Building an International Canoe

Why Vacuum Bag?

When working with fibreglass the epoxy content with respect to fibreglass is not as significant most of the time, though it does affect the final weight of the product. Working with carbon fibre for items that are under high loads, such as a mast, makes the epoxy content and final weight much more significant.

If too much epoxy is used compared to carbon fibre, the epoxy will take on load before the carbon does. The epoxy is significantly weaker than the carbon and its main roll is to hold the carbon strands together. When the epoxy takes the load first, it fractures. The epoxy can't hold the carbon together anymore and the mast breaks.

Its been found that [TODO check this:] one oz. of epoxy to one oz. of carbon is approximately the correct ratio. To achieve this ratio, roughly 7.5 psi of vacuum needs to be applied. On a small item such as a rudder with a surface area of half a metre this is the equivalent of 5812 pounds of pressure on the surface of the rudder. With larger surface area (such as a mast) this equivalent weight increases.

Apparatus

This section covers the equipment needed for vacuum bagging and how its setup.

Method

This section covers vacuum bagging methodology, including layup techniques and bagging the workpiece. It also covers a newer vacuum bagging method called vacuum infusion.