A friend just gave me 15 yds of 36" nylon bagging film knowing I am getting ready to try my first bagging project. Since I already have the tube material, can I use this film as a peel/release ply? And if so, what might be the downside…maybe despite the fact it’s non porous. I checked the archives, but couldn’t find anything specific. Any suggestions?
I recommend that after reading this you try your technique on some test panels. With too many holes or some of the commercial woven nylon peel-ply, it is possible to remove too much resin resulting in pin air in your laminate.
The nylon bagging material works fine as peel ply. Hammer a bunch of nails in a grid pattern (A grid pattern of 1" squares should do the trick) through a slat of wood and whack the membrane a few times to put some holes in it. Now it's porous. Just cut it lengthwise so you have a single membrane to wrap around the glassed surface and rails of your freshly laminated blank. Cut it wide enough to cover the deck or bottom plus the overlaps on the other side.
Place the membrane over your laminated blank and stretch it tight. Have a tape dispenser handy to pull the edges underneath the board every few inches. This will give you a tight membrane over the fresh laminate and prevent any wrinkles. I work from the center to the ends - kind of like when laminating cloth, and fold it over at the ends. Take a pointy knife/razor blade and 'pop' any residual air pockets that are visible. Get a roll of paper towels and roll out two or three layers - this works fine as a breather and to absorb any excess resin that works it's way through the holes you punched.
Now slide the whole thing in to your nylon tube and seal the ends before applying vacuum. Once it sucks down you'll see the resin start to saturate the paper towels where your holes were punched.
That's basically it - the 'poor man's' version. You can spend an arm and a leg for the professional/commercial grade peel-ply, absorbant/breather stuff and not do any better.
FWIW, it is arguably just as good to squeegee a tight outer laminate by hand but vacuum bagging is the real deal when it comes to applying sandwich composite skins or stiff heavy reinforcement fabrics that won't lay flat on their own.
Sounds like a great shed-dweller technology Mr. Mellor. Have you ever tried using polyethylene plastic sheet for your perforation technique?
Thanks johnmellor. Can’t say enough how much I appreciate your taking the time to type all that info out. I feel like vacuum bagging is like many endeavors…voodoo magic the first time you try it…then the light comes on and it’s like, “that wasn’t so bad”…and then in my case, I proceed to screw up the next half dozen attempts before I get it half-assed right. I just figure I’m doing my part to keep the economy going.
thanks again, that was great info!
Yes the bag material will work fine on a wet layup. Just start with a single side lamination to get the hang of pulling the bag tight over the lamination prior to pulling full vacuum. A full lamination to bagging operation on your very first board will most likely not go very smoothly.
I’d even recommend practicing a dry run on anything, even an unshaped blank. A couple of tips, make sure to cut the bag at least a foot longer than the board on both ends. Since the bag can be used many times I ususally have a few precut with one end sealed with ports installed. Get the hang of getting the board into the bag and then pulling vacuum slowly to give you time to pull the bag material tight over the lam. The extra material can be bunched on the non lam side. Any wrinkle on the lam will cause a crease that you will have to fix or at worst if the cloth folds over the bag then it will get stuck and you will have to ruin the bag to get the board out.
If you just get your lam wetout but not perfect as you would in a wet layup it will be fine with just the bag. The trick is to get the ratio just right. Vacuum pressure, resin absorbtion into the foam, type of bleeder, etc. will play a huge role in how it ends up. Aside from altering the rocker and or having a very dry lam it will be better to start simple first.
A common mistake is to use too much bleeder and or pressure on an unsealed blank. The lam will come out very dry. The ideal ratio is one to one cloth to resin. As most of what we do is a wet lamination without bagging you’d be surprised how off that ratio is. Any easy way to see how little resin is required to do a one to one ratio is to weight the cloth and then match that with same weight of resin.
If you need supplies ACP is a good reasonably priced site for everything you might need http://www.acpsales.com/Vacuum-Bags-Films-Peel-Plys.html If you want to save a little money any fabric store sells rayon (bleeder) and poly felt or backing (breather).
Also remember the core material of eps and poly are terrible cores and plain fiberglass cloth is on the lower spectrum of strength compared to what is out there. So essentially you’re just removing the air that is normally present in a wet layup of a very fragile final product. So don’t get too caught up in making a dramatically stronger board that is lighter
Peel ply cost pennies per foot. Why f*%k around? Why risk a sanding nightmare for $6 dollars worth of peel ply that is 60" wide?
Breather cloth lasts for years and is inexpensive too if is outside of your release film.
Good luck.