Needing Bondo Advice, fixed leaking sunroof Options

[d_boice]

I had decided to ultimately fix my leaking sunroof. So with a blow dryer, putty knife, piece of 22 gauge metal, and $150 bucks later I have a filled roof.

I have no idea who cuts a hole into a perfectly good roof. -______-
But nonetheless, I am going to bondo the slight dip it has in it now.
Does anyone have any advice that you wish you knew when you first delt with Bondo??
anything would help tremendously..
Thank You

[bigb1970]

have you welded the plate in?

[d_boice]

yes sir, its welded and sealed from the water.

[lagos]

Bondo is normally easy to work with, but with a large sufrace like that it might be tricky to get it to look good.
Personally, I think the key to it looking good would be to find an applicator that is the same width of the roof that can also curve to the surface of the roof. That way you can apply the bondo and then run the applicator from front to back along the roof to get a nice even application.

After you apply one coat, sand it with 80-100 grit using a block or electric sander. Just don't use your hand and sand paper alone as you will not get good results. Then check your work and reapply more coats of bondo as needed. After that sand it with something like 600 grit to get a smooth finish thats ready for paint.

[Special_Edy]

Just make sure to get all the rust off the panel first, the bondo is designed to adhere to rough bare metal. The coarser the sandpaper the better.

Lay 2-3 layers of bondo, one thick layer to fill the hole and one thin layer to feather it out into the rest of the car body. Of course you should never go thicker than a 1/4 inch with the bondo.

And filling primer is going to be your new best friend. Make sure to get a couple different colors of primer, it helps you find high and low spots when you apply multiple coats with different colors. And definately get a sanding block(the kind that can flex) for sanding the bondo/primer. Sanding with your hand or a sander will create an uneven surface. Of course a sander helps to cut down the excess bondo quick, and they make files/scrapers for this too.

Beyond that you may want to mix up a small quantity to play with first, it dries alot faster than you'd think(especially 100°+ outside)

[rivs]

I would second the sanding block. This is a MUST. Using only your hand/fingers will cause dips and unevenness. When I did my first bondo work, I thought I could just use my hand if I was careful and made sure to apply pressure evenly. Nope don't bother, get a block and it will always be flat.

Also it's hard to tell from the photo, but is the plate you welded in, indented? Meaning that it is not the same level as the rest of the roof? If that's the case, I would try to raise the center to be close to the height of the rest of the roof. Other wise you will have to fill the whole area with bondo. And if it's too thick it will crack over time.

It will be difficult to tell when you are done sanding. Meaning it will look like you still need to sand more, but in reality it is completely smooth. The best by to do this is to use your fingers. Just slide your hand, and if there are any dips or high spots, you will feel them. It's also a good idea to paint a "guide" coat. This is what the other person was saying about different color primer. When you think you are close, put a light coat of primer that is a different color and then sand that coat completely off. Because of the contracting colors, it is easy to see high or low spots that still need work.

I'm not sure how good you are hoping for this to come out. But bondo usually leaves pinholes as it dries. I usually put a very thin coat of spot putty over the top. This fills in the pin holes and other small scratches and whatnot.

[Syaoran]

Why not try and put another metal sheet of the same shape over it instead of filling the indentation with bondo?

[d_boice]

Rivs: the plate is not indented, it was just welded from the inside. Meaning instead of putting the plate over the hole on top o the roof, it was held on the inside of the car and welded from there. If that makes any sense. And to be honest, I don't expect it to look magnificent, this car is really my learning car, it's the car I learned how to drive stick in.. Take apart my dash, change light bulbs, but I hope to make it look as good as I can. Haha it's just tough to judge if it is going to take a lot of bondo or not, the roof has a ripple effect from the sunroof being put in and sealed. (i.e) getting hot from welding. I'm hoping to make it look as level as I can and then have a friend of mine airbrush something over it to hide the imperfections.
Thank you for all the help special_edy and riv