Hi
I'm going to make fiberglass fins (for freediving) with Epoxy infusion. I have made several tests to achieve a smooth surface on both sides. I have tried with peelply, it gives a rough surface. I have tried a silicone plate, it does not give enough epoxy flow and the epoxy tries to find roads that are not planned. I want to achieve a process where I can make two smooth surface at the same time. I have attached an image on which they have made an setup that I would like to make, but I need little help ....
Are there any suggestions on what their setup is? I can not see peelply is being used on the image. And what purpose is the string / rope that is at the edge of the mold?

Thanks for the answer. If peel ply is used, it will leave a rough side and the fins must be made of two laps to prevent the rough side. I do not think they are made of several laps, otherwise it will be too expensive and time consuming to make commercially. I have attached a picture of how they look (and they have smooth surface on both sides)

Please come up with suggestions on how the setup is made, as I run out of ideas soon.....