Fiberglass... Getting It Right

[ramblinrod]

Originally Posted by scarlet

I have watched dozens of videos showing how to make small repairs in fiberglass and or gelcoat, and not a single one looks good. In all of them I've seen, the finished holes are clearly visible, and look patched. What I want to know is how to fill and repair small holes so that they completely disappear. Is this impossible?

I have several spots on my boat that need attention. I'm removing a lot of "snaps" and "fasteners" from around my bench seating and windows... I have some dings where chips of gelcoat have come out... And, I have a larger repaired area that the previous owner did... it's smooth... dull... color is off, and is generally an eyesore. I haven't a clue where to begin on that area.

For the tiny screw holes, it looks like an epoxy would be the best bet... but how do I perfectly match the hull color and shine? (we have a 2011 Lagoon 450).

It is possible to match gelcoat in the field, but usually it takes many years of experience to get it "insurance job" quality (meaning the average person is not likely to see the repair, even under close scrutiny).

Purchasing colour matched gelcoat for any boat over about 5 years old is usually a waste.

One difficulty is that gelcoat changes colour with time and UV exposure, and even if a single gelcoat colour was used during production, the vessel may be various shades of that colour as time progresses.

For a single area, some gelcoat suppliers can use a tool to determine the exact shade and match it for you.

However, another difficulty is that gelcoat can change colour as it cures.

It is best to mix a large batch of uncatalyzed gelcoat, and then catalyze just a dab, see what colour its turns after it cures, and then adjust the colour, and try again. (This can take days and is why an "insurance job" costs about 3 times that of a "20 foot" job.)

Sometimes gelcoat will match perfectly initially and then after some time (months) will turn a slightly darker shade, possibly with a slightly pink or brown tone.

Note that polyester gelcoat will not play nicely with most epoxies, so if you wish to use gelcoat as the final finish, it is best to go with polyester resins for glass laminating and filling.

As mentioned prior, avoiding spot repair and doing an entire panel to natural breaks or curves makes it easier to complete an aesthetically pleasing repair even if the match isn't perfect.

Gelcoat pros also know how to blend the repair into the surrounding area to avoid the appearance of a sudden colour change at the repair edge.

We do spot repairs, including old dodger fastening filling all the time.

One can do the individual spots, but often it is better to do a complete band along the old snap line.

Ideally, ask your canvas guy to use the old snap fasteners, or ensure to extend the new dodger flap over the old snap line, so that a perfect match isn't required.

Note on painting. Most paint jobs are far less durable than gelcoat. First, single part paints just aren't as durable. But even 2 part epoxy paint that can be as hard or harder than gelcoat, is necessarily applied about 1/20th as thick, so can be easily scratched through.

My general rule of thumb for those who are fussy about appearance, is that plan redoing:

A) Single part paint in 5-8 years.
B) 2 part paint in 8-15 years.
C) 2 part paint with clearcoat in 12-20 years.
D) Gelcoat in 15-25 years.

On the application, gelcoat is far less forgiving than any other finish. But repairs are actually easier, in that scuffs and minor scrapes can just be buffed out.

Some 2 part paints have the gloss only on the surface, so if one uses any kind of abrasive for any kind of repair, the gloss is removed.

[StoneCrab]

I've been in many yards where the workers were doing fiberglass repairs. The final step was to reapply color matched gelcoat. They apply color mixes to the side of the hull, just like Andy demonstrates in the videos in post #12. When they get the color right, they add the catalyst and proceed with the finish coats which are always followed by a fine sanding and buffing. The repairs blend in perfectly.

They extend the gelcoat well beyond the repair area, just like in auto body work, so it can be feathered in.

I admire the skill that these workers possess. It does not look easy. They usually take more time mixing the color than applying and finishing the coat.