Poor Man’s Alternative to Vacuum Bagging

I’d like to share a trick I’ve been using. A person would have a hard time to tell the difference in a piece made from this method placed next to a vacuum bagged piece. I’ve been using this method for over 16 months and it works really well. All you need is a roll of 3M masking film, a flexible plastic body putty spreader, and some tape. All of these items can be purchased at any building supply store like Home Depot in the paint department and fairly cheap. A roll of the 3M film will last forever.

Vacuum bagging is great but it takes time to set-up and is costly. First there is the investment in the pump and hardware. Then the process it’s self is costly when you add up the cost of peel ply, bleeder cloth, perf cloth, dumb-dumb or liquid nails, bagging film, and what ever else you may need to make or buy for the job. Not to mention that you usually need about 6 hands. Any one thing that goes wrong and you have a large investment that went to hell in a hand basket.

I had near miss on the last lay-up of a hull half but pulled it out of the fire when I was shorted 5 feet of peel ply from my supplier. I was combining two steps into one and it was important to pull the extra resin and bog out of a wet lay-up. (I had my roll of 3M film it saved the over all lay-up but did not allow me pull out the extra resin.) Every time I look at the result I still get pissed but that is part of the game. I could have lost thousands of dollars and about 6 weeks of work from a simple mistake of a store clerk and I never double-checked before the lay-up so I can only blame myself for trusting that somebody else did their job correctly.

Here is the method as I do it on Divinycell foam in this example ½ inch H-80. I find it best to apply a thin layer of bog on the foam first to prime the foam and assure good adhesion. I mix 105 West System resin with 205 fast hardener and some 407 powder. I make it the consistency of hot maple syrup and apply the bog on the foam with the spreader. Just enough to fill the holes in the foam and make the surface of the foam look wet and glassy. I already have my fiberglass cloth cut in this case I’m working with 200-gram unidirectional carbon. I lay my first layer of carbon on the bog and spread the carbon out getting the wrinkles out and pressing it down with my hands picture below. Then I pour on a fair amount of straight resin and squeegee it in really good with the spreader making sure I wet the cloth out and forcing the resin through the cloth. The picture below will show a really wet lay-up with the resin pooling on top of the cloth after getting worked into the weave. Then I lay my next layer of cloth and work it straight with my hands then lightly with spreader. I add just enough resin to wet it out as I work the resin from the bottom layer up.

Now the magic! I cover the lay-up with the 3M film. Here is the important part the writing must be facing up so you can read it! If you have the writing down it will stick to your work! Keep the film tight to avoid wrinkle and lay it on the top laminate 3M side up. Then take your spreader, I dip it in some resin to lubricate it, and apply pressure on the film with long full strokes working from the middle work the excess resin and air from the laminate to the edges. Keep the spreader level and flat especially on the edged to avoid dry spots and you work the film with the long strokes. It usually only takes one or two strokes to compress the fibers and remove excess resin as long as you did not have a really wet lay-up. I tape the overlapping edges of the 3M film several inches past the piece I’m working on to keep the edges from lifting. As long as you applied the correct side of the film when the resin is dry it lifts right off. Don’t try to remove the film before the resin is dry it will remove the resin with it, but once it is cured - magic! You will have a beautiful lay-up with a smooth, compressed, and air free laminate that will be taken for a vacuum bagged job.

The Man Shed