The last few days have mainly concentrated on making the final corner pads out of marine ply, bevelling the edges and then gluing an identical bevel made out of balsa, this essentially to negate a hard edge.
Yesterday another vacuum sandwich was prepared and we arrived back at the boat in the evening.
Today another dry run was attempted with the vacuum – to start with things went badly, with the layers of the sandwich slipping all over the place. This was addressed with double sided tape between each layer – and success, a – .8 bar reading was obtained on the gauge – this being a new gauge with a separate breather unit placed away from the breather unit connected to the pump, this was evidence that a uniform vacuum was now achieved.
Good news is always followed by a challenge, there was hissing, the tape was checked and other seals but the noise persisted. The vacuum was that darned good it was pulling air through the chip in the fibreglass. A piece of tape over the chip negated the hissing and the vacuum gauge moved past 0.8 bar. First thoughts turned to just letting this fill with epoxy when the live run was done where the balsa will be coated with epoxy filler. However, if that epoxy filler pulled through to the surface, then the new polyester gel-coat would not adhere to the epoxy. Whilst the vacuum was still in place some polyester filler was used from the outer surface. After the vacuum was released it was clear that the filler had pulled through quite nicely – however, now did not seem like the time to take short-cuts as that’s what got us into this mess in the first place. Therefore a disc grinder was used to grind a bevel round the compromised area, the plan being to patch it properly before attempting to epoxy the balsa panel in place.
Some final sizing was done on the corner pads and the necessary holes were drilled, but after that we had to return home again to get some fibreglass cloth and resin. So this evening the task has been to fill the holes in the pads and balsa panel with epoxy to ensure there is no exposed wood when the final holes are drilled for the bolts – a picture should explain better, but the glue is wet presently – and the garage door has been locked to avoid the temptation of seeing how the glue is setting 🙂