Spider Crack Repair
 

I finally decided to fix the spider cracks around the rudder on my boat. A previous owner had gently hit something with the rudder, just enough to crack the gel coat, but not enough to damage the fibreglass or bend the rudder.
http://farm9.staticflickr.com/8011/7...51280189_z.jpg

Yesterday I ground out the cracks with a Dremel tool with a diamond tip bit.
http://farm9.staticflickr.com/8028/7...4ab241af_c.jpg

I used about 1/2 oz of white with 2 small drops of black pigment. The MEK was added and mixed at 2%. The repair was covered with plastic to cure. The colour match is very close to the original sanded gel coat, but is lighter to the discoloured hull.
http://farm8.staticflickr.com/7088/7...de0f76e0_c.jpg

The first layer of gel coat went on last night. Working upside down on the bottom makes for a rough first coat. After sanding today I applied the second coat to fill a few of the low spots. Sanding from 100 grit to 220 grit for the first knock-down. Tomorrow I will use 220-1000 for the final. Following that I will buff it out. Of course, the sanding will come after I return home from a day on the water. Why waste a good morning sanding...

Looking good so far. You're brave. I need to do this to my boat as well. Struck a submerged tree last year. Where did you get the gel coat for the repair from?

West Marine. About $20/quart. The colour additives are about $10/bottle (1-2oz)

Any updates? Did your color match well

The colour was off a bit and I had a few low spots.

http://farm8.staticflickr.com/7239/7...618ce528_z.jpg

I did a bit more work to it and the colour came out nearly perfect on the final pass. There are still a few more lines I need to fix.

http://farm6.staticflickr.com/5071/7...6eca4d77_z.jpg