Oyster 46 1981 - Whole deck core replacement

CanePazzo

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Good evening knowledgeable brethren.
So I went and brought my new (to me) Oyster 46 ketch to Italy from Greece for her refit, decided that the teak deck had to go having seen the amount of water entering through the holes of various deck fittings as they were removed. Once the teak was removed, I found that the last time the teak was renewed, the culprits had removed the teak and then cut all of the screws off at deck level ish, then laid two layers of CSM over the whole deck and then screwed down the new teak.
Removing the teak, quite a bit of glass fibre came up with it, then it was clear that the two layers of glass had been applied badly and water had been running between the layers over many years and filled up the core. The rest of the two layers of CSM have now been removed, the deck sanded to 40 grit. I got hold of a good moisture meter and all areas of sandwich deck returned a 99% reading. I have removed the top panel of glass on the aft deck as my first foray into this job. There was no surprise in what I found - balsa turned to compost where the davits are located, completely soaked balsa for most of the rest and not so wet balsa around the bulwarks.
I am running a few thoughts through my head at the moment -
  • Am I completely nuts?
  • I’m thinking to do the new core with pvc foam core material and good quality plywood in high stress areas.
  • I think that I will put a layer of 1708 glass on the bottom sheet of the sandwich once any repairs have been done.
  • I have been given a large quantity of ‘Proset 170/270’ epoxy adhesive. This is ready thickened epoxy, mixed on a one to one ratio. Is this suitable for installing the new core into place and remounting the cut out fiberglass deck panel eventually?
  • I think that vacuum bagging is probably going to give me the best results but there are an awful lot of holes in the lower layer of fiberglass to fill first.
  • once all the core has been replaced and the upper sheets of fiberglass epoxied back down, I want to lay down two layers of 1708 mat over the whole deck.
Question to you good people - how would you go about this game? Do you see anything that is completely wrong in my plan?
Many thanks and have yourselves an awesome day!
 

Bobc

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If it were me, I'd probably drill loads of small holes in the deck and inject epoxy into them, filling the core with it.
 

dankilb

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If it were me, I'd probably drill loads of small holes in the deck and inject epoxy into them, filling the core with it.
Is this a joke?! …given the OP’s account above…

I raise you expanding foam!

The forum has really descended to the point where we can only answer ‘how do I know what direction my sailyboat is pointing?’ or ‘where can I buy a paintbrush?’?!

The OP’s suggested repair schedule sounds reasonable (especially structural foam - if they can afford it), just a miserable amount of work.
 

Yngmar

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Yes, you're completely nuts, but it's been done by other nutters (that Sail Life guy from Denmark for example, whose episodes on the deck recoring you should watch). If you have the youthful enthusiasm for it, why not - you'll probably be cured by the end of it, if you get there.

Other than that, your plan sounds reasonable. Not sure why you want to put a layer of glass on the bottom? If vacuum bagging isn't doable, you'll get reasonable results with weighing it down with bags of sand or water. This will probably give better results anyways, as vacuum bagging on an old boat will overextract resin and show all the lumps and bumps through and you end up with more fairing work.

Then you have the wonderful job of a fairing it, applying a new deck surface (not teak again, I hope) and refitting all the things by drill-fill-drilling so your new core doesn't get soaked again. Plus whatever other surprises you discover during the job, of which there always are some.

Buon lavoro!
 

dankilb

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On reflection, the only part of the OP’s plan I’d question is reusing the old deck skin. What’s the condition like (you mention old screws plus holes)? Can you post/link pics? Presumably you’re hoping to preserve parts of the moulding like hatch surrounds?

I’d weigh up simply replacing all new ‘flat’ laminate with a new layup - perhaps retaining and glassing in only those select parts of the original moulding it’d be harder to reproduce. You’d get a better and easier bond to the foam that way (especially with your vac bag idea).

Any old thickened epoxy should work to bond the foam (re: your proset). For a better bond, I’d prime both surfaces with laminating resin even if using a premixed product. Test for compatibility first (I’ve found even solvented epoxy paints/fillers bond to my stock laminating resin better than unprimed substrates under destructive testing but YMMV).
 

B27

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I'm not convinced that gluing the old top panel of the deck onto the new foam will work well, or even at all.
The top panel needs great structural integrity at the edges, where it joins the toe rail and cabin sides or whatever.

Also as the deck is a structural element, the boat my change shape when you remove half of it.
 

Refueler

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Honest opinion ?

This is no simple job .. its a large boat with serious consequences if you get it wrong. I would suggest having a professional GRP person look at it and be retained as advisor for the work.
Do not be lulled into using some Yacht Surveyor who is Jack of all and Master of none.

Example - I looked over a boat I considered to buy ... it needed same deck work. It had already had foredeck done ... but my meter and just walking on it showed it was wasted effort.

I read the first post and I cannot help but feel its a job that may overwhelm the initial drive to solve.

I don't mean to be negative .. I just seen too many get abandoned.
 

CanePazzo

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Evening all. Thank you all for your helpful and some not as helpful replies.
Firstly, no, I’m not putting back a teak deck and not even a lookalike teak deck, I’ll be going down the painted non skid route, white so it reflects the heat as well.
I think to lay a sheet of glass on the bottom skin, after necessary repairs to it, to replace some thickness that came away with the core in places and that that will be sanded away during the prep.
Around all of the hatches, the sandwich stops a few cm’s from the hatch and there is no problem with the deck where it’s solid glass, thankfully, as that is all the way around the deck beside the bulwarks for about 15cm and the whole area of the chain plates.
I was thinking to put back the cut out panels and then glass them back in place around the border. I don’t think there would be voids as there are so many holes in them, in fact I was thinking to prep the holes with a countersink, drill new diameter hole and as I replaced the old skin, the thickened epoxy would have splurged out into them and filled the holes (two birds with one stone sort of thing!) but having read your thoughts, it may well be better to lay up new panels.
 

CanePazzo

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Honest opinion ?

This is no simple job .. its a large boat with serious consequences if you get it wrong. I would suggest having a professional GRP person look at it and be retained as advisor for the work.
Do not be lulled into using some Yacht Surveyor who is Jack of all and Master of none.

Example - I looked over a boat I considered to buy ... it needed same deck work. It had already had foredeck done ... but my meter and just walking on it showed it was wasted effort.

I read the first post and I cannot help but feel its a job that may overwhelm the initial drive to solve.

I don't mean to be negative .. I just seen too many get abandoned.
I understand your opinion and thank you for sharing it. I’m long enough in the tooth to have gathered what I hope is enough experience to get me through this part of a larger project. I have started with the aft deck, as it is an awful lot smaller than the foredeck and I want to see how my first foray into this goes and find my rhythm as I work along towards the foredeck. I have professional advice here and they come to see progress.
Maybe I should be fazed by this but I’m not, I think this should be within my skill set.
 

Refueler

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I understand your opinion and thank you for sharing it. I’m long enough in the tooth to have gathered what I hope is enough experience to get me through this part of a larger project. I have started with the aft deck, as it is an awful lot smaller than the foredeck and I want to see how my first foray into this goes and find my rhythm as I work along towards the foredeck. I have professional advice here and they come to see progress.
Maybe I should be fazed by this but I’m not, I think this should be within my skill set.

5 stars to you .. I applaud your commitment.

"I have professional advice here and they come to see progress."

That is best part ...

I have my old faithful 25ft boat on hard - stbd keel (bilge keel boat) is being repaired. Even though guy doing the work is experienced with GRP - we have on call another GRP guy to check and advise ...
 

geem

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I really enjoy building stuff in glass and epoxy. Over the last 30 years, I have undertaken many projects. The most recent was laying Devinycell core in the bottom of the 12'5" dinghy to make it stiffer and stronger. It wasn't a huge project compared to what you are undertaking but working with core is not hard if you have experience with epoxy and glass and the various additives. In some ways, the dinghy is more complex as you have to cut the core into strips to form to the curve of the hull. With a deck, there the opportunity to install large panels of foam core. Once the core is in place, you are faced with a relatively simple sheathing task. Laying up the multiple layers or cloth to get to the desired thickness.
When we removed our teak deck, we added two layers of 300g cloth to the whole area. The 2,500 holes needed something to cover them. The deck was painted with Awlgrip and looks perfect. You wouldn't know it ever had a teak deck.
Consider painting in cream not white. White is so reflective you will get snowblindness. Cream doesn't get hot and is so much easier to live with
 

Refueler

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Consider painting in cream not white. White is so reflective you will get snowblindness. Cream doesn't get hot and is so much easier to live with

Thread drift .... When I sailed with Shell .. we had two ULCC's (320,000 tonners) with test paint on decks ... it was only available in one colour - off white. It was a ceramic based paint .... we sent letters to Company advising it was leading to headaches / nausea .. AND safety concerns as the suns glare affected our watchkeeping.
Shell decided to paint over the deck - but only a section about 30m ahead of the accommodation..... this was no solution as the sun was glaring of the other 340m of deck !!
 

pandos

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Sounds like a good plan. This guy dealt with similar, might be worth watching.


I had similar issues on a HR352 which had the holes from the teak deck filled with adhesive which was used to fix on an artificial teak deck.

Because my core was manly divincell I drilled holes through to the inside, allowed the core to dry out. I drilled them to form a conical hole in the deck and filled each with fiber reinforced filler.

I sanded and painted the entire and all is still well after 15 years...
 

CanePazzo

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Sounds like a good plan. This guy dealt with similar, might be worth watching.


I had similar issues on a HR352 which had the holes from the teak deck filled with adhesive which was used to fix on an artificial teak deck.

Because my core was manly divincell I drilled holes through to the inside, allowed the core to dry out. I drilled them to form a conical hole in the deck and filled each with fiber reinforced filler.

I sanded and painted the entire and all is still well after 15 years...
Thanks Pandora for that. I’ve actually watched all of Richard’s videos and find them very interesting. I’m slightly concerned that his first posts are about 5 years ago or so! I’m hoping that my works are not going to take anywhere near that long!
 

CanePazzo

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Morning all.
In the high stress areas of the deck, ie: Genoa car track, inner forestay and the likes, I’m thinking to use G10 or similar material, that being the case, is there need to do the whole drill, fill, drill game in these areas?
 

geem

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Morning all.
In the high stress areas of the deck, ie: Genoa car track, inner forestay and the likes, I’m thinking to use G10 or similar material, that being the case, is there need to do the whole drill, fill, drill game in these areas?
Aren't the genoa tracks, attached to solid glass not core? In addition, are you sure there isn't reinforcement around the tracks already? There should be no need for reinforcement to the inner forestay area assuming the chainplate attachment is on a bulkhead
 

Yngmar

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Morning all.
In the high stress areas of the deck, ie: Genoa car track, inner forestay and the likes, I’m thinking to use G10 or similar material, that being the case, is there need to do the whole drill, fill, drill game in these areas?
No, G10 is just solid fibreglass. Not needed either if you use a closed cell foam instead of wood (in non-compression areas). These materials do not rot, and they do not absorb or transport (wick) moisture.
 

CanePazzo

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Thanks once again for your input gents.
The genoa car track is, I think, mounted on an area with a plywood core, which is for sure rotten (I‘ll see exactly when I open that area up, at the moment trying to deal with one area at a time).
The area of the inner forestay is clearly delaminated and has been well compressed with a pretty big deflection in the top skin of glass. I’m going to be using closed cell foam for all no stress areas, was thinking of G10 or similar only in high stress areas like under the davits for example.
 

srm

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A minor point, but just to reinforce the comment by @geem regarding cream for decks rather than white. My steel boat came with all white decks and was very uncomfortable on the eyes - and this was in the north of Scotland The following spring I over coated with none slip grey from the fishing boat chandler. That made the decks too hot for bare feet while sailing in the sun well north of 60N. The following season I used International deck paint in cream, and stayed with it until the boat was sold. Comfortable on the eyes and on the feet.
 
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