Fiberglass Door Panel Project, Sanding

Hiya :) I'm a noob to the forum, as well as fiberglassing - be gentle ;)

Well, for my first ever custom project, I took on a pretty hefty little job. Have an 89 Pontiac Grand Am, and the driver's side door panel was falling apart anyway so after a friend introduced me to the concept of fiberglassing and customizing; I figured I couldn't exactly hurt anything and jumped off the deep end. I started by taking the old door panel, taking a sheet of MDF and tracing around it to get a basic idea of the size. I took and cut around it, put it on the door, got everything sized right - built up my arm rest - a 6x9 spacer and did my cutting for the handles; etc. Then I took some fleece, stretched it, resined, fiberglassed; etc. and now I'm trying to get a baby smooth finish with my body filler. Since I can't really come up with any better ideas, I plan to probably paint the whole thing so I'm looking to get it as smooth as humanly possible.

Since it's my first time out, I've probably made every mistake in the book; but hey, that's how you learn. Any basic knowlege anyone feel like passing on as far as bondo/body filler work goes? I've been told to start with small thin layers and build up (which is what I have been doing), but with the belt sander I have - it seems like it will be easier to go with a thick coat and just sand down; but who knows. So far I still shave down to the glass or come up with very deep pockets. I'm guessing you can chalk it up to inexperience :) Any hints, or links to a nice tutorial to help through the rough spots out there though? Thanks, I figure I'll post pictures as it starts to look a little better ;)

Velocity Motors wrote:

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What you want to do is get some short strand fiberglass for strength and for ease of building up the door panel. You can get this at any autobody / paint shop or even at some hardware stores that stock automotive paint supplies. Now this short strand fiberglass is basically like Bondo but thicker and spreads nicer because of it. Place the same amounts of hardener as you would with Bondo and apply with the same tools.

After you apply it DO NOT LEAVE ! Make sure you have a sanding block ( preferrably a sponge block ) with a 25 - 50 grit sand paper. When the SSF ( short strand fiberglass ) starts to heat up from the hardener it will have a semi-hard texture to it where you can run your finger across it and it will not leave a trench behind BUT will flake off in a small chunk. This is the stage you want to start running the block with the 50 grit sand paper across the panel.

The short strand fiberglass will start sanding off in small rolls ( like your rolling up Play-Do on your fingers ). Keep doing this until you reach the desired flat spot in the door you want and continue to the next part of the door. Make sure that you do areas small enough that you can sand the short strand fiberglass like I explained above, if you take too long, you will know because it will take you 4X longer to sand hardened short strand fiberglass than it does regular Bondo.

After you have completed the door in short strand fiberglass and are happy with the smoothness of the panel, NOW you can use thin amounts of bondo to fill in any of the pin holes , dips & whatnot that the short strand fiberglass left behind. Use a 80-120 grit sand paper for the Bondo and do the same thing with the Bondo as you did with the short strand fiberglass and only allow it to dry to a semi tacky finish and then go to town with the 80-120 grit sandpaper.

Hope this helps and I gaurantee you that if you follow through with this technique it will shave off days of sanding and also block sanding ANY fiberglass project will ensure you of straight & flat lines bar none !

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The next door should go a lot quicker. I'll be trying that technique as well. I'm going to try going over the door in thick bondo tonight, and kind of sculpting  it out and then hand sanding. Very anxious to just get it over with

jt73]h wrote:

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nd sanding s*cks, but much better alternative than the belt sander...or get you a little palm sander from wal-mart

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i just pick up a sanding disk for your drill...like a 5" round rubber disk with mandrel...slap her in your drill and go to town...sure beats hand sanding and there is more control over it then a belt sander...plus being flexible rubber works well on curved sections...you will be forced to hand sand sooner or later theough...

and yeah if you dont catch the kitty hair in the clay phase it is a royal biotch to sand...

Basically, how it is looking as of the moment:

Not the prettiest thing in the world, for sure  Still, it's my first project, so I guess everybody starts somewhere, hehe. Still working on getting everything sanded down, trying to come up with ideas for what I truly want it to look like. Right now I'm thinking once it's sanded down I might cover it in flex-stone (I think that's a brand, no experience with it, but I saw a panel that looked really interesting using it the other day) and try to come up with some kind of fabric to cover at least that top portion above the arm-rest. Just an idea, since I work in embroidery it would be really neat if I could encorporate my own design on something like that.

The next panel, if by god I can finish this one, should be a breeze in comparison

Sessland wrote:

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That flex stone stuff (If I'm thinking of the same product) doesn't look so good after a while because it rubs off.

A few of my friends have done it over the years and have regretted it shortly there after.

It simply does not last.

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Hey   jargonscott you going to finish or what?....Did you do that test of the flex stone stuff yet?

...and that prog didn't do the menus is said it was going to do...

lor dude wrote:

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Hey   jargonscott you going to finish or what?....Did you do that test of the flex stone stuff yet?

...and that prog didn't do the menus is said it was going to do...

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The fleck stone turned out it probably would be too flakey, even after clear coating but I found some textured paint stuff over at Home Depot that seems more solid and I'll probably use that after I get the door as smoothed out as it can possibly get. Hopefully, providing I don't sand upon any holes, I can at least start thinking about that come Wednesday :D

Exactly, I have tried this bondo with resin thing and it does not work near as well as you would think.  The resin is more than three times as hard to sand and will clog your sandpaper up real quick, even if you are using 40 grit.

Bondo can lay very, very flat and smooth and be sanded quickly if you have some practice and get the timing right.  Start with 40 grit or comparable and when, and ONLY when, you think everything is perfectly straight and no waves or high spots or low spots ( low spots you have to re-fill) then go ahead and give it a thin coat of polyester filler for the sand scratches and pinholes, then once over with 80 grit for smoothness, and the thing will prime straighter and better than you could think.

Hope you can make it turn out good, it sounds easy typing, but it takes a whole lot of work.

i cant agree with that. Bondo is just resin and talc powder more or less. its easier to sand to some degree, but, as i have just finished a set of panels i was working on, the magic mix (rage extreme and resin) was the perfect finish for the doors. self leveling, smooth, and about as close to finished product as i could get anyway. i mixed it 50/50 so it was more like a thick house paint consistency, and with some mid-grade quality DA sander discs folded in half (80 grit) the panels were ready for high build primer in no time. i use the mix for a contiguous coating on the piece im workin on.. hope that helped.

-J