This was back when Swaylock’s was the leading surfboard tech forum, but all those guys were doing cored-skin stuff. They were sniffing around the edges of what was possible.
From diatex or airtech there is stretchable nylon realease film for glossy finish in vaccum bag. It s like perf ply whithout hole. Very efficient and cheap, can be use as vaccum bag in low dep process. I often use them for air plane model parts for direct finish of the bag.I do it with surf too but still need some work on rail join, and I don t make glossy finish.
I think separating the clamping function of the vacuum bag from the texture function of the perforated or non perforated release ply makes a lot of sense. Those $13 vinyl vacuum bags from ACP will wrap a rail if you work it, If you only get a few pulls off of it before it starts leaking then replacing it isn’t a big deal. Also no big deal if you’re using a bag with wrinkles in it because the release film is what is imprinting the lam, not the bag.
I’ve played around with the perforated release film but not the non-perforated. What I didn’t like about the perf-ply is the film itself is so thin that it distorts and wrinkles real easily, too. The thinness isn’t a problem near the edges where you can put a little tension on it but once you start doing that the stretch extends onto the flats and you just create more problems for yourself.
I don’t think the problem with these films for our use is that they lack sufficient stretch or flexibility; I think the problem is that we only need that much flexibility around the rails and that using it across the entire piece creates more problems that it solves.
When they do flat layups under vacuum they don’t use film - they use a solid piece of glass or other rigid non-porous to completely prevent any movement or distortion. That leads me to believe that what we need for the pieces we’re doing is a combination of less stretch for the “flats” of these shapes and the little more stretch for wrapping the rails and corners.
To phrase it in extremes, that thin plastic film we use for wrapping food (Saran Wrap or the like here in the States) is real flexible and will wrap anything but it’s wholly unsuable for what we do because it’s too flexible and it distorts way too easily. On the other hand a plastic film with the weight and consistency of a heavy plastic shower curtain (the flat film stuff, not the pleated stuff) will basically not wrinkle at all and has only a limited amont of stretch. I think that using a film with a limited amount of stretch on the flat areas will actively resist wrinkling there where you really can’t resolve them and will stabilize the lam itself and prevent it from being distorted when you apply a little tension around the edges.
But if using the no-bubble wet out technique on the wet out table Everysurfer mentioned a few weeks back I also think the heavier film won’t drape enough to wrap the rails. So I’m speculating that if we used a panel of the heavier film cut in template shape directly against the flats AND a layer of the lighter stuff over that to wrap the whole thing we might be able to get both functions. Less flexibility and stretch in the middle where you don’t want it and more flexibility around the edges where you do need it .
I’m thinking of using a little spray adhesive on the non-lam side of the heavier panel insert to adhere it to the larger piece of the non-perf release film before using it will stabilize the center of the lighter film and make it easier to localize the extent to which it stretches around the rails. If the center is stabilized then it should only take a little tension to get the film and lam around the rails to bend to our will.