Resin starved, resin rich...salvageable?

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#1

Im working on a project for a lab class Im taking at school that involves using a cardboard core hotcoated with poly resin and then covered with two ply fiberglass on each side as well as two ply carbon fiber. (Fairly heavy bidirectional, dont have the exact info with me at work though)

Due to time constraints and a couple others reasons I wont go into, I wasnt able to put it under vacuum/in the oven and had to do it as just a room temp cure/wet lay up. For the most part it came out great, but theres two spots on one side which are clearly resin starved and on the other side, its resin rich in a few spots.

This project doesn’t need to be load bearing, more or less it just needs to look good, so what Im wondering is can I coat the side that’s resin starved with more resin, let it cure, and maybe end up with a decent surface? Likewise, could I recoat the resin rich side and try to even out the surface?

Also, Is there also a clear coat that would work well in giving a nice finish? Id ask my professor, but hes out of town until mid next week.

#2

Moderators, if I put this in the wrong section of the forum, please transfer it or let me know and Ill repost appropriately.

#3

The only way to know for sure is to just go ahead and do it…

But I’d say it’s not possible. Voids/dry spots tend to be below the surface, so hard to reach once cured. If it was me I would cut out the dry areas and patch them up. Then perhaps put a surface coat over and sand it back to give a uniform appearance and level surface.

For the resin rich area you could just try sanding that area back. Or put a surface coat on and sand the whole area back.

But for a really nice looking part you need to get it right in the initial layup. Otherwise it just won’t look the same.

If you can, I would just start over and take this as a learning experience. Also do practice/test parts to get your layup technique sorted before moving onto the final one. If you have a visible carbon layer with voids I think starting over is your only real option…

#4

Starting over wasnt an option sadly because the materials were provided by the class. I decided to bring it home and use some large panes of glass I have as a mold to at least shoot for a smooth surface. I made the bonehead mistake of not double checking how level the table I was using was and the part slid on the glass as it cured. That ruined the side of the part, so I did an emergency salvage and applied two coats of polyester resin to the other side, sanded it smooth once cured, and then used polyurethane to finish it. Its going to be a control board surface for an arcade cabinet, so a perfect lay up wasnt required as much as aesthetics.

Considering everything that went wrong with making the part, and that I had one afternoon to make something out of almost nothing when everything seemed to go wrong, Im pretty happy with the finished product. It will certainly be strong enough for its use and I dont think it looks too bad.

Hot coated cardboard core with 6 ply fiberglass and 4 ply carbon fiber all together. Need to drill necessary holes for push buttons/joysticks, then trim the edge off so as to get it to size.

I just let the resin cure, then sanded it as smooth as I could, so the surface isnt 100%, but Ill be damned if it didnt turn out way better than I certainly expected while doing it yesterday afternoon.

#5

Glad that it turned out okay for you!

But that shows an important lesson… do a test piece first before going ahead with an actual part. That applies any time you have a new variable to deal with, like a change in work location. No need to use CF on the test piece, and it doesn’t need to be large. The idea is just to be 100% sure of your process after changing any materials etc.