What is this under my teak deck...

[glhotka]

I have a 51' Formosa. The deck is in rough shape (dry and cracking sealant between boards some loose, etc). So I opted to pull up a small section. I can see that there were several new holes drilled in the teak planks because there were slotted and phillips screws in them. Several of the bung holes had been filled with epoxy and when I removed them this is what I found.
It looks to me like it is some kind of an epoxy compound that may have been put down to hold the teak planks on (this is a plywood cored deck with Teak over the top).

So the question are as follows if someone happens to know them.

1) What is this under the planks, likely thickened epoxy or fiberglass?

2) How can I tell if the core is rotted below? I have attempted the tapping test, but this all sounds solid. I am assuming that is because of the additional glass (if that is what it is) that is on the deck. In this spot where I removed the planks, several were just rotted. They broke and in one case they are thin and you can tell about rotted through.

3) How would you recommend putting these back? I was going to use a grinder to get the surface flat, and then put thickened epoxy down and try to avoid screwing it in at all.

[JPA Cate]

If you're very lucky, the previous owner fixed it before there was much deck rot. If some of the teak is rotten, it will be all close to history. Sorry to bear sad tidings.

If you want to keep the boat, carefully take down the head liner underneath where the deck penetrations are, then you can see the under-deck. "Look" at it with an icepick. The ice pick will not easily penetrate sound timber. Anywhere water might have got to the ply is where the rot starts. Oh, by the way, you may be able to see the rot without scraping or penetrating it.

You need for the plywood to be sound, or for the epoxy and glass to be thick enough for a deck a 300 lg. gorilla could jump on. That is, if you want to safely cross oceans, you do.

Good luck with it.

Ann

Ann

[Ryan H]

It's hard to tell from your pick, but it looks just like what I found under the teak decking on my Formosa 41 last summer. If you take a wire brush and some acetone to it you'll find there's several layers of fiberglass over the plywood core along with a layer of gel coat the teak boards were pressed into before being screwed down. My only guess was that the gelcoat helped level the deck boards.

The fiberglass and the gel combined was a little over a half inch thick, sounding it wont do much good. Either cut a bit out and see what the plywood underneath looks like or drill a few exploratory holes and see what comes out.

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[DeepFrz]

That is a very poor picture but from the looks of it you have a big job ahead of you. Maybe if you posted a larger more detailed picture folks here would be able to give you more advice. Pictures from different areas of the deck might also help.

Is this a new to you boat?

[bletso]

I had some of the same problem. It is dirt which has worked its way down and under the separated sealant. In my case I lifted off a large area and reseated - re-caulked it. I would be concerned as well for the core material. I had to replace some on my deck.

[Dolphinblue-BOB]

I have rebuilt a Formosa 51 several years ago. The deck construction was a plywood core with fibreglass overlay. This looks like rotten plywood, although the picture is very bad, and small. On the other hand, i can not see any fibreglass. So If you can make a better picture, it will be easier to tell. But at this stage, the only advice i could give, is to take the whole teak deck off. If it looks like this on this spot, there is fairly good chance that other parts are in equal bad shape.

[lesterbutch]

Any partial deck repair would be unadvisable. You absolutely should replace the whole deck! Just think of a large wave breaking on your deck, will the deck break too?

[Cheechako]

No picture...?

[kellyp08]

I had a similar problem with a Cheoy Lee OS36 back in the 1970's. Overall she was a great boat, a pretty boat, a great sailer and I loved her. However, there was a major problem - two problems actually. A rotten plywood deck core and very thin (1/4") teak "planks" overlaying this. The teak was so thin that, with a bit of wear, glue holding the bungs (teak "dots") could not get sufficient purchase and the "dots" would pop out with the working of the deck. This exposed the fastenings and a "wick" effect and water leaking down into the "balsa" core. I contacted Cheoy Lee and they kindly shipped a bag of bungs from Hong Kong (the Chinese version of F*** You).

Well, eventually, when I removed large sections of the deck and fiberglass outer part of the "sandwich", I found out that it wasn't a balsa core - it was plywood and NOT even marine plywood! This had rotted out resulting in a trampoline for the fore and side decks.

I eventually removed, in stages, large sections of the outer fiberglass "sandwich" and removed all of the rotten wood - most of it came out with a Red Devil scraper and/or putty knife. Without going into a lot of detail (though will be happy to do this if someone would find this useful) I eventually replaced the entire deck over an 8 month period of time (using 5/8th inch teak).

In the end I felt like the cattle rustler in old Texas who is about to be hung and is invited to say a few last words: "Yessir", he says to the hangman; "This whole thing has sure been a lesson to me". Replacing the deck cost more than I paid for the boat!

And what were the lessons?

1. Avoid boats with "screwed on" teak overlayed decks. (Hinckley, Morris and other high-end builders, when a prospective new boat customer cannot be talked out of a teak deck, they grind off the non-skid made by the deck mold, and then EPOXY the teak overlay to the fiberglass deck - no fastenings!).

2. Beware of production boats built in the Far East and elsewhere with fastened teak decks. They may look pretty, but you don't know what's beneath the surface! And what you can't see CAN hurt you and/or cost you a s**t-load of money.

[Dolphinblue-BOB]

Unfortunately, this teak deck laying technique, with screws and bungs, was not typical for the far east boatyards only. In those times, there was no other way of fixing the teak deck to the boat, as the gluing techniques alone were not strong / durable enough then. Almost all builders of that time, have done it this way.

Today we also use the same "No screws" technique to fix the teak decks, and as a matter of fact, we offer complete teak deck replacement in a kit form, which is delivered in a box, and fixed by the owner. To all our clients, we recommend to thoroughly check the deck integrity first. Although HCY teak decks were screwed from below, the moment came where the deck started to leak.

However, the core material still remains the main problem of the decks, which, as stated by kellyp08, was very poor quality in the old times. Fixing the deck structure first, is a must in all such endeavours. Not only watertight, but strong deck is a question of safety on the sea much more important than just visual effect. Although I personally prefer teak decks over painted decks, if, for budget reasons, I had to choose between solid fiberglass deck and teak deck over questionable, old deck, teak would have to wait, for obvious reasons.

[rcmpegasus]

I just went through the same situation with my Formosa 51. Some bad planks, some leaking spots into the plywood. I ended up cutting all the deck off, most of the supports and all the cabin sides. A lot of work (6 months) in the yard. Hopefully you can get by with less, but partial jobs are hard. There is no way from the underside to tell what you have, you have to open it from the top. Remove teak and use a circular set shallow and cut a square out of the fiberglass and plywood. It should be two layers of plywood and a layer of bead board, set on the beams.

Here are some pictures.




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[Lepke]

What is under your teak is probably thickened polyester resin because it's cheaper. Most yacht boat builders seem to only use marine plywood in the hull. And not always there. I've been working on boats since the early 60's when most of the boats were wood. In my youth I worked as a shipwright and later built wood & steel commercial boats. I don't use polyester resin. It doesn't bond well to anything including itself.
The only enduring deck solution I have seen is putting a epoxy/mat layer over 2 layers of plywood that is laid in opposite directions and epoxied together. The plywood needs to be screwed down and together with stainless or bronze. No nails of any kind or material. Nails are for houses. I fill all the plywood seams and screw holes with thickened epoxy and put down 2 oz. csm with epoxy leaving a heavy top coat. Sanding it smooth after the cure so that the planking will fit tight to the epoxy. I have both epoxied the planking to the epoxy/mat and left the planking screwed only. When screwing the planking or anything to exposed wood, I have epoxy in a syringe that I put down each screw pilot hole (so when done the screw sits in epoxy). The epoxy seals the screw and lubricates (like soap used to) when driving the screw. The only leaks I have seen in one of these decks was caused by major damage like heavy dropped items or collision. And they're usually not to hard to fix. I know of a couple decks about 40 years old, done this way, and still dry. Screwing from the bottom is a great idea until water gets to the screw and over time works it's way down the screw hole and into whatever wood is around and below.
Teak is oily and needs to be cleaned if you're going to epoxy it down. After cleaning I use a slightly reduced epoxy to absorb into the teak and then regular mix epoxy before the reduced mix is fully cured to bond to the plank to the deck. It works best with a couple helpers for mixing and pre-drilling the teak.

[Oceandeep]

I have a similar problem with my Hudson 50. Here's a response to you questions based on my experience to date...

1. What's under your teak? It's supposed to be gelcoat and a couple of layers of glass cloth. Mine is actually shiny like the rest of the topside once you scrape off the tar-like bedding material that the teak is set in.

2. Is the core rotted? I would drill some test holes where the deck seems to have some spring in it. The core material on my boat is just plywood. It definitely has some dry rot here and there. So far I have just been injecting penetrating epoxy where it's needed as most of the deck is still mostly solid.

3. Re-attaching the teak? I've been re-attaching the teak by putting down a thick layer of black life caulk under it and attaching it with screws in the same manner that it was done originally. I inject epoxy down the screw holes first and countersink the screw so I can cover it with a bung. If a teak plank is bad I would consider replacing it . Jamestown sells teak planking that may match your deck. Someday you will have to replace your entire deck and you will probably have to re-core your deck as well but I would check things carefully to see if you need to do that now or just do some spot repairs.

As for me I'm removing all of the bad bungs and screws on my deck. Then I'm re-drilling each hole, pumping it full of penetrating epoxy where it will take it. (Most holes are coming out dry but a few areas have taken quite a bit of epoxy) . I'm also re-caulking the deck seams where it needs it. The teak is still about 1/2" thick so I hope I can get another 10 years out of it. Hopefully I'll be someplace like Thailand when I finally need to get it replaced.

[glhotka]

Thank you to everyone who replied. I am not sure what happened with the picture, it sure was bad and I didn't notice that at first. Here are a few additional pictures.
Since posting this I did use a scraper and scrape quite a bit of it off to get down to what looks like it may be gel coat. In some cases, I went a bit too far and exposed a bit of the glass map in the fiber so I know I got below whatever the adhesive type material was.
I removed all of the screws and did put epoxy in each hole. The tap test did sound solid, at least consistent in all areas even after removing the adhesive. I am going to expose a bit more of the deck and will try a few exploratory holes in the next couple of weeks to see what I am facing.

RCMPegasus. The photos of what you faced were really helpful, but I really hoping I don't have to take it down that far. I realize I don't have a large section up yet, but I have only felt 2 places on the deck that felt even the slightest bit spongy so will inspect them a lot closer but sure hope I don't have to remove that whole deck, I am looking to identify just the areas that need any core repair and repair it where needed as opposed to the baby and bathwater scenario. I am sure your boat will be better for it, but I still hope I don't need that.

Here are some additional photos and angle of pictures. If this changes your responses at all please let me know.
Thanks again for all of the great responses. It is really helpful to get a sense what others have or are facing.

Just after the teak sections were removed.


Cleaned up dust, this is just aft of the mast, and a fairly close up photo


Here is a full view of the section removed


Here is the way I used an ultrasonic scraper (like a Fein Tool)


And lastly, here is a section that has been scraped and vacuumed off.

[scuba0_1]

Wow I have to give kudos to all of you who have tackled this type of job. With the pics from the other boat all I can say is wow.

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