Fiberglass Deck Repairs

Question: After removing the core and outer fiberglass layer in a 2x2 foot area, when I replace the core do I need to use something other than solid fiberglass? Provided I can lay up that much fiberglass, is there any disadvantage to not using another coring material? other than cost and time?

You should put some new core into the deck. Solid glass is going to add an awful lot of weight for being up that high. Cored glass is more rigid than solid glass, I think. Also, you have to put the glass in a few layers at a time or the heat generated will weaken the bond. I recommend using a high-density foam core where you replace the balsa. I used klegecell (PL-75 3/8" thickness), a rigid polyester foam sheet. I got it from Fiberglass Coatings (800-272-7890). That's also a good place to get glass cloth and mat. They're good people, and their web site is improving. (As of 2011, I hate their current web site.) Calling on the phone works well, too. Ask for their catalog, while you're at it. There are other good sources, too. Many places that sell fiberglass and resin will also sell foam coring.

Jim Mennucci's articles on deck repair (in the Alberg 30 Maintenance Manual) are a good source of advice, as is Don Casey's book "This Old Boat." I recommend reading both of them. My short description of the process is as follows:

Cut away the top laminate and expose the wet or rotten core. You generally see recommendations for using a router or saw to cut away the laminate, but I just use the grinder figuring that I've got to grind a bevel for laying up the new glass anyway.
Dig out all the wet stuff. In some places, I had delamination but the core was still dry. I left that core in place.
Grind the top of the lower laminate to make it clean and give a good "tooth" for adhesion. Grind the edges of the hole in the upper laminate to a very gradual taper, at least 8 to 1. You want a broad area for a strong bond.
Cut the foam core to fit the hole. It doesn't matter how many pieces it takes, just fill the space fairly completely. Take the core back out and set it in a convenient spot. I generally cut the fiberglass to fit at the same time so I can lay it down dry to make sure it fits. It doesn't have to be perfect, it's going to stretch and move, anyway.
Mix up some polyester resin and add some thickener, such as glass beads, to make a wet paste, something like toothpaste.
Pour this into the hole and put the foam core back in on top of it. Lay a small sheet of plastic down on top and put a weight on top. This holds the core down to ensure a good bond. The plastic is just to prevent the weight from being glassed into the boat. You can also do fancy stuff with vacuum-bagging, but that takes a bit more knack. I've done better using a weight.
Clean up your tools and such while you let this harden. You don't need to let it cure completely before continuing, but it does have to be solid.
Laminate new glass on top. I like to start with some thickened resin on top the core, to fill any gaps, and then a layer of glass mat. Then I alternate glass cloth and mat, one or two times depending on the thickness. If I've got a low spot, I'll add more mat on top of that. This new cloth should come up on the beveled edge around the hole, extending further out with each piece.
Let this cure overnight. The surface will cure better if you paint some PVA (poly-vinyl alcohol, used as a mold release) on top. Air inhibits the cure.
Sand the surface smooth. Fiberglass laminate is tough stuff to sand, and I recommend using a fairly powerful sander like my 6-inch random orbit sander.
If there are any low spots, sand these roughly and fill with thickened resin, coating with PVA. After it cures, sand smooth again. Repeat as needed.
Voila! Now you're ready to paint.

Question: After removing the mast-step plate I noticed that the six screws in this plate are screwed into the deck. How are they held there, were they screwed into fresh fiberglass? What kind of holding strength is that? I literally peeled the plate off with the screws still attached using a screwdriver as a pry bar. Has anyone ever thru bolted the mast-plate thru the deck? What do you think about that? Or maybe glassing the bolts in upside down so they can have nuts screwed on them topsides?(I think Scott Maury "Bill of Rights" did this.) What should I do?

Steve Weingart wrote an article about this and it got included in the Alberg 30 Maintenance Manual.

FYI: water leaked into the core thru the six bolts in the mast-step plate, and through the bolts for the hinges for the forward hatch. If I had rebedded these when I first got the boat in 1996 I probably could have prevented the majority of the damage. Removing and resteping the mast several times aggravated the problem. You might want to check your if you just acquired your boat.

I'll second that notion. I'm in the same boat, so to speak. It's better to do a bad caulk job than to wait until you can do a better one. Also, you have to remove things to caulk them. It doesn't work to put caulk around the edges. I've just recently fallen in love with Rule elastomeric caulk. I did my chainplates with it, and so far, I like it better than BoatLife. Save the 5200 for metal things that you can heat with a torch if you need to remove them.

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Page last modified: Friday 03-Feb-2023