Recently I needed to vacuum another laminate over the core reinforcements in the hatch lids and found I had no vacuum sealing tape (tacky tape). I have for a while thought there may be another way, so I purchased some cheap external silicone roof plumbing sealant and ran a bead on each side of a small tubed bag. It worked very well and was in fact a perfect seal immediately.
I then put one lid laid up with wetted laminate, peel ply and release film in a tubed bag and sealed with silicone. I waited for as long as I dared for it to cure without having the epoxy go off, then pulled the vacuum while the silicone was still wet. Same again, a perfect seal, although the bead flattened and widened by 50%. I have since achieved another perfect seal on the second lid with the silicone newly applied and quite wet and soft.
See photos below, first a close up of the seal and material used and then the hatch lid being vacuum bagged.
Yes, I was pleased with myself regarding this and immediately shouted myself a beer (encased for drinking in our climate).
The Scrumble Project 