Bolt Maritiem - Satellite 44
Vacuum Infusion - Outer skin

Infusion of the outer skin was Done at Thursday 14 March 2002. This is a typical example for infusion of a hull using a combination of a flow medium on top of the reinforcement with spiral tubes for delivery of the resin. Click the picture for an animation.

First of all, the vacuum is applied. It is very important that there is no leakage, because that will lead to voids in the laminate.

The resin components have to be mixed before the infusion starts. For edge injection of a flat plate, the progression of the front is proportional to the square root of time, e.g. the infusion starts very quickly and slows down in time. Gravity causes a more pronounced slow down at the end of fill - the first part is almost flat, when the sides are reached gravity effectively reduces the pressure gradient that drives the resin. Therefore, there simply is no time to mix additional resin until about 80% of the total amount is infused.

Visualisation of pressure difference due to gravity

Above, the influence of gravity is visualised by RTM-Worx. Note that only the pressure difference is relevant - all ports were closed to show the pressure differences due to gravity only, so there is no absolute value to fix pressures. What it means is that at the end of fill, the actual pressure difference is 0.24 bar less than the applied vacuum!

If a hull is infused on a male mould (here the foam core), it is important to control the shape of the flow front to avoid a lot of air traps on the symmetry line where the fronts meet. Especially in this case, because the laminate in the keel area has a thickness of 10 mm (0.4"). To achieve this, the length of the runners was tuned to produce a flow front with an elliptic shape with the vacuum point at the center. With RTM-Worx, you can do this (simply do lots of trial infusions) and minimize the total injection time too.