Wet core repair without major surgery.

Sep 12, 2021
1
R&C Leopard 43 Ft. Lauderdale
This is awesome! Thanks for sharing your ideas and experience.
How did you keep epoxy from getting sucked into the pump?
 

NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
I cut the skin from the top on my last boat. From the foredeck back to the cockpit. Cabin top was fine. Mine was balsa and it looked like a sponge. Redid core with nidacore (sp), and my fiberglass guy did a reverse mold of the original non skid pattern and attached it. Looked beautiful. Pretty good results.

greg
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
This is awesome! Thanks for sharing your ideas and experience.
How did you keep epoxy from getting sucked into the pump?
The suction tube was always ran through a water seperator so any epoxy what was sucked that far would end up in the jar and not in the pump. In actual practice, I began as far away from the pump and I could and worked back toward it with several ports and at the end, when I saw epoxy in the suction tube I stopped sucking.
 
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Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
Hayden, thank you for sharing your brillant system. I think it can give new life to a lot of old boats and less work and worry for a lot of owners.
Many of us may have difficulty visualizing the system without more pics. Please consider repeating the repair on an old junk yard boat with pics and publishing it in Good Old Boat magazine. They would glady buy your article. Or maybe you could sell kits of fittings?
Glad you are on the forum.
 
May 11, 2009
52
2 MK IV Warwick, RI
This is truly brilliant. I have a small leak somewhere, with a small hole inside the boat that water leaks out of whenever there is a heavy rain. Once I find and fix the leak, I'm going to try this to fix the damage. So far the deck is still solid, and this should help keep it that way. Thanks!
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
It is possible that a high-vac pump could help to find the leak. The pump is quiet and tiny leaks whistle.
 
Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
Awakening an old but awesome thread.
Dear Hayden, first, loved the post about your sailer daughter !!
Second if you still have questions about seacock winterization please private message me as your orginal thread had been closed to new posts.
While I am still sailing my oday we crossed to the dark side this past season as we arent as young as before. The new boat has a 4 by 5 foot saturated cored deck area by the forward hatch. Using the winter time to gather up the materials to follow your plan. Other than the hatch hardware how many additional holes and how far spaced fo the rest of the area? About how many hours and days might it take to dry the core? I know its just a guess with all the variables.
Thank you so much and hope all is well.
 

PaulK

.
Dec 1, 2009
1,222
Sabre 402 Southport, CT
Hayden's system worked well with his plywood cored decks, but might perhaps do less well with balsa-core, where the little squares of balsa tend to cut off the air and water flow from spreading over large areas. The vacuum system would work, but with balsa there might be many small wet sections, each cut off from the others by ridges of builder's resin. Each section would need to be attacked separately, and it might be difficult to determine whether you'd gotten all of the wet sections, and if you'd gotten all of the moisture out of them. Removing the laminate to expose the core (usually from the inside) enables you to see exactly what has gone on, let it dry out, and to repair it with new core.
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
The logic that I used in my repair was that if moister could get into a space, than water vapor could get out. I did not drill any additional holes into my deck. I put a vacuum port into every existing hardware hole and the one crack in the deck caused by frozen water trapped inside. In the chilling Pacific Northwest, it took me all summer by turning on the pump on any sunny day when the temp was over 70º. I probably could have speeded up the process by using additional heat.
 
Mar 26, 2011
3,399
Corsair F-24 MK I Deale, MD
I've replaced balsa core a number of times. If the area is soft, the balsa has rotted, literally, to the consistency of wet potting soil. I wish I had saved some and potted a plant in it just to graphically prove the point. Unless you would core your boat with peat moss, I don't see the point in drying and injecting. Open it up and install a core.

It was a neat article, really. But it only worked because it was a relativly low stress area that barely needed a core. I would consider it with foam core.
 
Sep 23, 2009
1,475
O'Day 34-At Last Rock Hall, Md
Yes it can be as bad as peat moss but not sure if that matters since as you say it is in non high stress areas. Once the area is dried out and filled with epoxy it should remain solid.
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
Actually, if the balsa is mostly mush it would make it easier to pull the water vapor out. The risk would be if the core was so soft that the vacuum pulled the two faces together and cracked the skin. If the skin starts getting depressions, you would need to have some supports spaced out to keep the skins flat. That could be done by drilling holes in a grid pattern of 6"-12" depending on skin thickness and injecting thickened epoxy into the hole to make small columns of epoxy to hold the gap. After it is dry the resulting void would be filled with the infusion epoxy which would make it heavier than a foam fill but if the area is small it would not have a significant affect on the weight of the boat.
 
Mar 26, 2011
3,399
Corsair F-24 MK I Deale, MD
So you built a panel with peat moss for the filler and no surface prep or cleaning.

It took a whole summer. I've replace core from the inside twice. Two half days and back to sailing, if you know your glass work.

I praise your ingenuity, but I don't believe it's a great answer for any boat that has much value left in it. I wouldn't want to explain it to a buyer. I had a boat with a jackleg core repair; the roof colapsed and the repair was made far more difficult by the bodged repair. Replacing core just isn't scary surgery. Cut, clean out, butter and replace, sand level, and reglass. Good as new and 100 days faster.
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
[Point] So you built a panel with peat moss for the filler and no surface prep or cleaning.

It took a whole summer. I've replace core from the inside twice. Two half days and back to sailing, if you know your glass work.

I praise your ingenuity, but [Point] I don't believe it's a great answer for any boat that has much value left in it. I wouldn't want to explain it to a buyer. ...
[Rebuttal] I would not say that it had no surface prep any more than an I would say that on an infused boat the glass was not "properly wetted out" because you cannot use a fin roller. The prep was done by removing all moister from the space between the skins, leaving a completely dry lattice. Any "mush" (your term not mine) is dust or a bone dry sponge framework which will be fully wetted out by the infusion resin as it is pulled into every void by the vacuum. "Mush" implies wet which I agree would be a very bad idea. vacuum drying that mush produces dust at the worst and a fully dry lattice framework at the best which is a completely different thing.
If I was to take some actual saturated peat moss and sandwich it between a couple of skins of fiberglass and put it under a 30"/hg vacuum until it has a moister reading of 0% moisture and then infused it with epoxy resin it would make a stronger (although heavier) sandwich laminate than one made with foam core.
[Rebuttal]
The reason that I chose to go this route was BECAUSE the boat has great value for its make, model and year. The open surgery method is sound but at best leaves a major scar in the form of a deck with painted non-skid rather than the factory molded non-skid which prompts any future buyer to ask why it needed to be painted and that is assuming that the open repair was done well.
On my boat there is no scar. The only mark on the boat anywhere is the one 2" long crack in the deck cause by the freezing water inside the sandwich that alerted me to the problem. That was repaired after infusion with color matched gelcoat and a pulled basket-weave rubber mold so it is invisible. The deck is absolutely solid and moister readings in the repaired area are all between 0%-12% on the comparative scale which is low in the green scale and are as low or lower than anywhere on the boat whether cored or solid laminate.
I personally do not like painted non-skid because the surface roughness make it hard to keep clean. I several friends with Kiwi decks and they are always dirty looking even after washing. On my molded basket weave, I buff it every 4-5 years with a light compound and protect it with Woody's Wax and it shines like the day it was pulled from the mold and is a breeze to wash and always looks clean.

As for cost, all-in, this repair cost me $100 for the vacuum pump, $10 for 1/4" tubing and fittings and $30 for the infusion resin. An open repair would have cost far more just in the non-skid paint and I cannot even guess how much the resin, glass and core would cost.

As for time, I had maybe 1 hour per sunny day for 2.5 months which was probably in the range of 30-40 hours in total. In my original post, I mentioned a friend who was doing a traditional "remove and replace" repair to his cabin top at the same time I did mine. I started after him and finished before. He was younger than me and given that he has a 9-5 job had far more time available than I do given that I am sole proprietor of my firm. Had I known about thermostatically control silicone heating matts at the time I probably could have dried out the boat in 1-2 weeks by drying 24-7 with the deck heated to the 80ºC-90ºC used by Hot Vac.

Different strokes for different folks but I am more than happy with my results.
 
Mar 26, 2011
3,399
Corsair F-24 MK I Deale, MD
core replacement
Working from the inside

I've always worked from the inside when possible. No visible scar. That is why it only took two half days--no finish work, just reinstall the head liner. I guess that is what made it just 2 half days and a few hours.

I should have mentioned this. I've seem some terrible topside surgeries that didn't have to be done that way. glassing overhead has a few tricks (pre-wet the glass) but it's basically easy.
 
Apr 5, 2009
2,774
Catalina '88 C30 tr/bs Oak Harbor, WA
core replacement
Working from the inside

I've always worked from the inside when possible. No visible scar. ...
On a C30 it is not possible to do an inside repair. The deck is a sandwich laminate of glass/ply/glass. Then there is a seperate fiberglass molded full cabin headliner that is bonded around the perimeter but has a 1/2" air gap between it and the deck. An inside repair would require cutting a huge hole in the FG head liner just to get to the deck and that would greatly decrease the value of the boat.
 

Blitz

.
Jul 10, 2007
672
Seidelmann 34 Atlantic Highlands, NJ
may I ask what kind of moisture meter are you using? Any particular setting?

thanks for the thread and the explanations