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Old 20-03-2013, 13:32   #16
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Re: Repair on balsa core rot in deck

"This is where gravity will be my enemy"
Cover the topside. Vacuum bag your patch on the underside. Gravity is a weak force, the vacuum can hold your patch up tight against the deck, tight and uniform, without any problem. Repeat with new coring and new skin.
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Old 20-03-2013, 13:35   #17
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Originally Posted by hellosailor View Post
"This is where gravity will be my enemy"
Cover the topside. Vacuum bag your patch on the underside. Gravity is a weak force, the vacuum can hold your patch up tight against the deck, tight and uniform, without any problem. Repeat with new coring and new skin.
You would vacuumbag a 6cm patch?!
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Old 20-03-2013, 13:50   #18
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Re: Repair on balsa core rot in deck

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Originally Posted by roverhi View Post
Balsa core has gotten a bad name because of shitty jobs installing hardware.

I wonder!!! Any below the water line thin skinned cored hull risks severe damage just being on the water. As mentioned in another thread, a cored hull does not have the compression strength of a solid material such as fiberglass. There are to many things one can inadvertently bang into that can result in cracks in the thin and some cases very thin outer fiberglass. Sure, improperly installed deck fittings add to core problems.

Last year I saw a NEW, big, expensive cat lifted out of the water with a travel lift and one of the lifting straps cut right though an entire section of the hull.
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Old 20-03-2013, 14:14   #19
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Re: Repair on balsa core rot in deck

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Originally Posted by foggysail View Post
Last year I saw a NEW, big, expensive cat lifted out of the water with a travel lift and one of the lifting straps cut right though an entire section of the hull.
pls. guys, this thread is about repairing a soft spot in the deck...
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Old 20-03-2013, 14:38   #20
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Re: Repair on balsa core rot in deck

The vacuum will suck things together just like clamping would, so why not? One irrigation syringe would provide enough suction to do that job, then just toss it afterwards. Unless you'd rather improvide a clamp to compress the patch somehow.

Don't think it is needed? Size is that small? My mistake, I thought someone said gravity was creating a problem there.
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Old 20-03-2013, 14:55   #21
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Re: Repair on balsa core rot in deck

What the he** is oven paper?

I'm sort of lucky, I have access to lots of syringes (not the needle type), so the injection part is easy.

Overall, I like your approach to the task!
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Old 20-03-2013, 15:16   #22
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Re: Repair on balsa core rot in deck

I may be able to skip the whole injecting phase because progress is much better than expected; that darn matt cures faster than I thought, so I could go ahead again

First a little cleanup after that messy part; I felt like a surgeon pushing things back in where they belong, eww...
I cut away some of the excess and then sanded everything flat again; most of the holes had filled up with epoxy and some excess came out ofcourse; this was unthickened epoxy:


Next was the 1st phase to fill it up; I can't do that in one go because the mass of filler is too big and will create so much heat (exothermic reaction) that it would start to boil. So my first phase is to fill up all the voids in between the fibers that you can see above. This means keep on pushing it in until as much comes out as goes in. I used 6 little pumps of epoxy resin, 6 pumps of hardener, 4 heaping table spoons of microfiber filler and 6 heaping spoons of colloidal silica (=Cabosil) to make it thick like peanut butter. The colloidal silica prevents the drips while the fibers make it tough:

After this I need at least two more rounds to fill it up without overheating. Each next round must happen when the previous one is gelling, i.e. getting hard but still very sticky. I need it a bit hard so that I don't push it out with the next load. I always aim for 10mm layers.
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Old 20-03-2013, 15:18   #23
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Re: Repair on balsa core rot in deck

"Oven paper" is parchment paper, similar to wax paper, used to keep baked goods from sticking to the baking pans in an oven. Less wax, more paper, than regular wax paper. Doesn't burn at normal baking temperatures.
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Old 20-03-2013, 16:15   #24
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Re: Repair on balsa core rot in deck

I had to do a similar deck core repair on my sloop (balsa).

Had to come at it from the underside. Deck was fine, but you could see the rot underneath from the cabin.

Grinding cutting and filling on your back upside down, not very fun.
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Old 20-03-2013, 16:24   #25
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Re: Repair on balsa core rot in deck

Three more pumps and lotsa filler further and we're almost there... except that the right one got too hot and boiled a bit. You can already see on previous photo's that it needed more filler than the other holes so I was taking a risk:


But with the epoxy not fully cured, the Fein Multimaster with plunge-saw blade makes quick work of that; after full cure it would have been hell because this mix of fillers I use gets very hard!
Here we need just a bit more cure time for the other holes and then we can fair it:
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Old 20-03-2013, 16:36   #26
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Re: Repair on balsa core rot in deck

Still black (?) or is that just stains on the laminate?
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Old 20-03-2013, 16:50   #27
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Re: Repair on balsa core rot in deck

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Still black (?) or is that just stains on the laminate?
Yes, that is on the top of the lower skin. They are stains that I didn't bother to sand off. They are now part of the new core

Just got the fairing on; this is with just the West System Microlight fairing filler so that the sanding tomorrow will be easy. After that, we will have to restore the lower skin.
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Old 20-03-2013, 17:52   #28
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Re: Repair on balsa core rot in deck

I hate to ask, but why didn't you just cut the whole section out from the inside, tape patch the cracked section to seal it, epoxy new balsa to it, and cloth it over?
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Old 20-03-2013, 18:07   #29
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I hate to ask, but why didn't you just cut the whole section out from the inside, tape patch the cracked section to seal it, epoxy new balsa to it, and cloth it over?
I was close to doing that and if there would have been a but more wet core I would have. But the way I did it now, most of both original layers of glass, which were okay, are still intact which is stronger than glueing in a new square piece of core and fiberglass that up.

I would only remove good material to get to bad material that I can't fix otherwise.
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Old 23-03-2013, 08:10   #30
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Re: Repair on balsa core rot in deck

After the fairing was cured, a little sanding was done, then I cut some fiberglass 9oz cloth:


and put it in place:


Which finishes the underside, last step is the topside
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