The bottom came out very smooth. Putting down the coat of resin first and letting it cure worked well. No sign of the uneven surface of the core due to the carbon tape. Color came out a bit blotchy. This is the second time I've had the white pigment separate out under pressure and I'm starting to think that the pressure is sufficient to cause the different molecular weight components to separate.
Overall there were a lot of improvements in finished product that I'll carry over into the next one. Two things of note straight away that did work.
i) I layed the board up on a flat table and then bagged in and evacuated it down to c 20 in Hg. This meant that when I bent it into the rocker table the top skin could not slide over core and so it buckled. I noticed this while it was under the vacuum but it was too late by then. The buckling is very obvious in the right light. Fortunately it shouldn't affect it structurally as the potential voids underneath are filled with resin
ii) With an impervious top sheet almost no resin was squeezed out from the top of the board. This was exacerbated by the curves on the top with the surface stepping down from one layer to the next. This seems to have created a resin trap for resin being squeezed out and around the contours there is a noticeable deposits of resin under the topsheet. Also the board turned out heavy as a result of this and the extra resin for the topsheet and the 'gel coat' bottom each of which used around 200 gms of resin. As a result the board came out at 2.7kg without accessories. Well over 500gm heavier that other similar efforts.
|Ripples due to 'pre-clamping' the topskin to the core before bending in rocker table. Pink color is courtesy of Picassa!|