July 2013

Vacuum infusion flat panels

Juni-juli 2013:

There are still some finishing touches needed on the inside of the hull before we can start with reinforcing the hulls with fiberglass. First we will make the bulkheads and floor parts for the hull. This way we gain experience and practice with the theory of vacuum infusion on relatively small projects before starting the big infusion project on the whole hull.

As you can see below there are plenty of parts to be fabricated.

Backbone catamaran 1500 Cruise

The parts will be fabricated by putting green Airex plates on two sides together and reinforcing them with fiberglass. After the epoxy has cured we can draw and saw the parts from the bigger Airex plate. By placing 2 or 3 plates together and covering them with fiberglass we save allot of preparation time and it enables us to get multiple parts from one plate. After puzzling with AutoCAD Paul has made an efficient lay-out of the parts.

The materials a bulk of epoxy and fiberglass purchased 5 months ago are finally in use, a great and special feeling, so far we have been able to work without a mess, unique considering the mess that usually goes hand in hand while working with fiberglass and epoxy. We are very satisfied with the vacuum infusion compared to the hand layup method Paul has used while building the “Double Twenty.” The preparation time is a bit longer because the fiberglass, compoflex and a vacuum bag has to be placed on the ‘glue’ table without moving the mats or puncturing the vacuum bag.

Materials deliverd for the vacuum infusion flat panels  Storage for fiberglass and vacuum infusion materials

Before we begin we made a residue pipe (traps) to trap the excess of epoxy and ensure that our vacuum pump remains clean and clear of epoxy. A couple extra traps will come in handy for when the epoxy starts heating up during the process of infusion, the spares will enable us to disconnect and replace the filled traps. The traps that have become to hot will implode and become useless, therefore we will try to empty them before this happens.

Resin traps from PVC tubes

The preparing of the Airex plates

To ensure the 2 Airex plates will fit smoothly we will mill a tongue and groove connection. A simple mold works easily and ensures a constant thickness. The groove is made with a standard setting so that we get the same dimensions every time.

Mold for connecting bevel in airex panel  Airex connecting bevel  Airex connecting bevel  God fit 2 Airex panels

The Airex panels have a hole pattern (perforated) that enables us to glue the fiberglass mats on both sides simultaneously.

This means that we also have to build everything in mirror image.

From top to bottom:

  1. Vacuum bag (will be closed with tape)
  2. Compoflex (temporary canvas, that enables the flow of epoxy without sticking to the fiberglass and is easily removable)
  3. Strip peelply (serves as a brake in order to stop the epoxy from flowing over the edge)
  4. Fiberglass mats
  5. Foam panels
  6. Fiberglass mats
  7. Strip of peelply (again closes the bag and stops the epoxy from overflowing)
  8. Compoflex (temporary canvas)
  9. Connection tubes for epoxy and the vacuum pump
  10. Vacuum bag

To ensure that the bottom mats are in place we tape the shape of the plates on the glue table. Now the construction can begin.

Tape marks the infusion aerea

In this photo album you can see step by step build-up of the laminate. Open the 1st foto to read the comments.

Finally; the infusion process

A good preparation will save you allot of work, and with infusion this certainly deemed to be true. When you take all the right steps you will end up with an airtight package en the rest of the process will pretty much run itself. Nevertheless, during the preparation allot of things can go wrong, usually these problems are minor and are easily fixed (most of the time these are small holes in the bag that prevent a full vacuum). These quick fixes are usually done with some tape. After some trial and error we needed less quick fixes and things went more smoothly.

The first project was done with 1 centralized epoxy inlet line, the epoxy has to flow 1 meter in both left and right. We knew it would take a bit longer but this way we had the time to follow the process. The total project took us 2,5 hours, afterwards it took an additional 8 hours for the epoxy to begin “gelling”. All this time we wanted to be close while this happened.

Vacuum infusie flat panels epoxy flows from inlet line to both sides of the panel  relaxed proces

Only a few centimeters to go  Final check, epoxy flows everywhere

The testing was not really in the vacuum method, but more in the time that it took to complete a project. Some adjustments were welcome, which is why we implemented the following improvements:

  • Set up the project the day before and start the project the next morning
  • We added one more infusion line on both the left and the right side of the central line.
  • Pre-heated the epoxy to circa 30-32 degrees Celsius.
  • After the infusion keeping the project on temperature with infra-red lights to speed up the gelling process.

We tested this all first on a leftover piece of CoreCell. The measures described above worked well and in less than 30 min the project was ready to start hardening. Below you will see that the resistance drops after the second line is opened and that the flow of epoxy went allot faster.

Vacuum infusion test with 2nd inlet lines, see marks every 3 minutes

From this moment it took 30 minutes for the test project to finish. With the extra heat from the lamps the process of hardening accelerated. The temperatures in the summer also helped out and therefore enabling to ‘unpack’ the project the next day. Sometimes the bottom of the project took a while longer and it needed some more time before removing the compoflex. Off to the preparations for the next project!

Much faster with 2nd inlet lines  Speed up the cure process with infrared heating

Compoflex is easy to release  Also at the bottom a good laminate

Eventually this became our favourite set up for flat panels:

Favorite set-up

In this clip you can see how a project goes and the flow of epoxy.

Laminate flat panels with vacuum infusion method

After 2 projects we got the hang of it. Paul was preparing the glue table for the next project. Jolanda made the blueprint for drawing and cutting out the parts from the finished projects. This worked just as easy as with the construction molds. Printing on an A0 plotter, copying the lines with a hammer and nails and redrawing it with a marker, after sawing even out the rough edges with an eccentric sander.

Align the drawings on the laminated panels  Mark with nail and draw the lines

Cut out the parts with electric saw  Grind the egdes

Lots of parts for the underfloor web  Bulkhead 4 with roughly cut out doorway