Both. You need to use a material that will wick off excess resin. If you research vacuum bagging here you’ll see. I don’t do lams in the bag, so I haven’t messed with the different material. We used to use a thin sheet of a poly material with tiny holes that allowed resin to flow through and a layer of a fibrous material that would absorb that extra resin. We were only attaching wood skins to foam, so we stopped using the green film. I use the kind of plastic material you would use to make a hot house now with the fibrous cloth but it’s more for breathing than absorbing resin.
A lot of guys will use a wet out table and weigh the cloth to get as close to a 50/50 ratio of glass to resin, then lay it all out on the board after it is wet. Lots of steps, so you’ll need a slow curing resin. The temps we have here in Hawaii tend to make even slow resin go off quick. If I mess around with a hand lam too much I risk it starting to cure. I lam with a slow cure hardener, then switch to fast cure for fill coats and final coats.
Windsurfers will do vac bag lams to get the highest glass to resin ratio, and they make very strong yet reasonably light boards.
PM BB30, he’s done a lot of vac lams, mostly with carbon fiber, and he’s posted them here. He may have valuable info. Then you can decide if the extra work, equipment and materials are worth it. I’m slowly working my way towards a vac lam, but not ready yet.
i try some full sandwich as windsurf but really long end difficult build light end easily stiff. Then i go to wood deck sandwich only. light build was 1.5 lb stringerless eps, 6oz glass bottom, 2.5 oz balsa 1.5mm 4oz over. boards were flexible but feel stiff mostly because of hardness of deck. then y go with full glass deck 6oz + 4oz patch, really light boards with soft feeling, guys like them in small surf but they buckle easily. i didn’t want to come back to wood or pvc stringer so i experiment with others kind of composites stiffeners like T and Omega stringer, same use in boat and plane for stiffen thin panels. vacuum bag fiber need lot of consummables, peel ply breather etc…, it’s a plus for light fibers that float on resin like carbon kevlar innegra spectra xynol … and for thick multiple layers of fiber composits. for one or two layers of light open wave glass it’s not needed. low fiber/resin ratio is an improvement of composits that work in tension but not in compression, plus low ratio composits are not water proof so you must had resin over. know i use more fiber make thicker skin and heavier board (like standard pu pe), guys like then more and they are way more durable.
You mention using thicker skin/more fiber to help compression, and the tensile strength of E glass is more than enough for surfboards. Very helpful, thank you! Also, the idea of the T or Omega stringer is very interesting, a stringer than does not go all the way to the other side - gives me ideas and makes me realize that where a stringer passes through the center of the composite, where it will experience no extension or compression, it is simply adding weight (I think)
Curious what you think about this:
3.0 oz (105gsm) cloth, like a Style 120, e glass, with a nice soft Volan finish - 2 layers bottom, each at an angle, and 3 layers deck (2 layers at angle)
Reduced foam density (perhaps 1 or 1.5# eps)
2 very thin and light stringers, each 2ply, about 2mm wide, and about 20cm apart, maybe getting wider near nose, closer together in tail for strength.
deck channels
Traditional materials but using a better design maybe.
you can’t have light foam thin skin and durability. Stiffners like stringers, springers, corrugations, help to fight against full buckling but not against local buckling between. 3x3oz is too thin over 1lbeps it will dent a lot under feet, dents initiate local buckling. best is to try your build it’ll probably be light an as durable as you want. durability really depend how you take care of board and how and where you surf. i make board for guys that mostly surf aggressively heavy close out shore break, they are board destroyer, happy mine last a season, other like me surf carrefully mellow beachbreack my boards last many years.
Several years ago, a member named Benjamin Thompson did a test where multiple blanks were identically shaped, laminated with various constructions, painted to look identical, and tested by a group of riders of different abilities.
I believe the one that came out on top was with a 3-oz satin weave. Three layers on deck and two on bottom, over a PU blank. This schedule over a light EPS would not hold up well, though.
Probably no reason to go 1 pound EPS on a small surfboard. B Thompson also found that the best path to durability starts with a better core.
Good info, thanks for passing that along. I think that glass schedule sounds superior such that you can save the weight back on the core or stringer. More fibers on the rails, the main structural component, but no overall weight gain, seems like the way to go. I will look for that thread.
B Thompson also posted a chart detailing his tests (done with master builder George Gall) on various types of lay-ups… I will leave interpretation to the experts.
https://www.swaylocks.com/forums/tests-results-13-unique-constructions