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Vacuum Bagging
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An investigation into the art of Vaccum Bagging.
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| The 'WHY' of this page ... |
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This is an attempt to gather together some of the bits and pieces of information on the net on Vacuum Bagging.
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| First things first .. some links: |
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Vacuum Bagging : The technique of vacuum bagging is used to construct foam core wings,
either with a wet layup of fiberglass cloth and resin or to apply a wood veneer skin. Both practices use the same principal: enclose the wing in an airtight "bag",
then remove the air from within the bag allowing atmospheric pressure to hold the wing skin against the core while the adhesive cures ....
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Basic Vacuum Bagging : Vacuum Bagging of fiberglass and resin parts is becoming a
widely accepted and useful tool. From solid glass lay ups to complex composite structures, vacuum bagging is a technique that should, and can, be explored by even
the novice boat builder. This will be the first of a two part article and will only touch on the basic elements of the technique ....
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Motorcycle Parts From Carbon Fiber
This is a description of how to make a carbon fiber molding by ‘skinning’. You could, I suppose, describe skinning as a reverse of molding; in molding, carbon
fiber is applied into or over a mold and the finish that will eventually be seen is the surface that was next to the mold. In skinning, it is the opposite way
round; you apply a carbon fiber skin over a mold and the finish is achieved by building up successive coats of resin and rubbing down till you end up with a
smooth surface.
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Vacuum Bagging
An ideal fiberglass layup minimizes the amount of resin because resin by itself adds weight without adding strength. When doing fiberglass layup by hand,
it is hard to get the minimum amount of resin because you need enough to soak the cloth and the cloth doesn't lay completely flat against the surface. The
solution to this is vacuum bagging.
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| Principal of Vacuum Bagging |
Vacuum bagging is a process that allows you to create solid glass lay-ups with fiberglass or carbon fiber, to complex composite structures such as skinning foam with
fiberglass, carbon fiber and wood. You use the minimum amount of resin since the resin by itself adds little to the strength and allows the cloth to lay completely
flat against the surface. It uses an airtight bag from which the air is removed allowing atmospheric pressure to hold the 'veneer' against the core while the resins sets up.
At sea level, one atmosphere weighs 14.7 psi or 29.92 inches of mercury. By removing the air in the bag, pressure is equal to the amount of vacuum generated. A vacuum pump
drawing 20 inches of mercury from the will result in about 10 lbs psi to the core.
A technique for using the FoodSaver (Tilia) as the vacuum pump and bags has been used in building model rockets. Price runs in the $200-$300 range. Another brand is
FreshGUARD (Black & Decker) which is around $50 and has been sold by Wal-Mart in the past. The FoodSaver pulls 24.2 inches Hg while the FreshGUARD pulls 21 inches Hg.
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| (.... to be continued ....) |
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