How to make custom bumperettes

[azygoustoyou]

I shaped and sanded the first bumperette. I coated it with another coat of resin to cover some of the cloth that seems dry. I'll sand and paint it later after the insert nuts are installed. I recoated the inside of the mold of the first bumper. I think the spot glaze putty might have held the bumper in the mold somewhat. It was on the bumper when I pulled it out of the mold. But then maybe it was just transferred some over due to all the heat within the mold.
I think I might try to make the molds thinner on the next one to see if it helps in the separation process.

[azygoustoyou]

I posted pic's on the first page of what it will look like. One is end result and the other is out of MDF. I'm working on the MDF mold now.

[So Cal Mark]

that is quite a nice piece of wall art you've created! Now if you attach the rear of the car to the outside wall you can start charging visitors to your gallery

[azygoustoyou]

You know, I waxed this damn bumperette 11 times. I also made the mold thin so I could possibly get it off without any tough issues. Well, look at it. It wouldn't separate. The mold and bumperette is nearly destroyed. It pulled all the fiberglass off the bumper and stuck in the mold. It's going to take some work to fix the mold. I'm afraid that when I do the back ones. They won't come out. I think I'll make the mold with three layers and then fiberglass stirring sticks to it to help it from coming apart.

[bwilson27]

What if you just sanded down four random chunks of fiberglass that have about the right dimensions? Then painted them, like I think you're planning here? Would that be easier? Where could you source something like that?

[Foster48x]

Hey Brady, man that's gotta be really frustrating. I've never made fiberglass molds before but I have done a little research on them in the past for car stereo speaker applications. Here's a great video series about making fiberglass molds (you may have already seen it).

http://www.wonderhowto.com/how-to-make- ... ld-259755/

In the video the guy is making a nose piece for a model airplane. The way he creates the mold in two smaller parts may help with your release issues. Keep the faith!

Rick

[azygoustoyou]

I plan on fixing this mold and calling a Fiberglass store. I think I need the PVA. The heat must not interfere with it. I'll let you know what I find out.

Here is a link to good info on mold releasing. http://winshipmodels.tripod.com/pva_mold_release.htm

[kmead]

A few suggestions:

When you rework your master, make sure there is some draft on the sides of the part.
Instead of making your molds from fiberglass or other materials, use plaster of paris in a shallow pan. Attach your master to a base plate with a fillet where you want to trim the finished part. Wax the master and the base plate and cover with a thin coat of vaseline. Using plaster of paris pour it over the master. Let it set up (make your plaster slightly thick so it won't run off or make a dam around the part (cut off a milk jug or other plastic container to make a deep enough well to fill up with plaster). I usually do it in a couple of pours, the first around the part and "painting" the part so its completely covered in plaster, then a second layer with "horse hair" straw to reinforce the mold.

Let it sit over night in a warm, dry environment. Remove the master with base plate from the mold. Now let the mold dry for several days or put it into an oven on LOW (as in under 200°) for a day to fully dry it. Once it is dry the mold should ring like a bell when you twack it with a finger.

The next step is to shellac the mold after making any minor repairs to the mold you may need to do to true the surfaces. After applying coats of shellac, wax the entire surface the fiberglass and anything else will cover.

To mold a part, spray the interior surfaces with a coat of PVA release agent and after that dries, a healthy coat of gel coat in black (or other color if you wish) making sure it doesn't go over the edge of the base or area you have waxed. Then do your lay up. Let it sit overnight to ensure the polyester has completely cured. Carefully pry the finished parts, starting on the face of the base and it should pop out.

Trim the part on a band saw with the bed at 45 degrees, cutting just outside the edge of the desired final part. Then take it to a disk sander to finish the final trim.

This technique should net you as many parts as you want if you are careful in removing the cured parts.

Using the gel coat gives you a good primary surface you can sand fairly easily and accepts filler if needed.

[azygoustoyou]

Thanks for the input Karl,
I'll try your method the next time I go to mold something.
I was able to fix the mold. I bought some PVA and a spray bottle to apply it. It cost about $20. I wish I would have bought this stuff in the first place. I also have the back two bumpers waxed. So maybe that will help with the release also. The PVA said it was best if sprayed on. Before I start on the back I want to see how the 2nd bumper comes out of the mold. I'll try to do it within a couple days.

[azygoustoyou]

I think I might have a working system now. I waxed the inside of the mold three times. Then sprayed a thin coat of PVA. Followed by a thick coat. I think I may have sprayed it a little too thick. I had to pour a little out. It kept rolling around in the mold. I did get a good coat on it as you can see.
I did some of the bumper and as I was cleaning up the edges. The mold separated from the sides which never happened before. I'll let it dry until tomorrow and pull it out. This one will need some touch up.

[azygoustoyou]

Wow what a difference. It came out like butter. I know The back will turn out great now. I have to do some touch up on the second front one. Finally some good results.

[azygoustoyou]

Front bumpers are done.

[SLOSpider]

Looks great! interested to see the mounting set up. Brian

[Foster48x]

Awesome!

[azygoustoyou]

I have two stainless bolts that are welded together using a bracket at the top of the heads. I will inset them inside each bumperette within resin. I will drill two holes in the body and add a metal bracket. Add two nuts with some lock tite.

If you wanted to place these in front of the bumper holes. All you have to do is take a 1 3/4 pipe and add a plate on the end. Use insert nuts within resin in the bumper and some bolts to hold it on. Slide the pipe in the bumper supports and drill a hole in it to put the bolts through.