wet core replacement

[lance on cloud nine]

if anyone has a very favorite how-to link they followed on core replacement....I would love to hear from you. I need to repair the area directly under the deck stepped mast on an O'Day 26. I hope you are all having some fun. Thank you.

[Bubba the Pirate]

I don't have a link. And I've discovered I'm missing some posts on my blog from 2009/2010. 

I had a very small area. Using a multi cutter and a straight blade, I popped though the top skin. It peeled up fairly easily. The really wet core came right out with a putty knife. Using a hunk of cardboard, I made a pattern, chopped it out of plywood and in one case planed the plywood down to the right thickness. I slathered it all up with thickened epoxy, and placed the plywood. After cleaning up any squeeze out, I replaced the top skin with more thickened epoxy. 

The hardest work I did was in replacing the cockpit floor, not all of the core was wet. The dry core had to be chopped out with a hammer and chisel. Also, the the top skin in the cockpit was pretty bad and didn't come out as a whole piece. I glassed over the plywood on the cockpit floor. It came out very solid and the glass looked good. A little non-skid-ish.

The multi tool was a great way to do this in my opinion. It was easy to pop through the glass into the core and not do any other damage.

[lance on cloud nine]

thank you for that reply Bubba! when you placed the original cutout piece back in....did you just glass the seams? or did you completely glass over the top of it? and how far out, past the seams did you lay glass? Thanks a bunch.

[Bubba the Pirate]

I did not glass over the any of the small repair. And that was 3 boats ago, so I don't know how that worked out. Today, I probably would have. It was a small area between thd cocpit and the rail - no traffic to speak of. The cockpit floor, where it really mattered, is where I ended up ditching the original skin and put down a couple layers of glass.

For a large area, I would probably glass the seam, but for small enough area it would prkbably be just as easy to cover it all. Without seeing the spot, I would probably make the glass 1/2" bigger on each side or a 1" strip over a seam.

[lance on cloud nine]

ok. Thank you. I will post some pics when I start....hopefully get further advice.

[lastgreatgeneration]

Buy a fein oscillating tool. It will cost about $250. Best investment ever. I did a ton of fiberglass deck cutting with a half moon disc I bought at harbor freight. I own an unused genuine fein half moon disc, but the harbor freight one just keeps cutting. It will also slice through long  SS bolts on backing plates! The model I bought came with a small amount of accessories.

[lance on cloud nine]

Thanks for that suggestion lastgreatgeneration. I have been meaning to check out those tools.

[CharlieJ]

Agree totally on a multitool. But living on Soc sec I need a tad
Cheaper.  I've been totally satisfied with my Porter Cable at 1/3 the cost of a fein

Main reason I chose it was the quick release blade system. At the time I got mine the Fein needed a tool to change blades. Too slow for me

Excellent tool no question though

[ralay]

The cost of the tool is directly proportional to its likelihood of being dropped overboard.   ;)

[Godot]

Several years ago I bought the cheap Black & Decker copy. You know what they say about getting what you pay for? This tool is the exception. It's my favorite tool. I probably bought it for around $50 at one of the -Marts a decade ago. Best thing I have found for cutting fiberglass. It doesn't kick up a dust cloud. The particles just kind of drop straight down into a nice little pile.

I did in fact drop mine overboard. Managed to recover it, and it has been going strong ever since. Love that tool. A bit hard to find the blades for it (Walmart sometimes has them). The Dremel blades sort of work; but I needed to take a regular Dremel tool and do two minutes of modification to make it work right. Amazon has everything, if you can wait a day or two.

Lots of clones out there. Since the patent expired even Kleins are sort of (kinda) affordable, though still twice or more what even the pricier clones cost

[lance on cloud nine]

thank you for that info....I will also check out the B&D.

[lastgreatgeneration]

IIRC most of the universal blades will fit. The multi use blades IMHO are just as good as the no name brand accessories. Ditto for the triangle sanding discs. The fein standard box also fits my 4.5 dewalt angle grinder with discs. I liveaboard and they live in the vee berth and take up little space. It's a real can't live without item, assuming you DIY everything. I can also run it off of the EU2000i generator. I can help or let someone from sailfar borrow the tool in the Annapolis area.

As fort books, don Casey's fiberglass repair and "gold old boat" are my reference books. More or less a reminder on how to lay up certain weights of fiberglass and a reprimer on the process of cleaning and prepping.

[Bubba the Pirate]

Done right, cheap tools can pay off.

My dad was a wood shop guy, when I bought an orbital sander at Harbor Freight he nearly disowned me. It was $35 IIRC, but I had a plan and bough the replacement guarantee for another $5 or so.

I had a huge project prepping a hull, stripping bottom paint, working on topsides and massive fairing project after glassing the hull and deck joint.

When the sander quit working, once or twice, I could blow the dust out and fiddle with it to get it working agsin. Once it died for good, I'd go into town, visit HF and walk out with a replacment. I think I went thru 3 sanders for $35. 

Granted I wasnt going to need another sander for some time after that so longevity didn't enter the calculation.

[CapnK]

I can report good things about the Rockwell oscillator variant. I've been using it for several years. Also, WalMart now has a 'Rigid' branded version of the tool, and their blades & such are cheap but work on most other brands.

Just replaced the soaked balsa mulch that was residing in the transom of my Hobie Power Skiff. Used Divinycel foam for the core material; good stuff, more $ than plywood, but any future water intrusion will never be an issue.

[lance on cloud nine]

thank you all for the great advice! much appreciated that you take the time to give the pros and cons of these tools.
CapnK....very nice job on that project!

[lance on cloud nine]

Hi - I have yet to start my under mast core replacement....and was wondering....has anyone ever incorporated an aluminum plate along with the new wood core under the deck....to try and spread the load out a bit more? I am speaking about when one has a thick core to build up....using it in the schedule to get the right thickness. Maybe say 3/16 or 1/4 plate....maybe 12 or 18" square. Any thoughts on this? Thank you!

[Frank]

I'm no expert, have only done core twice, but can't see an issue with your idea. Seems logical actually. CJ and others with more experience should chime in. Keep us posted and ....you know......"PICTURES" 😄
Good luck

[CharlieJ]

I see no reason why not

[CapnK]

That should work - but :) - there'll be no real mechanical bond between the glass and the aluminum "pad", not one of much shear strength at least.
So, on the high end, check out a material called G10 (or FR-4, which is flame retardant G10). It is composite material with very high compression strength that will actually bond to your epoxy. It ain't cheap! But it is good and very strong.
More affordable, you could buy some pre-made 'regular' epoxy/glass sheet material from a supplier like McMasterr-Carr in ~.25" thickness and use it stacked in layers to get a quick, solid layup.

Or make your own sheet: Get a sheet of glass larger than the pad you need to make, or any flat material will work if you have mold release agent, or cover it in waxed paper.
Pre-cut glass cloth into pieces a bit oversize than you need in the end product, and then laminate them to each other on top of your flat surface until you get the thickness built up that you'd like to have.
You can use some mat in there for a 'quicker thicker', but I'd recommend using woven roving on the outer layers for a better (smoother) finish.
Use a slow cure catalyst, because the thickness will allow heat to build up more than in a 'regular' layup where you only have a few layers of cloth/resin.
A resin roller will come in handy to get air bubbles and excess resin out of your layup as you make it, but if you don't have one already a squeegee will also do the trick for you.

Some ideas. :)

[lance on cloud nine]

Thank you Frank, Charlie, and CapnK. I will post pictures when I get the job going. I appreciate your responses!