Making the mold

What a week! We started to make the mold and had a couple of very long and late ending sessions. In the fist session we spread a thin coat of tooling gel coat (Formenharz P, R&G Faserverbundwerkstoffe GmbH) and strew a mixture of glas shred and cotton fluffs (coupling layer) on top of the fresh gel coat:



Properly spreading the gel coat is the most important step to obtain a high gloss surface (along with the pattern’s finish). The coupling layer is needed to have a surface on which glas fabrics can be laminated in a later step. Without a coupling layer one has to keep on laminating before the tooling gel coat has completely cured, i.e. after it started to gel. Going on wouldn’t be problem for a small mold. However, when you have several m², such as here, mixing and spreading the gel coat is already enough hard work for one session:


One day later, after the gel coat cured, we went on laminating several layers of glas fabrics to stiffen the mold. We started with filleting the corners and filling the surface with thickened epoxy resin (glass shred and cotton fluffs). This reinforces the corners substantially and prevents air bubbles. Then we laminated four layers of glas fabric (two 160 g/m² and two 280 g/m²). Each layer of a given weight was laminated with two different orientations (0°/90° and ±45°) to obtain a quasi-isotropic laminate. We would have wanted to keep on with the next two layers of 390 g/m², but it was late enough (about 3 o’clock in the morning!), and we, thus, decided to stop and close the session with a layer of peel ply:


Two days later, we laminated the two remaining layers of 390 g/m² (quasi-isotropic), glued the core material and cured everything in vacuum. This time we wanted to get sooner to bed, but to be honest, we had a terrible time to build enough vacuum. Somehow it was again 3 o’clock in the morning and we were still looking for a large leakage. As in the last session, we had to get up at 7 o’clock the next morning and get to work… A consequence of this, was that I decided to buy a stronger vacuum pump with much more volume flow!

Anyway, we started to get everything ready for the next and final layers of the sandwich. I separated the external ribs and trimmed the surpluous border. We hope to end this side of the mold this week.

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