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Deck core moisture and rot
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thataway



Joined: 02 Nov 2003
Posts: 20779
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Tue Apr 03, 2012 6:45 pm    Post subject: Deck core moisture and rot Reply with quote

I keep harping on the issues of deck moisture intrusion. Here is a good example and what to do to repair it. I wanted to replace the factory hatch with the ones which do not leak. I expected to find a little moisture around the screw holes....but not this! Thisaway is a 2006 boat, and was kept in Nothern Virginia its first 5 years. Remember this is not just a C Dory issue--almost all boats have this type of problem. It is not usually found at survey. But, any factory can prevent it with just a little extra care and work in the building process.

First photo is after the hatch is removed. The screws came out, and were well coated with silicone sealant, the sealant had come up into the screw holes in the hatch.


You can see that there is a perfect mold of the hatch under flange, that there is some gel coat painted over the exposed balsa core--but also that there is some dark balsa, suggestive of rot in the corners

As I put a knife blade into the areas from the exposed core to the screw holes this was soaking wet. The knife would go in easily up to an inch. This means that core is compromised and water has penetrated it, with mold growth:



The core is cut away and the moisture extends back over an inch from the where the core is exposed in the cut out. The area behind the gel coat painted over the core, is also saturated!



Here is the knife blade into the screw hole (already drilled out with 1/4" bit to get rid of any silicone sealant.



The above photo shows the rotted area cut out, and ready for drying. After drying, a Dremel tool will be used to cut it back further to good balsa.



The above photo shows that on the Starboard side, there is little rot, and minimal water intrusion. The entire inner edge is painted with thicker gel coat-and peeling it back does not reveal moisture. Epoxy would have been much better.



Above the photo shows the under cutting of most of the back outboard corner of the Port side. All of the gel coat on this side had to be removed, and all of the balsa was under cut, will be dried and then filled with epoxy and filler.



Above the port side has had the new holes drilled (5/16) and the outline of the new hatch penciled in. Note that the caulk is removed--after the epoxy fill, a Fein triangle sander will be used to remove the last of the silicone. (I used a chisel so far)



Above the new hatch is checked for position. The balsa has been dried with a heat gun and will be allowed to dry overnight before the epoxy filler will be put in place. All new screws will be put into the epoxy plugs--the balsa will be undercut where it is good--and where the balsa is not good, the entire void filled with epoxy and filler.

Stay tuned for the next installment--literally! I just finished "spring break" with the grand kids--which included a 7 mile canoe paddle, a visit to a prehistoric shark, a tour of the "Drum" and " Alabama" (ships), several days at the beach (with swimming), lots of pool time at home and a couple of boat trips both in the Caracal and C Dory 22.

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Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
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mcc272



Joined: 05 Jun 2008
Posts: 233
City/Region: Long Island Sound
State or Province: CT
C-Dory Year: 2004
C-Dory Model: 22 Cruiser
Vessel Name: C-Star
Photos: C-Star
PostPosted: Tue Apr 03, 2012 7:58 pm    Post subject: Reply with quote

Bob --

My '04 CD22 had exactly the same problem but no evidence of gelcoat to attempt a seal so I had problems on both sides. Did the repairs exactly as you are illustrating. Your photos and description are excellent (as usual) and probably, this is an area where all owners should check as it seems to be a systematic issue from the factory. Just another reason to put the new lazarette hatch covers on and it makes you check for core issues. Also, in that location, the sooner the issue is found and remedied, the better as the further back the rot goes, the harder it is to dig out and repair.

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Connecticut Side of LI Sound
C-Star, 2004 22 Cruiser (sold 10/10)
North Star, 2011 Rosborough RF-246
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naptime
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PostPosted: Tue Apr 03, 2012 8:23 pm    Post subject: Reply with quote

Bob,

Thanks for the picture of the new hatch cover. I think I will replace mine. The 2012 C-Dorys still have the same leaky hatch cover. One would hope user problems would get back to the factory and corrections would be made. As Sara questioned, how is this hopey change thing working for you, not well. Sorry for the political reference, but it is appropriate.

Dick
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thataway



Joined: 02 Nov 2003
Posts: 20779
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Tue Apr 03, 2012 9:25 pm    Post subject: Reply with quote

The question has been asked off line as to the adhesion of the silicone to the plastic of the old hatch, and what I will use for bedding the new hatch.

There was no adhesion between the hatch and silicone. (I don't know what specific silicone the factory used, but it was not a structural adhesive).

I will be using Boat Life "Lifeseal" which is a mixture of urethane and silicone, which will not attack the plastic, as most urethanes will. (Do not use 5200 etc for this application).
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ferret30



Joined: 22 Mar 2011
Posts: 569
City/Region: Seattle
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 22 Cruiser
Vessel Name: Lily Pad
Photos: Lily Pad
PostPosted: Tue Apr 03, 2012 9:50 pm    Post subject: Reply with quote

How about butyl tape?
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Moxieabs



Joined: 02 Nov 2003
Posts: 208
City/Region: Cape Neddick
State or Province: ME
C-Dory Year: 2003
C-Dory Model: 22 Cruiser
Vessel Name: Widget
Photos: Widget
PostPosted: Tue Apr 03, 2012 10:10 pm    Post subject: Reply with quote

Bob,
My 2003 had the same issues with the deck fills for fuel and water in addition to the hatches. They all received the epoxy treatment as per your instructions. Makes one wonder about every breach of the deck skin such as the cleats, rails and hawsepipe.

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island park



Joined: 18 Apr 2011
Posts: 19
City/Region: Ft Myers
State or Province: FL
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Island Girl
Photos: Island Park (Name TBD)
PostPosted: Tue Apr 03, 2012 10:14 pm    Post subject: Reply with quote

Dr. Bob, please forgive my simple questions but I am trying to educate myself about caring for my wonderful little boat. Who manufactures the hatch cover that you used to replace the original? What type/brand of epoxy do you use to back fill the areas where the wet/rotted wood is removed? What areas should most concern me as far as core rot? Do I need to oversize drill and epoxy fill every single hole on my boat (motor mount, swim platform, transducer mount, cleats, windlass etc.)? Thanks for any information you can give me. Paul
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thataway



Joined: 02 Nov 2003
Posts: 20779
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Tue Apr 03, 2012 11:11 pm    Post subject: Reply with quote

Island Park, you ask a very good question. When ever I put a new hole in one of these boats I do the over drill, under cut, and epoxy. If a fitting is tight, not leaking and there is no sign of water or drips on the inside, I tend to leave them alone. These hatches were leaking and thus needed to be replace. Some of the fittings near the edge of the deck are not thru cored material--and thus safer.

I have suggested that a block of King Starboard be used to put depth sounder transducers on. The hull aft plugs I have checked have been OK. On my boat the trim tab screws are OK. The motor holes should be OK--and my boat has a foam core transom. I did the epoxy liner of the hole for the transducer cable in the transom.

I have had to re-bed the foreward hatch on almost every boat I had--no rot there, but I did seal them because of leaks. On several occasions the cutout is too big. You want it snug. Be sure there is enough "meat" for the screws. I have also sealed the windlass and hawse pipes.

The hatch is the 4000 series by SoPac Imtra specifically the 40154 is the dream white. However the only hatch I found in stock was Go2Marine, and they had two of the 40155 which are "white" The match seems close. They did not have the "dream White". I would suggest calling Go2Marine--and I will PM Joel and see where he got his order

Epoxy: I happen to have been using West Systems for over 40 years, so it is what I am most familiar with. I use 105 epoxy, this time of the year I use 206 hardener, later in the summer I will use 209 hardener. I use the pumps and gallon size of the 105. I use #406 colloidal Silica (Cabosil) and #404 high density filler and microlight # 410 filler for most of my work. I use 6 oz cloth or 1208 and 1708 biaxial cloth. But Systems 3 or MAS also make excellent Epoxy--I just stick with what I have been using.

I have used Butyl tape for the RV windows and various appliances. However I have not used that on boats.

Please remember that there are many different silicone products--what we buy in West Marine or the hardware store are the most common, and do not make good adhesives. However there are many structural silicone adhesives which are used for glazing plastics--such as I used for the large lexan windows in my Cal 46.

I have not been able to find anything but grey. I have PM Joel to see where he got his.
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thataway



Joined: 02 Nov 2003
Posts: 20779
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Apr 04, 2012 1:35 pm    Post subject: Reply with quote

I also pulled some of the bolts on the factory hand rails (I am putting in rope interior hand holds)--each of these had some moisture around the bolt (It has been raining the last 12 hours). The rail was bedded with silicone sealant (not a good choice). The good news is that this area is not cored: slightly over 1/4" glass (I'll put a micrometer on it when I pull the entire railing).

So definitely the hand rails should be rebelled if there is moisture and if they were bedded with silicone, rather than a urethane, such as 4200 or 5200. One of the problems is that it is more difficult to get good adhesion of 5200 to glass, once silicone has been used. All vestiges of the silicone has to be removed.
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20dauntless



Joined: 23 Jan 2008
Posts: 879
City/Region: Mercer Island and Decatur Island
State or Province: WA
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: Retriever and Nordic Tug 37
Photos: Retriever
PostPosted: Wed Apr 04, 2012 2:23 pm    Post subject: Reply with quote

Bob, how much do you think it would cost C-Dory to build boats with solid glass in areas that they know will be drilled into or cut out? Places like cleats, hatches, rails, etc...

I don't have a lot of time that I can spend on the boat, and when I do have time I prefer to be using to boat, not fixing it.

I think the core rot issue is a big stumbling block for potential buyers and it would be awesome if C-Dory took care of the known issues at the factory.

C-Dory could even put a section on their website detailing why they use balsa core and the measures they take to prevent problems.

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Matt Gurnsey
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Joined: 11 Nov 2008
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PostPosted: Wed Apr 04, 2012 2:38 pm    Post subject: Reply with quote

The coring, properly done, does add strength and reduce weight. Synthetic coring materials (like used in the transom and on thn the Venture series during the Fluid days) are available, but at considerably more cost. They are also slightly heavier, and the light weight is one of the selling features of the 22 C-Dory.
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thataway



Joined: 02 Nov 2003
Posts: 20779
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Wed Apr 04, 2012 2:53 pm    Post subject: Reply with quote

As Matt says--coring is almost essential in decks--Balsa core is an excellent product. Foam and hexacell cores are also good, but have different characteristics.

Some builders will put plywood in the way of the cleats and windlass etc--a few do solid glass, but thinner deck at that place.

Doing a solid area just where the bolts go thru would be a bit more expensive. Probably less than properly treating the holes with epoxy.

One issue, is how things are bedded--and what product is used. For example the aft deck lazaretto hatches, where a better hatch product which would not allow water intrusion could have been used. But also using a better bedding compound is important. For example using silicone for the railing is not acceptable. Not sure what is being done currently.

Another issue, is that C Dories last a lot longer than most boats. If you have a 20 year old Bayliner---that is probably the end of the line. A 20 year old C Dory is still a good boat, and commands as decent price on the used boat market.
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island park



Joined: 18 Apr 2011
Posts: 19
City/Region: Ft Myers
State or Province: FL
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Island Girl
Photos: Island Park (Name TBD)
PostPosted: Wed Apr 04, 2012 5:44 pm    Post subject: Reply with quote

Bob, thank you so much for the detailed response. I really appreciate the help.
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potter water



Joined: 12 Apr 2011
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PostPosted: Wed Apr 04, 2012 6:45 pm    Post subject: Reply with quote

These tech articles WITH PIX are absolutely the finest service that C-brats can provide to the forum. Excellent information and a picture is worth a thousand words.
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BRAZO



Joined: 29 Jul 2008
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PostPosted: Wed Apr 04, 2012 6:59 pm    Post subject: Reply with quote

It is a relative easy task to remove all the hardware and epoxy all the holes. I did that last year on our 2008. Now I can read these posts without having slight panic attacks. I sleep much better now...
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