gel coat repairs

[paraman]

Hello everyone, I'm new to this site and I'm very impressed with what I have been reading and seeing here. I would like to do some gel-coat repairs on my own and would like to find out what is the best way to repair the minor cracks which drive me nuts. Basically I need help from start to finish with type of prep, sandpaper, gelcoat, buffing pad, compound, the works. Is there a good book reference also would be helpfull. I know its alot to ask, so any help would be appreciated. TIA, Paraman [img]images/icons/tongue.gif[/img]

[Ed]

Paraman-

For those annoying spidercracks that seems to appear everywhere on older boats (except of course on my Mako [img]images/icons/shocked.gif[/img] ) here is what I would do.

Take a small die grinder (or Dremel rotary tool) and grind out every crack with a v-shape groove until you can no longer see any cracks. Then take some 36grit sand paper and rough up the edges along each crack. Then blow off or vaccum off all of the dust and wipe clean with acetone.

Next, get yourself some 24 ounce roven fiberglass (it looks like a braided basket) and pull out 3-4 strands that are the length of each crack. Take the strands and braid them together and lay on a piece of cardboard. Next, wet out the strands with resin and place them in each crack.

After the fiberglass cures, you'll need to go over each section and grind and fair them match the surface. Since this is kind of an art and you are a new to it, I would only grind down enough so that the surface of the repair area is slightly higher than the rest of the boat. Then, take a sanding block with 80grit paper and sand down the repair until smooth/flat. (Most pro's can grind down most of the repair flush on the first try and then clean it up with either a block, da or airboard depending on the size & shape of the repair area). If your cracks are not on an existing flat surface (i.e. a channel on the edge of the floor that drains water to the stern)....forget the sanding block and wrap the sand paper around something (PVC pipe)that closely matches the shape of the surface you are trying to duplicate.

Once that is done, fill in any pin holes with white fairing putty (use white hardener too....don't use the red or blue stuff...it will cause color problems later on). Next, brush on some white gelcoat and fair (sand again). The white gelcoat will help hide the repair.

Blow off dust, and wipe clean with acetone. Now you are ready for spraying ongelcoat that is tinted to match your boat. ( I could write 10 pages about this...but I think you get the picture).

Let me know if you have any questions. Also if I left something out...I am sure one of the real experts will chime in.

Good luck.

Ed

[paraman]

Ed, Thanks, I do have a question on the final finish step. What should my final sandpaper grit be, before I use buffing compound and is there a specific buffing compound that works better to bring back the finish. PS If the cracks are really small can I just grind out and use gel-coat and a filler. Again Thanks for your help. Paraman

[Ed]

Paraman-

Almost forgot.....before you spray on gelcoat.....you need to sand entire area around repair with 180 grit. This will give some bite for the gelcoat to adhere to but will also buff out if you don't spray over everything you sanded.

Once gelcoat is cured (depends on temperature and humidity).....wait a couple of days....you'll need to wet sand the repair area with some 600 grit, and then 1000 grit. After that is done....buy yourself some gelcoat buffing compound (it is a white paste....the regular red liquid buffing compound is more for paint but does work) and start buffing. Use heavy pressure at first and then gradually lighten up and allow the pad to polish the surface.Be sure to dress (clean) your buffing pad often.

As far as using gelcoat to fill in spider cracks...I wouldn't because they will most likely come back. If the cracks are fairly small....you can use fiberglass putty (yellowish/green with bits of glass mixed in)instead of the strands from the 24 ounce roven.

Hope this helps.

-Ed-

Ed

[paraman]

Ed, I can't wait to try out the repairs. I will have to wait until the weather gets warm because my boat is stored outside. I will post the out come when I do it. Thanks again, Paraman

[abl1111]

Ed,

Great explanation. I have a few questions.

How deep do you grind the initial "V" in the cracks ? Through the gelcoat into the laminate a bit ?

I am sort of familiar w/ roving. When you say take out a few strands and braid them - you mean a few of the tiny, hair-like strands, right ? And your experience has proven that the repair holds-up pretty well ?

Lastly, what is your way of mixing gelcoat to match it right ?

thx,

alan

[Ed]

ABL-

If you have a die grinder...use a tapered grinding bit and while holding it an angle, grind out the crack. This will give it the v-shape which gives the glass or putty something to hold on to.

The amount needed to grind depends entirely on each crack. It it is a very small, hairline crack....start by just grinding away a little bit. Once you've ground out some of the surface....blow it off and look to see if the crack continues deeper into the laminate. If so...you'll need to grind some more.

As far as braiding roven is concerned.....just pull one or two of the existing braids out of it...and then braid them together. It will most likely be bigger than you need...but it will fill the crack and you can grind away an excess.

Hope this answers your questions.

[Ed]

Almost forgot about your question regarding gelcoat.

Nine times out of ten, oem gelcoat from the the boat manufacturer that is supposed to match one's boat will need to be tinted, because of the fading affects that uva rays have on gelcoat. With this said, using the oem gelcoat for your boat is a good place to start.

When trying to match your boats particular gelcoat....make up 3-4 small samples of gelcoat (dont add the catalyst yet) with various combinations of tint and hold them up next to the area you are repairing. Then select the one that is closest and keep repeating the tint process until it matches. It is a tedious process but once you get familiar with the effects of the various tints it should make sense.

Spectrum's tint kit has some pretty good instructions in it as far as which color tint to add etc.

Just remember that gelcoat can fade differently....so the gelcoat on ythe topsides of your boat may not match your hull gelcoat 100%

-Ed-

[abl1111]

Thx Ed. I will be trying this process in the Spring...

Happy Snow Storm !