On the photo above, I've forgotten to use my roller on the line there the top layer bridges with the core.
I think this is a must to bridge the fiberglass properly. As a result the FG didn't bridge perfectly, good but not perfect.
Something to think about on a new build. Or I may dump the top layer and go with the triax + carbon and a veneer.
AND, the topsheet is not for faint hearted
I think more and more that the topsheet is good only for pressing with a pneumatic press. It is extremely hard to do the topsheet with a vacuum. The air pockets are bastards to fix. More elbow grease...
Your bag is too tight, as you are using a breather fabric you can bunch the bag up around the changes in levels so you don't get bridging. The folds will not show on the final finish as you have the breather fabric, peel ply / mesh / release film under
Crappy photo but kind of shows the idea
Pull 1/2 vac so you can still move the bag around and work the folds around the lumps so it won't bridge then pull the full vacuum.
I went with the top sheet (well, bottom actually). Had a few dramas with that like taking it off two times and that:( It is ultra shiny but still has got a protective film so can't take photos.
Ended up with 2826 grams before the final cut, varnish on top, etc.
I recon this is due to a bottom sheet, extra SS inserts (2) + almost 90 grams epoxy (50% more and was not enough, you need to "bath" a FG not to get some visible dry spots under the bottom sheet).
Used only 120g/m^2 FG which makes soft flex.
This is interesting since a foam top layer and biax carbon on top of the foam only (not the length of the board), makes more rigid board with the same bottom layout. Remember, my boards are "exposed" wood and every single mistake can't be hidden (ie. hidden with the graphics).
I'll double the FG for the bottom and use only 120g/m2 on top for my next one. The reason I've used 200g/m^2 on top has to be seen and I'm not ready to reveal that yet:)
did not get any better results with folding the plastic:
It is easier to work out the plastic around the bridging line but I think this is not the solution for the problem. It actually made it worse since more air is trapped as tiny air bubbles.
I think the cause of bridging problem is the perforated film (PF) which is under tension. Pulling some vacuum and work out the folds is good but not enough because the vac will tension PF again where the board core finishes:
One can work out the gap but not two gaps. Either way, one is always tensioned when one pressed.
My proposal is to cut the PF just before the board edge. Then a vac can't pull the PF and open the air gaps.
But than, is the whole idea of using the PF to have it tensioned???
Or the other method might be to perforate the PF on the bridging line to let the air escape (but PF will be still tensioned, and not pressed down to close the gap).
Of course, not having a step down like my 45 degrees routed lines, is a much better go. Like I did on my Carbon Shinai, about 30 degrees:
The above carbon top layer was made on a perspex table as well.