Mon Nov 14 2022

Interior side panel trimming and fiber:resin ratio

These pockets need another coat of paint. They don't need to be perfect, so I'm not filling all the pinholes or any such nonsense. Just want a little more paint on them where the first coating was a bit thin.

Yesterday, I saved this little sample. It was a scrap piece that was headed for the trash can. Anyway, I saved it in order to see what kind of fiber:resin ratio I was getting.

Weighed (32.6g) and measured (13.5" x 2.75") the sample. It's three layers of fiberglass thick just like the rest of the side panel.

Also weighed (54.6g) a 16" x 18" piece of cloth I didn't use.

After doing some quick calcs, the specific weight of the fiberglass cloth was .196 g/in^2/layer. The specific weight of the layup is .293 g/in^2/layer. So, the specific weight of the epoxy was .097 g/in^2/layer. Thus, the percent glass is 67% and the epoxy is 33%. Probably could have used a bit more epoxy as I understand the ideal ratio is 60%/40%. Regardless, it'll make for a nice, light part.

Here is the part all cured with peel ply removed.

The packing tape and the thin layer of mold release I wiped on did their job...the side panel released reasonably easily.

Trimmed off the excess from all the edges. Fits in and out pretty easy now.

...and here is the part on the table saw. Total weight is 780g (about 1 lb, 11.5 oz). Of course, the completed side panel will be heavier once the felt backing and (planned) vinyl covering is added; but for now, I'm pretty happy with how this is coming out.