Cheapest, down and dirtiest, diy, enclosure form
This process uses easy to source materials, designed for epoxy or fibreglass direct layup.
I wanted to figure out how to make a “form” for making enclosures on, that almost anyone could do. I know it can often be a tricky part to get or people want to customize their own.
I picked EVA foam or L200. It’s the yoga mat stuff, anti fatigue mat, high density foam. I bought this at Michael’s it was $1.50 per piece (Canadian). I grabbed six of the 9x12 and four of the 12x18 large thin sheets. I ended up using all six of the small sheets and two of the large. You can get this foam in all sorts of places and getting a overall larger single thin piece for the finishing layer will save you a seam later on if you care. I found that three of the thicker mats stacked together were approximately the same height as a 30q cell.
I grabbed an analog to do my pattern on.
These are the rough cut shapes. These will be stuck together and formed still. If you had a single piece or different thickness it doesn’t matter, you just need to decide on the shape and style you want. You want a rounded edge on things to help with your layup later on. The shape you create with be the INSIDE of your enclosure.
These are all the parts before I stuck them together.
I used this rasp and sanding block to round the edges out and shape things. You can use a rotary tool (Dremel) and any electric sanders to shape this foam. Super friendly to use. These pieces don’t need to have perfect edges it’s the form that’s important. The other thin layer will go on top and will soften all the imperfections.
I used double sided tape to hold everything down. Between the stacked foam and to the deck.
The final skin layer is on, it’s the thin skin stuck down and pushed in place. This is where having one large piece would have been nice. I put black paper tape across the gap. This is more or less where I ended taking pics.
If I had continued to do the glassing. I would have used a heat gun to form and harden the final foam more. Then added tape and cardboard on the grip side to support the extended foam outer lip. You want to keep that from moving while doing your layup.
•WARNING THIS FOAM NEEDS TO BE SEALED IF YOUR USING FIBERGLASS!•
Polystyrene doesn’t like setting up against this type of foam. You need to give it a barricade. PVA glue or wood glue works well. Brush or sponge on 4-6 layers making sure they are dry between costs and fully dried before moving onto glass. In a pinch you could do a tape layer over the surface as this will be the inside of your enclosure.
Alternatively, you can spray glue the foam then stretch a garbage bag or plastic sheeting down and press out any wrinkles. Then glass on top of that. It never sticks and the resin won’t eat your foam or stay tacky. It’s just a different option then the glue sealer.
If you draft your angles enough and use a thin epoxy/fiberglass mat opposed to cloth for your layup, you should be able to do your coverage in one single piece per layer. If you crumble your mat in your hands (when it’s dry during prep) in the areas that will be your corners, that helps it soften and conform. Once you have your cast trim your flange and drill any holes. You can bodyshop it, cut it, paint it and customize it any way you want. Hopefully that makes sense and helps out! 
Bonus method
If foam isn’t your thing, you can go EVEN CHEAPER! Following the same process as above, substitute your foam and pva glue for cardboard and packaging tape!
