Fiberglass help

[clint78z]

I have the hnag of fiberglass down fairly decent, using a roller helped a ton. I am going to try a sub box in the rear trunk fender. I am going to tape and tinfoil it so I can remove the box after. The problem is the upper part of the fender starts to go upside down. I have never had any luck keeping it stuck on a funky angle. Could I use 3m adhesive on the mat to keep it stuck to contour and then use resin over top ?? Any suggestions would be helpful.

 

Thanx C

[blueovalz]

upper part of the fender starts to go upside down

 

I'm guessing this is the part of the quarterpanel the brakes over and turns into the C pillar. These kinds of areas are tough to do because the more layers of mat that are placed in the area like this, the more apt these layers are to fall away from the surface due to their weight. I'm not an expert on this, but I'd handle it this way:

 

I would coat the entire area you need to place adjacent to the sheet metal with a thin "starting" layer. Depending on the weight of the mat (or cloth) depends on how many layers this will entail. 2-ounce mat will be marginal at 2 layers max, but thinner mat or cloth could include more layers. The less resin you use to "wet" this, the lighter, it will be, but the mat will need to stick to the metal, so this is where the resin will need to be, not on the outside (not on the inside of the speaker box). One characteristic I've found about resin is that it will not bond to the metal surface until about the last 25% of its kicking time. In other words, if a glob of resin were put onto a piece of metal (or any substrate), and it takes 20 minutes for the resin to get glassy hard, then the bond is not created to the metal until the last 5 minutes or so. At this point in the "kicking" process, the resin gets firm and almost like a hard rubber, and can be easily popped off the metal surface without distorting the shape of the blob. The blob could then be replaced back onto the same area it was just removed from, and the blob will continue to harden, but will not be bonded to the metal, and can thus be removed easily when needed. This same idea can apply to resin soaked mat. Allowing the mat to firm up on the sheet metal, and then CAREFULLY pulling it off to prevent permanent bonding, will allow you to maintain the shape you want, and after a thorough cleaning of any "wet" resin between the mat and the metal is quickly cleaned up (with acetone or lacquer thinner), you can then place the soft, removed part (still firm, but not glassy hard), back into the contoured metal quarterpanel (to keep the shape accurate for final hardening), for final hardening. When it is finally hard, pull it back out, rough up the surface (speaker side only) with 30 grit paper, apply more layers of mat, place back into the quarterpanel area (again to maintain the accuracy of the shape) until it is fully hard. This takes more time to do, but will provide a firm shape for more reinforcement at a later time. Don't forget to keep this simple in shape so that the part can be pulled off without distortion. This may require multiple pieces to be made, and then bonded together later. I would STRONGLY suggest you experiment with a narrow strip of mat that crosses the area you want to cover, and do the above procedure, and get a "feel" for when the strip should be pulled off. Pulling it early will cause a distortion of the shape, and attempting to pull it late may make it extremely difficult to pull it off at all without destroying the part. Experimenting with the timing (using the corners of the experimental strip to gauge when the strip should be pulled off) will pay big dividends in the final part. Waxing the area, or spraying with WD-40 has also helped in releasing the part without causing the mat to separate while still wet, but with the part hanging like you suggest in your post, I would experiment on this first to see if its a viable option.

[clint78z]

Yes you are dead on it is the fender to c-pillar area I plan to make the sub box for. Fiberglass is kinda like cooking, a few recipes end up in the trash !!!!

 

That is an awsome desciption, thank you Terry. I know that it will probably take some time to get the hang of it, but this wil point me in the right direction. Just to clarify you are telling me not to use anything between the metal and the first layup ?? Then pull if off when it's cooked enough, wipe er down and reinsert to maintain shape.

 

One quick question, I made a door pod from floral foam and layed the first layer on one side it didn't kick after a day. Will it eventually harden with heat applied ?? Or do I remove it and start over again ?? The other batch kicked in 1.5 hours and I am very pleased. It almost made me look like I know what I am doing .