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Deck core moisture and rot
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ferret30



Joined: 22 Mar 2011
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PostPosted: Mon Jun 25, 2012 5:49 pm    Post subject: Reply with quote

We've actually been out on the boat at least once a week since we moored it in the ship canal. Lots of trips through the canal and around the lakes, but we're itching to go out the locks. We were going to do a trip out 2 Saturdays ago, but the small lock had just been taken out of service after the Argosy boat crashed into it.

We have the gear to go out the large lock, but for whatever reason they wouldn't open it for over 45 min for us and another sailboat. Nothing happening in the lock as far as we could tell, so we just turned around and headed east.

It's just fun to be at the dock after work or in moments of free time. Working on the boat is more fun than working on the house!
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Will-C



Joined: 21 Aug 2007
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PostPosted: Thu Aug 16, 2012 4:18 pm    Post subject: Deck core moisture and rot Reply with quote

Golerud,
We recently used these exact hatches on our 2008 Venture. Some holes even lined up but we had drill and fill some also. But the covers fit the existing cutouts perfectly. And they keep water out.
D.D.

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Golerud



Joined: 22 Sep 2007
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City/Region: Bella Vista
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Vessel Name: SLOGO
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PostPosted: Wed Oct 24, 2012 5:04 pm    Post subject: Potting holes Reply with quote

I have a slight problem, I want to "Pot" the holes in the deck where lag screws have been used to secure the fuel tanks. My problem is that the holes go all the way through both the top and bottom layer of the deck composite into the void between the deck and the hull. There is an inspection deck plate but not enough space between the deck and hull to reach in to place something to block the holes to keep the epoxy filler in the hole.

I appreciate any and all suggestions or solutions.

Thanks
Gary
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Sunbeam



Joined: 23 Feb 2012
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PostPosted: Wed Oct 24, 2012 5:44 pm    Post subject: Reply with quote

The old "bottomless hole" Cry

Couple of thoughts (without being able to see it):

1) Although there is not room to reach in (with hands?) from the inspection-plate hole, could you reach over there with something like long tweezers? or even a flat piece of bar stock? If so, then I would try to get something flat/rigid/adhesive over the bottom of the hole. If you are a bit careful when you pot them from the top, then it doesn't need to be anything too strong.

2) There is also the method where you fold up something that naturally wants to unfold and become flat, and tie a light string/line/etc. through the center of it. Then push the folded piece down through the hole until it clears the bottom and "unfurls" below, at which point you pull it tight against the bottom of the hole with the string (which is coming out the top of the hole), and then fill the hole, then later cut off the string.

For this one, if you could even get a stick or something in to reach the area from the inspection plate, you could help the patch to unfurl or stick in place.

3) I've read about people inflating something in or beneath a hole (say if you could get a balloon in there), or using but I've never used that method, and obviously if you inflated it in the hole column itself, then you would not be potting part of the hole. Clay or wetted out glass shoved down from above would probably create the same issue. Since there can be water under the cockpit sole (from what I have read), I would want to pot it completely.

When you wet out the hole (with neat epoxy), if you let that tack up (green stage) before going back in with the thickened stuff, then the thickened will tend to "stick" to the initial wet-out layer. This may help to keep it from "falling heavily" onto whatever you block off the bottom of the hole with.

Sunbeam Hot

PS: One last thought, if none of the above will work: You could go ahead with the wet-out, let it tack up, and then go in with slightly-extra-thick thickened epoxy and just accept that some will bulge out or possibly even drop beneath the hole. This would not be my first choice as it just seems messy and who wants an uninvited blob in the bilge (although maybe you could let it tack up and then get it out with a stick or something from the access plate hole).
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ferret30



Joined: 22 Mar 2011
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PostPosted: Wed Oct 24, 2012 7:08 pm    Post subject: Reply with quote

I was thinking something like expanding foam insulation (not much!). Shoot a bit of that into the inner hole, letting it expand in the void and also up into the area you want to fill. After it hardens, re-drill to clear the foam from the area you want to fill, and undercut with a dremel bit if you want to. Then vacuum out the debris and fill with thickened epoxy.

Be careful to use a foam that doesn't expand too much, and don't use a lot of it. Just enough to seal the hole from the void.
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rogerbum



Joined: 21 Nov 2004
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PostPosted: Wed Oct 24, 2012 7:42 pm    Post subject: Reply with quote

There's epoxy filler that comes in a putty form. That can be used to fill holes that won't hold liquid.
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Golerud



Joined: 22 Sep 2007
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City/Region: Bella Vista
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PostPosted: Wed Oct 24, 2012 8:43 pm    Post subject: Potting holes Reply with quote

This C-Brats site is wonderful, in just a short period of time after posting a question, you get great ideas and answers. Tomorrow I will build a mockup and try the balloon, unfolding paper and foam ideas. I think I can get a balloon under the holes closest to the deck plate but the other two holes are maybe 18" or more from deck plate and are close to the outside of the hull and the void gets even smaller.

Thanks,
Gary
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thataway



Joined: 02 Nov 2003
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PostPosted: Wed Oct 24, 2012 10:38 pm    Post subject: Reply with quote

All great ideas--but I would just put enough filler and glass fibers in the epoxy mix that it is like a pledget. Stuff this in the hole and let it go off. As Sunbeam suggests coat the sides of the hole and the under cut with thinner epoxy and let it tack up
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Golerud



Joined: 22 Sep 2007
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PostPosted: Thu Oct 25, 2012 3:48 pm    Post subject: potting holes Reply with quote

Today I made a mockup and used the foam method and paper and string ideas and the expanding foam seemed to work the best. Haven't tried the balloon idea as I didn't get to the store to buy any. I didn't lose as much epoxy with the expandng foam as with the paper and string. I had to order a different hardener as the weather here has turned from the high 70's and low 80's to the 40's and 50's in less than 8 hours so the work has stopped for awhile.
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ferret30



Joined: 22 Mar 2011
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PostPosted: Thu Oct 25, 2012 4:47 pm    Post subject: Reply with quote

If you do end up using foam for the repair, be careful since some types of expanding foam grow a lot and can apply significant pressure.
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Grazer



Joined: 16 Dec 2011
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PostPosted: Fri Nov 16, 2012 1:02 pm    Post subject: Reply with quote

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
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Sunbeam



Joined: 23 Feb 2012
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PostPosted: Fri Nov 16, 2012 1:27 pm    Post subject: Reply with quote

Grazer wrote:
Bob and Others who have done the lazarette replacement


I've just done this job myself, so I'll give you some thoughts.

Grazer wrote:
My question is how does one know if its good balsa?


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 wrote:
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?


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 wrote:
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?


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 wrote:
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?


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
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Grazer



Joined: 16 Dec 2011
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PostPosted: Fri Nov 16, 2012 7:07 pm    Post subject: Reply with quote

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.
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Sunbeam



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PostPosted: Fri Nov 16, 2012 7:23 pm    Post subject: Reply with quote

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_published-literature.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 Angry)
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Grazer



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PostPosted: Sat Nov 17, 2012 1:07 pm    Post subject: Reply with quote

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 Mad .
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