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Old 05-30-2013, 10:30 AM
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Prepping gel coat for primer

Hi, I am about to begin painting a new glass coupe body and wanted to ask which grit would be best for sanding. The body is old enough to be fully cured, like 5 years. I want to begin with SPI epoxy primer followed by a high build for blocking. What would I begin with for sandpaper. SPI recommends 80 grit for metals, not sure for glass. thanks

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Old 05-30-2013, 12:56 PM
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Gel coat is much different than metal. Metal is a much denser material than gel coat as gel coat will powder and metal won't. If you where to use 240 or 280 grit you would be more than safe to achieve mechanical adhesion on gel coat...the Epoxy primer will give you the chemical adhesion.

Hope this helps.

Ray
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Old 05-30-2013, 02:24 PM
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did the same on mine you need it rough enough for primer to have something to bit in to and you will be good to go
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Old 05-30-2013, 06:02 PM
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I use Barry's (SPI) Epoxy all the time on f/glass
You need to open gel cot more than 220 for a good chemical bond.
Do 120 or 150 mininum.
2 coats of epoxy and yer good to go.
If any finer is used your lookin 4 trouble down the road
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Old 05-31-2013, 07:38 AM
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If any finer is used your lookin 4 trouble down the road
"Down the road..."? Don, Since when have you kept a car long enough to talk about down the road?
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Old 05-31-2013, 07:47 AM
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Quote:
Originally Posted by rod kent View Post
Hi, I am about to begin painting a new glass coupe body and wanted to ask which grit would be best for sanding. The body is old enough to be fully cured, like 5 years. I want to begin with SPI epoxy primer followed by a high build for blocking. What would I begin with for sandpaper. SPI recommends 80 grit for metals, not sure for glass. thanks
One of the most important things you can do to that glass body is put it out in the sun for 5-7 days before you do anything.
Does not matter if body is one year old or 20 if never used, it must have UV to finish curing.
Most good manufactures will send a tag, that says, has been UV cured or needs to set in sun for a few days.
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Old 05-31-2013, 08:01 AM
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"Down the road..."? Don, Since when have you kept a car long enough to talk about down the road?
Bob, Have seen my of my cars 5 -7 years after I sold them, and all still looked good.
Also follow Barry's advice about the UV cure time
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Old 05-31-2013, 08:11 AM
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Thanks for all the good information. I have heard about the need for sitting in the sun, I have rolled it out many times since purchasing and baked it in the good old Arizona sun for many days, hopefully she is good to go. thanks again
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Old 05-31-2013, 10:45 AM
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I have a fiberglass car that is cured. I'm running over it with 180 and hit it with urethane high build primer and start blocking. I hear SPI is good stuff! Never used it before.
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Old 05-31-2013, 10:58 AM
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Originally Posted by da34guy View Post
Bob, Have seen my of my cars 5 -7 years after I sold them, and all still looked good.
Also follow Barry's advice about the UV cure time
Don, I knew that, but couldn't pass up the opportunity to tease you!
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Old 05-31-2013, 11:18 AM
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Originally Posted by armentrout View Post
I have a fiberglass car that is cured. I'm running over it with 180 and hit it with urethane high build primer and start blocking. I hear SPI is good stuff! Never used it before.
Put SPI Epoxy on it 1st, then start blocking.
Add more epoxy and block more if needed.
SPI products are the best I've used in the 45+ years of doin this stuff.
Do yer self a favor-
Check out the SPI website
I've converted many a painter to SPI products.
Thay all love it.

BTW Bob, I knew U were pullin my leg, I felt the tug.
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Old 05-31-2013, 12:49 PM
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I use red scotch brite and then you can use coat of sealer and paint.
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Old 05-31-2013, 05:46 PM
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Why would you apply more epoxy over a high build primer? Would you just block the 2k and if it needed more, add more?
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Old 05-31-2013, 06:07 PM
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Originally Posted by Ryokoe2925 View Post
Why would you apply more epoxy over a high build primer? Would you just block the 2k and if it needed more, add more?
Yep! use 2k until you get it blocked, seal it and paint it. Some call any primer that needs a hardener "epoxy". 2k is epoxy
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Old 05-31-2013, 06:10 PM
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That's what I was thinking. I am about to repaint my whole truck but above my wheel wells was all rust so I cut out most of the rust. I'm just gonna throw some fender flares over the cutout metal. If I self-etch the metal should the rust stop?
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