Deck core moisture and rot

Bob and Others who have done the lazarette replacement,

I have recently removed my factory covers to find wet and rotten balsa core. Uhgg! It's good to know that this is a recognized problem with a repair solution. My question is how does one know if its good balsa? I started pulling some out and it seems to extend over an inch back. The wood is spongy and saturated with water. How do I know when to stop removing the balsa to allow it to dry? How far back does it go? Epoxying a void this large seems like it will be difficult to control exothermic heat production. It seems like it would be better to remove wet balsa and epoxy in a sealed plywood filler piece. Any thoughts? Also, once you have the oversized drilled holes filled with thickened epoxy, you then drill a fastener pilot hole into the epoxy. Do you need to coat the screw with epoxy when you put it in? Do you need to tap in treads for the fastener to prevent the epoxy from cracking once it is cured? Thanks
Grazer
 
Grazer":11c3raz3 said:
Bob and Others who have done the lazarette replacement
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I've just done this job myself, so I'll give you some thoughts.

Grazer":11c3raz3 said:
My question is how does one know if its good balsa?
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Good balsa will generally be a light tan (like birch wood or pine) and will be dry and somewhat "fluffy" when picked at. It should seem firmly adhered to top and bottom fiberglass skin. It should seem "obviously" dry and good (maybe you haven't reached any yet to see it). Wet will range from black soup to darker brown wet/sponge, to just damp (just damp can look pretty light colored, but still a bit darker than dry, usually). I like to get it all out back to dry; others are comfortable with "mostly dry."

I tend to pick small areas out manually with an old dental pick. When you get to slightly damp core it can be hard to tell for sure if it is damp or dry. What I do is carefully pick a bit out, and then pinch it between dry, ungloved fingers. If my fingers get damp/wet/sheen, then I keep on going (see above about standards).

Grazer":11c3raz3 said:
I started pulling some out and it seems to extend over an inch back. The wood is spongy and saturated with water. How do I know when to stop removing the balsa to allow it to dry? How far back does it go?
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As mentioned above, I don't stop until I'm completely back to dry-as-a-bone core, so I don't ever "let it dry" - I just remove it back to dry core. However, leaving in a bit of slightly damp core is probably okay in the real world (just depends on your mindset; I'm a perfectionist and once I'm doing the job of fixing core, I want anything not dry GONE). I would not leave in any wet/very damp/spongy core. Especially if there is any de-bonding (where it separates from either fiberglass skin).

As far as "how far back does it go," well, there is no real limit to that. I've had to re-core entire sailboat decks :cry My C-Dory was stored indoors, so I only had very slight "rims" of damp core, with one area that went back a couple of inches. You just have to check each individual boat/situation. As much as this expression drives me nuts, it's one of those "it is what it is" situations.

Grazer":11c3raz3 said:
Epoxying a void this large seems like it will be difficult to control exothermic heat production. It seems like it would be better to remove wet balsa and epoxy in a sealed plywood filler piece. Any thoughts?
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You are correct that heat/foaming/distortion is a concern with larger fills. I probably would not go back in with core unless there was 3" or more (or thereabouts). I don't do any re-coring with plywood -- I tend to use balsa. But there is probably no real harm in using ply. Another approach is to fill in stages. That is, paint area with neat epoxy, then fill up to a certain depth (width) with thickened epoxy and wait for it to get to the green stage; at that point you can add more thickened epoxy and wait for that to get to the green stage, etc. By using the green stage you only have to prep the first time, and can just add more epoxy on subsequent stages. An infrared thermometer can be very helpful to monitor the temperature. You can possibly cool things down with water/ice/etc. if it starts to get a shade hot (and then adjust for future batches). A slow hardener will also help.

Grazer":11c3raz3 said:
Also, once you have the oversized drilled holes filled with thickened epoxy, you then drill a fastener pilot hole into the epoxy. Do you need to coat the screw with epoxy when you put it in? Do you need to tap in treads for the fastener to prevent the epoxy from cracking once it is cured?
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I've used a few approaches. If strength is really important, you can wax the fastener and "cast" it right into the soft epoxy, then remove, clean, and re-insert later. I wouldn't use this method on the hatches though (the plastic rims are weak enough that there is no point in going super heavy-duty on the fastening). I do drill slightly larger pilot holes when screwing into (hardened) epoxy, as it doesn't "give" like, say, soft wood. What I did on the lazarette hatches on my 22 was switch from "pointy screws into core" to oval-head machine screws with washers, lockwashers, and nuts on the inside. So I just drilled the normal size clearance holes for the screws through the epoxy annuli, then bedded the hatch and fasteners as I installed them (with caulk/bedding compound).

Sunbeam
 
Thanks for assistance Sunbeam.
You said "If strength is really important, you can wax the fastener and "cast" it right into the soft epoxy, then remove, clean, and re-insert later."
What kind of wax? Please explain.
 
I have used a typical automotive paste wax (not on this job, but in other situations). A lot depends on the exact project and goals/requirements. In a recent example (on a non-C-Dory boat), I cleaned the fastener with denatured alcohol, then gave it a thin coat of wax. Then I painted the (over-drilled) hole with neat epoxy, and subsequently filled it with thickened epoxy. When it was in the early green stage, I put the fastener in. After it cured, I removed the fastener, cleaned off the wax with solvent, after which it could be used as normal (in the now-cast hole).

I find the free booklets put out by WEST System and System Three to be very useful, and I refer to them often (especially to get back up to speed if it's been awhile since I was in epoxy mode).

Here is a link to the WEST System "Use Guide." Each illustration leads to what would be a chapter in the paper booklet (which you can sometimes pick up at marine stores).

http://www.westsystem.com/ss/use-guides/

Here is a sub-link directly to the chapter on casting/bonding fasteners. As you can see there are various methods and "levels," depending on the project:

http://www.westsystem.com/ss/bonding-hardware/

And System Three's "The Epoxy Book":

http://www.systemthree.com/reslibrary/m ... rature.asp

Couple of notes:

1) If you do have a fastener that you need to get out but that is epoxied in place, you can touch the head with a soldering iron (to heat up the epoxy) and then probably back it out.

2) For the lazarette hatches, I would do it the same way again (if I were to do it again), which is that I went with holes all the way through (core was already eliminated) and machine screws with nuts on the inside. (Mine originally just had (pointy) screws into the core - "bedded" with silicone, no less :amgry)
 
Thanks again Sunbeam. I went to work last night and began pulling the wet core out from between the fiberglass on the port lazarette. I found the wood mostly wet, rotten all the way back approximately 3 inches. It dead ends there thankfully (or I suspect would go even further back). The starboard side of the opening seems to have some dry rot core with good core at the back. I am unsure whether to fill the void completely with thickened epoxy (seems like a lot of material will be required) or add some filler balsa core and epoxy that in place. Where would one get end grain balsa core in 1/2" thickness?
It turns out my boat had the same pointy screw attachment configuration with the silicon bedding. Some of the bedding material did not even cover the entire bottom of the hatch flange :x .
 
Grazer":3n0jeexq said:
I found the wood mostly wet, rotten all the way back approximately 3 inches. It dead ends there thankfully (or I suspect would go even further back).
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Ugh! Well, at least you are getting it out of there and will have it done right when you finish. It IS irritating when you realize how much easier it would have been to just do it properly from the start (or at least use a caulk we can remove when we have to go back and fix it :cry), in which case you wouldn't be doing it now, but.... at least you'll soon have it done. Right.

Grazer":3n0jeexq said:
The starboard side of the opening seems to have some dry rot core with good core at the back.
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You may be doing this already, but I would remove any rot, "dry" or wet. Might as well have 'er done right.

Grazer":3n0jeexq said:
I am unsure whether to fill the void completely with thickened epoxy (seems like a lot of material will be required) or add some filler balsa core and epoxy that in place.
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I would say you could go either way, but you're right in that it would be a fair bit of epoxy ($), and you'd have to do it in stages to avoid too much heat. Adding core would help to fill it in (but keep it to just epoxy where your new fasteners will go, obviously).

Grazer":3n0jeexq said:
Where would one get end grain balsa core in 1/2" thickness?
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I've usually ordered mine from Jamestown Distributors; not sure that is the most convenient to YT! (Of course, what is ;)) And you know, as much as I'm a perfectionist, and as much as a good bond between the skins and core is essential for strength of a flat panel.... I'm going to go out on a limb here and say that for that small area, you could probably just use anything reasonable and handy. (Marine plywood, clean foam, etc.) The reason I say that is because (presuming I'm envisioning it correctly) it's a small/finite area, and not a large, flat panel that needs ultimate strength in order not to sag or bounce. Just try to get the inside of both skins as clean (solvent) and flat as possible, then coat it with neat epoxy, then make a "bed" of thickened epoxy and mush the core into that. Of course there's nothing wrong with going in with "proper" core either. Or it might turn out that it's just as easy to use epoxy and do it in stages (unless that means you'd run out and have to buy more; that might be a factor).

Grazer":3n0jeexq said:
It turns out my boat had the same pointy screw attachment configuration with the silicon bedding. Some of the bedding material did not even cover the entire bottom of the hatch flange :x .
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I can relate. To make it even more of a project, if I had just tried to use the boat's old holes/edges, my new hatches would have had to sit off-center, and some of the holes would still have been *really* close to the edge. So I ended up building up a new long edge on the inboard side of each lazarette opening. (I used fiberglass and epoxy.)

Sunbeam
 
I've usually ordered mine from Jamestown Distributors; not sure that is the most convenient to YT! (Of course, what is ;)) And you know, as much as I'm a perfectionist, and as much as a good bond between the skins and core is essential for strength of a flat panel.... I'm going to go out on a limb here and say that for that small area, you could probably just use anything reasonable and handy. (Marine plywood, clean foam, etc.) The reason I say that is because (presuming I'm envisioning it correctly) it's a small/finite area, and not a large, flat panel that needs ultimate strength in order not to sag or bounce. Just try to get the inside of both skins as clean (solvent) and flat as possible, then coat it with neat epoxy, then make a "bed" of thickened epoxy and mush the core into that. Of course there's nothing wrong with going in with "proper" core either. Or it might turn out that it's just as easy to use epoxy and do it in stages (unless that means you'd run out and have to buy more; that might be a factor).

Thanks again Sunbeam. Your presumptions are correct. The area requires some strength to support the hatch hinge but remembering not to stand on that area plywood would suffice. You mentioned "clean foam". I hadn't thought of that but perhaps a spray in expanding foam may provide a lightweight structural filling agent to the void near the back of the cavity. Any experience with these products?

P.S. How do you do the quote function in these posts?
 
Grazer":2mdwyqbm said:
The area requires some strength to support the hatch hinge but remembering not to stand on that area plywood would suffice.
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Actually, I think plywood would more than suffice, from a strength standpoint. I mean, there are whole boat decks cored with it. I still prefer balsa, for a few reasons, but I really don't think you'd have any problems with good plywood. I don't think you'd be compromising the necessary strength in that small area (and I would "pot" the hinge fasteners in epoxy annuli anyway).

Grazer":2mdwyqbm said:
You mentioned "clean foam". I hadn't thought of that but perhaps a spray in expanding foam may provide a lightweight structural filling agent to the void near the back of the cavity. Any experience with these products?
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I have used the expanding foams in house projects, but I wouldn't use them in this case. For one thing, they can be hard to control, and you really want this area to stay flat (so the hatch will work properly). I also don't know for sure how they would interact with epoxy (I imagine you could find out, but I wouldn't even try, because I would use balsa or plywood or the foam that is meant for coring before it came to that).

I wish I were at home right now because I have plenty of balsa or coring foam scraps I'd be happy to send off to you. Still though, for this area (and being mindful to keep epoxy in the way of any possible water intrusion), and given your location, I would pretty happily use a proper plywood.

Grazer":2mdwyqbm said:
P.S. How do you do the quote function in these posts?
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If there is something you want to quote, then before you start your reply you go to the post you want to quote and in the upper right you will see "quote." If you click on that, it sets you up in a reply box with all the other post already quoted. You'll notice that there is a quote "opening phrase" (name and brackets, etc.), and then at the end a "closing" phrase, which is similar but without the user name.

If you want to quote the whole post, you just leave it as is and start typing below it.

If you want to remove some of the quoted text (often a good idea), then you just go up and delete those words, leaving the rest and the brackets as-is.

If you want to split up the quote (like I did here), then what I do is first go up and "copy" the opening quote phrase (in your case it's
Grazer said:
). Then I just "paste" that at the beginning of each section I want to quote. For the quote closing phrase, since it's easy to remember, I just type it in at the end of each new section of quote I'm making (that's the bracket, slash, quote, bracket phrase). You want to have the opening and closing phrase on each section of quoted material.

After you are done, you can hit "Preview" and it should show up just as you want to see it. If it doesn't, then there is some little error (maybe a missing bracket or something), so you can go back and fix it, re-Preview, and then when all looks good, hit Submit.

Sunbeam
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Well I am finally getting around to filling in the deck core that was removed around the lazarettes covers. I have purchased 2 of the imtra hatch covers indicated in Dr. Austin's project above (nice work by the way). It seems they are very close to the edge of the existing hole and may not purchase well. I've read somewhere that others have built up the edge to provide more material to surround the hatch flange. How does one go about this?
 
I did build up one of the long hatch edges on each lazarette to better fit the new IMTRA hatches. I could probably just have squeaked them onto the existing openings but there were two things I didn't like about that. One is that I would have to have set both of them in a bit "off kilter" to do the best with the opening, and the other is that some of the flanges would only have had sealant under about half their width. Actually, the holes were pretty close to the edge even for the original hatches (I presume some were cut more tidily than others). Since I was in there with the epoxy anyway, I decided to add width to the two long inside edges (on on each hatch). As a result, I was able to place them just where I wanted them, and there was plenty of engagement for the fasteners and the flanges. You know, I was going to write this up on my "Sunbeam" thread, with photos, but had just not got around to it yet (also, I really should have taken more photos!).

How about if I post the description there either tonight or tomorrow (the thread is called "Sunbeam ~ 22 Cruiser").

The job was one of those that has a lot of little steps, and requires some prep to avoid making a mess; but because of the location (under hatch flange), the level of finish required was not high or "artsy."

Sunbeam :hot
 
Sunbeam":399qg73x said:
How about if I post the description there either tonight or tomorrow (the thread is called "Sunbeam ~ 22 Cruiser").
Sunbeam :hot
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I look forward to your photos and description of project. Tell then...

Cheers, :beer

Grazer
 
First undercut and fill the balsa which is there. Same for the old screw holes. In several hatches I have had to cut thin (3/4" wide) strips of glass cloth, and epoxy that in place. that gives more structure and beef, as well as seals it. If it is going to be more than 1/8" build up, then put some glass cloth and epoxy in the mix.
 
thataway":2vau88e3 said:
In several hatches I have had to cut thin (3/4" wide) strips of glass cloth, and epoxy that in place. that gives more structure and beef, as well as seals it. If it is going to be more than 1/8" build up, then put some glass cloth and epoxy in the mix.
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Let me see if I understand you correctly Bob. You would cut thin (3/4" wide) strips of glass cloth, and epoxy (glue) in place. Does this mean adhering fiberglass stripes on edge to both the top and bottom laminates including the filled in cored portion of the hatch opening? It will likely be greater than 1/8" and you suggest putting in some glass cloth and epoxy in the mix. I will be using glass cloth and epoxy... I don't quite follow? Do you meaning adding glass chop strand into the thickened epoxy to adhere the glass cloth strips?

Grazer
 
I am sure that some where in my albums, probably on the hatch repair for the main forward hatch in the Tom Cat--I showed how I put the glass cloth strips oriented in a vertical manor, that is all around the opening, or at least on one or two sides of the opening. There are some places to add glass on top--and that would be to make the top fair and flush, as I did with the AC unit. Glass strands, only if there is a large area, which you need to fill.

Sorry, but I am band width limited and cannot search the photos etc--but go to the "thataway" album and you will find photos.
 
I have a good, fast Internet connection right now. Let me take a look and see if I can link your photos here. After all, your thread for "Thisaway" is what inspired me to start one for the work I'm doing on my 22 (and the info was very helpful as well :thup).

Okay, series of info/photos on Thisaway's hatch replacement starts here (bottom of page 14 in the album):

http://www.c-brats.com/modules.php?set_ ... hp&page=14


Sunbeam
 
Since I had to install a bottom pivot for our Garhauer davit, I asked around on the best way to do it. The gunwale and side decking are balsa cored, so I ended up doing the following:

-over-drilled
-filled with West System epoxy thickened with 404 thickener
-inserted machine screws into the wet resin, placed where I wanted them AND coated in dielectric grease

-let the resin go "off" and backed out the screws. Voila! The resin acts as a threaded nut and no worry about water intrusion into the balsa core.
 
Resurrecting this GREAT thread.
Doe anyone know where you can buy a sanding drum for the drill like Dr Bob shows in his excellent picture? We’re repairing the floor around the (unsealed) access ports.
Thanks!
 
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