Gored: Crack repair

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Postby GreenLake » Sat Aug 20, 2011 10:34 pm

The patch came out nicely - the three layers give it 1/16th of an inch. It's firm, but still bendy enough so I have a chance to fit it flush against the hull from the inside.

1038

I used an epoxy formulated as non-sagging glue, rather than more laminating epoxy to bond it to the hull and a few bags filled with sand and cat litter to press it flat.

1039

That wasn't quite enough, so I helped out with a hiking stick.

1040

I immediately filled the outside of the gap with a few strips of mat, using the same glue. Mainly because I didn't want to wait for a full cure of the patch and because I had the mixing tip primed and ready. GelMagic's ability to wet out fiberglass is still pretty good. The composite shows the area with patch installed and after adding the mat.

1041

After about 5 hours in the sun, the epoxy had cured far enough to allow sanding.
~ green ~ lake ~ ~
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Postby GreenLake » Tue Aug 23, 2011 2:34 pm

I finished off the repair over the weekend. I don't have pictures of the filling and painting stages. I used QuickFair, an epoxy-based product that sands nicely. Because I had added the patch on the inside, I didn't bother with getting the laminate to come completely to full strength. Instead, I stopped below the surface, just making sure not to exceed a reasonable depth for the fairing compound.

I used a single thick layer of fairing compound (mainly because that's how much I had mixed up) rather than going for successive coats. A half-sheet sanding block and touch up with an orbital sander gave a reasonably fair surface.

As the hull will need to be painted in its entirety in the near future (and dings filled), I didn't go for the ultimate invisible repair, but used an open can of EasyPoxy to cover that spot. I learned that, curiously, the EasyPoxy cures much more slowly over the QuickFair. It remained sticky for almost a day longer than where I applied it over the adjacent old paint.

Being an epoxy paste, QuickFair should not contain solvents, and should be inert after curing. So, I'm puzzled.

(As an aside: for the final repaint of the hull I wouldn't use this particular paint. Even when it has cured for weeks, it remains very soft and is easily damaged on contact - luckily, I only got a quart, and I'm using it up for temporary / misc. jobs like that. This curious reaction to the QuickFair is just another incident that puts me off this paint)

Anyway, job completed in time for this week's fun.
~ green ~ lake ~ ~
GreenLake
 
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Re: Gored: Crack repair

Postby GreenLake » Sun Nov 17, 2013 5:00 pm

A follow-up note on the easypoxy from the last post:

I used the remainder on the inside of some of our kitchen drawers, where the bottoms had been nicked by utensils. Amazingly, the paint does hold up well to the abuse, and it's been a couple of years now.

A follow-up on the repair:

The hull was repainted the following winter and still looks good after a couple of seasons. Needless to say, the repair is invisible from the outside. I used a water reducible LPU pain with roll an tip. These paints cure tough, but you really have to follow the manufacturer's advice and use an epoxy primer or neat epoxy as base - there's one spot on a different boat where I sanded through the primer and got adhesion problems.
~ green ~ lake ~ ~
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Re: Gored: Crack repair

Postby GreenLake » Fri Aug 25, 2017 6:08 pm

Another follow-up.

My original evaluation of the EasyPoxy (single can) paint (no epoxy in the paint despite the name) needs to be revised. It appears that curing to full strength takes more time than I anticipated; I did the transom with it several years ago now, and it's definitely very hard there.

In contrast the white WR-LPU paint I used on the rest of the hull following the repair described in this thread proved entirely disappointing. After less than a year it developed stress cracks all over the hull, and at each crack the edges are curling up. Could have painted the bottom with barnacles and gotten it smoother.

While a similar, transparent, water-based PU varnish from the same vendor has worked well on woodwork for me - it's not brittle, but tough and scratch resistant, the paint is another story. Either it's in the formulation, or in the application. For the woodwork I brushed it on, which has a tendency to give thick layers. I also don't thin quite as much as recommended. For the hull, we used roll and tip, thinning to recommendation, which was needed to get it to look right. Multiple coats (and I had help from a friend who's a professional painter).

I'm sure it's not the surface prep but stress in the fiberglass, because the damage is uneven and at times located near obvious stress points (bow eye).

Could be that the (epoxy sealed) wood (thwarts/coaming) is less given to less flexing/stretching than the fiberglass of the hull, but whatever the cause, I'm not using that paint again.
~ green ~ lake ~ ~
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