Cheap fiberglass enclosure with no special equipment
I needed custom shaped big volume enclosure for one of my decks, because available enclosures were either too small or bad fit. So I have decided to try working with fiberglass for the first time. But at the same time I didn’t want to invest a lot into it, buying special tools and special materials for mold making. Tips on this forum were super useful, so I want to share my experience, maybe it will help someone.
Mold
I have decided for positive single use mold. Enclosures made out of positive mold are generally not as good looking, but it’s easier to make inner dimensions correct for your electronics. I cut the inside dimensions of enclosure out of 10mm and 20mm polystyrene sheets which I hot-glued together. Then I cut chamfer around the corners, so the enclosure is not as stressed on corners. For cutting the polystyrene you need sharp blade.
I wrapped the whole thing with brown packing tape. I also wrapped whole deck, since I use the deck itself as part of the mold. I attached the polystyrene block to the deck with hotglue and covered the gaps with more packing tape. Brown tape doesn’t stick to fiberglass and doesn’t leave mess like clear tape.
Laminating
For laminating I have used 3 layers of 340gms fiberglass weave cloth and around 400ml of resin. I first put cloth, then resin, so I haven’t started with resin on the mold. First time the resin turned into gel when I started to work on first layer, so you have to work fast and prepare everything before putting activator into resin. Instead of brush and roller I used piece of wood and piece of cloth, worked fine.
After the cloth and resin was layed down, I used cheap vacuum bag for clothes to vacuum it. Once again, so special equipment like epoxy vacuum pump, I just used household vacuum cleaner. But I used piece of cloth on the vent to protect it so I don’t suck the resin accidentally. The vacuum bag can be reused.
And it worked good enough. It’s smooth from the outside. When the enclosure was still attached, I drilled holes booth through the enclosure end deck so I have them aligned well.
The polystyrene inside got eaten up. But it must have happened during curing from the vapors because the inside of the enclosure has good correct shape. Kinda rough, but no deformations from melted polystyrene.
The packaging tape left some marks on places there it was in contact with the epoxy. It doesn’t usually leave big marks. Nevertheless it protected deck well and didn’t stick to epoxy. Cleaning was easy with some alcohol.
Post processing
I used dremel to cut the enclosure corners. Not as easy as I thought, but doable. I used one of those FFP2 respirators that everyone nowadays have everywhere, but this is not a good protection since the rubber bands on the respirator are not pressing it enough on my face and there are gaps. I felt like shit in the evening from the fiberglass dust that I have inhaled.
There were some holes in the enclosure, so I had to use some extra epoxy and filler to fix them. Didn’t use enough resin at some places.
I then used rattle can spray paint, antracite gray color. At this moment the imprefections really showed up. The surface is not as nice as I originally thought and I could have play more with the filler. But functionality is more important for me than aesthetics, so it’s ok.
I used 10mm self-adhesive foam as gasket and 3mm art&craft foam as padding for the battery. For cutting holes into the foam gasket I used metal drill bit which cut the holed in the foam with no problem.
Conclusion
So the enclosure is ready. I mount it to the deck using M5 hardware, same hardware that I use for mounting trucks. This build is not yet finished, so it’s not properly tested yet, but I will write some of my thoughts from building the enclosure:
- Fiberglass enclosure can be made without special equipment for low price. It won’t look as good, but it will be functional.
- My bill of cost was €16 for 1liter of resin and 3m^2 fiberglass cloth, 4€ for foam padding and gasket, €1.50 for the vacuum bag, €1.50 for polystyrene. I also used packing tape, sandpaper, filler and rattle can, but I had these stuff already at some, but it’s nothing too expensive. I believe that the material I have bought would be enough for two enclosures if I didn’t waste some material by making mistakes (working slow with expoxy resin).
- Often time I read here that making your enclosures is not worth financially. Despite my total cost was low, I have to agree with this. It’s not amout the material cost, but about time. I have spend so many hours on this. Financially it would be worth it just work overtime and then buy premade enclosure. But DIY enclosure has still the benefit that I was able to achieve the desired shape/volume. And I have learned so much working with epoxy.
- Polystyrene is fine for the mold, but next time I would use two or three layers of packing tape instead of only one layer so it doesn’t get eaten up as much.
- Three layers of 340gsm fabric is not as much. The fabric looks thick, but the final enclosure is not as thick as I would have guessed. Next time I will use like five to eight layers of fabric, probably combine it with finer 100gsm weave as well. But still the enclosure is strong enough.
- Also next time I will prepare more resin, because at some places there was not enough resin and it created holes that later had to be fixed.
- Vacuum bagging is important. Without it the corners wouldn’t be as good. But the good thing is that cheap vacuum bag for clothes and household vacuum cleaner can be used.
