Question for wood /MDF experts

[azygoustoyou]

I want to seal the bumperettes I'm making and was wondering what should I use before covering it in Fiberglass resin and cloth? I tried a couple things and found that filler primer might be the easiest. I need input so I can finish the post. Any suggestion appreciated. Thanks in advance.

[Danno]

I think that would be fine, but let me just clarify that you are just going to completely cover the thing with fiberglass cloth/resin? I mean, you aren't using this as a form, needing a good seal to apply a release agent on, right?

[azygoustoyou]

Right Dan,
I think I would have to polyurethane it or something to get it to make the molds. These are specifically made for my car. I don't think anyone would want their bumpers in the same spots. So I figured I would just cover them. I want them to last. So I figured on covering them completely.

[Danno]

that should be fine, then. You might actually be able to get away without doing anything to them, but there is a chance the resin wouldn't set quite fast enough and you could have some swelling. it would be minor, though.

[Foster48x]

Brady,
The process your looking for is used in building boats. Take a look at this it may help and there are some good links to fiberglassing over wood at the bottom also.

http://newboatbuilders.com/docs/fiberglassoverwood.pdf

Rick

[azygoustoyou]

Thanks guys,
That helps

[manoa matt]

Just buy a couple cans of the black "Plasti-dip" and coat them with it. Its very thick so it will hide imperfections, (not that here is any in the substrate) Its rubber and will look good for years, hopefully. Its somewhat self leveling so it should provide an even surface. The fiberglass is going to be a lot of work sanding and filling, then painting.

If you don't like the plasti-dip it easily peels off and you can still recoat over the MDF with no adhesion issues.

[azygoustoyou]

Problem is that the MDF wouldn't hold up. I have to structurally make these stronger. That's why they need fiberglass.

[manoa matt]

MDF wouldn't hold up to what? If the MDF is not FULLY encapsulated on all sides it will swell as it absorbes moisture, regardless of what its wrapped in.

Is the bumper block mounted to the sheet metal, or is there a firm support behind it tied to the bumper shock location? If attached to the sheet metal, the sheet metal will deform before the block crunches. If its tied to the frame, the block will crunch before the sheet metal, provided its high enough and sticks out far enough to do something.

I would take the MDF blocks and use them as molds for the fiberglass. Make them like a cup where the top/open part is against the sheet metal. If there is ever a problem, you have the mold to make another one, or the molds to sell these as a kit.

[azygoustoyou]

After thinking about this. I think I'll just use these to make a fiberglass mold. I've done too much work to loose them later and trying to completely seal them is a pain. These are only decorative. Not functional. Anyways, when was the last time you saw a wrecked spider that actually had their bumpers used in an accident. It seems they get hit higher in the hood area and trunk areas.