I would like to ask for your help with my first vacuum bagging project. I am trying to review as many threads as I can but I would like to post my question for suggestions so I can finish project. I have written up a summary below how I built my diffuser if interested. I have a lot of pin holes and several shallow voids in finished project. I can fill and sand voids easily enough but I am trying to decide if I should spray or roll/brush a coat of thinned epoxy onto surface to fill in pin holes. I would prefer using epoxy and then I may spray an auto UV clear coat afterwards.  I have never sprayed epoxy but I have thinned it with methanol which worked well for brushing on some other projects. I am not afraid of wet sanding project to get a nice finish afterwards. Thanks,

I finally got around to building a diffuser for my 1990 Reynard Formula Continental race car that I run locally. I have never used carbon fiber cloth and I have limited experience with fiberglass and epoxy, but I thought I would give it a try. So I built a plug or mold out of cabinet quality 3/4 ply that I reinforced with 1x2 hardwood framing underneath.

I sprayed many coats of wood-grade polyurethane which was probably a mistake. I should have used auto paint that dries faster and harder. But I finally got a 2000 grit finish on surface that looked good enough for mold surface.

I laid up the cloth last week and item turned out pretty good for my first vacuum bagging project. It’s far from perfect with pin holes and several shallow voids. I guess I didn’t use a heavy enough epoxy coat initially and I should have waited for it so start setting up before I applied the first layer of cloth. I thought I got it wetted out before adding second layer. Then I used a 1/4" foam core with cutouts for several pieces of 1x2x.25 alum flat stock for mounting brackets. I punched small holes every 4-6 inches in foam since this was a large project, apprx 40”x 39”.

After foam was installed I added two more layers of CF with extra strips in between to reinforce the flange at front where it will bolt to floor pan of car. I used the nylon peel ply, perforated release film, and bleeder fabric before bagging board. I spent about five hours applying glue and all the layers involved before starting vacuum. I should have used a second vacuum gauge to monitor vacuum on mold. I did have a glue trap and gauge inline from port to pump. I had a couple of minor leaks in bag but vacuum stayed at 12-15 inches. I ran the pump for six hours till midnight then I decided to shut it off because epoxy was setting up pretty well.

I am satisfied with my first project that is definitely functional but I did learn from some mistakes I made that I can improve on next time. 

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