Ventolines

So after getting the boat washed out, in an attempt reduce the amount of salt on the inside, I explored the crack in the keel trunk.  It really did not look like much.  Just a crack, a tear even.  But as with anything else, the first look is often deceptive.  A good chunk of fiberglass, next to the crack, was delaminating.  I guess the force of the strike had stress the glass and resin well beyond its intended max PSI.

Beveled hole to be patched

So, I did what anyone else would do: cut away all damaged glass and opened up the hole.  I beveled the hole inside and out, giving my self a great deal of surface area to build in a patch.  The difficulty was not in the size of the hole, but that it curved in 3 dimensions.  I had to come up with a way to mold the first layup of glass and epoxy.  This took a while to decide on.

The idea came to me while I was underneath the boat trying to get the keel down without crushing myself (getting the keel off and on will be another post; for now check out: http://sailincat.com/boating/C25_proj/C25_sk_install.htm).  The idea was to use my noodle.  You know the swimming pool foam noodles designed to give you a little extra flotation.  They are cheap, bend easily and are cheap.

Wrap your noodle in plastic

I wrapped the noodle with plastic wrap and jammed it in the keel trunk and bent it through the keel slot.  It was a perfect fit and remained snugly in place while I worked.

The wrapped noodle provides a surface to mold the first layer to.  Once in place the first

The wrapped noodle from the interior

layer is the mold for all following layers of which there are many.  The layers eventually form a sandwich of sorts between the outside and inside of boat.  The sandwich is 12 oz cloth at the lowest layer, then Kevlar, then 6 oz cloth and finally mat fiber glass.  The layering goes easily for the fiber glass cloth and mat.  The Kevlar was a little hard to wet out with epoxy, so I practiced, on a form I had, a few times before putting on the patch.  It was difficult to roll out the air bubbles in practice and took some time.  I found that by using the slow hardener I had the time necessary to get the bubbles out, a technique I used for the Kevlar on my patch.

When the patch had set up but not fully cured I removed the noodle.  I applied the same layup on the exterior of the boat; in the keel trunk and slot.  The hope is that I get a solid mechanical bond on the beveled existing glass and that where the inside and outside patches touch, a solid chemical bond.

There are some good books on fiber glass repair and many articles on the web.  This is not very difficult for most people to do and a competent amateur can do a great job.  The first steps are critical:

1. Dewax the hull everywhere you expect to sand (for unpainted gel coat and fiberglass)
2. Dewax again
3. Dewax again
4. remove all paint from the areas to be beveled and patched
5. give your self a smooth bevel/chamfer at the patch site, I went with a 12 to 1 chamfer
6. clean with an acetone (or safe alternative) soaked rag.
7. clean again with the acetone.
8. One more time…

I was extremely cautious in my de-waxing and cleaning; likely paranoid.  But I want the patch to have the best chance to bond strongly to existing fiber glass.  The other area I was cautious was in removing all air spaces.  It is not difficult but requires patience and diligence.

A final note.  I finished the patch by applying a fairing coat of the concrete, err, I mean colloidal silica and epoxy.  From past experience with this I knew I had to get it as smooth as possible before the epoxy kicks.  If you don’t be prepared to go through a lot of sanding.  A lot.  If you happen to have a job hanging drywall, this is likely not a problem for you.