Sanding Fiberglass

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DjIQ

Copper - Posts: 107

Joined: March 10, 2003

Location: United States

Posted: April 15, 2003 at 8:31 AM / IP Logged

What grits should I use, and when i have it smooth enought to apply the body filler, and what grit do i sand the bondo with?

Velocity Motors

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Joined: March 08, 2002

Location: Manitoba, Canada

Posted: April 15, 2003 at 9:57 AM / IP Logged

When you first start off I always use 60 - 80 grit and work my way up to 120 - 150. Apply Bondo to low areas and filling in holes and sand again up to 400. After that you should be using 600 before priming and paint.

Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

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audiomechanic

Silver - Posts: 388

Joined: November 09, 2002

Location: United States

Posted: April 15, 2003 at 5:24 PM / IP Logged

i agree for the most part....the only difference is that for duraglass/marglass you need a really wicked grit to "grind" it i use a 24 grit roll lock pad on a 90 degree die grinder. you can actually sand it to a 40 or 60 grit then spray a polyester primer on it. this will eliminate a ton of sanding. assuming you have no unwanted low spots or warping you can go back over it with a 80 grit..then 220...then 400 grit. i recommend that you shoot a sealer primer coat in it and sand with 320 to 400 grit. this will get you all set to paint.

there are thimes when i have used a higher grit paper before paint.....but it is a case by case basis

wrencher_25

Copper - Posts: 101

Joined: March 23, 2003

Location: Canada

Posted: April 16, 2003 at 3:01 AM / IP Logged

We had a guy in school that used a bit more bondo than resin and it ended up creating a smoother surface when it actually dried. It DID take quite awhile to dry but when it did, it was really easy to sand b/c the excess bondo ended up making the finished drying product smoother. I dunno, if anyone has had better or easier experience i'm alway curious to know more.

Andrew Weitzel

MECP First Class Installer

audiomechanic

Silver - Posts: 388

Joined: November 09, 2002

Location: United States

Posted: April 17, 2003 at 4:22 AM / IP Logged

the only problem with that way is that you have quite a bit more sanding to do....and i dont know about you but i hate to sand.....the way i briefly listed above is a fast and easier way to get great results.....there are many ways out there to achieve the same results. some will take more time than others. and i found that the thicker the bodyfiller layer on the front, the more likely it is to crack.

wrencher_25

Copper - Posts: 101

Joined: March 23, 2003

Location: Canada

Posted: April 17, 2003 at 12:23 PM / IP Logged

Hmm,

So using primers can make it easier. That's cool. I'll have to try that.

Andrew Weitzel

MECP First Class Installer

audiomechanic

Silver - Posts: 388

Joined: November 09, 2002

Location: United States

Posted: April 17, 2003 at 5:38 PM / IP Logged

yeah ...the polyester primer uses mekp...the same hardener in it.....it hardens up and can be built up quite a bit....it is harder than regular primer....it will cover sanding scratches from 36 or 40 grit.

you can get it from any local autobody supplier like a finish masters. evercoat makes a couple different kinds both will do the same thing.....there are also several other brands available that will also do the same thing.

lycoming

Member - Posts: 7

Joined: April 18, 2003

Location: United States

Posted: April 18, 2003 at 12:35 AM / IP Logged

After applying the fiberglass to the suface or the rapair, be careful not to sand the glass itself but to bodywork over and around it. This will preserve the structural integrity of each fiber. You don't want to be cuting the fibers at every high spot on your project they only have tensile strength. Ending any number of fibers in one spot will cause it to crack. be sure to prep sand and clean with acetone first. scuff with 80 grit before applying bondo. Sand bondo with 80 grit first then step up to 320 before primer/surfacer. There will be pin-holes to fill with glazing putty after the first layer of primer/surfacer.

Don't primer over coarse grit scratches, the primer continues to shrink just a bit for months; where it's thicker (in the scratches) it will shrink more and you will see them after a year or so. take the time. good luck. any ?s just ask. I do this all day every day.

Jake

Proprietor of Cascade Composites, Carson WA

dishshacker200

Member - Posts: 3

Joined: April 18, 2003

Location: Canada

Posted: April 18, 2003 at 9:59 PM / IP Logged

i would use a primer product from dupont the # is 4004 dries in about 1 hour very good build sand with 320 grit then 500 grit thats all ready for paint

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Sanding Fiberglass

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