Deck core repair - Do I have everything I need?

[CarlF]

Unless your planning serious offshore passages, do you really need to tackle this job right now?

That deck could well have been wet for a decade. Rot in the location shown in your picture is not going to make the boat unsafe in coastal sailing or get appreciably worse over the next year. I'd focus on fixing things that absolutely have to be fixed before you can enjoy the boat (obviously this should include fixing the leak at the handrails that caused the rot)

When you are ready to fix the deck, first drill some holes to confirm the extent of rotted balsa. Hammer taps are simply not reliable. If the rotted area is only a foot square, then I'd consider a "good enough" repair like this:

Drilli 3/8" holes every 4" in the deck, let it dry over the winter (if you haul the boat) or run a shop vac for a few days, and then inject CPES. This is a proven solution for smaller areas. Your nonskid would make the hole repair invisible. If you're not happy with the results, you can always open up the deck the next year and do the full job.

Again, if you are planning a circumnavigation or going to the high latitudes "good enough" is probably not appropriate.

The CPES site has a lot of information on core repairs:

Q & A Boats - Wood preservation, rot repair, and restoration using epoxy resin on boats, homes and log homes.

[redpointist]

Originally Posted by minaret

No finishing resin. You want poly isotropic resin. Don't use ortho (laminating resin). Also get MEKP, pots, stir sticks, chip brushes, laminating rollers, acetone, shears, core material, glass tapes, core bond, a grinder and discs, Tyvek suits, a respirator and cartridges, boxes of rubber gloves, plastic spreaders, Rage for fairing, knives for spreading, notched spreaders for core bond, a longboard with assortment of grit, a DA, an 8" soft pad setup, a good shop vac, lots of masking tape and film, and probably a few other things too.


Do you know what your core material is? You want to order that sooner rather than later.


The cut here is critical. You want to carefully tape off 2" inside of the edge of the skid pad. Triple tape the smooth or tape with preservation seal right away to protect the smooth from scratches for the duration. Lay out the rest of the cut. Make it a rectangle. Cut off the top skin using a circ saw with a cheap abrasive blade (tile or masons blade). Set depth of cut carefully. Use a batten hot glued to the deck as a straight edge to run your saw against for perfect cuts. Then remove all core in the area exposed. Then decore the outboard strip under the 2" strip and the smooth, all the way out to the cabin sides (which are probably solid glass). Use a long drill bit and chisels to decore. Clean up well, make sure all bad core has been removed, the edges are dry, and grind the bottom skin for prep. Then install new core. I prefer vacuum bagging but I assume that is beyond your skill set. Just cut a piece if cheap ply to fit the core patch, stretch plastic over it wrinkle free, put it on top of your core patch, and load it with weight as evenly as possible. Use plenty of core bond and make certain there is squeeze out everywhere. You will have to cut a strip of core material to insert into the area at the outboard edge which you decored. Resin coat your core material first. Then grind the core material squeeze out for prep. Now install the top skin you cut off, grinding the bottom if it first as well. Use lots of weight to ensure it goes down even with no lumps and bumps, and use Core Bond for it as well. Now you have the original deck with a big rectangular saw kerf in it you need to fix. Remove the 2" tape you put over the skid around the edge, and grind a 2" taper either way from the seam into the upper skin. This will be a heavy grind. It will result in a 4" seam. Now go buy pre made rolls of 10 oz boat cloth tapes, one 2", one 3", one 4". Tapes have sewn edges and won't fray or come apart on you, easy to work with. Get a few yards of 1.5 oz matt too, and precut it into tapes as well. Then glass the 4" seam. Start with a 2" matt, then 2" cloth, then 3" matt, 3" cloth, 4" matt, 4" cloth, and a final matt to grind on. Finish with peel ply if you can obtain it, it makes a huge difference. Then grind the seam flat. Apply Rage fairing compound with a 6" wall knife. Longboard rough fair. Then get out the DA and/or 8", and sand the skid off the entire pad, after careful protective taping if course. This will be a bear. Then all you have to do is match the finish by the method of your choice. Color matched gelcoat thickened with cabosil and carefully applied by nap roller is how you get to your current nonskid finish. Good luck!

Thank you for this! I've done alot of reading/watching videos about the procedure, but people usually neglect the details such as the ideal cloth types/weights and whatnot. When you talk about "Core Bond" is this a product made by ATC chemicals? Is that product mostly used for synthetic core materials?

I was planning on using end grain balsa for the core, as I plan on plugging the areas the handrails attach with epoxy anyways so that they dont get wet again. I've seen that alof of people use 3" squares of end grain balsa. Is this a good technique?

[Cheechako]

Originally Posted by minaret

He's recommending decoring through a series of hole saw holes in the headliner there. How you gonna fill those and have them disappear, stipple or no?


Pic looked like molded headliner to me too. Perhaps the OP can clarify?

In my post I was suggesting drilling small holes, vacuum pumping out liquid (if any) and filling holes. Doesnt look like an area in the cabin that should be a concern for the strength of the boat.... go sailing! s you know some wet cores are just damp and some will have water running out of the first hole!
I wonder if he could cut a rectangle out from below and get at all the area then put it back in... with that stippling it still might not show much...?
Trying to think in terms of the non professional...

[minaret]

Originally Posted by smj

No. Secondary bonding with polyester is fine as long as the polyester it's bonding to is still green, if not green the adhesion strength of polyester goes way down. That's when I believe epoxy should be used. I've seen way to many polyester secondary bonds fail to feel comfortable with it.


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And I've seen way too many that are good as new twenty years on to NOT feel comfortable with it. It's not rocket science, just prep properly and you will delaminate plies instead of bond line when destructively testing. Just because six dollar an hour factory workers skimp on prep leading to failed bonds doesn't mean poly resin has a poor secondary bond, it doesn't. If all factory boats were built in epoxy, you'd see just as many failed bonds due to poor prep (probably more!). But they are all built in poly, so that's what you see.

[redpointist]

Originally Posted by CarlF

Unless your planning serious offshore passages, do you really need to tackle this job right now?

I don't know about a world circumnavigation, but I would like to go around South America (probably through the straights, not Cape Horn)! I hate the thought of having water in the core and its what bothers me most about the condition of the boat so I'd like to get it knocked out soon. I feel like I can tackle a recore if I plan everything out well, and would feel better about it than injecting epoxy, even if that might work well enough for now.

(also the boat and me are located in Tennessee for now, so I'm not missing out on any epic sailing or anything by taking on projects)

[smj]

Originally Posted by minaret

And I've seen way too many that are good as new twenty years on to NOT feel comfortable with it. It's not rocket science, just prep properly and you will delaminate plies instead of bond line when destructively testing. Just because six dollar an hour factory workers skimp on prep leading to failed bonds doesn't mean poly resin has a poor secondary bond, it doesn't. If all factory boats were built in epoxy, you'd see just as many failed bonds due to poor prep (probably more!). But they are all built in poly, so that's what you see.

Bottom line is epoxy is a much superior product when it comes to strength in a secondary bond. That has been proven and written up countless times. If you would rather use polyester so be it. The most common phrase I hear is polyester is good enough. I don't care for good enough when it comes to structural applications, especially when to put out a better job will cost a fraction more than a good enough job. Maybe the scope of work talked about in this thread would be ok to use polyester as it may not be structural.


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[minaret]

Originally Posted by smj

Bottom line is epoxy is a much superior product when it comes to strength in a secondary bond. That has been proven and written up countless times. If you would rather use polyester so be it. The most common phrase I hear is polyester is good enough. I don't care for good enough when it comes to structural applications, especially when to put out a better job will cost a fraction more than a good enough job. Maybe the scope of work talked about in this thread would be ok to use polyester as it may not be structural.


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What about the finish? I'd rather have "good enough" and also possible to match the existing finish, than "overbuilt" and you have to refinish the whole deck to match. It's a poly boat, fix it with poly. Or choose to make it something else, with all the work that entails. And for what? You've already said the poly is "good enough".

[minaret]

Originally Posted by redpointist

I don't know about a world circumnavigation, but I would like to go around South America (probably through the straights, not Cape Horn)! I hate the thought of having water in the core and its what bothers me most about the condition of the boat so I'd like to get it knocked out soon. I feel like I can tackle a recore if I plan everything out well, and would feel better about it than injecting epoxy, even if that might work well enough for now.

(also the boat and me are located in Tennessee for now, so I'm not missing out on any epic sailing or anything by taking on projects)

This is a very small recore, totally doable. The skills you pick up here will stand you in good stead too. Especially working with Gelcoat, as your whole boat is finished in it. If you can learn to match and blend, you will never need an expensive paint job and will be able to keep your exterior looking new all by yourself.

[leftbrainstuff]

Originally Posted by Dale Hedtke

Be careful with acetone. It is not recommended by some as acetone is sometimes a recycled product and can have contaminats that could interfere with adhesion. I got this information from MAS Epoxies BTW. Lacquer thinner, alcohol, or MAS's solvent are better choices.
Also, wear plastic gloves of some kind (latex, etc.) ALL THE TIME. Do NOT get epoxy on your skin. Try not to remove epoxy with laquer thinner from your skin (it will just drive the mix into your skin.)
Epoxy is easy to work with; take your time.

Check the CAS numbers. If you are buying industrial acetone it wont have contaminants.

Nail polish remover, typically acetone based, will have many cheap ingredients. Dont use this.

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[smj]

Originally Posted by minaret

What about the finish? I'd rather have "good enough" and also possible to match the existing finish, than "overbuilt" and you have to refinish the whole deck to match. It's a poly boat, fix it with poly. Or choose to make it something else, with all the work that entails. And for what? You've already said the poly is "good enough".

Good enough for you not me. I think your probably a very talented individual but can't understand your aversion to epoxy.


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[minaret]

ATC Core Bond should be the same thing. Make sure to get BPO. Do not catalyze with anything else, it won't be as flexible. Brittle is bad in a deck. Epoxy filler is brittle, not flexible. It's not designed ground up for this like core bond, which is very light and flexible with very long open time and low exotherm. Easy to work with. Here's what I use.

[minaret]

Website.

[minaret]

Originally Posted by smj

Good enough for you not me. I think your probably a very talented individual but can't understand your aversion to epoxy.


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I bet I've used more epoxy than everyone on this site put together. Many thousands of gallons certainly. I love the stuff, no aversion to it whatsoever. I just can't understand others aversion to poly. It has its place, and its a big one.

[smj]

Originally Posted by minaret

I bet I've used more epoxy than everyone on this site put together. Many thousands of gallons certainly. I love the stuff, no aversion to it whatsoever. I just can't understand others aversion to poly. It has its place, and its a big one.

You're absolutely right, for laying up hulls. Secondary bonds it's epoxy that excels.


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[Nicholson58]

If the top of the deck is to be wrecked, there is a way to duplicate the deep non-skid. It requires a bit of art work. Go back to the US Composites site I noted above. They also sell silicone modeling and casting materials. Apply mold release to the deck. Mix the casting compound and apply it to the deck. You may need to make a dam to hold it in place. Top off the pour with a piece of plywood. When it is cured, you will have a negative mold of the deck. Use this with mold release OR a very thin (Poly dry-cleaner bag) release film. Use this tool to duplicate-press the original non-skid pattern in the surface of your repair. You may need to do a bit of fix-it at the edges using small chisels. One of my dock mates did this quite successfully. It is fussy.