Novice Recore

[Jeremy]

So, in pursuit of a deck leak, I have (perhaps inevitably) embarked on that scary bit of old-boat maintenance I hoped to avoid: the deck recore. And, in such a convenient location: the bridgedeck/sidedeck/under the coamings.

With some difficulty, I've got the coamings off (and dispite their condition am hoping to save them - at least for this season). I've taken off the top skin and scraped out the rotten core. All of which, as far as I can tell, is a consequence of poorly bedded screws (wood screws) driven from below deck into the coamings. The majority of the problem seems to be the consequence of screws that were not replaced when the PO evidently removed coaming screws for some nearby core work (what appears to have been done with ordinary plywood and glop), and trusted too heavily in the water resistance of silicone to fill the old hole (I took out a bouncy ball of silicone injected between the skins as an ineffectual stopgap).

The winch pads (a nightmare to remove) were adjacent to the worst area of rot, but above an area of the deck cored with foam (apparently original) and apparently sound (although they initially seemed a possible suspect for the deck leak).

All this is a lead in to a few questions.

1. Should I replace the aged foam under the built-up winch pads with balsa? Solid lay up? Does the answer change if I forget the built up wooden pads (and the multiple long through bolts) and go with a bronze base (with only a few through bolts that could go through a solid layup?

2. Should I replace all core that was wet (and has now dried), or only the rotten stuff?

3. If in my vigor removing rotten core, I break through the bottom skin (ahem), how should I handle that? A layer of biax in resin to reinforce the skin and then proceed as "normal"?

4. Setting aside aesthetics, once I've replaced the core, can I simply epoxy the top skin back on? Do I need to grind and tape the edges for strength? Or (as I know Tim does) should I lay up a new top skin? I should note, that the rot I've dealt with is confined to the aft edge of the doghouse and the very edges of the bridgedeck. I'll upload some photos if I can figure out how.

I really don't want to unscramble the eggs and totally redo the previous goopy plywood sidedeck recore (I really want to get the boat in the water this season). If I successfully open up the area, dry it out, replace rot and seal the whole thing up, can I happily ignore the schlock job for at least a couple years?

Thanks all.

[Rachel]

With some difficulty, I've got the coamings off (and dispite their condition am hoping to save them - at least for this season). I've taken off the top skin and scraped out the rotten core. All of which, as far as I can tell, is a consequence of poorly bedded screws (wood screws) driven from below deck into the coamings.

I think I have seen what you are talking about. Some (most?) boats, like the Tritons, attach their coamings through the side, and into non-cored areas; whereas the swoopy Meridian coamings lie on top. When you re-core, I would make sure to have at least thickened epoxy annuli where the screws penetrate (unless you are going to lay in a whole fiberglass strip or something) (likely you were already planning one of these options).

The majority of the problem seems to be the consequence of screws that were not replaced when the PO ... trusted too heavily in the water resistance of silicone to fill the old hole

Evil double whammy! Silicone = agent of devil!

1. Should I replace the aged foam under the built-up winch pads with balsa? Solid lay up? Does the answer change if I forget the built up wooden pads (and the multiple long through bolts) and go with a bronze base (with only a few through bolts that could go through a solid layup?

If you have the pads off already, and you are doing work in the area so that it's not too much more inconvenient, you might want to put in solid fiberglass pads - either set in pre-made or laid up in place. On the other hand, epoxy annuli where the fasteners run through would probably be fine too. I think even with good foam I would want the firmness of those, at least. I think I would want the same (annuli) with the bronze, L-style bases.

2. Should I replace all core that was wet (and has now dried), or only the rotten stuff?

I tend to like to get out with all the old/bad and in with the new, and in many cases wet-then-dried balsa is just not the same as original dry balsa. It can de-bond or get kind of weak and "frizzly." But...I can't see yours, nor can I see how much more work it would entail to get it all out. Also, your comfort level with a possibly not quite as perfect repair might be different.

3. If in my vigor removing rotten core, I break through the bottom skin (ahem), how should I handle that? A layer of biax in resin to reinforce the skin and then proceed as "normal"?

The inner skin on the Meridians is rather thin (which is not uncommon on other plastic classics either), so I wouldn't be surprised if you do break through. Especially since if the core has been soft and weak for sometime it may have been repeatedly "stretched" when people walked on it, etc. I would add a layer before re-coring, like you suggest. If you need to you can shore up the inside with some combination of waxed/waxed paper/shiny taped plywood or etc. and some prop sticks.

4. Setting aside aesthetics, once I've replaced the core, can I simply epoxy the top skin back on?

You can either re-use the upper skins or lay up new ones. Sometimes using the old ones is a labor saver; other times it's more trouble than its worth, in my experience (like say it might be hard to get all the old core out without "cubing" the upper skin) (OTOH, if the upper skin is curved or shaped (maybe on the bridge deck?) it might help you to re-establish the proper shape.

Do I need to grind and tape the edges for strength?

Yes, if you re-use the old skins, you need to grind a taper onto both edges and "tab/tape" them back together. If you use new glass then you just need to grind the taper into the parts of the existing skin that you are glassing onto with the new layup (i.e. approximately 50% fewer tapers).

I should note, that the rot I've dealt with is confined to the aft edge of the doghouse and the very edges of the bridgedeck. I'll upload some photos if I can figure out how.

It would be great to see photos. Are the house sides or top cored on your Meridian? I seem to remember it may have been built somewhere other than DVL (although I think we weren't sure); I believe all of the DVL Meridians have un-cored cabin sides and tops (and, I would expect, after ends).

I really don't want to unscramble the eggs and totally redo the previous goopy plywood sidedeck recore (I really want to get the boat in the water this season). If I successfully open up the area, dry it out, replace rot and seal the whole thing up, can I happily ignore the schlock job for at least a couple years?

Well I probably wouldn't be able to, but then my boats stay out of the water WAY longer than they should; it's a personal weakness.

But okay... are you talking about two different areas? I would not open anything up and then not bother to fix it properly; but if you are going to fix the "new" area properly and just leave the other area for another time altogether, that might work. I'd be interested to see how bad it is (hard to tell what to advise otherwise).

Those are my thoughts for now -- would love to see more gory details! (She said chipperly, and then felt slightly guilty about it.)

Rachel

[Jeremy]

Many thanks for the detailed reply, Rachel. Here are a few photos:



The above photo shows the port area, after removing much of the rot but before grinding the inner skin. To the lower left is the brittle original foam that was under the winch pads. The dark stripe coming up from the lower left marks the location of the coaming boards, which were held in place with wood screws driven up from below (I had to spend a fair bit of time crammed uncomfortably in cockpit lockers to extract them). The holes for screws that would have been driven up through the bridge deck were not potted (and indeed did not even have screws in them. The effect was that the coaming boards acted to guide water to these holes, into the deck (and cabin).

To the top (hard to see) is the edge of a prior repair done with 1/2 inch ply and resin. Incidentally, the areas of rot I dug out extend under the lip to the left and on the aft ends of the cabin top (which, like the rest of the house are not cored).




Different views of the same thing (before and after grinding).



This is a view of the starboard side, which shows a similar situation (consequence of the same cause). To the top and right are the edges of a prior recore with plywood. I have not reached "clear horizons" here, and have some more work to do where rot extends beyond the edges of the skin I removed.

[Rachel]

Thanks for posting the photos - it's nice to have a visual (even if it is "mid-surgery). I sure can identify with where you are now. Seems like you're at that "Okay, do I try to keep this as minimal as possible? Or is that making it harder while I try to work around stuff? And should I just tear more/bigger off and do it right? Might this even be easier? But what about this season?" etc. etc. (Hope I'm not putting words in your mouth, of course.)

Let me also preface anything I say by letting you know that all the re-core work I have done was from below, and I always used new skin material. (Yes, totally against physics that way - groan - but I had reasons each time.)

So, a few thoughts that come to mind:

1) It may be too late now, but if you do any more cutting up against the coach side, or other edge, I might try to leave a wee bit more of a "lip" for where you are going to grind it down and attach the new top skin (or tab on the old one). Then you won't have as much fairing work up against the house side (although you then have to dig a bit under the lip, and probably fill that area with thickened epoxy vs. core).

2) Given the failing looking condition of that foam under the winch bases, the fact that you have the top skin off now, and the relative fiddlyness of potting each fastener hole individually, I think I would just cut out an area of the foam slightly larger than the winches and lay it up in pure glass (or you could lay in a section of pre-made FRP board). Then just glass over it all with whatever you use for a top skin, and re-drill the winch fastener holes.

3) On the coaming boards, I would make sure to go with some sort of annuli or etc. where the screws go up from below. Just to keep the screws and new car separated.

4) Some of the shapes you have cut out look a tiny bit complicated, so if it were me and I did end up cutting out more, I would think about making them into more "simple" shapes as/if possible.

5) Since the bridge deck is somewhat arched (not sure about the other decks), and the inner skin is thin, I wonder if you will want to establish some sort of formed support under it now, while it's still "in shape" - just to make sure it does not inadvertently change shape as you work on it, weight down the new core, etc. (I am not sure on this from here - there may be enough shape support from below in the way of bulkheads, etc.)

Rachel

[Jeremy]

Thanks again Rachel.

Seems like you're at that "Okay, do I try to keep this as minimal as possible? Or is that making it harder while I try to work around stuff? And should I just tear more/bigger off and do it right? Might this even be easier? But what about this season?" etc. etc.

PRECISELY!

1) It may be too late now, but if you do any more cutting up against the coach side, or other edge, I might try to leave a wee bit more of a "lip" for where you are going to grind it down and attach the new top skin (or tab on the old one). Then you won't have as much fairing work up against the house side (although you then have to dig a bit under the lip, and probably fill that area with thickened epoxy vs. core).

I was worried about that. I wanted to be sure I could slot new core under the lip (but maybe that's not necessary). At least at the side of the deck house, that area will be covered by the curved blocking at the forward edge of the coamings. As an aside, I'm pretty sure I'll be laying up new - the removed pieces are a Swiss cheese of exploratory holes.

2) Given the failing looking condition of that foam under the winch bases, the fact that you have the top skin off now, and the relative fiddlyness of potting each fastener hole individually, I think I would just cut out an area of the foam slightly larger than the winches and lay it up in pure glass (or you could lay in a section of pre-made FRP board). Then just glass over it all with whatever you use for a top skin, and re-drill the winch fastener holes.

Makes sense to me. I can reinstall the built-up wooden winch bases (somewhat rotten/end grain bits) and original winches, but I picked up a pair of bottom action Murray winches for a song, and would have to increase the diameter and height of the bases to accommodate them. This leads to my consideration of L-shaped bronze pedestals (there are some Murray-specific ones available from Classic Marine in England at the same or lower cost (including exorbitant shipping) as appropriately-sized rig-rite/Spartan ones).

3) On the coaming boards, I would make sure to go with some sort of annuli or etc. where the screws go up from below. Just to keep the screws and new [core] separated.

Again, makes sense. This is only an issue in a few spots, chiefly where the coamings pass over the bridgedeck. Beginning a bit aft of the bridgedeck, the sidedecks appear to be solid layup.

4) Some of the shapes you have cut out look a tiny bit complicated, so if it were me and I did end up cutting out more, I would think about making them into more "simple" shapes as/if possible.

I was wondering about that - the current shapes are a consequence of trying to keep the surgery as minimal as possible (as you'd guessed), but I see what you mean and think I'll simplify the shapes despite the bigger incisions.

5) Since the bridge deck is somewhat arched (not sure about the other decks), and the inner skin is thin, I wonder if you will want to establish some sort of formed support under it now, while it's still "in shape" - just to make sure it does not inadvertently change shape as you work on it, weight down the new core, etc. (I am not sure on this from here - there may be enough shape support from below in the way of bulkheads, etc.)

Good thought. So far, there remains sufficient rigidity due to the placement of bulkheads etc., but I'll monitor this and reconsider as I go. If there comes to be a sag, is it already too late (in other words, should I provide support even if it doesn't appear necessary at the moment?

* * *
I sure appreciate the guidance from your replies and this site in general! This is my first year of boat work, but It's been an enjoyable hobby, even if I may have gotten in a bit over my head.

[Rachel]

PRECISELY!

Now how did I guess that.... heh.

I wanted to be sure I could slot new core under the lip (but maybe that's not necessary). At least at the side of the deck house, that area will be covered by the curved blocking at the forward edge of the coamings. As an aside, I'm pretty sure I'll be laying up new - the removed pieces are a Swiss cheese of exploratory holes.

I think you will/would be okay (or maybe even better) just jamming thickened epoxy under there too, if that works out. Good to know (or be pretty sure) you are going to lay up new skins. I think it would be a pain to work with the little pieces. The holes would not be bad; but all the little corners and seams... ugh.

but I picked up a pair of bottom action Murray winches for a song, and would have to increase the diameter and height of the bases to accommodate them.

Ooh, drool! Although, if you don't go that route, you may be able to fix up the existing bases with some thickened epoxy, depending on how bad they are and where the bad bits are. I do like the bronze pedestals though, and they probably make for fewer places for varnish to want to lift or go bad since I think they only contact the coaming in a couple of spots (?). So on the wooden pedestal bases... you just have million mile long machine screws?

This is only an issue in a few spots, chiefly where the coamings pass over the bridgedeck. Beginning a bit aft of the bridgedeck, the sidedecks appear to be solid layup.

Naturally those would be the places where a previous owner used silicone plugs... augh!

Good thought. So far, there remains sufficient rigidity due to the placement of bulkheads etc., but I'll monitor this and reconsider as I go. If there comes to be a sag, is it already too late (in other words, should I provide support even if it doesn't appear necessary at the moment?

I'm having a hard time answering that for sure from here. I don't think you are suddenly just going to have the whole thing going out of shape. I think I would just keep it in mind as you go along - maybe make some measurements or put some little "tell tale" sticks in place now so that you will see if things are likely to move. It may be perfectly fine as-is. I mean, it is a smallish boat/shape. Hmmm.....

Okay, I was just looking at this photo:

I suppose I would give things a bit of a "heave on them and see if they move" test. Again, I may be "worrying" for no reason, but I'm just looking at the after end of the cabin, and wondering if you have the core out of the bridge deck, and the side decks alongside the after end of it, well, could things sag at all? If I had to guess I would say no, but on the other hand if the inner skin is really thin, and you do have to weigh the new core down.... I would keep it in mind, and potentially do some bracing (which of course would have to go down to the galley flat, so you would want to make sure that was sturdy enough. Or maybe you could brace to the bilge by taking the companionway steps out). But again... may not be necessary, and I hate to think you might make things more complicated just on my "maybe" from afar. [Okay, looking at it again as I previewed the post... if the galley flat is reasonably strong, maybe it wouldn't be a bad idea to make a temporary mini-bulkhead of vertical ply that spans the cabin just beneath the forward end of the bridge deck, inside the boat. That would perhaps hold the shape of everything, plus spread out the load below. What does anyone else reading think of this?]

I sure appreciate the guidance from your replies and this site in general! This is my first year of boat work, but It's been an enjoyable hobby, even if I may have gotten in a bit over my head.

Before you know it you'll be an old hand with the re-coring :) I imagine you may have seen them (and by all means I hope you keep this thread going), but there are some good threads in the archives here, and quite a number of Tim's project logs include re-core jobs (including the most recent Cape Dory 27... Angelina, I believe it's called).

I hope you'll post more photos as you go! I see you already have a MultiMaster (or MM like tool). Doing my first re-core is when I fell in love with that tool (borrowed one from a friend).

[Quetzalsailor]

The only thing I would have suggested is working from below to preserve appearances of the non-skid. However, with your mention of previous repair and your current condition, think no more! It's a pretty miserable business, anyway, to work from underneath.

Now, simply work to an easy shape to scarph and feather-in your repair. In other words, make a nice round or rectangular shape for the repair. You'll want at least 6:1 or better 8:1 slope to the 'glass. Think a little about continuity, that is, the new work should be similarly flexible as the adjoining work so that there is no enthusiasm for the structure to crack there. Ditto at curved transitions at corners, between deck and house side; be sure to either stop shy of the corner for the start of your scarph or include the corner (obviously the former is easier!).

Read up on all those instructions about copying non-skid to make an invisible repair; it's supposed to be possible. (I've read it in Books! It must be true.)

[Rachel]

The only thing I would have suggested is working from below to preserve appearances of the non-skid. However, with your mention of previous repair and your current condition, think no more! It's a pretty miserable business, anyway, to work from underneath.

I did that on one boat that had really lovely deck gelcoat and non-skid, and it was a pain. On another boat the decks had a lot of crown and shape, plus some other contingencies that made it seem more favorable to work from below, so chalk up #2. Both boats had just "plain" laid-up and painted fiberglass overheads in the to-be-recored areas, so I didn't have much to live up to in terms of a perfect finish - that was a benefit.

Gravity was less so. Not so much for laying in the core - as it was not that hard to get it to stick up - but more for the hours of sawing/grinding/digging/sanding/dust upside-down or overhead. Oh my aching arms.

Read up on all those instructions about copying non-skid to make an invisible repair; it's supposed to be possible. (I've read it in Books! It must be true.)

It sounds like you're half kidding anyway, but unless this Meridian has much nicer non-skid or deck surface than most I've seen, I think I would be seriously considering a complete sand-down/re-paint of the decks, with new rolled-on type non-skid. Even if not going for the whole project now, maybe just patch/paint the new area for this year, and then plan on the full deal next time. Of course a lot depends on the current condition of the decks.

[Jeremy]

Ooh, drool! . . . So on the wooden pedestal bases... you just have million mile long machine screws?

On the Murrays - the guy I bought them from had an additional set of MW5s at $175 apiece. Don't know if he still has them, but if anyone's interested, let me know. Yes, the current pedestals have seriously LOOOONG machine screws.

I suppose I would give things a bit of a "heave on them and see if they move" test.

Only thing that flexes when pressed is the inner skin in the immediate area of pressure - the rest of everything is solid as anything.

I imagine you may have seen them (and by all means I hope you keep this thread going), but there are some good threads in the archives here, and quite a number of Tim's project logs include re-core jobs (including the most recent Cape Dory 27... Angelina, I believe it's called).

Yes, have followed with interest. Hoped not to have to deal with it myself!

The only thing I would have suggested is working from below to preserve appearances of the non-skid. However, with your mention of previous repair and your current condition, think no more! It's a pretty miserable business, anyway, to work from underneath.

I contemplated that, but the decks are in a state anyway - between prior repairs, a skid pattern filled with paint, the pain of working against gravity, and the apparent ease of the paint-on type of nonskid products (Kiwigrip etc), top down seemed a hell of a lot easier than bottom up.

Now, simply work to an easy shape to scarph and feather-in your repair. In other words, make a nice round or rectangular shape for the repair. You'll want at least 6:1 or better 8:1 slope to the 'glass. Think a little about continuity, that is, the new work should be similarly flexible as the adjoining work so that there is no enthusiasm for the structure to crack there. Ditto at curved transitions at corners, between deck and house side; be sure to either stop shy of the corner for the start of your scarph or include the corner (obviously the former is easier!).

Here's where I really should have sought advice before cutting. I've read about grinding the appropriate bevel, but cut so as to be able to get to all the rot - requiring the harder - 'round the corner option - in a few places. I spent some time tonight carving out some more wet/rot and making the shapes a bit simpler (yes, the Multimaster is a great tool for this - last year's big X-mas present).

Read up on all those instructions about copying non-skid to make an invisible repair; it's supposed to be possible. (I've read it in Books! It must be true.)

Maybe it's possible - but it's not plausible for me. I'm trying very hard not to let "perfect" (or the closest to it that I can manage) be the enemy of "good enough" - I plan to go sailing this season! After all, my (prepaid) moorage fees for a season in Boston Harbor cost more than I paid for the boat!

Edit: I should add, lest I seem blasphemous here, that I aspire to perfection, but am also trying to maintain perspective in light of my abilities (modest) and priorities.

[Jeremy]

Okay; I've made some progress.

Because of the thinness of the inner skin, which I broke through in a number of places, I first reinforced the corners of the bridgedeck from below. Working against gravity in those tight and awkward confines wasn't easy, but it wasn't as hard as I thought it would be - making me regret a bit not having initiated the whole process from below.

I enlarged and simplified the shape of the deck cutouts (they probably should have been simpler still), ground the inner skin and taper and cut and installed the new 1/2" core using my pizza box trick discussed in another thread.

Here's where things stand now:



Detail of the starboard side (before fully grinding the taper and refilling voids at the edges) with the coaming dry fitted into its ultimate location, and the new winch stand resting in its approximate home. To be the appropriate height, its foot will rest on an appropriately sized bit of varnished mahogany.



So, on to a couple questions.

The top skin was of variable thicknesses in these areas, and I think about building up the deepest recesses with layers of cloth beginning within the new core area itself, and then with larger bits going to the edge of the taper. I know this is a bit backwards, but I worry that otherwise, I'll be left with voids. I may not have explained this well enough to allow it, but if I have, any problems with this approach?

I'm also thinking of finishing off the project with a layer of cloth spanning the whole arc of the bridgdeck. Since I'm repainting anyway, I think this may will help me achieve a fair surface across the whole span. Any thoughts?

I've got the rest of the pieces of cloth cut, and was about to work on installing them yesterday, but somebody insisted I make them a knight's helmet . . .



. . . Which at least made good use of the foam that didn't work as rub rail for a dinghy project (discussed elsewhere)!