Filling a gap on fiberglass 420 sailboat deck

The air cavity behind the centerboard has delaminated from the hull due to freezing water damage. I opened up the crack with a dremel and removed all parts of the deck that I could lift up and separate from the hull with my hand. The vertical fiberglass above the crack was in good shape so it is only removed up to an inch above the bare hull. I'm thinking about using total boat total fair epoxy to fill this area (not the air cavity but the 1/16" depth I had to remove) but I'm worried about how stable and flexible this will be. Would 3m 5200 be a better choice for this job?

The picture I uploaded shows the beginning of my demolition, but I had to remove much more on the deck.

 

Welcome to the forum.

If you don't want these cracks to return, you'll need to grind them back quite a bit more than you have. It looks like you've chipped out along the gelcoat, in the area of the crack, but I'll bet the laminate is also cracked under the gelcoat. The only way to know, is to grind away the gelcoat and have a look see. Additionally to make the repair stick (and stay stuck), you need a lot of surface area exposed, so you have enough to bond too. Use a small disk and plow through the gelcoat, down to good laminate, push and flex the area to see if any cracks show up, or white spots in the laminate appear, both indications of damaged laminate. Once ground to good material, fill with a little fabric and thickened regular epoxy, vinylester or polyester resin. Lastly re-gelcoat or paint the area (regardless of resin choice and yes, gelcoat sticks to epoxy).

3M-5200 is an adhesive/sealant (think tough caulk here) and not suitable. Total Fair epoxy is a rebadged product, so you're paying more then you need to. This is also a topical fairing compound and has no strength. If the area has broken laminate below the surface, this stuff will just pop right out, once you bounce off a few waves.

 

The picture was before I really got going, and I dug it out to all sturdy glass. I will grind down the gel coat for more surface area to work with, that's good advice. So as far as the fabric goes, should I go with 4-5 layers of cloth over the gap and soaked in 105 west system? Also, what do you reccomend for fairing if total boat is overpriced?

 

You'll use as much fabric as it takes to get the divots brought up to nearly flush with the surface. This is just replacing laminate that was damaged or ground away. How much depends on how deep these puppies are and the amount of grinding preformed. You can use West System and it's good stuff, but also one of the most costly too. There are several discount epoxy formulators and you should look around, unless you just like to pay 2 - 3 times as much as you need to for goo. I'm not sure what you mean with over priced, but for the novice I'd recommend System Three QuikFair as a good fairing compound. It's more costly than mixing your own, but it is consistent, which is hard for the novice to get with home brew formulations.

 

What kind of epoxy resin would you reccomend that is more cost efficient than west sysytem? I was looking at sc110 epoxy resin on amazon which is $60 for a gallon. I'm planning on buying a 1 square yard fiberglass that weighs 6 oz for that repair.

 

SC110 is Epoxy King goo out of Michigan and one of the lower cost goo makers, for small qualities.

 

I'm glad I asked about it. What epoxy resin should I buy if that's out of the question?

 

From the picture you posted it doesn't look like you'll need much epoxy. Could you post a better picture of the area you're fixing?

 

Yes I will post a picture when I get home from work. I'm leaning toward 105 west system

 

Yeah, if you only need a small amount of epoxy it doesn't make lots of sense to spend much time trying to save 5 or 10 dollars.

 

I just wasn't sure how much epoxy I would need because there are multiple spots I want to repair with cloth. But it's a 14 foot boat how much epoxy could I really use?

 

The picture you posted was a little dark I couldn't get a real understanding of what type of repair need to be made. I've sailed 420s and I'm not even sure what part of the boat that was. Were did those voids come from? Is this the result of a manufacturing mistake? So it was just an air bubble under some gel-coat until the gel-coat failed?

 

Maybe you ground away a much larger area than I can see in that first picture. But as it stands right now, you won't need anywhere near a full gallon of epoxy. Post some better pictures, looking forward to it.

 

the area shown in the picture is an air pocket channel that runs from the stern to bow. I took a picture of the section of it before it goes around the centerboard. The most logical explanation of the delamination and cracking must have been some water stored in this air pocket that froze during the winter. I ground away a lot more until there wasn't any soft fiberglass remaining. I'll post some pictures as soon as possible.

 

Here are the pictures