CD27 - Let's recore a bench

[csoule13]

As mentioned in a previous post, I'm recoring one of the lazarette hatches as a way to learn some skills before tackling recoring the cockpit sole.

This should come as a shock to nobody, but get the old gummed up nuts and bolts off of the hinges is a real treat, especially if you don't have a second hand. With that fun behind me, I brought the thing home, taped off a 2 inch border, and attacked the fiberglass. I can not recommend an oscillating multi-tool with a carbide "grout removal" attachment highly enough. It took maybe 15 minutes to get the outline cut out, and the amount of dust generated was low(and didn't fly all over the work area).

Even after seeing dozens of photos of wet core material, it was still amusing to pop this open and find and completely sodden mess. Another 15-20 minutes with the oscillating tool with a horizontal blade attachement, and I feel like I'm 90% of the way done removing the old core.

Question - For getting out material under the lip, what level of perfection are we aiming for? When is good enough good enough?

Onward.

[jbenagh]

When I did CC's cockpit sole I didn't get too fussy about getting out all the debris from under the lip. I used the oscillating tool offset saw blade on the outer and cut sides to separate most of the core material then a screwdriver. I followed up with a wheel wire brush attachment on a drill. I did hit it with the heat gun on the low setting to dry it out and then vacuumed a lot. If you're below freezing, don't skimp this step; I had a lot of ice crystals stuck in there.
When you go to fill it with core material, the more careful you are to shape that material to the curve under the lip, the less epoxy you'll use.
Looking great so far!
Jeff

[jbenagh]

PS you may want to bevel the lip while the old material is still there as it keeps the lip stiff to get a good bevel. Any minor damage to the feather edge removing the core doesn't have much effect as you layer on new skin.

[csoule13]

Update - Most of the old core came out without much struggle. Ran an angle grinder with 40 grit flap disc around the edge for my "bevel". As a first time angle grinder user, holy moly this thing can do some damage in a hurry. This took 5, maybe 10 minutes. Took longer to suit up than to do the work.

Just about done getting the old core out from under the lip. Some pieces are being more tenacious than others. They are no match for the oscillating tool.

Lastly, ran a RO sander with 40 grit over the main area. There's still a very thin layer of old core here. I'll hit it again before I'm done, but I assume this is another area where good enough is good enough.

Looking forward to piecing out the new core this coming week and getting my first taste of working with epoxy and fiberglass. Onward.

[Jim Walsh]

Very nice work. Something I’ve never done and with any luck......

[jbenagh]

Looking really good! The strength of the finished product will amaze you.
Jeff

[csoule13]

Looking really good! The strength of the finished product will amaze you.
Jeff

How finicky should I be on sanding down the bed of this? I can basically see the print of the fiberglass through what's left of the old balsa in almost the entire area. A few more passes would get it even better, but I'm not convinced another, say, hour of sanding is going to get me a measurably better end product. The idea is to just get a pretty good surface to slop thickened epoxy onto, yes?

[csoule13]

Dry fit the new core. Two questions for everyone. How critical is it for the core to get all the way under the lip? I feel like it spots I've got 1/8 to 1/4 an inch where it just won't go. Also, as you can see in the photo below, I've got one corner where the balsa just won't get in there. My thinking is to just run a bead of thickened epoxy around the entire thing at the start of assembly? The holes for the hinges are get drilled-filled-drilled anyway, so I'm less concerned there.

Lastly, there are a few thin gaps between a few pieces. Thin line of thickened epoxy to fill that, or is that over thinking things?

Tools for this stage were an RO sander with 80 grit to bevel the balsa enough to get it under the lip, and an exacto knife to trim the wood. Reminded me of building model rockets as a kid.

[John Stone]

Trim the balsa core back where it won’t fit. I would radius the edge so the cloth (biaxial?) will make the turn without creating an air void. Wet out the surfaces with neat epoxy. Then apply a bit more mixed with colloidal silica. Kind of soopy. Lay the balsa down. Don’t rush. You have lots of time. Once the balsa is positioned like you want brush in soupy epoxy/silica mix. Mix it a little thicker and fill all the voids use a yellow spread to make it smooth. I’d make some fillets around the edges. Then wet out the biaxial (which you precut and test fit with everything dry) and squeege out excess then lay the biaxial down. Bigger one first then smaller one. If you apply peel ply you get a smoother finish.

There are other ways to do this. Vacuum bagging is a good technique but it’s beyond my skill set and I am happy with the results of my approach.

All this is covered in detail in the West Systems guides free in their website.

[csoule13]

Thanks John, I assume that everything needs to cure before laying the glass? Also, since this is the underside of the hatch, I hadn't planned on fairing after the glass is cured. Just a coat or two of bilge coat and get on with it.

[John Stone]

Thanks John, I assume that everything needs to cure before laying the glass? Also, since this is the underside of the hatch, I hadn't planned on fairing after the glass is cured. Just a coat or two of bilge coat and get on with it.

Lay the cloth on while it's still wet if you can. That way you get a chemical bond. If it cures, depending on the type of epoxy you use you may have to was the amine blush off. Let it dry. Sand with 80 grit then apply the cloth. So if you can do it all before it cures hard much better. If you can make an indentation with your thumbnail you don't need to sand--you will get a chemical bond. Make sense?

[csoule13]

Update and lessons learned - New core is in and 3 layers of glass is on and curing as we speak. The new core pieces didn't quite go in as planned. The wetted out surfaces added some lubrication, which allowed some pieces to slide in better than planned. But crooked, and then jammed into place. Alas.

Used a bunch of sandbags to weigh things down. Scuffed all the shiny spots up with 80 grit, vacuum, acetone wipe, and on to the glassing. Filled the old bolt holes with thickened epox and will redrill when I install the hatch on the boat.

I know all the literature says this, but I still likely used a little too much epoxy on the glass. I made sure everything was flat and clear and any excess I at least tried to get up or spread thin and out of the way. I'll let this cure for an hour or two and trim off the excess glass.

John, thanks for the tip about gap filling with runny thickened epoxy. Worked wonders.

For having never worked with any of these techniques or materials before, I'm good with where things stand. Lessons learned for the next time where final cosmetics will be more important. My overarching goal of this was to not screw the pooch.

[John Stone]

Good job.

There is a learning curve in epoxy and fiberglassing. You are going to get better and your technique will be refined with practice. One thing builds upon another. As you can just a bit more skill a whole world of opportunity begins to open up.

Once again...good on you for tackling something new and a little intimidating for those without experience. It’s something to be proud of.

[csoule13]

To wrap this up, it looks like running a sander over the edges of the new glass is going to be the way to. Some of it didn't lay down as well as it could, there are some sharp bits, etc. I think a quick with the RO will resolve that, then a coat of bilge coat and we can get the cover off the boat and on with the season.

Hope this encourages others who might be a little leery of tackling this, and that the thread proves some usefulness to the greater community. None of this was hard, and I think there is real value in picking a project with the wiggle room to screw up.

[Dick Villamil]

Great project - it gave me the guts to start on the wet core replacement for my Typhoon on the aft deck. I used a Dreml tool with a diamond cutting blade from Harbor Freight - worked like a dream and only took 10 minutes to remove 3 square feet of upper skin. The core was really wet and sticky. Have just applied the sealing coat of epoxy when the rain appeared - covered for a few days and work resumes next weekend. I do not have the baltec balsa and am planning on using either pieces of marine plywood or layers of woven roving covered by the original deck skin (which looks like swiss cheese from a previous failed attempt at repairs). This will all be covered by a layer of fg cloth with resin and fairing compound - any suggestions? Or does this seems like a suitable repair?