not yet showing final stages of the repairs. The core is not even cut so that the ports can be fitted. The core (close cell foam) will be cut to size, than we will use a router to grove a recess all around the porthole footprints and fasteners holes. Once that is done, we will fill with thickened epoxy. Finally ports will be bed in butyl as shown in the link bellow (a special thanks to Maine Sail for these instructions).

http://www.pbase.com/mainecruising/nfm_port_lights&page=1

Cariana, I do not get your comment... I've been using these clamps around the house for a few years now, for sure they are cheap, but for a casual user, they do what the've been designed to do AND I'm not afraid to get them spoiled with resin.

Cheers
Phil

 

[DianaOfBurlington]

I filled all of the 'rotted'/'questionable'-core spots on my deck with epoxy. It's so rigid you could hold a teenagers' hip-hop dance party on it.

Once I made a mistake and began filling too close after a rainstorm. I don't know what I was thinking; but when I filled I saw that the epoxy actually pushed the water up to the surface. I was very surprised-- thought I had wandered into a really fine mess. What I found was that by continuing to inject epoxy, the ugly baby-vomit-looking water/epoxy slime that migrated upwards eventually stopped-- all the water (and not very much had ever got in) was gone and now the epoxy was doing its job, saturating to the bottom of the void and filling towards the top. The result was a deck area as stiff as any of the other places I have filled.

The only drawbacks to my system of 'drilling and filling' is that epoxy weighs more than does foam or balsa. In very large repairs the weight difference could be a problem. In my 40 years of boatbuilding experience I have never found a point at which this is a problem. The sides of a small production sailboat's cabin are just not enough volume to warrant worry about any increase in weight. The average owner's toolbox would probably negate any theoretical savings.

While it is very true that 'Water migrates very far from the point of entry', it is also true that epoxy does the same thing, perhaps even better than does water. Penetrating epoxy is made to do this. I have been filling voids successfully with epoxy since I first heard of the stuff in the 1970s and the only significant mess I ever encountered was when the epoxy would not seem to stop sucking in, and more and more got pumped in with the syringe, until I happened to notice an uninstalled drawer sitting in the pilot-berth area with one whole corner full of the stuff. Through the tiny voids between plywood edge-grain and the fiberglass, the epoxy had migrated 10 or 12 feet along the flange of the boat (and fortunately found something to drip into that was more or less replaceable). To this day that part of the flange on that boat is probably the strongest hull-deck joint we've ever had on one of those boats.

I would trust WEST epoxy with any wood-to-wood or wood-to-raw-fiberglass joint with my life-- and, oh, wait-- I do; because my boat has been restored, remodeled and improved based on that ethic.

 

[Pilotocopilot]

John (DianaOfBurlington) can you describe the process and the materials you would use. Specifically the typical hole size drilled the distance between holes and the number of holes for a given area. I've read other articles for epoxy injection but would like a builders take on this process.
My boat was surveyed 3 years ago and an area around the windlass was found to have an elevated moisture level. Rather than pull the windlass and start replacing plywood core and all that's involved in that, injecting may be the solution that stems the moisture migration and solidifies the deck.
My own personal thoughts on wet core and soft decks is, it's a distraction, and after 37 years of sailing on many different boats some that I've owned I have never seen a catastrophic failure based on moisture or soft decks.

 

[Pilotocopilot]

Phil your work as always is impressive.

 

[DianaOfBurlington]

JC's secret system for filling deck-core rot

Pilot, thanks for your question. I get asked this a lot. Phil should put me on as a resident expert in this! :dance:

If you know there is water present you can drill a hole-- only through the fiberglass layer(s)-- from one side or the other and then apply a vacuum hose to suck it out. This works surprisingly well-- it's the first step I recommend in fixing rotted outboard-skiff transoms. They all rot (motorboaters don't seem to care for their boats like we do ours); and this is the best way to save them. (I am doing my motor bracket's backing board the same way.) You then drill a few smaller holes, sized to fit the syringe, maybe about 3/16" or 1/4", into the top of the transom and pump in the stuff.

I used to thin the epoxy with acetone (not what Gougeon Brothers recommend; though when I told of them of this they said 'Who are we to argue with the Cherubinis about treating wood?" ) But you really do not need to thin it; as it's only doing its job by penetrating the way it does.

You might go cautiously at first, with just a little (3-5 pumps' worth?)-- it will migrate down. When it comes out the hole you drilled for the water, at the bottom, you know it's done what it should (and you know the transom was toast). Next batch, tape over the hole and after it's kicked off, go for broke and really pump it in.

For a deck, you do basically the same thing. You might drill a hole into the underside for your vacuum hose. Tape it securely to make an 'airtight' seal-- I have done this adequately enough with duct tape-- and run it till the vacuum cleaner's motor labors. For Diana I knew the deck to be already dried-out (but for a mistake involving a recent rain, as I said). Be sure to plug up or tape over any openings in the underside-- for the epoxy will definitely find them. You might station a partner below to watch for drips! --and be very wary of when you are pumping in tons of epoxy and apparently making no progress! Spots to watch are along the flange/toerail seam and anywhere silcone (or something worse) was used to bed down through-bolted deck hardware.

Topside, you drill a few holes to begin (you can always drill more if you think you have to). The best tactic is to choose a spot, maybe a few square feet and outboard (low) on the deck, drill pilot holes-- into the core only (mark the bitt with tape if you're worried, to be sure)-- near the highest border of the spot, and fill till you see the epoxy is no longer soaking down in your pilot holes. Don't make the mistake I've made too many times and go silly drilling too many holes-- when the epoxy makes it down to the lower holes you get a dribbling mess all over.

I generally make the holes about 4 inches apart; but it depends on the size of the area you are working with and how serious the rot is inside the core. In theory even rotted core is still 'there'; and epoxy will bond very well with wood or foam dust. As I said before, it is heavier than core material; but as I said too it's never been a terrible concern in the proportions we're talking about. For odd isolated areas it is a very solid, reliable, permanent fix. And if you do not get it all, the parts you do get remain strong and make a good base or boundary for you to fill other places.

If you choose to drill only in places where there is nonskid, you have only to fair over the holes and repaint the nonskid patches. For my deck, which was pretty bad, I resigned myself to repainting the whole deck (with Perfection) and I was redesigning the pattern of the nonskid patches anyway. The little indentations left when the epoxy is done flowing in can be faired with Marine-Tex or epoxy with silica gel, either of which will be rugged enough to not fall out in future and will be able to take paint (after the usual proper prep). Gelcoat, being polyester-based, will not stick well to epoxy (though the reverse is true). So in using epoxy you've pretty much given over the hope of refairing the affected area in polyester- (or vinylester-) based products.

This system should also be used any time you have to mount or re-mount hardware to a cored deck. Drill a pilot hole-- only through the fiberglass to the core-- for each mounting screw and fill it. Do the same in the area under the bit of hardware, like a winch and especially anything in compression or tension, like a padeye or halyard-lead block. When it's cured, drill through the solid-epoxy core you've just filled and bed down the part with 5200-- which will keep out water, hold like crazy especially in shear or tension, and provide needed flexibility. In many cases you will need only fair-sized fender washers with the under-deck locknuts because the epoxy block you just made can serve as an adequate backing plate, especially for anything in shear, like cleats and halyard stoppers.

I had doubts about the integrity of my hull after I rebedded the keel and so drilled a few exploratory holes into the bottom strata, between the keel bolts, to probe them with epoxy. This was supposed to be only solid fiberglass; and it was. No hole took more than a fraction of the syringe's worth. It was-- and is-- solid.

For Diana I had made a new, short little bulkhead at the back end of the cabin sole on which I stood the ladder/cooler shelf structure. I used 'high-quality' 3/4" MDO for it. Within too short a time this board was rotten from water behind it (from the cockpit-seat locker leaks), even though it had been well saturated (so I thought) before I installed it. (I blame it on using Dave's MAS and not my own WEST epoxy. MAS just does not penetrate as well; period.) Removing the bulkhead was out of the question; and it could not stay like it was. I drilled pilot holes down into the top edge of the plywood, straight into the depths of the laminations, just like I would have done for a plywood motorboat transom, and poured in the epoxy. It took three or four tries and made an awful mess (the stuff ran straight through the spoiled core and gushed out the bottom edge, finding gaps in the 5200 and dribbling into the bilge, where it glued down a stray PVC fitting that I still haven't ground completely away) but I sorted it and now it's solid.

I think this is a good solution for your windlass mounting bolts. Given enough epoxy in the surrounding core, it will take the very severe shock and shear loads very well. Once epoxy has found something to latch onto-- the rough inner surface of the fiberglass deck, the rotten core, the remnants of any plywood-- it will stay in place and provide a very sturdy inner stratum through which you can drill even big bolt holes. And it takes 5200 very well, adds stiffness, and displaces all gaps that might otherwise find condensation or stray moisture. The one thing it does not do well is flex-- but for a windlass mount you had better not have much flex (let the nylon rode take the shock loads!) and a rigid deck is always stronger and thus more secure underfoot than one that moves and flexes to the point of fatiguing the glass fibers within and weirds you out when you step on something you'd prefer to feel solid.

Epoxy and wood = perfect together.