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Wet core repair without major surgery.

Jan 27, 2008
2,989
ODay 35 Beaufort, NC
It's important to get the water out first or it will keep freezing and likely fracturing the brittle cured epoxy. Hayden's use of a vacuum pump to lower vapor pressure is a good solution along with some hot sun beating down on it for heat. Vacuum bagging works well with prepreg and a curing oven. This is more like using an enclosed mold and using a vacuum on one end and a resin reservoir on the other end. It will be heavy and ideally a lightening mixture added to the resin that is also waterproof will get some weight out but you also need low viscosity to flow and wet out the core.
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
I am surprised that the tubing you used didn't collapse under a 30" vacuum.
The secret is small diameter. The standard aquarium tubing is 3/16"ø (not 1/4"ø previously sited) and the wall thickness / diameter ratio is high enough that the wall will provide compression hooping force sufficient to prevent collapse. If you kink it, then the entire length will collapse flat. I had this happen in a few places and would just replace it with new. The pump I used was a 2.5 CFM pump from Harbor Freight that is rated at 75 micron which is pretty good. Water at 70º will boil at vacuum below 1500 micro so this pump should get into the range for boiling water.
https://www.harborfreight.com/25-cfm-vacuum-pump-98076.html
http://www.aircondition.com/tech/questions/68/Vacuum-Level-Required-to-Boil-Water
 
Oct 29, 2016
1,703
Hunter 41 DS Port Huron
Interesting process and you did capture my attention, while I have no immediate use for this process I will certainly store this idea in the annals of my brain.
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
There have been 3 guys at my marina who have been picking my brain on this after watching the process a couple of years ago. In northwestern Washington it took me all summer to accomplish given the cool temps we have but it was far better than the hack and slash alternative. There are two critical requirements to get this method to work.
#1 The deck must be air tight. If there are any leaks you will not get a vacuum. I found a couple of bolts that were leaking and needed to seal them with butyl.
#2 The deck core must have enough integrity that it does not crush the core under vacuum.
As long as these to requirements can be meet I think the process should work.
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
I am not quit sure what you mean. When I would first start the pump it would take 10-15 second for the pressure to drop below 29". In the early stages of the process I got a lot of free water condensing out of the tubs. I used a simple water separator like on this pump. I used a 1-qt mason jar with a couple of holes drilled in the lid to run inlet and outlet tube into. The first day I emptied it twice. After that I would empty it once a day for the first week and then I quit getting free water. At the end of every day that I ran the pump I would change the pump oil because some of the water vapor would condense into the oil. It only takes two ounces so it wasn’t a problem. I would let the oil separate and then use the water level as a gauge as to how much I removed that day. Toward the end I would get very little water in the oil but would see steam coming out of the pump vent. I used the moisture meter and the final gage to determine that the core was dry.
 

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Oct 26, 2008
4,917
Catalina 320 Barnegat, NJ
How many square feet was the area of your repair? Did you drill holes through the upper surface of the deck at a prescribed spacing? What was the spacing ... how many holes per square foot? What size were the holes ... 1/4" diameter so that you fit the tubing directly into the holes? How deep? Did you just penetrate the FRG skin or did you drill about half way into the core, or more?
Sounds like an interesting process for an old boat with some moisture in the decks. I have to tackle this issue at some point in time.
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
There are varying degrees of repair for core rot but once was told to drill holes after checking with a moisture meter say 1/2 inch every foot and pour down epoxy resin spreading it by use of an air nozzle. In some cases weight had to be added to the deck if raised any but suggestion of a cover so the weight applied would not scratch. In the extreme of course was to dig out the rot and repair. Then reverse non skid was used to put back the non skid patteren.
The affected area per my pin-less moisture meter was about 2' x 7'. I drilled no holes. I put a port into every bolt hole into the affected area. My thinking was the water must have gotten in through the existing holes so I should be able to get the WATER VAPOR back out by means of the same holes. I probably could have dried it out faster by drilling more holes but I did not want to do any additional cosmetic damage.
I did not have some water. I got more than a gallon of water out if you add the water that was between the headliner and the composite deck to that in the deck. I was able to get about 2 quarts of epoxy back into the deck. When I started, the moisture meter was off the scale saturated and when I infused the epoxy it read 12% max.
 
Jan 29, 2021
1
J-Boat J-46 Wye River
I have read your post with interest. My J Boat has wet core issue below the waterline (yes J boats are build with balsa core below the waterline) and wonder if you have an opinion about how well your method will work if the water is salt water instead of fresh rainwater?
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
I have read your post with interest. My J Boat has wet core issue below the waterline (yes J boats are build with balsa core below the waterline) and wonder if you have an opinion about how well your method will work if the water is salt water instead of fresh rainwater?
I think it should work for any situation where there is infiltration of water but the core material has not gone to mush. In my case, the deck was wet but not soft. I know of another J-boat that had a wet deck and they recently rehabbed the deck with some type of injection poly sulfide foam that reacts with the moisture to cure and fixed the core in place. I will send them an email to see if i can get more info.
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
I have read your post with interest. My J Boat has wet core issue below the waterline (yes J boats are build with balsa core below the waterline) and wonder if you have an opinion about how well your method will work if the water is salt water instead of fresh rainwater?
I talked to my J-Boat friend about what they used and it was Injectadeck Marine Structural Foam
They did their foredeck last fall which was scary soft and so far it is solid. I don't know any more about it that that but it might be worth looking into. Much cheaper than scraping the boat and far easier than cut and fill. If it does not work, you can always go back to the old way of cutting out one of the skins and replacing the foam and reglassing the skin.
 
Feb 15, 2021
12
O'Day O'Day 25 Port Stalishun
Soft Foredeck

Does anyone know if there is wood or foam in between the glass in the fore deck construction ? foam ? balsam? I also have a small soft fore deck area on the starboard side of my O'day 25. Was planning on drilling a series of holes and injecting git rot if it's a balsam core but I'm not sure if what the core material is. I will drill a hole from the interior to investigate first. Any help appreciated. Looking forward to adventures in the spring and summer in the Georgia Straight.
 
Dec 28, 2015
1,258
Laser, Hunter H30 Cherubini Tacoma
Www.injectadeck.com. I did a bunch of research in preparation of fixing my compression post and expecting to have to fix soft spots in the associated area. This is what I will be going with when the time comes and I think it is a winner. Not as perfect as a full removal/rebuild but applied right I think it would be a excellent fix.
 
Jun 29, 2010
1,239
Beneteau First 235 Lake Minnetonka, MN
Soft Foredeck

Does anyone know if there is wood or foam in between the glass in the fore deck construction ? foam ? balsam? I also have a small soft fore deck area on the starboard side of my O'day 25. Was planning on drilling a series of holes and injecting git rot if it's a balsam core but I'm not sure if what the core material is. I will drill a hole from the interior to investigate first. Any help appreciated. Looking forward to adventures in the spring and summer in the Georgia Straight.
Its balsa, as I stated in your nearly identical other post, cut it open and replace the core. Or, do what I should have done sooner, instead of replacing bulkhead and core, sell it and buy a better boat.
 
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Mar 26, 2011
2,867
Corsair F-24 MK I Deale, MD
Www.injectadeck.com. I did a bunch of research in preparation of fixing my compression post and expecting to have to fix soft spots in the associated area. This is what I will be going with when the time comes and I think it is a winner. Not as perfect as a full removal/rebuild but applied right I think it would be a excellent fix.
I tested several methods (epoxy, inject-a-deck, Gorilla Glue), repairing test beams and then breaking them. I think you will find the injected foam is quite weak and does not bond well.

testing core injection repair

After determining that Gorilla Glue was the strongest repair, I fixed a couple of banged-up SUPs. Gorilla Glue foams when it hits moisture, forcing its way into voids, spreading much farther than epoxy, but it is also MUCH stronger than injectable foam. Easiest to work with, and also loads cheaper, for the small amount you will need, but that's really not the point. It was much stronger.

That said, more field testing is needed. I'm sure interested to read people's experiences. That was mine.

Yes, I have also done whole-hog peal-and-replace core work. It came out nice and was the right answer for a high load area.
 
Mar 29, 2017
573
Hunter 30t 9805 littlecreek
I use same described method for rudders .
Without the vacuum in epoxy just drill a hole on bottom let water run out heat with heat gun to see how much more water I can get out then put on vacuum pump while sanding down to gel coat and then roll on epoxy paint to seal all while vacuuming to pull epoxy paint into any voids or pin holes for first 4 coats then seal bottom hole and 2 more coats epoxy e2000 heavy on bottom patch
 

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May 24, 2021
2
Pearson P-40 St. Joseph
Hayden Watson, I have been reviewing this brilliant thread. It is very helpful. I am gathering materials to do a similar repair on my boat deck. I assume the mason jar was able to take full vacuum without imploding? Do you have any product information on the air /water separator you referenced in the picture as an alternate to the mason jar? Also the source for your vacuum gauge, air / water / separator / regulator that was shown on the picture of the vacuum pump and tubing? Thanks for your help.
 
Apr 5, 2009
1,517
Catalina '88 C30 tr/bs Oak Harbor, WA
Note that I said Mason jar (old fashioned thick walled "canning" jar) and not glass jar (pickles, mayonnaise, etc.) The canning jars are made for vacuum. to seal them, you heat them to boiling in a pressure cooker and then tighten the lid to seal them and as they cool, the create a vacuum.
You could probably also use a air/water separator for removing the water from compressor air but I have never tried that.
The first thing to remember when thinking about useing this system is that the area to be dried MUST BE ABLE TO BE SEALS WITH NO VACUUM LEAKS!!!
Fortunately, vacuum leaks are reactively easy to seal if you have access to the point of the leak. Small pin-holes are sealed with a blob of butyl tape (or better yet, use butyl and plastic sheeting to make that leak into another vacuum port).
Remember that a perfect vacuum is less than 15-psi and anything is pulled towards the solid base.
 
Oct 29, 2016
1,703
Hunter 41 DS Port Huron
Its balsa, as I stated in your nearly identical other post, cut it open and replace the core. Or, do what I should have done sooner, instead of replacing bulkhead and core, sell it and buy a better boat.
Do you practice being abrasive or does it just come naturally?