Dull gelcoat

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  #1  
Old 09-18-09, 11:20 PM
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Dull gelcoat

I have an 88 Capri 1750 Bayliner with a dull gelcoat. I got most of the blue stripe buffed up with an ultra cut compound by Presta, but it seems like the transom area is super dull/dead, and I can't really get it to shine up like most of ther boat did, I has some water droplets in the compound from the washing, do you think this is part of the reason. A friend said no and that some actually add water to help keep the coat cooler. This is a auto product. How long do you buff a 24X24" area before moving on? I haven't done this before. I don't have any blisters in the finish but I saw a few spider cracks in the gelcoat, should I be concerned? I trailer this boat. Am I using the wrong product?
 
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Old 09-18-09, 11:49 PM
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At 1/8 inch or more, the gel coat is a lot thicker than the coat of paint on a car, so you can bear down with rubbing compound and a power buffer. Keep the area wet, and don't let the power buffer touch any stainless steel or aluminum, or it will scorch. Wet sand with 400 and 800 to finish the shine.

It's not really about how long you work on a 24x24 area. Work it until all of the chaulk is removed.

Spider cracks a.k.a stress cracks are not structural. They're common because the gel coat is rigid, while the underlying glass has a bit of give. If you don't like the way they look you can use a gel coat repair kit. Matching the origingal color may be harder than just living with the cracks. If the cracks are under the waterline they should be repaired.
 
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Old 09-19-09, 11:39 AM
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Sanding???

This sounds a bit backwards ??? Buff then sand??? The buffer is finer than the sanding...
 
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Old 09-20-09, 12:27 AM
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Try it. Rubbing compound will take off the chaulk. Then wet sand it.
 
  #5  
Old 09-20-09, 07:13 PM
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If you have metal flake be careful as it is thicker than pain but if you sand or buff too much it will turn the top flake a silver color that won't match the rest of the deeper flake.

I did my 81 brown with flake boat last year. I wetsanded it with 600 rear light because my gell felt rough. Then I went to 1000 grit and got it smooth. After that I buffed with 3m finess it 2. Then I waxed it with 3m marine hard wax. It took all day but it does look great. But you need to keep it out of the sun or it will chock up fast like within 2 weeks.


When sanding try a small spot first to see if you go through the top layer you will see it when it it dry.

I'm not saying this was the right way just what I did.Beer 4U2
 
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Old 09-20-09, 08:55 PM
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Originally Posted by samuari View Post

I'm not saying this was the right way just what I did.Beer 4U2
doesn't sound like anything wrong with the way you did things.

and your point about metal flake is a very good point.

after working in fiberglass factories for way more than I like to remember, I have never used anything finer than 400 grit wet/dry paper. 400 grit will buff out completely. If you want to use a finer paper, there is nothing wrong with it and actually, for the inexperienced, it would probably be a good idea as the finer the scratches you need to buff out, the less work it will take and the less chance of causing a heat burn to the gel coat.


as to Rick's suggestion: can't say I have ever heard or seen anybody do such. Factory process was start with whatever grit was deemed necessary ( when manufacturing fiberglass products, if the mold is not in good condition, there can be some quite poor spots created where the mold needs to be reworked ) and work down to 400. Be sure to sand well enough with each subsequent grit to remove all the scratches from the previous grit.

wet sanding allows the paper to last much longer.

final sanding was done using worn 400 as the sharpness of the grit was reduced and it was not as aggressive (similar to using a finer grit paper).

then, polishing compound (such as 3M polishing compound) (not buffing compound. buffing compound is actually more course than polishing compound). We used a high speed polisher with a wool bonnet. It does take practice and care to use a polisher (as opposed to a buffer) as it is much faster and can cause a lot of damage quickly if not used properly.


You want to be sure to not heat up the gel coat. The compound should remain wet. If it is dry, more compound would be added. Heat can actually cause a burn in the gel coat and discolor it and it does not remove easily.


after it is polished to a high shine, it should be washed thoroughly and then waxed using a marine wax. You should not have chalking problems as quickly as samuari did if you wax it well. Just like a car, it needs to be cleaned and waxed regularly to keep it shiny and protected.
 
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Old 09-21-09, 01:33 PM
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We're talking about the gel coat on the transom of a 1988 boat. It's been subjected to all kinds of abuse over those 21 years, so the gel coat is probably in pretty bad shape.

I used the above method (suggested by a marine gel coat repair guy) to bring back the burgundy gel coat accents on a 1983 Larson. Red colors are the hardest to bring back. The Larson had laughed at my attempt to hand-rub with auto-store compounds that were designed for paint.

The buffer with (wet) rubbing compound -- not a high-speed polisher with polishing compound -- removes most of the chalk that causes the dull finish on the gelcoat. After a weekend of buffing, my arms kill me from the surprising amount of pressure necessary in order to feel the buffer grab hold of the chalk. As I said, you have to bear down.

Using the 400 wet sandpaper takes care of the corners, close-ups, and really difficult stuff that the buffer doesn't remove. 800 grit smoothes and shines it enough so a polish & wax can bring back the gloss.

A lazy person would just smear Vaseline on the entire hull every couple of weeks and be done with it.
 
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Old 09-21-09, 02:37 PM
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Originally Posted by Rick Johnston View Post
We're talking about the gel coat on the transom of a 1988 boat. It's been subjected to all kinds of abuse over those 21 years, so the gel coat is probably in pretty bad shape.

)




If you are going to sand anyway, why bother using a buffer at all?

In my opinion, it is less work to sand than to use a buffer anyway (way too slow and takes to much effort) and the sandpaper finish will leave a sheen where a polished finish will shine. If one is happy with the sheen of a sanded finish then there is no reason to even mess with a buffer.

but I would never use a buffer to begin with. As I suggested, a high speed polisher is what is used and a wool bonnet. Not only will it remove more scratches, it will require less work for the same amount of action but more attention must be paid lest one would burn the gelcoat.
 
  #9  
Old 09-21-09, 08:45 PM
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The finish

I bought a velcro back and wool bonnet, wet sanded with 400 then 600 on the transom area by hand, then used the ultra cut with the buffer, then applied Blue Coral Fombilin sealer protectant for car finishes...It looks good. The chaulk is gone. An automotive book I read recomends using 1000 grit to finish the coat...
 
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